Experiments on physical ablation of long bone using microwave ablation; defining optimal settings using ex- and in-vivo experiments

BACKGROUND

Improved survival of cancer patients leads to more skeletal metastatic lesions that need local therapies for tumor control and pain relief. Not all tumors are radiosensitive and alternative therapies are direly needed. Microwave ablation (MWA) is a technique for minimally invasive local tumor control by physical ablation. In soft tissue local temperature ablation is more common, but studies on bone tissue are limited. To ensure safe and effective treatment, studies on local tumor ablation in bone are needed.

METHOD

Microwave ablation was performed on sheep bone, for both in- and ex-vivo settings. Both a slow-cooking MWA protocol (gradually increasing wattage in the first two minutes of ablation) and a fast-cooking protocol (no warm-up period) were used. Heat distribution through the bone during ablation was determined by measuring temperature at 10- and 15mm from the ablation probe (= needle). Ablation size after procedure was measured using nitro-BT staining.

RESULTS

In-vivo ablations led to up to six times larger halos than ex-vivo with the same settings. Within both ex- and in-vivo experiments, no differences in halo size or temperature were found for different wattage levels (65W vs 80W). Compared to a fast cooking protocol, a two-minute slow cooking protocol led to increased temperatures and larger halos. Temperatures at 10- and 15mm distance from the needle no longer increased after six minutes. Halo sizes kept increasing over time without an evident plateau.

CONCLUSION

Microwave ablation is technically effective for creating cell death in (sheep) long bone. It is recommended to start ablations with a slow-cooking period, gradually increasing the surrounding tissue temperature in two minutes from 40 to 90°C. Ex-vivo results cannot simply be translated to in-vivo.

Contribution of pathogenic T helper 1 and 17 cells to bursitis and tenosynovitis in polymyalgia rheumatica

Background

Although polymyalgia rheumatica (PMR) is a very common rheumatic inflammatory disease, current insight into the pathobiology of PMR is limited and largely based on studies in blood. We investigated T helper 1 (T_H1) and T helper 17 (T_H17) cell responses in blood, synovial fluid and bursa tissue of patients with PMR.

Materials and methods

Blood samples were collected from 18 patients with new-onset PMR and 32 healthy controls. Synovial fluid was aspirated from the inflamed shoulder bursae or biceps tendon sheath of 13 patients. Ultrasound-guided biopsies of the subacromial-subdeltoid (SASD) bursa were obtained from 11 patients. T cells were examined by flow cytometry, immunohistochemistry and immunofluorescence staining.

Results

Besides an increase of T_H17 (CD4⁺IL-17⁺IFN-γ^-) cells and T cytotoxic 17 (T_C17; CD8⁺IL-17⁺IFN-γ^-) cells, no other major changes were noted in the circulating T cell compartment of patients with PMR. Absolute numbers of CD4⁺ and CD8⁺ T cells were similar in blood and synovial fluid of patients with PMR. Synovial fluid T cells showed an effector-memory (CD45RO⁺CCR7^-) phenotype. Percentages of T_H1 (CD4⁺IFN-γ⁺IL-17^-) cells and T_H1/T_H17 (CD4⁺IFN-γ⁺IL-17⁺) cells, but not T_H17 or T_C17 cells, were increased in the synovial fluid. Bursa tissue biopsies contained a small number of T cells, which were mostly CD8 negative. The majority of bursa tissue T cells produced IFN-γ but not IL-17. For comparison, B cells were scarcely detected in the bursa tissue.

Conclusion

Although the circulating T_H17 cell pool is expanded in patients with PMR, our findings indicate that T_H1 cells are involved in the inflammation of bursae and tendon sheaths in this condition. Our study points towards the T_H1 cell pathway as a potential target for therapy in PMR.

