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.     

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.     

Obscure gastrointestinal bleeding: diagnostic performance of 64-section multiphase CT enterography and CT angiography compared with capsule endoscopy

Objective:

To compare the diagnostic capabilities between capsule endoscopy (CE) and multislice CT (MSCT) enterography in combination with MSCT angiography for assessment of obscure gastrointestinal bleeding (OGIB).

Methods:

A total of 127 patients with OGIB were looked at in this study. 82 patients (aged 42.7 ± 19.1 years; 34 males) were assigned to receive MSCT diagnosis and 67 patients to (aged 53.9 ± 16.2 years; 28 males) receive CE diagnosis. Among them, 22 patients (aged 54.1 ± 19.1 years; 12 males) received both examinations. Oral isotonic mannitol and intramuscular injection of anisodamine were performed; non-ionic contrast (iopromide, 370 mg I ml⁻¹) was intravenously administered; and then multiphase scanning was conducted at arterial, small intestinal and portal venous phases in MSCT. The results were compared with findings of reference standards including double balloon enteroscopy, digital subtraction angiography, intraoperative pathological examination and/or clinical diagnosis.

Results:

Administration of anisodamine markedly increased the satisfaction rate of bowel filling (94.67% vs 28.57%; p < 0.001) but not the diagnostic yield (p = 0.293) of MSCT. Compared with MSCT, CE showed an improved overall diagnostic yield (68.66% vs 47.56%; p = 0.010), which was also observed in overt bleeding patients (i.e. patients with continued passage of visible blood) (76.19% vs 51.02%; p = 0.013) and in patients aged younger than 40 years of age (85% vs 51.28%; p = 0.024). However, CE had similar positive rates to MSCT (p > 0.05). Among the 22 cases in whom both examinations were conducted, CE showed no significantly different diagnostic capability compared with MSCT (p = 0.4597).

Conclusion:

Both CE and MSCT are safe and effective diagnostic methods for OGIB.

Advances in knowledge:

CE is preferred for overt bleeding or patients aged younger than 40 years. The combined use of CE and MSCT is recommended in OGIB diagnosis.Obscure gastrointestinal bleeding (OGIB), which accounts for approximately 5% of all gastrointestinal haemorrhage cases,¹ is defined as persistent or recurring gastrointestinal bleeding without an obvious aetiology after gastroduodenoscopy and colonoscopy.^2,3 Based on the presence or absence of clinically evident bleeding, OGIB could be divided into occult (no visible blood) and overt (continued passage of visible blood, such as haematemesis, melaena or haematochezia) bleeding.^3,4 OGIB frequently occurs in the small bowel and is caused by small bowel diseases such as intestinal erosions, ulcers, vascular anomaly, gastrointestinal tumours and inflammatory bowel and parasitic diseases.^5,6Multiple diagnostic techniques have been developed to elucidate the causes of OGIB. Among them, two non-invasive technologies, capsule endoscopy (CE) and multislice CT (MSCT) markedly improved the ability to determine the causes of OGIB by allowing the visualization of the gastrointestinal tract.^2,3,6 CE is able to obtain direct visualization of mucosal surface of the entire small intestine.^4,7,8 However, capsule retention remains a major risk of CE diagnosis.^4,9–11 In addition, the visual field restriction limits the value of CE in diagnosis of umbilicate or extraluminal lesions, since the small bowel is difficult to evaluate owing to its large length and tortuous course.^4,10 Conversely, MSCT, including MSCT angiography (MSCTA), MSCT enteroclysis and MSCT enterography (MSCTE), has full capacity to depict the extraintestinal lesions, owing to the combination of the advantages of enteral volume challenge with the ability of cross-sectional imaging.^4,12 Yet, substantial patient radiation exposure is one of the major disadvantages of MSCT diagnosis.^3,13 Careful preparation is also needed before examination.¹⁴ Considering that both CE and MSCT have advantages and disadvantages, a limited number of published data have compared the two diagnostic tools in patients with OGIB.^4,6,15–17 However, most of these studies did not refer to MSCTA, and apparently different results were obtained owing to the advancement of the two technologies. Thus, an updated and comprehensive comparison is required.Hence, we compared the diagnostic capability of MSCTE in combination with MSCTA with CE in patients suffering from OGIB. In this study, MSCTE and MSCTA technologies performed with a 64-slice spiral CT scanner were combined by non-contrast-enhanced scanning after oral administration of a neutral enteric contrast material (isotonic mannitol, 2.5%) and the intramuscular injection of anisodamine to restrain enterocinesia, and the following multiphase scanning at arterial, small intestinal and portal venous phases followed the intravenous infusion of non-ionic iodinated contrast material (iopromide, 370 mg I ml⁻¹). In addition, the influences of the clinical bleeding pattern and age on the diagnostic capability were also investigated.     

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.     

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.     

Femoral neck shaft angle width is associated with hip-fracture risk in males but not independently of femoral neck bone density

Objective:

To investigate the specificity of the neck shaft angle (NSA) to predict hip fracture in males.

Methods:

We consecutively studied 228 males without fracture and 38 with hip fracture. A further 49 males with spine fracture were studied to evaluate the specificity of NSA for hip-fracture prediction. Femoral neck (FN) bone mineral density (FN-BMD), NSA, hip axis length and FN diameter (FND) were measured in each subject by dual X-ray absorptiometry. Between-mean differences in the studied variables were tested by the unpaired t-test. The ability of NSA to predict hip fracture was tested by logistic regression.

Results:

Compared with controls, FN-BMD (p < 0.01) was significantly lower in both groups of males with fractures, whereas FND (p < 0.01) and NSA (p = 0.05) were higher only in the hip-fracture group. A significant inverse correlation (p < 0.01) was found between NSA and FN-BMD. By age-, height- and weight-corrected logistic regression, none of the tested geometric parameters, separately considered from FN-BMD, entered the best model to predict spine fracture, whereas NSA (p < 0.03) predicted hip fracture together with age (p < 0.001). When forced into the regression, FN-BMD (p < 0.001) became the only fracture predictor to enter the best model to predict both fracture types.

