Long-term results of radiofrequency ablation for unresectable colorectal liver metastases: a potentially curative intervention

Objective

The long-term results and prognostic factors of radiofrequency ablation (RFA) for unresectable colorectal liver metastases (CRLM) in a single centre with >10 years of experience were retrospectively analysed.

Methods

A total of 100 patients with unresectable colorectal liver metastases (CRLM) (size 0.2–8.3 cm; mean 2.4 cm) underwent a total of 126 RFA sessions (237 lesions). The mean follow-up time was 29 months (range 6–93 months). Lesion characteristics (size, number and location), procedure characteristics (percutaneous or intra-operative approach) and major and minor complications were carefully noted. Local control, mean survival time and recurrence-free and overall survival were statistically analysed.

Results

No direct procedure-related deaths were observed. Major complications were present in eight patients. Local RFA site recurrence was 12.7% (n = 30/237); for tumour diameters of <3 cm, 3–5 cm and >5 cm, recurrence was 5.6% (n = 8/143), 19.5% (n = 15/77) and 41.2% (n = 7/17), respectively. Centrally located lesions recurred more often than peripheral ones, at 21.4% (n = 21/98) vs 6.5% (n = 9/139), respectively, p = 0.009. Including additional treatments for recurring lesions when feasible, lesion-based local control reached 93%. The mean survival time from RFA was 56 (95% confidence interval (CI) 45–67) months. Overall 1-, 3-, 5- and 8-year survival from RFA was 93%, 77%, 36% and 24%, respectively.

Conclusions

RFA for unresectable CRLM is a safe, effective and potentially curative treatment option; the long-term results are comparable with those of previous investigations employing surgical resection. Factors determining success are lesion size, the number of lesions and location.Colorectal carcinoma is one of the most common malignancies in Western countries. In 20–25% of patients with colorectal carcinoma (synchronous) liver metastases are present at the time of diagnosis of the primary tumour [1-3]. Another 20–30% of patients develop (metachronous) liver metastases, which usually arise within 3 years of initial treatment of the primary tumour [1,3]. In Europe and the USA, colorectal liver metastases (CRLM) are the most frequent cause of malignant hepatic tumours [4]. The prognosis of patients with untreated CRLM (receiving only symptomatic therapy) is poor, with a median survival rate of 4.5–12 months, depending on the extent of metastatic disease at the time of diagnosis [5]. Chemotherapeutics, using oxaliplatin and fluorouracil (5FU), can prolong survival in a palliative setting with a median survival of approximately 18 months [6-8]. More recent results show a median survival of 21.7 months for patients treated with capecitabine, irinotecan and oxaliplatin [9]. Surgical resection is still considered the only method for definite treatment of malignant liver tumours by many [10-17]. Resection of liver metastases with curative intent results in a 5 year overall survival rate of 24–58% and a 10 year survival rate of 28% [11-19]. It is not uncommon, particularly in patients with primary colorectal carcinoma, for the liver to be the only site of metastatic disease [19]. Unfortunately, approximately 70–80% of patients with metastases confined to the liver are not suitable candidates for resection, owing to tumour anatomy (number, size and/or locations), extended extrahepatic disease and/or impaired general health status [20-22]. Therefore, several other local treatment methods such as tumour ablation, originally considered palliative procedures, have been investigated. Radiofrequency ablation (RFA) has shown promising results in the recent literature. It is a procedure with a relatively low complication rate (<10%, mostly minor complications that are often unnecessary to treat) and a very small risk of death (<1%), notably when compared with resection [20,23]. The aim of this study was to retrospectively describe the long-term results and predictive factors of RFA for unresectable CRLM.     

Effect of CT fluoroscopy-guided transpulmonary radiofrequency ablation of liver tumours on the lung

Objective

We retrospectively evaluated the effect of transpulmonary radiofrequency ablation (RFA) of liver tumours on the lung.

Methods

16 patients (10 males and 6 females; mean age, 65.2 years) with 16 liver tumours (mean diameter 1.5 cm) underwent transpulmonary RFA under CT fluoroscopic guidance. The tumours were either hepatocellular carcinoma (n=14) or liver metastasis (n=12). All 16 liver tumours were undetectable with ultrasonography. The pulmonary function values at 3 months after transpulmonary RFA were compared with baseline (i.e. values before RFA).

Results

In 8 of 16 sessions, minor pulmonary complications occurred, including small pneumothorax (n=8) and small pleural effusion (n=1). In two sessions, major pulmonary complications occurred, including pneumothorax requiring a chest tube (n=2). These chest tubes were removed at 4 and 6 days, and these patients were discharged 7 and 10 days after RFA, respectively, without any sequelae. The pulmonary function values we evaluated were forced expiratory volume in 1 s (FEV1.0) and vital capacity (VC). The mean values of FEV1.0 before and 3 months after RFA were 2.55 l and 2.59 l, respectively; the mean values of VC before and 3 months after RFA were 3.20 l and 3.27 l, respectively. These pulmonary values did not show any significant worsening (p=0.393 and 0.255 for FEV1.0 and VC, respectively).

Conclusion

There was no significant lung injury causing a fatal or intractable complication after transpulmonary RFA of liver tumours.Percutaneous radiofrequency ablation (RFA) has been established as a local therapy for liver cancers, including both hepatocellular carcinoma (HCC) and liver metastasis [1]; meta-analysis that included a total of 5224 treated liver tumours showed a local progression rate of 12% (647/5224) after one or more RFA sessions [2]. In this procedure, a radiofrequency (RF) electrode is generally inserted using the transabdominal and/or transhepatic route under ultrasonographic guidance. However, depending upon the tumour location, it is often difficult to detect these by ultrasonography (e.g. tumours located in the hepatic dome). In such tumours, certain modified approaches, such as artificial pleural effusion [3], artificial ascites [4], artificial pneumothorax [5] or thoracoscopic guidance [6], are often used.The transpulmonary approach under CT guidance is another method that can be used for needle insertion into such liver tumours. Some investigators have reported the feasibility, effectiveness and safety of transpulmonary RFA of liver tumours [7-12]. Further, certain pulmonary complications—such as pneumothorax and pleural effusion caused by puncture of the pleura, lung and/or diaphragm—have been reported too, along with these being common complications of RFA of liver tumours. To our knowledge, however, although there are no reports of fatal or intractable pulmonary complications of this procedure, there are also no reports that evaluate its effect on the lung.The purpose of this study is to retrospectively evaluate the effect of transpulmonary RFA of liver tumours on the lung.     

Switching bipolar hepatic radiofrequency ablation using internally cooled wet electrodes: comparison with consecutive monopolar and switching monopolar modes

Objective:

To evaluate whether switching bipolar radiofrequency ablation (SB-RFA) using three internally cooled wet (ICW) electrodes can induce coagulations >5 cm in porcine livers with better efficiency than consecutive monopolar (CM) or switching monopolar (SM) modes.

Methods:

A total of 60 coagulations were made in 15 in vivo porcine livers using three 17-gauge ICW electrodes and a multichannel radiofrequency (RF) generator. RF energy (approximately 200 W) was applied in CM mode (Group A, n = 20) for 24 min, SM mode for 12 min (Group B, n = 20) or switching bipolar (SB) mode for 12 min (Group C, n = 20) in in vivo porcine livers. Thereafter, the delivered RFA energy, as well as the shape and dimension of coagulations were compared among the groups.

Results:

Spherical- or oval-shaped ablations were created in 30% (6/20), 85% (17/20) and 90% (18/20) of coagulations in the CM, SM and SB groups, respectively (p = 0.003). SB-RFA created ablations >5 cm in minimum diameter (D_min) in 65% (13/20) of porcine livers, whereas SM- or CM-RFA created ablations >5 cm in only 25% (5/20) and 20% (4/20) of porcine livers, respectively (p = 0.03). The mean D_min of coagulations was significantly larger in Group C than in Groups A and B (5.1 ± 0.9, 3.9 ± 1.2 and 4.4 ± 1.0 cm, respectively, p = 0.002) at a lower delivered RF energy level (76.8 ± 14.3, 120.9 ± 24.5 and 114.2 ± 18.3 kJ, respectively, p < 0.001).

Conclusion:

SB-RFA using three ICW electrodes can create coagulations >5 cm in diameter with better efficiency than do SM- or CM-RFA.

