Ultrasound-guided percutaneous laser ablation of liver tissue in a rabbit model

The present report evaluates the efficacy and safety of percutaneous interstitial laser tissue ablation of the liver in nine New Zealand rabbits. A Nd: YAG laser was coupled to a quartz fibreoptic guide (600 m) with a flat tip. The fibre and a thermocouple were placed in the lumen of two Chiba needles (18G) and these were inserted into the liver 10 mm apart under ultrasound guidance. The laser was fired for 5 min at 1, 3 and 5 W power, respectively, in three groups of rabbits. There were no acute complications and all the rabbits except one survived until the established time of sacrifice. The procedure induced a cavity surrounded by a zone (about 10 mm) of coagulative necrosis. After 2 weeks a strong peripheral inflammatory response was evident and after 4 weeks a capsule of connective tissue enclosed the lesions. Our study seems to offer a safe and rapid technique producing a guaranteed kill radius for the treatment of small hepatic neoplasms. Correspondence to: C. M. Pacella     

US-guided percutaneous laser ablation of liver tissue in a chronic pig model

The authors evaluated the safety of ultrasound (US)-guided percutaneous ablation of liver tissue using a neodymium-yttrium-aluminum-garnet (Nd:YAG) laser fiber placed through a skinny needle. The US appearance of the lesion was correlated with the pathologic findings in 19 pigs killed at 1-7 weeks. A 20-gauge needle was percutaneously placed in the liver, and a fiber with a 0.5-cm cladding-stripped tip was inserted. The Nd:YAG laser was fired for 6 minutes at 1-4 W. The early sonographic appearance was recorded, and the US appearance before the pigs were killed was correlated with the gross and histopathologic findings. There were no cases of abdominal bleeding or infection. Mild transient changes in liver function were seen. An initial strong echogenic focus decreased slightly in echogenicity for 10 minutes and then stabilized. Over 1-7 weeks, the 1-cm-diameter lesion decreased in size and developed an echogenic rim that correlated with a peripheral zone of inflammatory repair around a small central cavity and zone of necrosis. US-guided laser ablation of liver tissue is safe in this pig model, and the US appearance corresponds to a process of repair and removal of necrotic liver tissue.     

Stereotaxic laser ablation of intracranial lesions

A technique is described which combines computed tomography-based stereotaxic localization and CO2 laser ablation of certain intracranial lesions with a high degree of accuracy. In 24 patients operated on with this technique, total ablation of the lesion was achieved in 19 and incomplete ablation in the other five. Though not perfect, this method is a new approach to intracranial lesions that promises to be more efficacious as future developments occur.     

Mathematical model of the otolith

This paper describes a mathematical model of the otolith of mammals represented as a system with parameters of distribution. Two versions of the model are analyzed and the lowest frequencies of natural oscillations of the system are evaluated.     

MRI monitoring of laser ablation using optical flow

The optical flow method is used for visualizing and quantifying the dynamics of tissue changes observed by MRI during thermal ablations. An approach was implemented for parallel two-dimensional optical flow calculations including the replacement of spurious velocities. Velocity magnitude results were found to be accurate in low-noise cases in tests using series of synthetic images. Optical flow results are presented from thermal ablation experiments utilizing a homogeneous polyacrylamide gel phantom and heterogeneous rabbit liver tissue in vivo, exhibiting heating and cooling with the accompanying quantitative characterization of the dilation and contraction of the thermally affected region. Results demonstrate that optical flow is capable of noninvasive real-time monitoring and control of interstitial laser therapy (ILT).     

Magnetic resonance-guided percutaneous laser ablation of uterine fibroids

Laser ablation of uterine fibroids using a percutaneous approach under local anesthetic in an open magnetic resonance (MR) scanner was performed in 12 symptomatic women awaiting hysterectomy. Accurate laser fiber placement was assisted by the use of an MR needle tracking system, as well as laser heat dissipation monitored during treatment by a real-time imaging processor. This day case procedure was well tolerated by all women, with eight women subsequently declining their planned surgery. Follow-up measurements of treated fibroid volume by MRI demonstrated a mean decrease of 37.5% at 3 months. This novel minimally invasive approach offers an alternative to surgery for women with fibroids, but longer follow-up is required to ascertain maximal fibroid shrinkage and to compare outcome with traditional surgery.     