Semi-Quantitative Characterization of Post-Transplant Lymphoproliferative Disorder Morphological Subtypes with [18F]FDG PET/CT

Background: Post-transplant lymphoproliferative disorder (PTLD) is a complication of organ transplantation classified according to the WHO as nondestructive, polymorphic, monomorphic, and classic Hodgkin Lymphoma subtypes. In this retrospective study, we investigated the potential of semi-quantitative 2-[¹⁸F]fluoro-2-deoxy-D-glucose ([¹⁸F]FDG) PET/computed tomography (CT)-based parameters to differentiate between the PTLD morphological subtypes. Methods: 96 patients with histopathologically confirmed PTLD and baseline [¹⁸F]FDG PET/CT between 2009 and 2019 were included. Extracted semi-quantitative measurements included: Maximum, peak, and mean standardized uptake value (SUV_max, SUV_peak, and SUV_mean). Results: Median SUVs were highest for monomorphic PTLD followed by polymorphic and nondestructive subtypes. The median SUV_peak at the biopsy site was significantly higher in monomorphic PTLD (17.8, interquartile range (IQR):16) than in polymorphic subtypes (9.8, IQR:13.4) and nondestructive (4.1, IQR:6.1) (p = 0.04 and p ≤ 0.01, respectively). An SUV_peak ≥ 24.8 was always indicative of a monomorphic PTLD in our dataset. Nevertheless, there was a considerable overlap in SUV across the different morphologies. Conclusion: The median SUV_peak at the biopsy site was significantly higher in monomorphic PTLD than polymorphic and nondestructive subtypes. However, due to significant SUV overlap across the different subtypes, these values may only serve as an indication of PTLD morphology, and SUV-based parameters cannot replace histopathological classification.

Radiofrequency ablation of atypical cartilaginous tumors in long bones: a retrospective study

Purpose: To determine the size of the ablation zone after radiofrequency ablation (RFA) of atypical cartilaginous bone tumors (ACT) using temperature-controlled 20 and 30 mm RFA straight non-cooled electrodes.Materials and methods: Sixteen patients with ACT in their long bones, who had undergone a single-session single-application CT-guided temperature-controlled RFA, were included retrospectively in the study. Tumors with a diameter of 10-25 mm were treated with 20 mm electrodes (n = 10), and tumors of 25-35 mm, with 30 mm electrodes (n = 6). The ablated zone was measured after three months on MRI images.Results: All the tumors were within the ablated zone on the 3-month follow-up MRI scan. The mean ablation time with the electrode, at a target temperature of 90 °C, was 7.6 minutes (range 6-10). The median of the largest ablation diameters, on applying the 20 and 30 mm electrodes, were 42 mm (IQR 8.5, range 30-51 mm) and 44.5 mm (IQR 4.5, range 42-63 mm), respectively.Conclusions: All the retrospectively viewed tumors in the long bones of ACT patients treated with RFA were completely ablated. The ablation zone diameters in the bones were larger than expected, when compared to other tissues, such as the liver.

Whole-body MRI using a sliding table and repositioning surface coil approach

Objective

To introduce and assess a new way of performing whole-body magnetic resonance imaging (MRI) using a non-integrated surface coil approach as available on most clinical MRI systems worldwide.

Methods

Ten consecutive asymptomatic subjects prospectively underwent whole-body MRI for health screening. Whole-body MRI included T1-, T2- and diffusion-weighted sequences, and was performed using a non-integrated surface coil to image four different stations without patient repositioning. The four separately acquired stations were merged, creating seamless coronal whole-body T1-, T2- and diffusion-weighted images. Anatomical alignment, image quality at the boundaries of adjacent stations, and overall image quality of all stations were qualitatively assessed.

Results

The average time (±SD) taken to change the surface coil from one station to the next station was 53.8 (±7.1) s. The average total extra examination time ± SD was 2 min 41.4 s (±15.3 s). Anatomical alignment, image quality at the boundaries of adjacent stations, and overall image quality of all stations of T1-, T2- and diffusion-weighted whole-body MRI were overall graded as “good” to “excellent”.

Conclusion

This study shows that a time-efficient and high-quality whole-body MRI examination can easily be performed by using a non-integrated sliding surface coil approach.

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-009-1674-1) contains supplementary material, which is available to authorized users.

[Chylous ascites after tumor nephrectomy with retroperitoneal lymphadenectomy]

Chylous ascites is a rare postoperative complication in pediatric surgery. Small numbers of cases are reported from abdominal tumor- and vascular surgery. Following a case report about a 2 year old girl with Nephroplastoma, a review about etiology, course and therapy of described cases in the literature is given.