Advances in knowledge:

SB-RFA can create large, regular ablation zones with better time–energy efficiency than do CM- or SM-RFA.Radiofrequency (RF) tumour ablation is increasingly being utilized as an alternative option in patients with unresectable primary and secondary liver malignancies.^1,2 In the treatment of small hepatocellular carcinomas (HCCs), RF ablation (RFA) has been shown to yield satisfactory local tumour control, with one study pathologically demonstrating complete tumour necrosis in 83% of HCCs <3 cm.³ Indeed, according to the recent Barcelona Clinic Liver Cancer staging and treatment strategy guidelines for HCCs, RFA is favoured over surgical resection for very early stage HCCs (single nodule <2 cm) in patients with Child–Pugh A liver cirrhosis.⁴ Furthermore, a recent systematic review paper by Cucchetti et al⁵ reported that for very early HCCs (single nodule <2 cm) in Child–Pugh Class A patients, RFA provided similar life expectancy and quality-adjusted life expectancy at a lower cost than did surgical resection.However, for single HCCs 3–5 cm in diameter, resection was shown to provide better life expectancy and to be more cost effective than RFA owing to high local tumour progression rates after RFA.^5–12 This is in large part owing to the limited ability of currently available RFA devices in creating a sufficiently large ablation zone encompassing HCCs 3–5 cm in diameter along with a safety margin.^7,11,13,14 Therefore, an ideal RFA system would provide the capability to create coagulations >5 cm in short-axis diameter within a reasonable time frame (<30 min) for the treatment of tumours >3 cm in diameter considering a sufficient safety margin (5–10 mm in thickness). Currently, multiple overlapping ablations are often used for the treatment of liver tumours >2 cm in order to cover the complete tumour volume as well as to create a 1-cm-thick peripheral ablation margin.^15,16 However, there is considerable technical difficulty in probe repositioning during overlapping ablations, especially under ultrasound guidance, owing to gas bubble formations, ultimately resulting in incomplete ablations.^17–19Recently, multiple-electrode RFA approaches, including the switching monopolar (SM) mode, bipolar mode and multipolar mode, have been attempted with each demonstrating efficiency in creating a larger ablation zone in liver tissue than in the standard monopolar RF technique.^2,20–26 Theoretically, RFA in switching bipolar (SB) mode using multiple electrodes should further improve the thermal and electronic efficiency of RFA devices compared to conventional monopolar modes. However, until now, the efficacy of SB-RFA with internally cooled wet (ICW) electrodes, which allow simultaneous internal cooling and saline infusion, in creating 3- to 5-cm coagulation areas, have not been tested in previous in vivo studies.Therefore, the purpose of this study was to evaluate whether SB-RFA using three ICW electrodes can induce coagulations >5 cm in diameter in porcine livers with better efficiency than consecutive monopolar (CM) or SM mode.     

Assessment of ablative margin by MRI with ferucarbotran in radiofrequency ablation for liver cancer: comparison with enhanced CT

Objectives

Our aim was to determine whether ablated liver parenchyma surrounding a tumour can be assessed by MRI with ferucarbotran administered prior to radiofrequency ablation (RFA) compared with enhanced CT.

Methods

55 hepatocellular carcinomas (HCCs) in 42 patients and 5 metastatic liver cancers in 3 patients were treated by RFA after ferucarbotran administration. We then performed T₂* weighted MRI after 1 week and enhanced CT after 1 month. T₂* weighted MRI demonstrated the ablated parenchyma as a low-intensity rim around the high intensity of the ablated tumour in these cases. The assessment was allocated to one of three grades: margin (+), high-intensity area with continuous low-intensity rim; margin zero, high-intensity area with discontinuous low-intensity rim; and margin (−), high-intensity area extending beyond the low-intensity rim.

Results

Margin (+), margin zero and margin (−) were found in 17, 35 and 5 nodules, respectively. All 17 nodules with margin (+) and 13 of those with margin zero were assessed as having sufficient abalative margins on CT. The remaining 22 nodules with margin zero had insufficient margins on CT. The overall agreement between MRI and CT for the diagnosis of the ablative margin was moderate (κ=0.507, p<0.001). No local recurrence was found in 15 HCC nodules with margin (+), whereas local recurrence was found in 4 (11.8%) out of 34 HCC nodules with margin zero.

Conclusion

Administration of ferucarbotran before RFA enables the ablative margin to be visualised as a low-intensity rim, and also enables the evaluation of the ablative margin to be made earlier and more easily than with enhanced CT.Radiofrequency ablation (RFA) has become a widely used treatment for hepatocellular carcinoma (HCC) [1], with some studies reporting significant long-term survival results [2,3]. One of the most difficult and troublesome issues in RFA is the lack of a reliable method for confirming that complete necrosis has been achieved in the treated lesion. CT and MRI are commonly used to evaluate the therapeutic response in the ablated tumours. The imaging hallmark of successful treatment is a lack of enhancement in the index tumour on CT or MRI [4,5]. However, previous pathological examination has demonstrated the presence of microsatellite nodules around the original tumour [6,7]. Therefore, it is necessary to ablate liver parenchyma surrounding the original tumour, as well as the tumour itself, and the ablation zone of the surrounding normal tissue needs to be recognised. In fact, several studies [8-10] have reported that the local recurrence rate in nodules with sufficient ablative margin is lower than that in those without sufficient ablative margin. The ablative margin is conventionally assessed by comparing enhanced CT images before and after RFA for HCC tumours.Mori et al [11] reported a new method of evaluating the ablative margin using ferucarbotran (Resovist; Bayer Schering Pharma, Berlin, Germany), and demonstrated that the ablative margin is easily assessed by MRI. Ferucarbotran is a clinically approved superparamagnetic iron oxide (SPIO) that is liver specific on MRI. It is composed of SPIO microparticles (γ-Fe₂O₃) coated with carboxydextran. After intravenous administration, ferucarbotran is phagocytosed by Kupffer cells and equally distributed throughout the entire liver [12]. Kupffer cells are much more dominant in hepatic parenchyma than in cancer tissue. Therefore, the signal intensity from cancer in T₂* weighted sequences becomes relatively high compared with that from hepatic parenchyma. Ferucarbotran in ablated hepatic parenchyma would remain after ablation, showing low intensity around high-intensity cancer on post-ablational MR images.The aim of this study was to determine the usefulness of ablative margin assessment by enhanced MRI using ferucarbotran administered before RFA in patients with liver cancer in comparison with post-ablation enhanced CT images after 1 month.     

Assessment of early treatment response after CT-guided radiofrequency ablation of unresectable lung tumours by diffusion-weighted MRI: a pilot study

The aim of this study was to evaluate prospectively the early treatment response after CT-guided radiofrequency ablation (RFA) of unresectable lung tumours by MRI including diffusion-weighted imaging (DWI). The study protocol was approved by the ethics committee of our hospital and signed consent was obtained from each patient. We studied 17 patients with 20 lung lesions (13 men and 4 women; mean age, 69±9.8 years; mean tumour size, 20.8±9.0 mm) who underwent RFA using a LeVeen electrode between November 2006 and January 2008. MRI was performed on a 1.5T unit before and 3 days after ablation. We compared changes in the apparent diffusion coefficient (ADC) on DWI and response evaluation based on subsequent follow-up CT. 14 of the 20 treatment sessions showed no local progression on follow-up CT, whereas 6 treatment sessions showed local progression (range, 3–17 months; mean, 6 months). For the no-progression group, the ADC pre- and post-RFA were 1.15±0.31 × 10⁻³ mm² s⁻¹ and 1.49±0.24 × 10⁻³ mm² s⁻¹, respectively, while the respective ADC values for those that showed local progression were 1.05±0.27 × 10⁻³ mm² s⁻¹ and 1.24±0.20 × 10⁻³ mm² s⁻¹. The ADC of the ablated lesion was significantly higher than before the procedure (p<0.05). There was a significant difference in the ADC post-RFA between no-progression and local progression groups (p<0.05). Our prospective pilot study showed that the ADC without local progression was significantly higher than with local progression after RFA, suggesting that the ADC can predict the response to RFA for lung tumours.After the first report in 2000 [1], lung radiofrequency ablation (RFA) is now considered effective in the treatment of lung cancer, which is traditionally considered unresectable owing to compromised pulmonary function or advanced age. In general, complications associated with lung RFA are minimal, and favourable local control has been reported in a number of studies of tumours with a diameter of 30 mm or less [1–5]. However, only a limited number of studies have been published regarding the treatment outcome after lung RFA [6–10]. In this process, a layer of normal lung tissue surrounding the tumour is also ablated as a safety margin. Inevitably, the ablated lesion depicted on a CT scan immediately after the procedure is larger than the original tumour mass. However, this region of increased density shrinks with time, but follow-up CT may still show the ablated lesion being as big as, or larger than, the tumour size before the procedure [6, 7]. Thus, radiologists sometimes encounter difficulty in distinguishing scarred tissue from a tumour residue/local progression when the size of the lesion remains the same. Accurate assessment of RFA outcome would have important consequences, as recurrent tumours can be treated again if detected at an early stage. Different modalities of early-stage follow-up examination, such as contrast-enhanced CT [8] and fluorodeoxyglucose positron emission tomography (FDG–PET), have been of great interest and their usefulness has been reported by several groups [9, 10]. Another approach — MR diffusion-weighted imaging (DWI) — which is based on the measurement of motion of water molecules, has also been reported as a non-invasive evaluation modality [11–19]. In this method, the apparent diffusion coefficient (ADC) represents the water content and distribution, the cellular density and the cell membrane integrity, suggesting the potential usefulness of an ADC map for estimating tumour viability. Indeed, DWI has been successfully used to assess the efficacy of radiotherapy [11, 12], chemotherapy [13–15] and transcatheter arterial embolisation [16, 17]. To our knowledge, only two studies have reported the use of DWI to evaluate the therapeutic outcome of RFA [18, 19]. A previous study reported that the ADC value of an ablated rabbit tumour model (VX2 tumour) was significantly higher than that of untreated tumours, and that FDG uptake on micro-PET for small animals with ablated tumours was significantly lower than for untreated tumours. These results indicate that DWI at 2 days and FDG–PET at 3 days after RFA are both potentially feasible modalities for monitoring the early effects of the procedure [19]. In this study, we calculated the ADC in tumour lesions before and after clinical lung RFA and examined the usefulness of DWI in the early detection of tumour response to RFA.     