Influence of intrahepatic vessels on volume and shape of percutaneous thermal ablation zones: in vivo evaluation in a porcine model

OBJECTIVES: Aim of the study was to evaluate the precise influence of different intrahepatic vessels, vessel sizes, and distances from the applicator on volume and shape of hepatic laser ablation zones in an in vivo porcine model. MATERIALS AND METHODS: The study was approved by the institutional animal care and use committee. Eighteen computed tomography-guided Nd:YAG laser ablations were performed in the livers of 10 pigs at varying distances from hepatic veins and portal fields. After hepatectomy the livers were cut into 2-mm slices perpendicular to the laser applicator axes. For each ablation zone the maximum achievable (ideal) volume, the segmented (real) volume, the maximum radius, and the radius at the position of adjacent hepatic vessels were determined. The shapes of the ablation zones were evaluated qualitatively. Comparative statistics using the unpaired t test and a multiple linear regression analysis were performed. RESULTS: Ideal and real ablation zone volumes differed by 27.3% (8.6 +/- 1.5 mL vs. 6.4 +/- 1.1 mL; P < 0.0001). Thirty-eight of 60 (63%) hepatic veins versus 28 of 31 (90%) portal veins within the central slices of the 18 ablation zones led to a reduction of the ablation zone's radius, depending on the distance between the vessel and the applicator and the vessel type. Portal fields revealed stronger effects than hepatic veins. The vessel diameter showed no independent effect (P > 0.05). When influencing, all hepatic veins showed a focal indentation whereas portal fields always showed broad flattening of the ablation zone. CONCLUSIONS: Portal fields lead to more heat sink than hepatic veins. The effects decreased with the distance between vessel and applicator tip, but less so for portal fields. The 2 vessel types induced considerably different shape alterations of the ablation zones. These results were not dependent on vessel size. This should be considered in the planning of thermal tumor ablations.     

Influence of large peritumoral vessels on outcome of radiofrequency ablation of liver tumors

PURPOSE: The effect of large vessels (>/=3 mm) contiguous to hepatic tumors was evaluated with respect to clinical tumor recurrence rates after radiofrequency (RF) ablation. MATERIALS AND METHODS: The first 105 malignant liver tumors treated by RF ablation therapy at our institution with pathologic analysis or a minimum of 6 months of clinical follow-up were reviewed. The original pretreatment imaging studies were reviewed by a radiologist who was blinded to the cases, and, based on lesion contiguity to vessels of at least 3 mm, the lesions were categorized as perivascular or nonperivascular. Treatment outcomes with respect to local tumor recurrence between these two groups were then compared. Logistic regression analysis was performed to take into account other variables and to determine whether this categorization was an independent predictor of treatment outcome. RESULTS: There were 74 nonperivascular tumors and 31 perivascular tumors. Mean tumor size was 2.4 cm and mean follow-up was 11.3 months. Residual or locally recurrent tumors were documented in 20 of 105 cases (19%). In the nonperivascular group, five of 74 (7%) had either incompletely treated tumor (manifested within 6 months) or local recurrence beyond 6 months. In the perivascular group, 15 of 31 (48%) had incompletely treated or locally recurrent tumor (P <.001). Subanalysis of lesion size (61 tumors 4 cm), tumor type (40 hepatocellular carcinomas, 48 colorectal metastases, and 17 other metastases), access (53 intraoperative, 52 percutaneous), and RF device (45 Radiotherapeutics electrodes, 18 Rita electrodes, and 42 Radionics electrodes) showed similar results. Multivariate logistic regression analysis showed that presence or absence of a large peritumoral vessel is an independent, and the dominant, predictor of treatment outcome. CONCLUSION: The presence of vessels at least 3 mm in size contiguous to hepatic tumors is a strong independent predictor of incomplete tumor destruction by RF ablation. Modified ablation strategies should be considered to improve destruction of these tumors.     

Endovenous laser ablation for the treatment of varicose veins

Lower extremity venous insufficiency secondary to saphenous vein insufficiency is a common medical condition that decreases a patient's quality of life. Traditionally treated with high ligation and stripping, minimally invasive procedures using endovenous thermal ablation techniques, such as endovenous laser ablation, have evolved. The use of detailed imaging and advances in the understanding of the anatomy of truncal vein insufficiency are important for performing the endovenous laser ablation procedure successfully. Endovenous laser ablation eliminates reflux with less morbidity, faster recovery, and improved cosmetic results with high patient satisfaction. As such, it has become the preferred treatment method for varicose veins since it was first introduced a decade ago.     

Ultrasound guided laser ablation of a parathyroid adenoma.