Conclusion:

NSA is associated with hip-fracture risk in males but is not independent of FN-BMD.

Advances in knowledge:

The lack of ability of NSA to predict hip fracture in males independent of FN-BMD should depend on its inverse correlation with FN-BMD by capturing, as the strongest fracture predictor, some of the effects of NSA on the hip fracture. Conversely, NSA in females does not correlate with FN-BMD but independently predicts hip fractures.Hip fracture is the worst osteoporotic fracture with regard to cost^1,2 and adverse consequences,^3,4 so its prevention by checking for the related fracture risk factors is an important goal. Although low bone mineral density (BMD) is generally recognized as the main risk factor for hip fracture,^5,6 there is growing evidence that other bone characteristics, such as proximal femur geometry (PFG) parameters, are implicated in determining the risk profile for hip fracture.^7,8 This evidence, however, mainly derives from studies carried out in females,^9–13 whereas contradictory results characterize studies carried out in males.^14–20 Authors'' opinions seem to vary widely about the ability of the neck shaft angle (NSA), one of the PFG factors, to predict osteoporotic hip fractures in males,^14–16,21 whereas its association with the risk of hip fracture in females^10,11,14,22 is generally accepted. Gender differences in the hip anatomy²³ have been put forward as a possible explanation for the different relationship of NSA with the hip-fracture risk between genders, whereas geographic and racial differences²⁴ among the examined male populations have been advocated as a possible cause of authors'' discrepancies on the relationship between NSA and the hip-fracture risk in males.This topic is therefore still under debate, and further studies are required to clarify the association of the NSA with hip-fracture risk in males. The authors of the current study contribute to this topic by studying the relationship between NSA and the hip fragility fracture in a sample of white Italian males.     

The challenge of segmental small bowel motility quantitation using MR enterography

Objective:

Analysis of “cine” MRI using segmental regions of interest (ROIs) has become increasingly popular for investigating bowel motility; however, variation in motility in healthy subjects both within and between scans remains poorly described.

Methods:

20 healthy individuals (mean age, 28 years; 14, males) underwent MR enterography to acquire dynamic motility scans in both breath hold (BH) and free breathing (FB) on 2 occasions. Motility data were quantitatively assessed by placing four ROIs per subject in different small bowel segments and applying two measures: (1) contractions per minute (CPM) and (2) Jacobian standard deviation (SD) motility score. Within-scan (between segment) variation was assessed using intraclass correlation (ICC), and repeatability was assessed using Bland–Altman limits of agreement (BA LoA).

Results:

Within-scan segmental variation: BH CPM and Jacobian SD metrics between the four segments demonstrated ICC R = 0.06, p = 0.100 and R = 0.20, p = 0.027 and in FB, the CPM and Jacobian SD metrics demonstrated ICC R = −0.26, p = 0.050 and R = 0.19, p = 0.030. Repeatability: BH CPM for matched segments ranged between 0 and 14 contractions with BA LoA of ±8.36 and Jacobian SD ranged between 0.09 and 0.51 with LoA of ±0.33. In FB data, CPM ranged between 0 and 10 contractions with BA LoA of ±7.25 and Jacobian SD ranged between 0.16 and 0.63 with LoA = ±0.28.

Conclusion:

The MRI-quantified small bowel motility in normal subjects demonstrates wide intersegmental variation and relatively poor repeatability over time.

Advances in knowledge:

This article presents baseline values for healthy individuals of within- and between-scan motility that are essential for understanding how this process changes in disease.Dynamic “cine” MRI acquired during MR enterography is increasingly utilized to assess bowel motility in a range of conditions, notably inflammatory bowel disease and enteric dysmotility syndromes.^1–4 Analysis of the data remains primarily subjective in clinical routine, but the ability to apply quantitative techniques makes this a potentially powerful methodology to explore gastrointestinal physiology in disease as well as an emerging application as a biomarker for drug efficacy.^5–7Despite the growing literature, a consensus has yet to be reached as to the best method of quantitatively analysing small bowel data and indeed a range of motility metrics are proposed.^2,3,8–12 The most commonly used metric is the change in luminal diameter at a fixed anatomical position through the time series. By tracking bowel diameter, a characteristic curve can be produced with the number of contractions expressed per minute (CPM) to give an intuitive and broadly accepted metric for small bowel motility (SBM).^{2–4,9,11,13–15} To date, several studies have reported a relationship between CPM and dysmotility in disease, either compared with a histopathological standard or “normal” reference bowel loops.^2–4,12 An array of additional metrics derived both from bowel diameter measures and more abstract processing techniques have further been implemented with varying degrees of effectiveness in disease and health.^{2,4,5,8,10,14,16}Although intuitively attractive, the robustness of assessing overall enteric motility using only an isolated loop of bowel has received relatively little attention to date irrespective of the precise metric applied. It is unclear how representative the selected bowel loops are of overall SBM and if normal motility intrinsically differs between bowel segments, for example, between the jejunum and ileum. Furthermore, the repeatability of single loop metrics, even in normal individuals, is not well described, knowledge of which is vital if segmental analysis is to be used to diagnose, guide treatment and monitor enteric pathology.The purpose of this study is to explore segmental variation in SBM in healthy volunteers measured using two commonly reported small bowel metrics [CPM and Jacobian standard deviation (SD)] looking at (1) within-scan motility variation between different segments and (2) between-scan variation (repeatability) across two time points.     

Radiographers' professional knowledge regarding parameters and safety issues in plain radiography: a questionnaire survey

Objective:

To review the knowledge of radiographers and examine the possible sociodemographic and situational contributors to this knowledge.

Methods:

A questionnaire survey was devised and distributed to a cohort of 120 radiographers. Each questionnaire contained two sections. In the first section, background data, including sex, age, highest academic level, grade point average (GPA), length of time from graduation, work experience as a radiographer and the status of previous refresher course(s), were collected. The second section contained 17 multiple-choice questions concerning radiographic imaging parameters and safety issues.