Right thoracic paravertebral anaesthesia for percutaneous radiofrequency ablation of liver tumours

Objectives

Percutaneous radiofrequency ablation (PRFA) of liver tumours performed under local anaesthesia and intravenous sedation can cause severe pain to patients. This prospective study evaluated the efficacy of a right thoracic paravertebral block (TPVB) for anaesthesia and analgesia during PRFA of liver tumours.

Methods

20 patients, aged 44–74 years, with liver malignancies received a multiple injection TPVB at the T6–10 levels 30 min before the PRFA. An intravenous infusion of propofol (3–5 mg kg^–1 h^–1) was administered to patients who requested to be sedated and intravenous fentanyl (25 µg bolus) was administered as rescue analgesia. Pain during the TPVB and PRFA was assessed using a numerical rating scale (NRS; 0, no pain; 10, worst imaginable pain). Patients were also assessed for residual pain and analgesic consumption during the 24 h after the intervention.

Results

The TPVB was well tolerated and produced ipsilateral sensory anaesthesia with satisfactory spread (median (range); 8 (6–11) dermatomes). The PRFA procedure caused mild pain (mean (standard deviation, SD); NRS 1.4 (1.9)) during the insertion of the ablation needle and the peak pain intensity during the therapeutic burn was moderate (mean (SD); NRS 5.0 (3.3)) in severity. During the 24 h after the PRFA, patients reported minimal pain and consumed very few analgesics. The mean (SD) satisfaction score (0, totally dissatisfied; 10, very satisfied) of the patients was 8.9 (1.1) and that of the radiologists was 8.8 (1.4).

Conclusion

A right TPVB is safe and effective for anaesthesia and analgesia during PRFA of malignant liver tumours.Percutaneous radiofrequency ablation (PRFA) is currently the mainstay of management, at most centres, for patients with primary and secondary malignant liver tumours [1-3]. Anaesthesia for PRFA of liver tumours usually involves local anaesthesia and intravenous sedation [1,4]. However, intraoperative and early post-operative pain is frequently reported by the majority of patients undergoing such procedures [5-8].Thoracic paravertebral block (TPVB) is the technique of injecting local anaesthetic adjacent to the thoracic vertebra close to where the spinal nerves exit the intervertebral foramina [9]. This produces ipsilateral, segmental, somatic and sympathetic nerve blockade without causing major haemodynamic changes [9]. TPVB is effective in managing liver capsule pain after blunt trauma and for analgesia following radiofrequency ablation of a liver mass [10,11]. It has been used extensively at our centre for chest and upper abdominal surgery, including hepatectomy [12]. However, there are no data on the safety and efficacy of TPVB as the sole anaesthetic technique for PRFA of liver tumours, which this study was designed to investigate.     

Comparison of four radiofrequency ablation systems at two target volumes in an ex vivo bovine liver model

PURPOSE

We aimed to validate actually achieved macroscopic ablation volumes in relation to calculated target volumes using four different radiofrequency ablation (RFA) systems operated with default settings and protocols for 3 cm and 5 cm target volumes in ex vivo bovine liver.

MATERIALS AND METHODS

Sixty-four cuboid liver specimens were ablated with four commercially available RFA systems (Radionics Cool-tip, AngioDynamic 1500X, Boston Scientific RF 3000, Celon CelonPower LAB): 16 specimens for each system; eight for 3 cm, and eight for 5 cm. Ablation diameters were measured, volumes were calculated, and RFA times were recorded.

RESULTS

For the 3 cm target ablation volume, all tested RFA systems exceeded the mathematically calculated volume of 14.14 cm³. For the 3 cm target ablation volume, mean ablation volume and mean ablation time for each RFA system were as follows: 28.5±6.5 cm³, 12.0±0.0 min for Radionics Cool-tip; 17.1±4.9 cm³, 9.36±0.63 min for AngioDynamic 1500X; 29.7±11.7 cm³, 4.60±0.50 min for Boston Scientific RF 3000; and 28.8±7.0 cm³, 20.85±0.86 min for Celon Celon-Power LAB. For the 5 cm target ablation volume, Radionics Cool-tip (48.3±9.9 cm³, 12.0±0.0 min) and AngioDynamic 1500X (39.4±16.2 cm³, 19.59±1.13 min) did not reach the mathematically calculated target ablation volume (65.45 cm³), whereas Boston Scientific RF 3000 (71.8±14.5 cm³, 9.15±2.93 min) and Celon CelonPower LAB (93.9±28.1 cm³, 40.21±1.78 min) exceeded it.

CONCLUSION

While all systems reached the 3 cm target ablation volume, results were variable for the 5 cm target ablation volume. Only Boston Scientific RF 3000 and Celon CelonPower LAB created volumes above the target, whereas Radionics Cool-tip and AngioDynamic 1500X remained below the target volume. For the 3 cm target ablation volume, AngioDynamic 1500X with 21% deviation was closest to the target volume. For the 5 cm target volume Boston Scientific RF 3000 with 10% deviation was closest.Radiofrequency ablation (RFA) is a minimally invasive technique for eliminating both primary tumors and metastases. It may be particularly useful for treating patients with inoperable lesions or contraindications to open surgery. Since its introduction, percutaneous ablation has been established as an effective and safe treatment (1, 2), especially in patients with primary and secondary malignancies of the liver (3, 4), the kidney (5, 6), the lung (7, 8), and the breast (9, 10).As radiofrequency (RF) energy can only be deployed in a closed electrical circuit, monopolar RFA devices may require up to four neutral electrodes (grounding pads), commonly placed on the thighs. The large surface of the grounding pads (manufacturer-specific, up to 200 cm²) is intended to prevent excessive heating at the skin level; the surface of the active part(s) of the RF electrode(s) is about 100 times smaller (manufacturer-specific, usually 1–5 cm²) than the grounding pad surface area.Instead of monopolar systems with grounding pads, a different technique to apply RF energy is to use bipolar or multipolar devices (3, 11, 12). In bipolar devices, both the cathode and the anode are positioned within the active tip of the electrode, separated by an insulator. The current is applied between the electrodes; no grounding pads are needed. Multipolar systems induce synergetic heat effects by using a switching algorithm between two or more electrodes to induce synergetic heat effects (3).The volume and shape of the coagulation necrosis (due to possibly different diameter extensions in the three spatial dimensions) achievable with standard clinical RF generators (apart from the generators’ monopolar, bipolar or multipolar nature) depend especially on the impact of the energy applied, probe geometry, duration of heat exposure, fluid content of the target tissue, organ perfusion, and blood vessel density (13). Additionally, in in vivo settings, the so-called heat-sink effect has to be taken into account. The fluid content and perfusion of the tissue and blood vessel density in the target organ have been described as the main factors dissipating heat from the target site and thereby resulting in a smaller ablation volume (6).For hepatocellular carcinoma for example, based on commonly accepted patient selection criteria, only some patients are suited for conventional surgery, mainly because patients present with poor Child-Pugh status and/or metastases in both hepatic lobes at diagnosis. Delis and Dervenis (14) report that less than 30% of hepatocellular carcinoma patients are eligible for liver resection; thus, approximately 70% require different treatment approaches.RFA may be regarded as the most commonly used interventional modality in clinical practice, either for sole intervention or in combination with other methods, such as transarterial chemoembolization.In a patient, the actual volume of an induced RFA can usually not be dissected and assessed macroscopically after the procedure. Interventionalists have to rely on imaging to assess the ablation volume and geometry of the induced coagulation necrosis after ablation, and hence therapeutic success. With the different RFA systems available on the market, it is valuable to have a sound understanding of the systems’ behavior, especially in terms of ablation volume and geometry the specific RFA system creates, that one intends to clinically use.The objective of this study was to validate the measured size of actual ablation volumes in relation to mathematically calculated expected ablation volumes of four different RFA systems using default settings and protocols for 3 cm and 5 cm target ablation volumes in bovine ex vivo liver.     

Hepatocellular carcinoma in cirrhotic patients at multidetector CT: hepatic venous phase versus delayed phase for the detection of tumour washout

Objectives

Our aim was to compare retrospectively hepatic venous and delayed phase images for the detection of tumour washout during multiphasic multidetector row CT (MDCT) of the liver in patients with hepatocellular carcinoma (HCC).

Methods

30 cirrhotic patients underwent multiphasic MDCT in the 90 days before liver transplantation. MDCT was performed before contrast medium administration and during hepatic arterial hepatic venous and delayed phases, images were obtained at 12, 55 and 120 s after trigger threshold. Two radiologists qualitatively evaluated images for lesion attenuation. Tumour washout was evaluated subjectively and objectively. Tumour-to-liver contrast (TLC) was measured for all pathologically proven HCCs.