We present a case of primary hyperparathyroidism with severe hypercalcaemia, treated successfully with ultrasound (US) guided percutaneous interstitial laser photocoagulation (ILP) of a single parathyroid tumour. To our knowledge, this is the first reported case of ILP applied in primary hyperparathyroidism. US guided thermic tissue coagulation with ILP may be a non-surgical alternative in patients with symptomatic hypercalcaemia due to a parathyroid tumour when surgery is contraindicated.     

Angiologic diagnosis and therapy for radiologic interventions in arteriosclerosis obliterans of pelvic and leg vessels

Angiographic diagnosis and therapy are discussed in relationship to the indications and follow-up of radiological interventions in patients with obliterative atherosclerosis located in the arteries of the pelvis and lower limbs. Various noninvasive diagnostic procedures permit reliable clinical information to be obtained on the localization, extent and geometry of arterial lesions, and the velocity of blood in the vascular system. Determination of symptom-limited ergometry and oscillographic, plethysmographic, Doppler sonographic, light microscopic and magnet resonance techniques are all described in more detail. The therapeutic interventions are mentioned with regard to angiography and percutaneous transluminal angioplasty (PTA), with particular emphasis on the treatment of risk factors, training, and medication. The long-term results are given after PTA for the Freiburg patient series. Thus, the cooperation of angiologists, radiologists and vascular surgeons considerably optimizes the treatment of patients suffering from occlusive arterial disease.     

Thermal ablation of liver metastases from colorectal cancer: radiofrequency,microwave and laser ablation therapies

Surgery is currently considered the treatment of choice for patients with colorectal cancer liver metastases (CRLM) when resectable. The majority of these patients can also benefit from systemic chemotherapy. Recently, local or regional therapies such as thermal ablations have been used with acceptable outcomes. We searched the medical literature to identify studies and reviews relevant to radiofrequency (RF) ablation, microwave (MW) ablation and laser-induced thermotherapy (LITT) in terms of local progression, survival indexes and major complications in patients with CRLM. Reviewed literature showed a local progression rate between 2.8 and 29.7 % of RF-ablated liver lesions at 12–49 months follow-up, 2.7–12.5 % of MW ablated lesions at 5–19 months follow-up and 5.2 % of lesions treated with LITT at 6-month follow-up. Major complications were observed in 4–33 % of patients treated with RF ablation, 0–19 % of patients treated with MW ablation and 0.1–3.5 % of lesions treated with LITT. Although not significantly different, the mean of 1-, 3- and 5-year survival rates for RF-, MW- and laser ablated lesions was (92.6, 44.7, 31.1 %), (79, 38.6, 21 %) and (94.2, 61.5, 29.2 %), respectively. The median survival in these methods was 33.2, 29.5 and 33.7 months, respectively. Thermal ablation may be an appropriate alternative in patients with CRLM who have inoperable liver lesions or have operable lesions as an adjunct to resection. However, further competitive evaluation should clarify the efficacy and priority of these therapies in patients with colorectal cancer liver metastases.     

Mathematical model of cyclic kinetics of granulocytopoiesis

A model of time-course variations of granulocytopoiesis which is a system of three non-linear differential equations has been developed. The model describes the basic stages of granulocyte development and includes the chalone mechanism regulating the proliferation of granulocyte precursors in bone marrow. Theoretical investigations applying the vibration theory and computer-aided calculations have shown that the model presents aperiodic and vibrational kinetics of reduction processes in the system of granulocytopoiesis as well as steady-state vibrations of concentrations of mature granulocytes and their precursors (limiting cycles). The variations of the model parameters within which the above dynamic modes occur have been identified. The conditions under which the limiting cycles arise have been examined. The fact that the model simulates various experimentally observed situations suggests that it can be used to predict changes in granulocytopoiesis induced by adverse effects responsible for hemopoietic abnormalities.     

Postinterventional MRI findings following MRI-guided laser ablation of osteoid osteoma

Objective

To evaluate postinterventional magnetic resonance imaging (MRI) characteristics following MRI-guided laser ablation of osteoid osteoma (OO).

Materials and methods

35 patients treated with MRI-guided laser ablation underwent follow-up MRI immediately after the procedure, after 3, 6, 12, 24, 36, and up to 48 months. The imaging protocol included multiplanar fat-saturated T2w TSE, unenhanced and contrast-enhanced T1w SE, and subtraction images. MR images were reviewed regarding the appearance and size of treated areas, and presence of periablation bone and soft tissue changes. Imaging was correlated with clinical status.

Results

Mean follow-up time was 13.6 months. 28/35 patients (80%) showed a postinterventional “target-sign” appearance consisting of a fibrovascular rim zone and a necrotic core area. After an initial increase in total lesion diameter after 3 months, a subsequent progressive inward remodeling process of the zonal compartments was observed for up to 24 months. Periablation bone and soft tissue changes showed a constant decrease over time. MR findings correlated well with the clinical status. Clinical success was achieved in 32/35 (91%).