Results:

The response rate was 63.8%. In univariate analytic model, higher academic degree (p < 0.001), higher GPA (r² = 0.11; p = 0.001), academic workplace (p = 0.04) and taking previous refresher course(s) (p = 0.01) were significantly associated with higher knowledge score. In multivariate analytic model, however, higher academic degree (B = 1.62; p = 0.01), higher GPA (B = 0.50; p = 0.01) and taking previous refresher course(s) (B = −1.26; p = 0.03) were independently associated with higher level of knowledge. Age, sex, length of time from graduation and work experience were not associated with the respondents'' knowledge score.

Conclusion:

Academic background is a robust indicator of a radiographer''s professional knowledge. Refresher courses and regular knowledge assessments are highly recommended.

Advances in knowledge:

This is the first study in the literature that examines professional knowledge of radiographers in terms of technical and safety issues in plain radiography. Academic degree, GPA and refresher courses are independent predictors of this knowledge. Regular radiographer professional knowledge checks may be recommended.The Joint Commission on Accreditation of Healthcare Organizations mandates “processes that are designed to ensure that the competency of all staff members is assessed, maintained, demonstrated and improved on an ongoing basis.” Tests with practical questions that reflect the knowledge required to perform daily examinations have been proposed as effective tools to attain this purpose. The results enable us to take on existing blemishes and improve the competency.¹Medical imaging, as a field with growing complexity and increasing impact on diagnosis, plans of management and patient health status,² is a good example of raised requirements for competency.^3–8Knowledge assessment may be useful for detecting possible weaknesses in an organization and spotlighting existing educational flaws and shortcomings.⁹ According to some reports, knowledge assessment takes priority over checking competency,^7,10 particularly in professions that are completely mediated by technology.¹¹In addition, although clinical education is the mainstay for developing skills, it has been shown that the combination of practical and theoretical education would lead to a significantly better outcome in the field of teaching. This integrated approach of using both knowledge and practice in education enables the trainee to work more competently and be prepared to take responsibility in his/her future career.¹²Although radiography using film for imaging the internal organs of the body has been introduced for over a century,¹³ it is still among the most widespread and useful imaging modalities all over the world. Radiographers are generally in charge of radiological equipment, imaging examination and frequently nursing care.^7,14,15Incompetent radiographers could render radiographic examinations suboptimal. A poor radiographic technique, in turn, may lead to unnecessary exposures to X-radiation, poor image quality, repeated views and examinations, patient discomfort or further injury because of poor positioning and the possibility of a missed diagnosis or misdiagnosis.¹⁶Furthermore, a rapid shift from conventional to fully digitized radiology departments, along with rapidly evolving changes in healthcare administration¹⁷ entails knowledgeable, up-to-date radiographers who utilize the technology.¹⁸Except for very limited number of studies that have described radiographers'' self-reported competency^7,16 and the level of awareness pertaining to the protection against radiation,^19,20 to the best of our knowledge, there is no study in the literature regarding radiographers'' level of knowledge with a dedicated focus on technical parameters and safety in plain radiography.This study sets out to examine knowledge amongst a cohort of radiographers and to investigate possible association of some sociodemographic and situational factors with the level of this knowledge.     

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.     

Medial temporal lobe atrophy in Alzheimer's disease/mild cognitive impairment with depression

Objective:

Depression is common in patients with Alzheimer''s disease (AD) and mild cognitive impairment (MCI). Patients with depression have an earlier onset and rapid progression of cognitive decline. Medial temporal lobe atrophy (MTA) is common in AD and MCI, and some degree of atrophy is found in almost all patients. In the present study, an attempt was made to know if MTA is more common in patients with AD/MCI with depression than those without it.

Methods:

Patients reporting to the outpatient department of a neurology centre of a tertiary care hospital were recruited for the present study. After initial general physical and neurological examination, they were evaluated using National Institute of Neurological and Communicative Disorders and Stroke and Related Disorders Association criteria for diagnosis of AD. Clinical Dementia rating scale was used for the diagnosis of MCI. Cornell scale for depression in dementia (CSDD) was used.

Results:

We found 20 cases with depression as per CSDD out of a sample of 37 patients (male:female = 30:7). There were 26 patients with AD and 11 with MCI. The mean age of all patients was 72.33 ± 6.45 years. The mean mini mental status examination score was 19.00 ± 6.73. The mean time since diagnosis was 4.19 ± 3.26 years. The mean Scheltens visual rating scale score for right MTA was 2.08 ± 0.95 and was 2.05 ± 0.94 for the left. Both scores did not differ statistically when analyzed using paired t-test (p > 0.05). However, difference in those with depression (2.36 ± 0.95) from those without depression (1.60 ± 0.74) was significant (p < 0.05).

Conclusion:

MTA scores were higher in those with AD/MCI with depression than those without it.Depression¹ is common in patients with Alzheimer''s disease (AD) and mild cognitive impairment (MCI). Relationship between depression and cognitive decline is a complex one, and depression is both an aetiological risk factor² and comorbidity for dementia.³ Incidence and prevalence of depressive symptoms in MCI range from 15% in population-based studies to 44% in hospital-based studies.⁴ Likewise, up to two-thirds of patients with AD have been reported to have depression.⁵ Because in many studies, depression has been seen to be an early manifestation of AD, it has been suggested that it may represent a continuum⁴ from depression to MCI to AD (late-life depression → MCI → AD). Two recent meta-analyses have found that a history of depression approximately doubles an individual''s risk for subsequent dementia in general and AD in particular.⁶ Depression is known to be neurotoxic to medial temporal lobe structures and can contribute to their atrophy.^7–9 Atrophy is more so, when depression is severe or recurrent⁷ and medial temporal lobe atrophy (MTA) has a temporal association with depression.⁹ Continued treatment of depression has been shown to protect the hippocampus from the ill effects of depression.¹⁰ Although volumetric method could be a preferred mode of measuring the hippocampal volume in AD, qualitative rating of MTA is a good alternative.¹¹ Visual rating of the hippocampal volume^12–14 can be carried out using Scheltens et al¹⁵ rating scale that is based on the width of the choroid fissure, the width of the temporal horn and the height of hippocampal formation and is a quantitative scale.     

Stage T3a renal cell carcinoma: staging accuracy of CT for sinus fat,perinephric fat or renal vein invasion

Objective:

To study the accuracy of CT for staging T3a (TNM 2009) renal cell carcinoma (RCC).