Results

48 HCCs were detected at MDCT. 46 of the 48 tumours (96%) appeared as either hyper- or isoattenuating during the hepatic arterial phase subjective washout was present in 15 HCCs (33%) during the hepatic venous phase and in 35 (76%) during the delayed phase (p<0.001, McNemar’s test). Objective washout was present in 30 of the 46 HCCs (65%) during the hepatic venous phase and in 42 of the HCCs (91%) during the delayed phase (p=0.001). The delayed phase yielded significantly higher mean TLC absolute values compared with the hepatic venous phase (−16.1±10.8 HU vs −10.5±10.2 HU; p<0.001).

Conclusions

The delayed phase is superior to the hepatic venous phase for detection of tumour washout of pathologically proven HCC in cirrhotic patients.Multiphasic contrast-enhanced multidetector row CT (MDCT) plays a pivotal role in the diagnostic work-up of cirrhotic patients, who are at increased risk of developing hepatocellular carcinoma (HCC) [1]. Increased enhancement of the tumour compared with the surrounding liver parenchyma during the hepatic arterial phase is the cornerstone for the diagnosis of HCC at multiphasic MDCT [1,2]. However, a variety of entities—dysplastic nodules [3], confluent hepatic fibrosis [4], non-tumourous arterioportal shunts [5] and haemangioma [6]—can also manifest with increased arterial enhancement and thus mimic HCC, particularly if they are smaller than 2 cm in diameter.Tumour washout, i.e. hypoattenuation relative to the adjacent hepatic parenchyma during the hepatic venous or delayed phase, has been recognised as a strong predictor of HCC [7,8]. This sign has been included, along with the presence of hypervascularity, in the latest American Association for the Study of Liver Diseases (AASLD) guidelines for the diagnosis of HCC at multiphasic MDCT, MRI or contrast-enhanced ultrasonography [1]. Although it is well known that tumour enhancement is best visualised during the late hepatic arterial phase [9,10], there is no consensus regarding the correct timing for the detection of tumour washout at multiphasic MDCT of the liver. Most commonly, the hepatic arterial phase is followed by the hepatic venous phase, acquired 60–70 s after injection of contrast material [9-12]. In addition, a delayed phase, acquired from 2–10 min after contrast material injection, can follow the hepatic venous phase [13-20] or can occur alone after the hepatic arterial phase [21-23]. Regardless of the phase sequence chosen, to the best of our knowledge, no study has yet compared the hepatic venous and delayed phases for the detection of tumour washout in patients with HCC. The purpose of our study was to compare retrospectively the hepatic venous and delayed phases for the detection of tumour washout during multiphasic MDCT of the liver in patients with HCC who underwent liver transplantation.     

Comparison of therapeutic efficacy and safety of radiofrequency ablation of hepatocellular carcinomas between internally cooled 15-G and 17-G single electrodes

Objective:

To compare the ablation volume, local tumour progression rate and complication rate of radiofrequency ablation (RFA) for small hepatocellular carcinomas (HCCs) using 15-G and 17-G single electrodes.

Methods:

This retrospective study was approved by the institutional review board and informed consent was waived. We reviewed percutaneous RFA cases for HCCs using 15-G or 17-G electrodes without multiple overlapping ablations. A total of 36 pairs of HCCs matched according to tumour size and active tip length were included. We compared ablation volume and complication rate between the two electrode groups. Cumulative local tumour progression rates were estimated using the Kaplan–Meier method and compared using the log-rank test.

Results:

Tumour size and ablation time were not significantly different between the 15-G and 17-G groups (p = 0.661 and p = 0.793, respectively). However, ablation volume in the 15-G electrode group was larger than that in the 17-G group (14.4 ± 5.4 cm³ vs 8.7 ± 2.5 cm³; p < 0.001). No statistical difference in complication rates between the two electrode groups was found. The 10- and 20-month local tumour progression rates were not significantly different between the two groups (2.8% and 5.6% vs 11.1% and 19.3%; p = 0.166).

Conclusion:

Ablation volume by the 15-G electrode was larger than that by the 17-G electrode. However, local tumour progression rate and complication rate were not significantly different between the two electrode groups.

Advances in knowledge:

RFA of HCC using a 15-G electrode is useful to create larger ablation volumes than a 17-G electrode.Radiofrequency ablation (RFA) is now considered to be one of the curative treatment modalities for the management of small hepatocellular carcinomas (HCCs).^1–5 There are various types of electrodes for RFA, including internally cooled electrodes, multi-tined electrodes and perfusion electrodes.^6,7 Among them, an internally cooled electrode is frequently used because it is simple and easy to use. The ablation zone created by an internally cooled electrode is usually cylindrical in shape along the longitudinal axis of the electrode. Hence, the horizontal diameter of the ablation zone is relatively smaller than the longitudinal diameter. Therefore, an internally cooled electrode frequently requires overlapping ablations to achieve a sufficient ablative margin for large tumours (i.e. size >2.5 cm). However, it is sometimes technically difficult to achieve a sufficient ablative margin under ultrasonography guidance since both the boundary of the index tumour and the active tip of the electrode are obscured by the echogenic zone generated by the previous ablation cycle. Therefore, it is ideal to achieve a large ablation zone using a single electrode without multiple overlapping ablations.Electrodes with a larger diameter have a larger contact surface with the surrounding tissue than smaller ones and thereby have a higher active electric field.^8–10 This in turn delivers a larger amount of radiofrequency energy and thus produces a greater amount of heat around the active tip. Consequently, large electrodes create large ablation zones. However, to our knowledge, commercially available internally cooled electrodes are not large and are almost exclusively 17-G.^11,12Recently, larger sized 15-G electrodes have been introduced and used for RFA of liver tumours in our institution. We have found that the 15-G electrode created a larger ablation volume than did the 17-G electrode, while the complication rate differed little. However, to our knowledge, there are no comparative data in the literature regarding the therapeutic efficacy and complication rate after RFA between 15-G and 17-G single electrodes. Hence, the purpose of this study was to evaluate and compare the ablation volume, local tumour progression rate and complication rate after RFA of HCCs using 15-G and 17-G single electrodes.     

Hepatic radiofrequency ablation: in vivo and ex vivo comparisons of 15-gauge (G) and 17-G internally cooled electrodes

Objective:

To compare the performance of the 15-G internally cooled electrode with that of the conventional 17-G internally cooled electrode.

Methods:

A total of 40 (20 for each electrode) and 20 ablation zones (10 for each electrode) were made in extracted bovine livers and in in vivo porcine livers, respectively. Technical parameters, three dimensions [long-axis diameter (Dl), vertical-axis diameter (Dv) and short-axis diameter (Ds)], volume and the circularity (Ds/Dl) of the ablation zone were compared.

Results:

The total delivered energy was higher in the 15-G group than in the 17-G group in both ex vivo and in vivo studies (8.78 ± 1.06 vs 7.70 ± 0.98 kcal, p = 0.033; 11.20 ± 1.13 vs 8.49 ± 0.35 kcal, p = 0.001, respectively). The three dimensions of the ablation zone had a tendency to be larger in the 15-G group than in the 17-G group in both studies. The ablation volume was larger in the 15-G group than in the 17-G group in both ex vivo and in vivo studies (29.61 ± 7.10 vs 23.86 ± 3.82 cm³, p = 0.015; 10.26 ± 2.28 vs 7.79 ± 1.68 cm³, p = 0.028, respectively). The circularity of ablation zone was not significantly different in both the studies.

Conclusion:

The size of ablation zone was larger in the 15-G internally cooled electrode than in the 17-G electrode in both ex vivo and in vivo studies.

Advances in knowledge:

Radiofrequency ablation of hepatic tumours using 15-G electrode is useful to create larger ablation zones.Radiofrequency ablation (RFA) is the most widely used local ablation technique for the management of primary and metastatic liver tumours. However, previous studies have reported that RFA showed a relatively higher local tumour progression rate than did hepatic resection.^1,2 One of the most important factors affecting local tumour progression was insufficient tumour-free ablation margin of hepatic parenchyma around the tumour margin.^3–6Several strategies have been developed to obtain sufficient ablation margin. In the aspect of RFA techniques, overlapping technique and combined treatment with transcatheter arterial chemoembolization can be used.^7–9 Another strategy is to use switching monopolar, bipolar or multipolar modes to deliver radiofrequency (RF) energy more efficiently.^10,11 Sufficient ablation margin can also be achieved by more efficient electrodes: internally cooled electrode increases the size of ablation zone by preventing charring around the electrode tip.^12,13 Perfusion electrodes can also enlarge the ablation zone by increasing electrical conductance and thermal conductivity.^14–16The diameter of an electrode is also known to be associated with the size of the ablation zone. Theoretically, as the diameter of an electrode becomes larger, the contact surface of the electrode with the surrounding tissue becomes bigger, thereby increasing the active electric field.^17,18 As a result, an electrode with a larger diameter is likely to create a larger ablation zone. In a previous study, Goldberg et al¹⁷ reported that the extent of coagulation necrosis by RFA increases as the diameter of an electrode increases through an in vivo experimental study. However, this study was performed with an electrode without an internal cooling system. Recently, a clinical study comparing therapeutic efficacy and safety between 15-G and 17-G internally cooled electrodes of RFA for hepatocellular carcinoma was published.¹⁹ According to that study, the 15-G internally cooled electrode created a larger ablation volume than did the 17-G electrode. However, the study was limited by selection bias owing to the retrospective study design. In addition, the ablation protocol was not exactly the same between the two groups. Therefore, the issue whether an internally cooled electrode with a larger diameter creates a larger ablation volume should be verified with ex vivo and in vivo experimental studies.The purpose of this experimental study was to compare the performance of the 15-G internally cooled RF electrode with that of the conventional 17-G electrode in both ex vivo and in vivo studies.     