Conclusions

Evaluation of long-term follow-up MRI after laser ablation of OO identified typical postinterventional changes and thus may contribute to the interpretation of therapeutic success and residual or recurrent OO in suspected cases.     

小腿肌肉、肌间血管全部坏死并感染的肢体保留术式介绍

目的 探索全部去除小腿感染坏死肌肉和肌间血管，仅保留小腿皮肤筋膜、胫骨时，踝足延时成活的影响因素以及重建动脉循环对避免足坏死或缺血挛缩的作用。方法 对1例左小腿肌肉及肌间血管坏死并感染患者，在全部去除小腿肌肉、骨间膜、肌间血管和腓骨，仅以小腿皮肤筋膜包绕胫骨连接踝足，术中发现踝关节水平下胫后动脉内无血栓，并有微量暗红色血液外溢，一期经踝行健侧胫后动脉转位与患肢胫后动脉吻合，二期进行健侧胫后动脉长段分离，向患侧转位，完成患肢胭动脉直接向足和小腿的动脉供血。结果 术后7个月患足基本恢复了触痛觉，患肢皮温、皮色正常，足部肌肉及关节无挛缩畸形，可平稳站立，可持拐行走。结论 当小腿肌肉、肌间血管因坏死感染被全部去除时，小腿皮肤、深浅筋膜组织与胫骨内血供系统之间形成的网状侧支循环，能为患足提供微量供血，延缓足的坏死或缺血挛缩；对此类患者进行动脉血运重建，可使伤肢获得良好的成活效果。     

MR-guided laser thermal ablation of primary and secondary liver tumours

AIM: To test the hypothesis that magnetic resonance (MR)-guided hepatic tumour ablation is (i) safe and feasible, (ii) is associated with favourable patient survival, and (iii) decreases viable tumour. MATERIALS AND METHODS: One hundred and twenty-five MR-guided laser thermal ablations (LTA) were performed on 35 patients with hepatocellular carcinoma (HCC, n=19), hepatic metastases (n=11, mainly colorectal) and carcinoid liver tumours (n=5). RESULTS: Mean overall survival was 14.8 months (HCCs 14.6 months, metastases 15.2 months). Near real-time T1-weighted colourized thermal maps correlated moderately with follow-up gadolinium-enhanced MR imaging in predicting ablated tumour area (Pearson correlation coefficient=0.5). There was a significant difference in percentage enhancing pre- and post-LTA (Wilcoxon signed ranks test=0.0001). An average of 50.7% of tumour was ablated by each treatment. In patients with multiple liver tumours ablated tumours grew significantly less than untreated tumours (108%compared with 196% growth, follow-up period 5.8 months, WSRTp=0.07). CONCLUSION: MR- guided LTA of primary and secondary liver tumours is safe, feasible, and significantly decreased amount of enhancing or viable tumour. MR-guided LTA produces a better survival in patients with HCC than would be expected in untreated patients, and has a mean survival in patients with metastases at least equal to the longest median survival in untreated patients.     

Percutaneous laser ablation of unresectable primary and metastatic adrenocortical carcinoma

PURPOSE: To evaluate the feasibility, safety, and clinical benefits of percutaneous laser ablation (PLA) in patients with unresectable primary and metastatic adrenocortical carcinoma (ACC). PATIENTS AND METHODS: Four patients with hepatic metastases from ACC and a Cushing's syndrome underwent ultrasound-guided PLA. In one case the procedure was performed also on the primary tumor. RESULTS: After three sessions of PLA, the primary tumor of 15 cm was ablated by 75%. After 1-4 (median 1) sessions of PLA, five liver metastases ranging from 2 to 5 cm were completely ablated, while the sixth tumor of 12 cm was ablated by 75%. There were no major complications. Treatment resulted in an improvement of performance status and a reduction of the daily dosage of mitotane in all patients. The three patients with liver metastases presented a marked decrease of 24-h urine cortisol levels, an improved control of hypertension and a mean weight loss of 2.8 kg. After a median follow-up after PLA of 27.0 months (range, 9-48 months), two patients have died of tumor progression, while two other patients remain alive and free of disease. CONCLUSIONS: Percutaneous laser ablation is a feasible, safe and well tolerated procedure for the palliative treatment of unresectable primary and metastatic ACC. Further study is required to evaluate the impact of PLA on survival.