Methods:

Unenhanced and nephrographic phase CT studies of 117 patients (male:female = 82:35; age range, 21–86 years) with T1–T3a RCC were independently reviewed by 2 readers. The presence of sinus or perinephric fat, or renal vein invasion and tumour characteristics were noted.

Results:

Median (range) tumour size was 5.5 (0.9–19.0) cm; and 46 (39%), 16 (14%) and 55 (47%) tumours were pT1, pT2 and pT3a RCC, respectively. The sensitivity/specificity for sinus fat, perinephric fat and renal vein invasion were 71/79%, 83/76% and 59/93% (Reader 1) and 88/71%, 68/72% and 69/91% (Reader 2) with κ = 0.41, 0.43 and 0.61, respectively. Sinus fat invasion was seen in 47/55 (85%) cases with T3a RCC vs 16/55 (29%) and 33/55 (60%) for perinephric fat and renal vein invasion. Tumour necrosis, irregularity of tumour edge and direct tumour contact with perirenal fascia or sinus fat increased the odds of local invasion [odds ratio (OR), 2.5–3.7; p < 0.05; κ = 0.42–0.61]. Stage T3a tumours were centrally located (OR, 3.9; p = 0.0009).

Conclusion:

Stage T3a RCC was identified with a sensitivity of 59–88% and specificity of 71–93% (κ = 0.41–0.61). Sinus fat invasion was the most common invasive feature.

Advances in knowledge:

Centrally situated renal tumours with an irregular tumour edge, inseparable from sinus structures or the perirenal fascia and CT features of tumour necrosis should alert the reader to the possibility of Stage T3a RCC (OR, 2.5–3.9).Current guidelines¹ recommend nephron-sparing procedures (either partial nephrectomy or ablation) for Stage T1a (<4 cm) renal cell carcinomas (RCCs), but the indications for nephron-sparing procedures are widening.² Successful surgical series have been reported with Stage T1b (<4–7 cm) tumours and even Stage T2 RCCs.³ Central location is not necessarily a barrier to good clinical outcome after partial nephrectomy,³ but nephron-sparing procedures are contraindicated for stage ≥T3a renal cancers.¹ Thus, prior accurate recognition of T3a stage is important, especially with central renal masses, as any pre-operative suspicion of local invasion should contraindicate nephron-sparing surgery or ablation.In the most recent TNM iteration, Stage T1 and T2 tumours are defined by tumour diameter (T1a, ≤4 cm; T1b, 4–7 cm; T2a, 7–10 cm; and T2b, ≥10 cm) and the absence of any local invasion. Stage T3a RCC was redefined to include invasion of either renal sinus or perinephric fat.⁴ Renal vein invasion [main renal vein and/or segmental (muscle-containing) branch invasion], without caval involvement, was downgraded from Stage T3b to Stage T3a, whilst adrenal invasion was upgraded from Stage T3a to Stage T4. Size is not a governing factor with ≥T3a tumours, and some renal masses <7 cm in diameter will be locally advanced. Nearly half of all pT3a RCCs (n = 309/623) in one study were <7 cm in diameter.⁵ Other studies have confirmed the poor prognostic significance of sinus fat or venous invasion in masses <7 cm, with a 4–6 times increased risk of cancer-related death.^6,7 Centrally located masses are more likely to demonstrate local invasion with positive surgical resection margins after partial nephrectomy,^8,9 and unrecognized sinus invasion may explain the recurrence of cancer, and subsequent death from metastatic disease, in some cases of presumed T1 RCCs.⁸However, in previous studies, CT staging has been variably accurate^10–18 for RCCs, and staging inaccuracies, usually understaging, are said to be most common with Stage T3a disease.^12,17 For venous invasion, the specificity and sensitivity have ranged between 58–97% and 32–96%,^10,14–16 and for perinephric infiltration, the figures have been 32–96% and 85–93%,^14–16 respectively. The CT accuracy for sinus fat invasion has not been previously investigated. The primary aim of this study was to define the accuracy of contrast-enhanced CT for identifying any of the three defining features of Stage T3a RCC, that is, sinus or perinephric fat invasion, or renal vein invasion. Secondary study objectives were to identify any tumour characteristics that increase the odds of T3a disease and may be used as accessory CT signs to alert the reader to an increased likelihood of local invasion by RCC.     

Diffusion-weighted MRI in the follow-up of chronic periaortitis

Objective:

To evaluate the usefulness of diffusion-weighted MRI (DWI) for the assessment of the intraindividual follow-up in patients with chronic periaortitis (CP) under medication.

Methods:

MRI data of 21 consecutive patients with newly diagnosed untreated disease were retrospectively examined before and after medical therapy, with a median follow-up of 16 weeks. DWI parameters [b800 signal, apparent diffusion coefficient (ADC) values] of the CP and psoas muscle were analysed together with the extent and contrast enhancement. Pre- and post-treatment laboratory inflammation markers were acquired parallel to each MR examination.

Results:

Statistically significant lower b800 signal intensities (p ≤ 0.0001) and higher ADC values (p ≤ 0.0001) were observed after medical treatment within the fibrous periaortic tissue. Extent and contrast enhancement of the CP showed also a statistically significant decrease (p ≤ 0.0001) in the follow-up examinations, while the control parameters within the psoas muscle showed no differences.

Conclusion:

DWI seems to be a useful method for the evaluation of response to treatment without contrast agents. The technique may be helpful in the assessment of disease activity to guide further therapeutic strategies.