Combining diffusion-weighted MRI with Gd-EOB-DTPA-enhanced MRI improves the detection of colorectal liver metastases

Objectives

To compare the diagnostic accuracy of gadolinium-ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA)-enhanced MRI, diffusion-weighted MRI (DW-MRI) and a combination of both techniques for the detection of colorectal hepatic metastases.

Methods

72 patients with suspected colorectal liver metastases underwent Gd-EOB-DTPA MRI and DW-MRI. Images were retrospectively reviewed with unenhanced T₁ and T₂ weighted images as Gd-EOB-DTPA image set, DW-MRI image set and combined image set by two independent radiologists. Each lesion detected was scored for size, location and likelihood of metastasis, and compared with surgery and follow-up imaging. Diagnostic accuracy was compared using receiver operating characteristics and interobserver agreement by kappa statistics.

Results

417 lesions (310 metastases, 107 benign) were found in 72 patients. For both readers, diagnostic accuracy using the combined image set was higher [area under the curve (Az) = 0.96, 0.97] than Gd-EOB-DTPA image set (Az = 0.86, 0.89) or DW-MRI image set (Az = 0.93, 0.92). Using combined image set improved identification of liver metastases compared with Gd-EOB-DTPA image set (p<0.001) or DW-MRI image set (p<0.001). There was very good interobserver agreement for lesion classification (κ = 0.81–0.88).

Conclusions

Combining DW-MRI with Gd-EOB-DTPA-enhanced T₁ weighted MRI significantly improved the detection of colorectal liver metastases.In patients with colorectal cancer, accurate assessment of the size, location and segmental distribution of liver metastases on a per-lesion basis is critical for treatment planning [1]. Accurate depiction of the size and distribution of liver metastases helps the selection of patients to undergo radical surgery [2,3] or minimally invasive therapy, such as radiofrequency ablation (RFA) [4], chemo-embolisation or radio-embolisation [5].The image contrast in diffusion-weighted MRI (DW-MRI) is based on differences in the mobility of water between tissues [6]. In tumour tissues, such as liver metastases, water mobility is often more impeded compared with normal parenchyma. Hence, metastases appear to have high signal intensity on DW-MRI, facilitating their detection.Compared with conventional T₂ weighted imaging, DW-MRI has been found to be superior for lesion detection in the liver [7-9]. When compared with contrast-enhanced MRI, DW-MRI had a higher diagnostic accuracy compared with superparamagnetic iron oxide (SPIO)-enhanced MRI [10] and similar diagnostic accuracy compared with gadolinium contrast-enhanced imaging [11] for detecting colorectal liver metastases. DW-MRI has also been found to be more sensitive than fluorodeoxyglucose (¹⁸FDG) positron emission tomography (PET) CT [12] for the same clinical indication. In another study, combining DW-MRI with T₁ weighted imaging after liver-specific contrast medium mangafodipir trisodium (MnDPDP) administration improved the diagnostic accuracy of colorectal liver metastases detection compared with either technique alone [13].Gadolinium-ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA; Eovist or Primovist; Bayer Schering Pharma, Berlin, Germany) is a relatively new hepatocyte-selective MR contrast medium that has been shown to be useful detecting liver metastases measuring <1 cm in diameter [14,15]. Delayed T₁ weighted imaging in the hepatocellular phase of contrast enhancement at 20 min to several hours after contrast administration demonstrates metastases as T₁ hypointense lesions against the avidly enhancing liver parenchyma.Both DW-MRI and Gd-EOB-DTPA-enhanced MRI are useful for the detection of liver metastases [7,8,14-16]. One study performed at 3 T compared the diagnostic performance of the two techniques for the identification of small (<2 cm) liver metastases [17]. Another study at 1.5 T independently compared the diagnostic performance of DW-MRI, dynamic phase MRI and hepatobiliary phase Gd-EOB-DTPA-enhanced MRI [18]. However, the possible incremental value of combining DW-MRI with Gd-EOB-DTPA-enhanced MRI for detecting colorectal metastases has not been reported. Hence, the aim of this study was to compare the diagnostic accuracy of Gd-EOB-DTPA-enhanced MRI, DW-MRI and a combination of both techniques for the detection of colorectal hepatic metastases.     

Contrast-enhanced ultrasonography of hepatocellular carcinoma: correlation between quantitative parameters and histological grading

Objective

The quantitative parameters in the contrast-enhanced ultrasonography time–intensity curve of hepatocellular carcinoma (HCC) were studied to explore their possible implication for histological grading of HCC.

Methods

A total of 130 HCC patients (115 males and 15 females; age: 48.13±11.00 years) were studied using contrast-enhanced ultrasonography time–intensity curve and histological pathology. The quantification software Sonoliver® (TomTec Imaging Systems, Unterschleissheim, Germany) was applied to derive time–intensity curves of regions of interest in the interior of HCCs and in reference. Quantitative parameters of 115 patients were successfully obtained, including maximum of intensity (IMAX), rise time (RT), time to peak (TTP), rise slope (RS) and washout time (WT). Histological grading of HCC was performed using haematoxylin–eosin staining, and monoclonal antibodies specific for smooth muscle actin were used to observe unpaired arteries (UAs).

Results

There were significant differences among WTs in the three differentiated HCC groups (p<0.05). However, there were no significant differences among RT, TTP, RS and IMAX in the differentiated HCC groups. Moreover, the number of UAs in the differentiated HCC groups showed no statistical significance.

Conclusion

WT plays an important role in predicting well, moderately and poorly differentiated HCC.The majority of hepatocellular carcinomas (HCCs) develop through multistep hepatocarcinogenesis [1]. Various types of hepatocellular nodules are seen in cirrhotic livers. The International Working Party of the World Congress of Gastroenterology classifies hepatocellular nodules into six types: regenerative nodules, low-grade dysplastic nodules, high-grade dysplastic nodules, well-differentiated HCC, moderately differentiated HCC and poorly differentiated HCC. The histopathological grades and types constitute well-established prognostic factors [2]. Thus, early diagnosis and confirmation of the type of hepatocellular nodules present and cellular differentiation before treatment are important.Although definite differentiation among HCC by imaging is usually impossible, the relationship between tumour cellular differentiation and image findings has been studied using contrast-enhanced (CE) CT, CEMRI and CE ultrasonography (CEUS). Tumour pathological differentiation correlates well with image findings [,3−8].Dynamic CEUS during the past decade has noticeably improved the detection and characterisation of focal liver lesions [9]. A previous study showed that CEUS and spiral CT provided a similar diagnostic accuracy in the characterisation of focal liver lesion [10]. The appearance of HCC on CEUS has also been described well. Current low-mechanical-index techniques for CEUS using second-generation microbubble agents have advantages in characterising HCC, including real-time demonstration of continuous haemodynamic changes in both the liver and hepatocellular nodules. Some studies postulated that variations of enhancement patterns may be related to the pathological function of HCC [,5−8]. Moderately differentiated HCCs generally show classic enhancement features, with presence of hypervascularity in the arterial phase and washout during the portal phase, whereas well and poorly differentiated tumours account for most atypical variations in the arterial phase and portal venous phase [7].Reports assessing hepatocellular nodules have been based on visual analysis, despite the disadvantages of interobserver variability and low reproducibility of results. Although quantitative analysis CEUS perfusion provides more objective, reliable and reproducible results [11], the time–intensity curve (TIC) of CEUS has been obtained by quantification software for offline analysis [,12−14], from which a series of semi-quantitative perfusion parameters is extracted and analysed. An analysis of the parameters of TIC in HCC has proven the correlation of CEUS with unpaired arteries (UAs) in HCC [14]. In the present study, we compare the quantitative parameters in CEUS and UAs in different pathological gradings of HCCs to explore their possible implication for histological grading of HCC.     

Percutaneous radiofrequency ablation of spinal osteoid osteoma under CT guidance

Objective:

Osteoid osteoma (OO) accounts for approximately 10–12% of all benign bone tumours and 3% of all bone tumours. Spinal involvement appears in 10–25% of all cases. The purpose of this study was to evaluate the safety and efficacy of CT-guided radiofrequency (RF) ablation in the treatment of spinal OOs and report our experience.

Methods:

13 patients suffering from spinal OO and treated at the authors'' institution using CT-guided RF ablation were retrospectively evaluated. The RF probe was introduced through a 11-G Jamshidi® needle, and the lesion was heated at 90 ^°C for 6 min.