Advances in knowledge:

DWI detects significant differences in the intraindividual follow-up of CP under medical therapy.Chronic periaortitis (CP) is a proliferating fibroinflammatory disease of the perivascular retroperitoneal space and aortic wall.^1–4 Owing to adventitial inflammation, some recent theories consider CP as a large vessel vasculitis.⁵ Clinical manifestations of CP include idiopathic retroperitoneal fibrosis, inflammatory aortic aneurysm and perianeurysmal retroperitoneal fibrosis.^2,6,7 The three manifestations with very similar histopathological characteristics are distinguished by the diameter of the abdominal aorta and concomitant ureteral affection.^1,3,7Specific clinical symptoms are caused by extrinsic compression of the ureters or retroperitoneal veins, resulting in hydronephrosis, oliguria, lower extremity oedema and deep vein thrombosis.^1,8Under medical treatment with steroids, CP has a good prognosis.⁷ Today tamoxifen is suggested as a safe and effective therapeutic alternative, and immunosuppressive drugs can be considered in patients with suboptimal responses to these drugs or multiple relapses.^9–11CT and MRI are the modalities of first choice for diagnosis and follow-up of CP.^1,7,12 The fibrotic para-aortic tissue shows significant contrast uptake in gadolinium-enhanced MRI.^12–14 Dynamic contrast-enhanced MRI was suggested for the assessment of the disease activity.^15,16 However, in cases with impaired renal function (e.g. by ureteral compression), gadolinium-independent imaging methods should be preferred owing to the potential development of a nephrogenic systemic fibrosis.¹⁷Diffusion-weighted MRI (DWI) is a non-contrast MR modality that has been successfully applied for the assessment of retroperitoneal masses, inflammatory abdominal aortic aneurysms and for the differentiation between retroperitoneal fibrosis and malignant retroperitoneal neoplasms.^18–21DWI indicates restricted diffusion of water, for example caused by a high cellularity in malignant disease or active inflammation. The apparent diffusion coefficient (ADC) is a quantitative parameter for the level of restricted diffusion, which is calculated from the signals of different diffusion gradients (b-values).²²In the context of untreated CP diffusion-weighted MRI may detect restricted inflammation as a sign of high cellularity caused by active inflammation.There are no data for the evaluation of intraindividual follow-up and the response to treatment by DWI of CP so far. Therefore, the aim of the present study was to analyse differences in DWI signals during follow-up in patients with CP before and after treatment. In addition, we sought to elucidate the potential of DWI in the therapy monitoring of CP.     

A planning target volume margin formula for hypofractionated intracranial stereotactic radiotherapy under cone beam CT image guidance with a six-degrees-of-freedom robotic couch and a mouthpiece-assisted mask system: a preliminary study

Objective:

A planning target volume (PTV) margin formula for hypofractionated intracranial stereotactic radiotherapy (SRT) has been proposed under cone beam CT (CBCT) image guidance with a six-degrees-of-freedom (6-DOF) robotic couch.

Methods:

CBCT-based registration using a 6-DOF couch reportedly led to negligibly small systematic positioning errors, suggesting that each in-treatment positioning error during the treatment courses for the patients employing this combination was predominantly caused by a random gaussian process. Under this assumption, an anisotropic PTV margin for each axis was formulated based on a gaussian distribution model. 19 patients with intracranial lesions who underwent additional post-treatment CBCT were consecutively selected, to whom stereotactic hypofractionated radiotherapy was delivered by a linear accelerator equipped with a CBCT imager, a 6-DOF couch and a mouthpiece-assisted mask system. Time-averaged patient-positioning errors during treatment were estimated by comparing the post-treatment CBCT with the reference planning CT images.

Results:

It was suggested that each histogram of the in-treatment positioning error in each axis would approach each single gaussian distribution with a mean of zero. The calculated PTV margins in the x, y and z directions were 0.97, 1.30 and 0.88 mm, respectively.

Conclusion:

The empirical isotropic PTV margin of 2 mm used in our facility for intracranial SRT was consistent with the margin calculated by the proposed gaussian model.

Advances in knowledge:

We have proposed a PTV margin formula for hypofractionated intracranial SRT under CBCT image guidance with a 6-DOF robotic couch.Frameless radiotherapy for treating intracranial lesions has been widely adopted under the guidance of on-board cone beam CT (CBCT) and a mask system with a six-degrees-of-freedom (6-DOF) robotic couch^1–3 or a semi-robotic couch including manual angle adjustments.⁴ Reported maximum registration errors along any Cartesian co-ordinate axis were 0.5 mm for a phantom;¹ and 1.0 or 3.2 mm (mask dependent),² 2.0 ³ and 1.2 mm⁴ for patients. The mean ± standard deviation (SD) along any Cartesian co-ordinate axis was 0.07 ± 0.17 mm for a phantom based on 12 plans and 5 repeated CBCT acquisitions,¹ 0.2 ± 0.4 mm for 10 patients with 6 fractions³ and 0.4 ± 0.3 mm for a phantom and 0.5 ± 0.3 mm for patients including manual couch angle adjustments.⁴ Meyer et al¹ stated that there was no systematic error because they observed a small mean error for their phantom study.Margins between clinical target volumes (CTVs) and planning target volumes (PTVs) are often calculated using a formula proposed by van Herk et al.^5,6 This formula employed two independent statistical models including a patient-to-patient variation model that gives a mean preparation error in all fractions for each patient, and a random error model during treatment delivery owing to random tumour movement. A patient population coverage probability of 90% in a facility was calculated by the patient-to-patient variation model, and the random error model was used to add further margins by increasing penumbra widths. Our intracranial stereotactic radiotherapy (SRT) utilizes an Elekta Synergy® (Elekta AB, Stockholm, Sweden) linear accelerator (linac) equipped with a CBCT imager, XVI and a 6-DOF robotic couch, HexaPOD™ (Elekta AB), which are identical to the system that Meyer et al¹ described. Consequently, our study can be based on the small mean preparation error reported by Meyer et al, and the above margin model may not be applicable. In addition, the previous margin model assumed that the tumour was spherical, and the margin was defined in the radial direction of the spherical co-ordinate system. For example, Guckenberger et al² calculated the PTV margin in the radial direction using registration results for 47 patients with various treatment sites and fixation means, leading to a PTV margin of 1.7 mm that achieved 90% population coverage. Meanwhile, a more accurate margin formula in the Cartesian co-ordinate system that complies with patient couch movements was proposed, in which the margins were anisotropically defined along the x, y and z directions.⁷The purpose of this study was to propose a PTV margin formula as per the Cartesian co-ordinate system for hypofractionated intracranial SRT under CBCT image guidance with a 6-DOF robotic couch.     

3-T diffusion tensor imaging (DTI) of normal uterus in young and middle-aged females during the menstrual cycle: evaluation of the cyclic changes of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values

Objective:

To evaluate cyclic changes of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values of normal uterus in different age groups during the menstrual cycle, and the correlation with serum female hormone levels.

Methods:

29 normal volunteers accepted diffusion tensor imaging of the uterus on menstrual phase (MP), follicular phase (FP), ovulatory phase (OP) and luteal phase. FA and ADC values of different uterine layers on midsagittal images were measured. Differences between two age groups during the menstrual cycle were evaluated using liner mixed models and one-way analysis of variance. Pearson correlation analysis compared variation of FA and ADC values with serum female hormone levels measured in MP.

Results:

During menstrual cycle, endometrial FA values declined, whereas ADC values increased with significant differences (p < 0.05). Serum oestradiol (E) levels correlated moderately with variations of FA values between MP-FP (p = 0.045; r = 0.389) and MP-OP (p = 0.008; r = 0.511). FA and ADC values of junctional zones showed no significant difference (p > 0.05) as well as FA values of myometrium (p = 0.0961), while ADC values of myometrium showed significant increase from menstrual phase to luteal phase (p < 0.05). FA and ADC values of uterine three zonal structures showed significant differences (p < 0.05) at each phase during the menstrual cycle. No significant difference of FA and ADC values was found between age groups (p > 0.05).

Conclusion:

Dynamic changes of uterine FA and ADC values were observed during menstrual cycle. Variation of FA values between MP-FP, MP-OP correlated moderately with serum E levels.

Advances in knowledge:

No publications on the relationship between FA and ADC values and the female hormone levels were found; our study prospectively investigated the cyclic changes of FA and ADC values of the normal uterus and the correlation with the basic serum female hormone levels in MP.Diffusion tensor imaging (DTI) is a well-established technique, which has been widely used in variable neurological diseases^1–4 and other parts of the body, such as the musculoskeletal system,^5,6 prostate^7,8 and kidney.^9,10In recent years, limited publications of its application in the female pelvis have been emerging. Current published studies include ex vivo and in vivo studies.^11–16 In 2006, three-dimensional fibre architecture of the normal human uterus based on DTI has been ex vivo evaluated in five samples by Weiss et al.¹¹ Toba et al¹² ex vivo study showed that DTI might be a useful tool for the diagnosis of myometrial invasion of uterine endometrial cancer. However, fractional anisotropy (FA) value of a normal uterus has not been thoroughly investigated yet. What is more there is no known publication, to the best of our knowledge, found on the relationship between FA value and female menstrual cycle. It would be ambiguous to use this MR parameter to evaluate malignancy situations without knowing the possible differences in various uterine structures, including endometrium, myometrium and junctional zone. In 2012, Fiocchi et al¹³ investigated the feasibility of depicting fibre architecture of the human uterus in vivo using 3-T MR-DTI based on 30 volunteers in different menstrual phases (MPs). In 2013, Fujimoto et al¹⁴ compared the DTI parameters in the different uterine layers of nine subjects in vivo, but limited their study group to the luteal phase (LP) only. A more comprehensive study based on 11 normal young females was reported by Kido et al;¹⁵ however, only apparent diffusion coefficient (ADC) value changes were evaluated during three phases of menstrual cycle. To the best of our knowledge, there are no published data focused on the cyclic changes of FA value in a normal uterus during four phases of menstrual cycle with a larger study cohort. Moreover, as it has been learned from MRI studies, anatomical and physiological characteristics of uterine structures, such as the endometrium and junctional zone, are heavily related to female hormone levels.^17–22 Nevertheless, no publications on the relationships between FA or ADC values and the hormone level were found.So, the aim of our study was to prospectively investigate the cyclic changes of FA and ADC values of the normal uterus in a larger population divided into different age groups during the four phases of the menstrual cycle, and the correlation with the basic serum hormone levels in MP.     

Diffusion-weighted imaging vs STIR turbo SE imaging: capability for quantitative differentiation of small-cell lung cancer from non-small-cell lung cancer

Objective:

To compare the capability of differentiation of small-cell lung cancer (SCLC) from non-SCLC (NSCLC) between diffusion-weighted imaging (DWI) and short tau inversion recovery (STIR) turbo spin-echo imaging.

Methods:

The institutional review board of Kobe University Hospital, Kobe, Japan, approved this study, and written informed consent was obtained from each patient. 49 patients with NSCLC (30 males and 19 females; mean age, 66.8 years) and 7 patients with SCLC (5 males and 2 females; mean age, 68.6 years) enrolled and underwent DWI and STIR. To quantitatively differentiate SCLC from NSCLC, apparent diffusion coefficient (ADC) values on DWI and contrast ratios (CRs) between cancer and muscle on STIR were evaluated. ADC values and CRs were then compared between the two cell types by Mann–Whitney''s U-tests, and the diagnostic performances were compared by McNemar''s test.

Results:

There were significant differences of mean ADC values (p < 0.001) and mean CRs (p = 0.003). With adopted threshold values, the specificity (85.7%) and accuracy (85.7%) of DWI were higher than those of STIR (specificity, 63.3%; p = 0.001 and accuracy, 66.1%; p = 0.001). In addition, the accuracy of combination of both indexes (94.6%; p = 0.04) could significantly improve as compared with DWI alone.

Conclusion:

DWI is more useful for the differentiation of SCLC from NSCLC than STIR, and their combination can significantly improve the accuracy in this setting.