Results:

All procedures were considered technically successful as the correct positioning of the probe was proven by CT. 11 of the 13 patients reported pain relief after RF ablation. In two cases, RF ablation was repeated 1 month after the first procedure. Pain relief was achieved in both cases after the second procedure. No recurrence was reported throughout the follow-up. No complications like skin burn, soft-tissue haematoma, infection, vessel damage or neurological deficit were reported.

Conclusion:

This study demonstrates that CT-guided percutaneous RF ablation is a safe and effective method for the treatment of spinal OOs.

Advances in knowledge:

The data of this study support the efficacy and safety of the recently applied CT-guided percutaneous RF ablation technique for the treatment of spinal OOs.Osteoid osteoma (OO) represents a benign bone tumour first described by Jaffe¹ in 1935. The lesion accounts for approximately 10–12% of all benign bone tumours and 3% of all bone tumours. It is characterized by a nidus, consisting of osteoid, osteoblasts and fibrovascular stroma, surrounded by sclerotic bone usually measuring <1.5 cm in diameter. OOs are characteristically seen in children and young adults with a predilection for long bones, particularly in lower extremities.² Spinal involvement usually affecting the posterior elements appears in 10–25% of all cases.^3,4 The typical symptom is localized pain typically worsening at night, ameliorated by the administration of salicylates (acetylsalicylic acid) or non-steroidal anti-inflammatory drugs (NSAIDs). In spinal cases of OO, radiation of pain distally to the lesion site might simulate radiculopathy similar to disc herniation especially if the lesion is located close to a nerve root. Painful antalgic scoliosis is frequent in thoracolumbar lesions in children and adolescents.^5,6 Spinal lesions are usually difficult to diagnose, and the reported delay from presentation to final diagnosis and treatment can be as long as 24 months in some cases.^7–9 Neurologic deficit does not generally appear.In the past, conventional surgical excision and more recently minimally invasive surgery techniques were the treatment of choice in cases of spinal OOs when conservative treatment with anti-inflammatory and salicylates fails or is contraindicated.^10–15Rosenthal et al¹⁶ first introduced percutaneous radiofrequency (RF) ablation for the treatment of OOs. The effectiveness of RF ablation of OOs localized in the extremities and pelvis has been proven by many studies.^16–19Percutaneous RF ablation for the treatment of spinal OOs is not widely used, probably owing to the potential danger to the adjacent neural and vascular elements. In recent years, however, some clinical studies reported good results in the management of spinal OOs using CT-guided RF ablation.^8,20–23The purpose of this study was to evaluate the safety and efficacy of CT-guided RF ablation in the treatment of spinal OOs and report our experience.     

Experimental study of single-pin puncture asymmetrical hydroablation using a conformational radiofrequency ablation electrode in ex vivo ox liver

Objective

The aim of this study was to evaluate the feasibility of single-pin puncture asymmetrical hydroablation in liver using the multipole cluster conformable radiofrequency ablation electrode.

Methods

The conformable electrode used in this study consists of both a main electrode in a central cannula and a circle of subelectrodes comprising two groups of six subelectrodes located on opposite sides (A and B) of the circle. The two subelectrode groups can be extended to different lengths independently of one another, resulting in asymmetrical shapes. Ablation experiments were performed using ex vivo ox liver. The experiments included six groups based on six potential electrode deployments in which the subelectrodes on sides A and B were fully extended, half extended or fully retracted. After ablation, the transverse diameters of the resulting necrotic tissue from sides A and B were measured. The experiment was conducted in 12 separate sites for each group.

Results

When the subelectrodes were arranged symmetrically (either fully extended or half extended on both sides), the mean transverse diameter of necrotic tissue was similar for both sides A and B. When the subelectrodes were arranged asymmetrically, the fully extended side showed a significantly greater mean transverse diameter of necrotic tissue than the half extended or fully retracted side.

Conclusion

In this study, the WHK 3-8-4 multipole cluster conformable radiofrequency ablation electrode was able to produce both symmetrical and asymmetrical necrotic tissue patterns in the liver.

Advances in knowledge

The size and shape of the ablation can be altered by both withdrawing and extending the subelectrodes to different lengths.Hepatocellular carcinoma is one of the most common solid cancers in the world with an annual incidence rate estimated at approximately 1 million patients per year. Surgical resection has been considered the best curative option but only a small proportion (5–20%) of patients undergo surgery for liver cancer. The reasons for patients not being candidates for resection include multifocal disease, proximity of the tumour to vascular or biliary duct structures and inadequate functional hepatic reserve owing to comorbid cirrhosis [1].Radiofrequency ablation (RFA) is one strategy that aims at decreasing the tumour volume and preventing growth, thereby leading to longer survival and a potential cure for some patients. RFA, using radiofrequency electric current to create local heat for destroying tumour cells, has the advantage that it is minimally invasive, simple and safe. It has a lower rate of complications and morbidity than other ablative techniques and the ablative success rate is approximately 94% [2-5].Several factors influence the outcomes of RFA in treating cancer. These include the skill of the physician, the abundant blood flow present in the normal hepatic parenchyma (which acts as a heat sink) and the ability to adequately kill both the tumour and the hepatic tissue adjacent to the tumour [6]. The last point is particularly difficult given that most tumours are irregular in shape, and the technique usually results in symmetrical necrosis of the tissue following ablation.In order to overcome the issue of irregularly shaped tumours, multiple treatments are superimposed [7,8]. However, these result in both increased numbers of punctures to the liver and possibly increased X-ray exposure as a result of CT scanning, which is often used to guide the positioning of the probe. Multiple treatments also increase the risk of damaging other organs and tissues close to the tumour [1,7,8].One way to overcome this problem is to design RFA electrodes that can be asymmetrically adjusted, which would allow treatment with a single puncture of the liver. The Wellfare Electronic Technological Company (Beijing, China) has developed the multipole cluster electrode in which subelectrodes extend from the central probe and can be separately adjusted to form asymmetrical shapes. The objective of this study was to assess whether this electrode could form a controlled asymmetrical necrosis with a single puncture of the tissue.     

Feasibility study on energy prediction of microwave ablation upon uterine adenomyosis and leiomyomas by MRI

Objective:

To evaluate the feasibility of energy prediction of percutaneous microwave ablation (PMWA) upon uterine leiomyomas and adenomyosis by MRI.

Methods:

63 patients (49 patients with 49 uterine leiomyomas and 14 patients with adenomyosis) who underwent ultrasound-guided PMWA treatment were studied during the period from June 2011 to December 2012. Before PMWA, contrast-enhanced MRI (ceMRI) was performed for all of the patients. Based on the signal intensity (SI) of T₂ weighted MRI, uterine leiomyomas were classified as hypointense, isointense and hyperintense. During ablation, the output energy of the microwave was set at 50 W, and T11a microwave antennas were used. ceMRI was performed within 7 days after PMWA treatment. Non-perfused volume and energy required per unit volume were analysed statistically.

Results:

When unit volume of lesions was ablated, uterine adenomyosis needed more energy than did uterine leiomyomas, and hyperintense uterine leiomyomas needed more energy than did hypointense pattern.

Conclusions:

MRI SI of uterine leiomyomas and uterine adenomyosis can be used to predict PMWA energy.

Advances in knowledge:

The conclusions indicate that MRI SI can be used to perform pre-treatment planning, which will make the treatment more precise.Uterine leiomyomas and adenomyosis are benign lesions that occur most commonly in females of childbearing age. Although many females with uterine leiomyomas and adenomyosis are asymptomatic, as many as 20–65% of them have symptoms^1,2 such as abnormal uterine bleeding, dysmenorrhoea, pelvic pressure, low abdominal pain and infertility. These symptoms often lead to reduced quality of life, as well as loss of work and increased medical costs.³ Hysterectomy has been the main mode of therapy for leiomyomas and adenomyosis. However, medical technology advancements have made less invasive treatment options available, such as uterine artery embolization (UAE),^4–6 high-intensity focused ultrasound (HIFU),^7–9 radiofrequency (RF)¹⁰ and percutaneous microwave ablation (PMWA).^11,12 PMWA is a minimally invasive technique for the treatment of uterine leiomyomas and adenomyosis by inducing tissue necrosis through heat. Previous reports^11,12 have indicated that PMWA provides a feasible, safe and reliable alternative for the treatment of uterine leiomyomas and adenomyosis. However, until now, the energy required per unit volume (EPV) of PMWA in uterine lesions has been unclear, which has limited the widespread use of PMWA therapy. In this study, we sought to investigate the relationship between the MRI signal intensity (SI) of uterine lesions and the EPV of PMWA to better predict PMWA energy before treatment and to make the PMWA procedures standardized.     

Accessory or additional renal arteries show no relevant effects on the width of the upper urinary tract: a 64-slice multidetector CT study in 1072 patients with 2132 kidneys

Objective

The aim of this study was to find out on an unselected patient group whether crossing vessels have an influence on the width of the renal pelvis and what independent predictors of these target variables exist.

Methods

In this cross-sectional study, 1072 patients with arterially contrasted CT scans were included. The 2132 kidneys were supplied by 2736 arteries.

Results

On the right side, there were 293 additional and accessory arteries in 286 patients, and on the left side there were 304 in 271 patients. 154 renal pelves were more than 15 mm wide. The greatest independent factor for hydronephrosis on one side was hydronephrosis on the contralateral side (p<0.0001 each). Independent predictors for the width of the renal pelvis on the right side were the width of the renal pelvis on the left, female gender, increasing age and height; for the left side, predictors were the width of the renal pelvis on the right, concrements, parapelvic cysts and great rotation of the upper pole of the kidney to dorsal. Crossing vessels had no influence on the development of hydronephrosis. Only anterior crossing vessels on the right side are associated with widening of the renal pelvis by 1 mm, without making it possible to identify the vessel as an independent factor in multivariate regression models.

Conclusion

The width of the renal pelvis on the contralateral side is the strongest independent predictor for hydronephrosis and the width of the renal pelvis. There is no link between crossing vessels and the width of the renal pelvis.Obstructions of the ureteropelvic junction (UPJ) can be caused by intrinsic or extrinsic factors [1]. Although there are no studies of this to date, crossing the UPJ by an aberrant crossing vessel is considered the most important [2] of the extrinsic factors [3]. Crossing vessels, which are thought to cause from 40% to over 50% of the extrinsic UPJ obstructions in adults [4, 5], are located ventral more often than dorsal to the UPJ. These are usually normal vessels of the lower pole segment [4, 6–9], which can be divided into additional renal arteries arising from the aorta, and accessoric renal arteries arising from branches of the aorta [10, 11]. The primary surgical therapy of choice is endoscopic endopyelotomy [12]. The success rate of 89–90% [12, 13] is thought to be noticeably poorer in patients with crossing vessels [12, 13]; however, this is not undisputed [14, 15]. Be that as it may, to prevent bleeding complications it is necessary to be familiar with the vascular situation around the UPJ prior to the procedure [3, 16–18]. CT angiography is used for this purpose, as it is highly accurate, quick to perform and shows all relevant anatomical structures in relation to one another [3, 19, 20]. The objective of this study was to determine whether or not there are vascular morphological patterns or other factors that influence the width of the renal collecting system, regardless of the definitions of hydronephrosis.     

Vascular invasion in hepatocellular carcinoma: is there a correlation with MRI?

Objective

Hepatocellular carcinoma (HCC) is one of the commonest malignancies worldwide. Prognosis is predicted by size at diagnosis, vascular invasion and tumour proliferation markers. This study investigates if MRI features of histologically proven HCCs correlate with vascular invasion.

Methods

Between 2006 and 2008, 18 consecutive patients, with a total of 27 HCCs, had comprehensive MRI studies performed at our institution within a median of 36 days of histology sampling. Each lesion was evaluated independently on MRI by 3 radiologists (blinded to both the radiology and histopathology reports) using a 5-point confidence scale for 23 specific imaging features. The mean of the rating scores across readers was calculated to determine interobserver consistency. The most consistent features were then used to examine the value of features in predicting vascular invasion, using a χ² test for trend, having eliminated those features without sufficient variability.

Results

22 of the 23 imaging features showed sufficient variability across lesions. None of these significantly correlated with the presence of vascular invasion, although a trend was identified with the presence of washout in the portal venous phase on MRI and the median size of lesions, which was greater with vascular invasion.

Conclusion

This study suggests that no single MRI feature accurately predicts the presence of vascular invasion in HCCs, although a trend was seen with the presence of washout in the portal venous phase post gadolinium. Larger prospective studies are required to investigate this further.Hepatocellular carcinoma (HCC) is one of the commonest malignancies worldwide, either arising de novo or on a background of cirrhosis. The incidence in Western countries is rising owing to increasing rates of alcoholic liver disease and hepatitis C infection. Untreated, the 5-year survival rate for symptomatic HCC is less than 5% [1]. At present, surgery is the only potentially curative treatment for HCC with options including either a partial hepatectomy or orthotopic liver transplantation (OLT). Following resection there is a 5-year survival rate of 40–50% [2] with a cumulative 5-year recurrence rate between 75 and 100% [3]. The 5-year survival rate in patients with cirrhosis following transplantation of small (<2 cm) HCC is up to 80% [4]. However, the use of OLT is limited owing to the lack of donor livers. Regional therapies such as transcatheter arterial chemoembolisation [5] and percutaneous radiofrequency ablation [6] may improve prognosis. The value of neo-adjuvant and adjuvant chemotherapy and immunotherapy in prolonging survival remains controversial [7,8]. However, a recent study evaluating sorafenib, a multikinase inhibitor, in patients with advanced HCC has shown an increased median overall survival of 2.8 months over a placebo [9].Studies of patients with explanted liver for end-stage cirrhosis have shown that MRI, with the use of dynamic gadolinium-enhanced sequences, has a moderate sensitivity for the detection of HCC of between 55 and 91% [10-12] and specificity between 55 and 86% [11-13]. The sensitivity is lower with lesions <2 cm in size [11-13]. In patients with cirrhosis, HCC is thought to develop as part of a spectrum of de-differentiation from regenerative nodule through to low-grade dysplastic nodule, high-grade dysplastic nodule, then to frankly malignant. Early diagnosis using non-invasive imaging leads to an improved prognosis but at present, unless biopsy is performed, only lesion size is used to determine patient management in those where gross vascular involvement or metastatic spread precludes curative treatment.Several factors predicting outcome have been identified including tumour pathological factors (such as size, stage, grade, the presence of vascular invasion, portal vein tumour thrombus and intrahepatic metastases) [14,15], the patient’s hepatitis status, the patient’s functional liver reserve [16] and the serum α-fetoprotein level [17]. Overall, one of the most strongly correlated factors is the presence or absence of vascular invasion. There is a 4.4- and 15-fold increased risk of recurrence following OLT for HCC in patients with micro- or macrovascular invasion, respectively [18].The aims of this retrospective study were twofold. First to identify the interobserver variability of MRI features for patients with histologically proven HCC, and second to determine if there was a correlation between imaging features on MRI and histologically defined vascular invasion; these MRI features could then serve as a surrogate marker of prognosis. There has been little literature to date attempting to correlate MRI features with microvascular invasion.     

Prognostic factors associated with a subchondral insufficiency fracture of the femoral head

Objective

The aim of this study was to identify the risk factors associated with the prognosis of a subchondral insufficiency fracture of the femoral head (SIF).

Methods

Between June 2002 and July 2009, 25 patients diagnosed with SIF were included in this study. Sequential radiographs were evaluated for the progression of collapse. Clinical profiles, including age, body mass index, follow-up period and Singh’s index, were documented. The morphological characteristics of the low-intensity band on T₁ weighted MRI were also examined with regards to four factors: band length, band thickness, the length of the weight-bearing portion and the band length ratio (defined as the proportion of the band length to the weight-bearing portion of the femoral head in the slice through the femoral head centre).

Results

Radiographically, a progression of collapse was observed in 15 of 25 (60.0%) patients. The band length in patients with progression of collapse [22.5 mm; 95% confidence interval (CI) 17.7, 27.3] was significantly larger than in patients without a progression of collapse (13.4 mm; 95% CI 7.6, 19.3; p<0.05). The band length ratio in patients with progression of collapse (59.8%; 95% CI 50.8, 68.9) was also significantly higher than in patients without a progression of collapse (40.9%; 95% CI 29.8, 52.0; p<0.05). No significant differences were present in the other values.

Conclusion

These results indicate that the band length and the band length ratio might be predictive for the progression of collapse in SIF.Subchondral insufficiency fractures of the femoral head (SIF) often occur in osteoporotic elderly patients [1-9]. Patients usually suffer from acute hip pain without any obvious antecedent trauma. Radiologically, a subchondral fracture is seen primarily in the superolateral portion of the femoral head [4,5,10]. T₁ weighted MRI reveal a very low-intensity band in the subchondral area of the femoral head, which tends to be irregular, disconnected and convex to the articular surface [2,4,5,7,9,11]. This low-intensity band in SIF was histologically proven to correspond with the fracture line and associated repair tissue [5,9]. Some cases of SIF resolve after conservative treatment [5,11-14]; other cases progress until collapse, thereby requiring surgical treatment [4-10,15]. The prognosis of SIF patients remains unclear.The current study investigated the risk factors that influence the prognosis of SIF based on the progression to collapse.     

Gd-EOB-DTPA-enhanced MRI for the assessment of liver function and volume in liver cirrhosis

Objective:

The aims of this study were to use dynamic hepatocyte-specific contrast-enhanced MRI to evaluate liver volume and function in liver cirrhosis, correlate the results with standard scoring models and explore the inhomogeneous distribution of liver function in cirrhotic livers.

Methods:

10 patients with liver cirrhosis and 20 healthy volunteers, serving as controls, were included. Hepatic extraction fraction (HEF), input relative blood flow and mean transit time were calculated on a voxel-by-voxel basis using deconvolutional analysis. Segmental and total liver volumes as well as segmental and total hepatic extraction capacity, expressed in HEFml, were calculated. An incongruence score (IS) was constructed to reflect the uneven distribution of liver function. The Mann–Whitney U-test was used for group comparison of the quantitative liver function parameters, liver volumes and ISs. Correlations between liver function parameters and clinical scores were assessed using Spearman rank correlation.