Advances in knowledge:

Pulmonary MRI, including DWI and STIR, had a potential of the suggestion of the possibility as SCLC.Lung cancer is the most common cause of cancer-related death among both males and females worldwide.¹ Lung cancers are divided into non-small-cell cancer (NSCLC) and small-cell lung cancer (SCLC), and the differentiation between SCLC and NSCLC is important in clinical practice because their therapeutic strategies, clinical course and prognoses are different.² In general, SCLC is usually determined with extensive hilar and mediastinal lymphadenopathy,³ and these cancers are mainly treated by chemotherapy or chemoradiotherapy.^2,4On the other hand, 5–10% of patients with SCLC were diagnosed as having solitary pulmonary nodules.^5,6 In this situation, the assessments of distant metastases before treatment play an important role in deciding the treatment. At present, although there are some different reports for patients with NSCLC regarding the assessment of distant metastases before surgery,^7–9 it is important to assess the distant metastases of these patients with SCLC because SCLC is known for its rapid doubling time, high growth fraction and early development of metastatic disease.^10–12 If patients with SCLC are diagnosed at Stage I or possibly Stage II, clinicians consider their treatment as surgery and/or neoadjuvant chemotherapy.^13–15 Therefore, the differentiation between SCLC and NSCLC and the suggestion of the possibility of SCLC may be important in routine clinical practice. However, the differentiation of SCLC from NSCLC is difficult on CT and positron emission tomography (PET) or PET/CT,^5,6,16 and fiberoptic bronchoscopy and percutaneous biopsy are recommended, although their diagnostic sensitivities range from 67% to 100%.^17–19Recently, the image quality and diagnostic capability of chest MRI has improved because of the advancement of MR systems and sequences, and short tau inversion recovery (STIR) turbo spin-echo (SE) imaging and diffusion-weighted imaging (DWI) have been reported as useful in differentiating malignant nodules and lymph nodes from benign ones in several articles.^20–25 Meanwhile, the utilities of chest MRI, including STIR and DWI, have been reported,²⁶ and, in addition, meta-analysis report for pulmonary nodules by means of DWI have been published.²⁷ However, to the best of our knowledge, there have been only reports of chest DWI regarding the differentiation between SCLC and NSCLC,²² but no major studies have reported a direct comparison of the use of DWI and STIR in chest MRI for the assessment of differentiation between SCLC and NSCLC. We hypothesized that both DWI and STIR were useful MR sequences for differentiation of SCLC from NSCLC and their combination might improve the differentiation capabilities. The aim of this study was to evaluate the diagnostic performances of DWI and STIR for differentiating between SCLC and NSCLC.     

Multiple-electrode radiofrequency ablations using Octopus(R)electrodes in an in vivo porcine liver model

Objectives

The objective of this study was to determine the in vivo efficacy of radiofrequency ablation (RFA) in porcine liver using Octopus® electrodes for creating a large coagulation compared with RFA using clustered electrodes.

Methods

A total of 39 coagulations were created using a 200-W generator and clustered electrodes or Octopus electrodes during laparotomy in 19 pigs. Radiofrequency was applied to the livers using four protocols: (1) Group A-1, monopolar mode using a clustered electrode (n=11); (2) Group A-2, monopolar mode using an Octopus electrode (n=11); (3) Group B-1, consecutive monopolar mode using three, clustered electrodes (n=8); and (4) Group B-2, switching monopolar mode using two Octopus electrodes (n=9). The energy efficiency, shape, diameters (D) and volume (V) of the coagulation volume were compared in each of the two groups.

Results

The mean maximum D and V of the coagulations in Group A-2 (4.7 cm and 33.1 cm³, respectively) were significantly larger than those in Group A-1 (4.1 cm and 20.3 cm³, respectively) (p<0.05). Furthermore, the mean minimum D, maximum D and V of the coagulations in Group B-2 were significantly larger than those in Group B-1, i.e. 5.3 vs 4.0 cm, 6.6 vs 4.9 cm and 66.9 vs 30.2 cm³, respectively (p<0.05). The energy efficiencies were also significantly higher in Groups A-2 and B-2 than in Groups A-1 and B-1 (p<0.05).

Conclusion

The Octopus electrodes were more efficient for creating a large ablation zone than clustered electrodes, and the efficacy of RFA with Octopus electrodes can be amplified in the switching monopolar mode.In recent years, image-guided percutaneous tumour ablation using radiofrequency (RF) energy has become increasingly popular and has gained wide acceptance as a valuable, minimally invasive treatment for primary and secondary liver malignancies [1]. Compared with conventional surgery, RF ablation (RFA) has many advantages in terms of reduced complications, morbidity and mortality as well as its cost-effectiveness. However, a major obstacle preventing the widespread use of RFA is its inability to reliably create adequate volumes of complete tumour destruction with sufficient safety margins, thus causing an increasing rate of marginal recurrence in large tumours due to the incomplete RFA. Most clinically available electrodes, including internally cooled electrodes, clustered electrodes, multitined expandable needle electrodes and perfusion electrodes, can induce coagulation necrosis in the range of 3–4 cm in diameter after a single ablation session [2,3]. Therefore, to treat liver tumours >3 cm in diameter, multiple overlapping ablations are often required to cover the entire tumour volume as well as the peripheral ablation margins [4,5]. However, in clinical practice, there is considerable difficulty repositioning the probe under ultrasound guidance during overlapping ablations as numerous microbubbles form in the heated tissue during RFA and may thus interfere with finding the electrode tip and the untreated portions of the target tumour on ultrasound [6].In order to avoid problems related to multiple overlapping ablations, including technical difficulties and a long procedure time, several approaches have been used to treat medium and large liver tumours. These include the use of cluster electrodes [7], multitined electrodes with saline infusion (RITA Medical Systems, Mountain View, CA) [2] and multiple electrodes in the switching monopolar mode or multipolar mode [8-11]. Although several previous studies demonstrated that the use clustered electrodes or multiple electrodes in the switching or multipolar modes could create larger coagulations [2,3,6,8-14], they also presented several potential unsolved problems. The clustered electrode problems include: (1) convergence of the three individual needles <5 mm; (2) limited access to the target tumour owing to narrow intercostal spaces; and (3) displacement of the liver due to its resistance to the electrode. Although RFA using multiple electrodes can successfully treat large liver tumours, it is still not widely used in clinical practice, primarily owing to its high cost and the complexity of using multiple electrodes.Recently, in order to improve the efficiency of clustered electrodes in creating a large ablation zone and to diminish any potential problems, we developed a separable clustered electrode (Octopus®; Taewoong Medical Co., Ltd, Goyang, Republic of Korea) with a specialised handle that can be incorporated into a larger handle in a single unit (Figure 1). Our electrode can be placed as a single electrode with variable interelectrode distances, according to the shape and size of the target tumour, or in a similar way to the clustered electrodes that are also composed of three electrodes as a single body at a fixed 5-mm interelectrode distance. Therefore, prior to their clinical application, we attempted to prove the in vivo efficacy of RFA using the Octopus electrodes to create a large area of coagulation necrosis in either the conventional or switching monopolar mode compared with RFA using a clustered electrode in porcine liver.Open in a separate windowFigure 1(a,b) Photographs of the Octopus® electrodes (Taewoong Medical Co., Ltd, Goyang, Republic of Korea), all of which have three individual needles. (c) Adaptor for the Octopus electrodes which connects the three cables to one port. (d) An illustration, which shows details of the connection between the needles and radiofrequency (RF) ablution system in a three Octopus electrodes system.     