Results:

Patients had larger parenchymal liver volume, lower hepatocyte function and more inhomogeneous distribution of function compared with healthy controls.

Conclusion:

The study demonstrates the non-homogeneous nature of liver cirrhosis and underlines the necessity of a liver function test able to compensate for the heterogeneous distribution of liver function in patients with diseased liver parenchyma.

Advances in knowledge:

The study describes a new way to quantitatively assess the hepatic uptake of gadoxetate or gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid in the liver as a whole as well as on a segmental level.In patients undergoing liver resection, post-operative liver failure is a major concern and has in current practice become the biggest cause for mortality after liver resection [1–3]. Residual liver should be of adequate volume and quality to sustain immediate post-operative function and to allow regeneration for complete restoration of hepatic function. Currently, surgical decision-making is predominantly based on volume calculation from cross-sectional imaging, sometimes in combination with liver function evaluation [4,5]. A variety of different methods for quantitative assessment of global liver function are available, including clearance–retention tests, redox chemistry and scintigraphy [6,7]. All currently available metabolic tests give a global assessment of liver function and do not account or correct for the possible heterogeneous distribution of function within the liver parenchyma. Scoring models, of which the Child–Pugh score (CPS) [8,9] and the model for end-stage liver disease (MELD) [10] are the most frequently used, are hampered by the same limitations.A number of published studies, using different scintigraphic methods, have verified the presence of heterogeneous distribution of function in the liver parenchyma. In a group of patients with diverse underlying liver pathologies investigated with ^99mTc-mebrofenin, it was found that liver function was unevenly distributed within the liver [11]. Regional variations in uptake were also demonstrated using ^99mTc-labelled galactosyl human serum albumin [12,13]. This phenomenon was also observed in patients with primary sclerosing cholangitis using ^99mTc-HIDA [14].Gadoxetate or gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA; Primovist®, Bayer Healthcare, Berlin) is a contrast agent developed for MRI. It is a gadolinium chelate that is actively taken up into the hepatocytes through the organic anion-transporting polypeptides [15]. This is a property Gd-EOB-DTPA shares with the iminodiacetic acid compounds used in hepatobiliary scintigraphy (HBS) and with indocyanine green (ICG) [16–20]. Pharmacokinetic studies show that about 50% of the administered dose of Gd-EOB-DTPA is extracted by the liver and eliminated through the hepatobiliary pathway. The remaining 50% is eliminated by renal excretion [21]. As the hepatic elimination of Gd-EOB-DTPA is dependent on the integrity of the hepatocyte mass, quantification of the uptake should represent the same aspects of liver function as assessed by ICG clearance or HBS.Dynamic hepatocyte-specific contrast-enhanced MRI (DHCE-MRI) has previously been used in animal models for the evaluation of hepatic function in various experimental settings, either using semi-quantitative parameters or using deconvolutional analysis (DA) [22–25]. In human studies, liver parenchymal enhancement after administration of Gd-EOB-DTPA has been shown to correlate with ICG clearance and with liver cirrhosis as assessed by the CPS [26,27], and subsequent biliary excretion has been shown to be delayed in patients with impaired liver function [28]. In a study of patients with primary biliary cirrhosis, quantitative parameters indicative of liver function derived from DA were shown to correlate with disease severity [29]. Also, compartmental modelling has been used to assess the hepatic uptake of Gd-EOB-DTPA, and the parameters derived were shown to be dependent on the CPS [30]. These findings support the hypothesis that results from DHCE-MRI have the potential to assess liver function.The present study should be regarded as a feasibility study aiming to investigate DHCE-MRI as a method to explore the inhomogeneous distribution of liver function in patients with liver cirrhosis compared with a control group and to explore the correlation between DHCE-MRI-derived liver function parameters with commonly used clinical scoring models. The primary outcome was the overall hepatic extraction capacity of Gd-EOB-DTPA, and secondary outcomes were measures of liver function heterogeneity, liver function indices and correlation analysis.     

Multimodality imaging of obliterative portal venopathy: what every radiologist should know

Obliterative portal venopathy (OPV) is an important cause of non-cirrhotic portal hypertension, which is often erroneously misdiagnosed as cryptogenic cirrhosis. It has a worldwide distribution with majority of cases hailing from the Asian subcontinent. However, recently the disease has gained global attention particularly because of its association with human immunodeficiency virus infection and use of antiretroviral drug therapy (didanosine). As the name suggests, the disorder is characterized by sclerosis and obliteration of the intrahepatic portal vein branches (with attendant periportal fibrosis) leading to portal hypertension amid intriguingly little liver dysfunction. It primarily affects young adults who present with clinically significant portal hypertension in the form of episodes of variceal bleed; however, contrasting liver cirrhosis, the liver function and liver structure remain normal or near normal until late in the disease process. Radiological findings during advanced disease are often indistinguishable from cirrhosis often warranting a liver biopsy. Nevertheless, recent studies have suggested that certain imaging manifestations, if present, can help us to prospectively suggest the possibility of OPV. At imaging, OPV is characterized by a wide range of intrahepatic and/or extrahepatic portal venous abnormalities with attendant changes in liver and splenic volume and stiffness. We shall, through this pictorial review, appraise the literature and illustrate the germane radiological manifestations of OPV that can be seen using different imaging modalities including ultrasonography, CT, MRI, elastography and hepatic haemodynamic studies.It is important to recognize that not all varices mean liver cirrhosis. Although liver cirrhosis constitutes the commonest cause of portal hypertension, we should be aware that portal hypertension can occur in the absence of liver cirrhosis—a condition termed as non-cirrhotic portal hypertension (NCPH).^1,2 NCPH represents a heterogeneous group of (primarily vascular) disorders where portal hypertension manifests amid absent liver cirrhosis. Pathologically, the insult is either pre- or intrahepatic involving the main portal vein or its smaller branches and/or the perisinusoidal area.^1–3Obliterative portal venopathy (OPV) represents an important cause of NCPH that is characterized by sclerosis and obliteration of the medium-sized portal venous branches leading to portal hypertension.^1–10 Liver biopsy characteristically shows phlebosclerosis and periportal and perisinusoidal fibrosis amid absent cirrhosis (Figure 1).^1–3 Although, the exact aetiology is contentious, infections and prothrombotic states have been implicated in eastern and western patients, respectively.^1,2 Additionally, xenobiotic exposure, autoimmune and genetic factors have also been incriminated.^1–4 Although the disease has a worldwide distribution, it continues to remain poorly understood primarily owing to its relative rarity.^1–3,5–8 Another potential reason is the use of diverse terminologies under which the entity has been described from various parts of the globe, such as non-cirrhotic portal fibrosis in India, idiopathic portal hypertension in Japan and hepatoportal sclerosis in the USA.Open in a separate windowFigure 1.(a) Atrophic small portal tract (arrow) showing absent portal vein [haematoxylin and eosin stain (HE), ×200]. (b) Two small portal tract (arrows) approximations (×100, HE). (c) Portal and central vein approximation (×100, HE). (d) Parenchymal extinction suggested by portal–portal and portal–central approximation (Masson''s trichrome stain, ×200).More recently, the disease has gained global attention because of escalating number of cases being reported in human immunodeficiency virus (HIV)-infected patients.^1–3,8–10 Also, US Food and Drug Administration has recently issued a warning regarding the potential association of OPV in patients with HIV on didanosine (antiretroviral therapy).³OPV primarily affects young patients usually in their third or fourth decades of life. The affected individuals typically present with clinically significant portal hypertension characterized by multiple episodes of well-controlled upper gastrointestinal (GI) bleed, massive splenomegaly and/or hypersplenism.^1–3 Advanced stages of the disease are often indistinguishable from liver cirrhosis especially on imaging. However, discrimination from cirrhosis is crucial in clinical practice because of differences in management. Management of OPV is primarily symptomatic, that is, focused on management of an acute episode of variceal bleed. The risk of rebleeding and bleeding-related mortality is low. Intriguingly, in contrast to liver cirrhosis, the liver function and liver structure remain normal or near normal until late in the disease process leading to a better prognosis and higher survival rates; the 10-year survival rate is around 86–95%.^1,2 Development of jaundice, ascites and hepatic encephalopathy is uncommon and if at all is seen only after an episode of GI bleeding.^1,2 Liver failure and the incidence of developing hepatocellular carcinoma are also much lower.^1–3,8–10 Nonetheless, in 20–33% of patients, the liver gradually atrophies and shows functional decompensation, occasionally needing liver transplantation.^1,2Although limited literature is available on the radiological manifestations of OPV, recent studies have suggested certain imaging manifestations to be more prevalent in OPV that can allow discrimination from cirrhosis. Moreover, use of newer techniques, including transient elastography, can allow prospective non-invasive diagnosis of OPV based upon the differential changes in liver and splenic stiffness. The aim of this review is to appraise the imaging findings of OPV described in the literature and illustrate them across a wide array of imaging modalities, including ultrasonography, CT, MRI and elastography, in a group of biopsy-proven cases of OPV diagnosed at our institute.