Repeatability of quantitative metrics derived from MR diffusion tractography in paediatric patients with epilepsy

Objective:

To quantify the test–retest repeatability of mean diffusivity (MD) and fractional anisotropy (FA) derived from diffusion tensor imaging (DTI) tractography in a cohort of paediatric patients with localization-related epilepsy.

Methods:

30 patients underwent 2 DTI acquisitions [repetition time/echo time (ms), 7000/90; flip, 90°; b-value, 1000 s mm⁻²; voxel (mm), 2 × 2 × 2]. Two observers used Diffusion Toolkit and TrackVis (www.trackvis.org) to segment and analyse the following tracts: corpus callosum, corticospinal tracts, arcuate fasciculi, inferior longitudinal fasciculi and inferior fronto-occipital fasciculi. Mean MD and mean FA were calculated for each tract. Each observer independently analysed one of the DTI data sets for every patient.

Results:

Segmentation identified all tracts in all subjects, except the arcuate fasciculus. There was a highly consistent relationship between repeated observations of MD (r = 0.993; p < 0.0001) and FA (r = 0.990; p < 0.0001). For each tract, coefficients of variation ranged from 0.9% to 2.1% for MD and from 1.5% to 2.8% for FA. The 95% confidence limits (CLs) for change ranged from 2.8% to 6% for MD and from 4.3% to 8.6% for FA. For the arcuate fasciculus, Cohen''s κ for agreement between the observers (identifiable vs not identifiable) was 1.0.

Conclusion:

We quantified the repeatability of two commonly utilized scalar metrics derived from DTI tractography. For an individual patient, changes greater than the repeatability coefficient or 95% CLs for change are unlikely to be related to variability in their measurement.

Advances in knowledge:

Reproducibility of these metrics will aid in the design of future studies and might one day be used to guide management in patients with epilepsy.Epilepsy is a common neurological condition defined by recurrent unprovoked seizures that affects 1% of the population, including 1 in 200 children.^1,2 Unlike in adults, developmental lesions predominate as the source of seizures in children; in particular, focal cortical dysplasia is the most common anatomical substrate for intractable epilepsy in the paediatric population.³ A high proportion of epilepsies occurring in the setting of cortical malformations are pharmacoresistant,⁴ highlighting the importance of alternative management strategies. In appropriately selected patients who fail medical management, surgical resection of the dysplastic cortex can be curative. In such cases, pre-operative identification and complete resection of the structural lesion are important prognostic factors.^5,6 Decision making surrounding the pursuit of invasive alternatives is rarely straightforward, however, and in practice relies heavily on supplementary information provided by novel diagnostic techniques.Although surgical management is an attractive option for many patients with focal seizures, medical therapy continues to be adopted as the “safe” strategy in a significant portion of this population. However, there is good evidence to suggest that ongoing seizures and treatment with antiseizure medication might be associated with progressive alterations in white matter integrity.^7–9 Furthermore, these same ongoing processes can contribute to progressive functional decline.^10,11 As such, the ability to confidently identify progression of network alterations in an individual patient with epilepsy, whether on the basis of ongoing seizure activity, antiseizure medication or both, would be of great value to informed decision making surrounding potential surgical intervention.With the advent of diffusion-weighted imaging (DWI), the microstructural properties of a tissue of interest can be non-invasively probed at a spatial scale that is otherwise unattainable using even the most advanced structural MR techniques. Diffusion tensor imaging (DTI) is a variation on the theme of DWI, which quantifies water motion in three orthogonal dimensions and, therefore, is better able to capture the anisotropic tendencies of diffusion in highly organized tissues, such as cerebral white matter.¹² Numerous scalar metrics can be derived from the tensor; the most commonly referenced are mean diffusivity (MD) and fractional anisotropy (FA). MD provides a measure of overall incoherent motion within a voxel without regard for direction and reflects tissue organization at the cellular level.¹³ Increased MD is a common manifestation of white matter pathology of diverse aetiology.^14–16 By contrast, FA provides a measure of the degree to which a single direction of water motion dominates overall diffusivity in a voxel. As such, FA has been shown to be a relatively robust measure of white matter integrity.^17–21 Diffusion tractography is an extension of DTI in which the directional tendencies of water diffusion are used to create three-dimensional representations of white matter tracts based on their structural coherence.^22,23 In many instances, the functional role of the constructed pathways is at least in part known, which enables assessment of brain parenchymal abnormalities in terms of functional systems.^16,24DTI and diffusion tractography already occupy a prominent place in epilepsy research, and they are increasingly used to guide clinical management of epilepsy patients.^7,25–30 Although preliminary results are promising, a thorough understanding of the test–retest reproducibility of metrics derived from DTI will be crucial to the widespread application of this technique. Such knowledge would inform the design of both cross-sectional and longitudinal studies, including appropriate sample size selection. Furthermore, the clinical utility of such quantitative techniques will be predicated on an understanding of their intrinsic variability at the level of the individual. In particular, an understanding of what represents true difference at the individual level will be required to ascribe significance to changes in these metrics that occur in an individual patient. To date, however, the reproducibility of quantitative metrics derived from tractography has not been widely studied and, in particular, there are very few data from either the paediatric or epilepsy populations.³¹ The goal of this study, therefore, was to measure the repeatability of MD and FA derived from DTI tractography in a cohort of paediatric patients with localization-related epilepsy.