Nils Rathmann

Microwave Ablation of Osteoid Osteomas Using Dynamic MR Imaging for Early Treatment Assessment: Preliminary Experience

PURPOSE To evaluate the efficacy of microwave ablation for osteoid osteomas by using dynamic contrast-enhanced magnetic resonance (MR) imaging in early treatment assessment. MATERIALS AND METHODS Ten patients (two female, eight male; mean age, 28 y; range, 16-47 y) presenting with osteoid osteomas were treated between June 2010 and December 2012 with the use of computed tomography (CT)-guided microwave ablation. Osteoid osteomas were found at the femoral neck (n = 4), tibia (n = 3), calcaneus (n = 1), navicular bone (n = 1), and dorsal rib (n = 1). Dynamic contrast-enhanced MR imaging at 3.0 T was performed 1 day before microwave ablation and again after ablation. The procedure was considered successful if the signal intensity (SI) of the lesion on MR imaging decreased by at least 50% and the patient was pain-free within 1 week of intervention. RESULTS All patients were pain-free within 1 week after microwave ablation and remained so during the 6 months of follow-up. No major or minor complications developed. On average, SI of the lesions decreased by 75% (range, 55.5%-89.1%) after treatment. The difference in lesion SI before versus after ablation was significant by t test (P < .0001; confidence interval, 120.26-174.96) and Wilcoxon test (P = .0020). CONCLUSIONS Microwave ablation treatment of osteoid osteoma was highly successful, without any complications observed. Dynamic contrast-enhanced MR imaging is a useful tool for diagnosing osteoid osteoma and evaluating treatment.

Small Field-of-view single-shot EPI-DWI of the prostate: Evaluation of spatially-tailored two-dimensional radiofrequency excitation pulses

PURPOSE Spatially-tailored (RF) excitation pulses in echo-planar imaging (EPI), combined with a decreased FOV in the phase-encoding direction, enable a reduction of k-space acquisition lines, which shortens the echo train length (ETL) and reduces susceptibility artifacts. The purpose of this study was to evaluate the image quality of a zoomed EPI (z-EPI) sequence in diffusion-weighted imaging (DWI) of the prostate in comparison to a conventional single-shot EPI using single-channel (c-EPI1) and multi-channel (c-EPI2) RF excitation, with and without use of an endorectal coil. MATERIALS AND METHODS 33 consecutive patients (mean age: 61 +/- 9 years; mean PSA: 8.67±6.23 ng/ml) with examinations between 10/2012 and 02/2014 were analyzed in this retrospective study. In 26 of 33 patients the initial multiparametric (mp)-MRI was performed on a whole-body 3T scanner (Magnetom Trio, Siemens, Erlangen, Germany) using an endorectal coil (c (conventional)-EPI1). Zoomed-EPI (Z-EPI) examinations of these patients and a complete mp-MRI protocol including c-EPI2 of 7 additional patients were carried out on another 3T wb MR scanner with two-channel dynamic parallel transmit capability (Magnetom Skyra with TimTX TrueShape, Siemens). For z-EPI, the one-dimensional spatially selective RF excitation pulse was replaced by a two-dimensional RF pulse. Degree of image blur and susceptibility artifacts (0=not present to 3= non-diagnostic), maximum image distortion (mm), apparent diffusion coefficient (ADC) values, as well as overall scan preference were evaluated. SNR maps were generated to compare c-EPI2 and z-EPI. RESULTS Overall image quality of z-EPI was preferred by both readers in all examinations with a single exception. Susceptibility artifacts were rated significantly lower on z-EPI compared to both other methods (z-EPI vs c-EPI1: p<0.01; z-EPI vs c-EPI2: p<0.01) as well as image blur (z-EPI vs c-EPI1: p<0.01; z-EPI vs c-EPI2: p<0.01). Image distortion was not statistically significantly reduced with z-EPI (z-EPI vs c-EPI1: p=0.12; z-EPI vs c-EPI2: p=0.42). Interobserver agreement for ratings of susceptibility artifacts, image blur and overall scan preference was good. SNR was higher for z-EPI than for c-EPI1 (n=1). CONCLUSION Z-EPI leads to significant improvements in image quality and artifacts as well as image blur reduction improving prostate DWI and enabling accurate fusion with conventional sequences. The improved fusion could lead to advantages in the field of MRI-guided biopsy suspicous lesions and performance of locally ablative procedures for prostate cancer.

Irreversible Electroporation for Surgical Renal Masses in Solitary Kidneys: Short-Term Interventional and Functional Outcome

PURPOSE To examine short-term outcomes and complications in patients with a solitary kidney treated with irreversible electroporation (IRE) for a potentially malignant renal mass. MATERIALS AND METHODS Five patients (2 female, 3 male; mean age, 66 y) with 7 lesions who underwent IRE for renal tumors in a solitary kidney between August 2014 and August 2015 were retrospectively reviewed. Changes in signal intensity (SI) of the treated lesion were evaluated on contrast-enhanced magnetic resonance imaging. To evaluate functional outcome, creatinine levels and estimated glomerular filtration rate (eGFR) were compared vs baseline after 1 day, 2-7 days, 3-6 weeks, and 6-12 weeks after the intervention. RESULTS Mean tumor diameter was 24.4 mm (range, 15-38 mm), with an average score of 7.7 (range, 4-9) per R.E.N.A.L. criteria (radius, exophytic/endophytic, nearness to collecting system or sinus, anterior/posterior, and location relative to polar lines). There was a progressive, significant decrease in treated tumor SI on follow-up imaging (mean, 70%-82%), suggesting a treatment response rate of 100% at a mean follow-up of 6.4 months (range, 3-11 mo). Two minor acute complications (Society of Interventional Radiology class A) occurred: transient gross hematuria and stage I acute kidney failure. Overall, there was no significant decrease in eGFR (-2.75 mL/min) over 3 months, even though 1 patients eGFR decreased from > 60 mL/min/1.73m(2) to 44 mL/min/1.73m(2). CONCLUSIONS The data suggest that percutaneous IRE for renal mass in patients with a solitary kidney is safe and feasible. It may help to preserve renal function and offers promising short-term oncologic results.

Radioembolization in patients with progressive gastrointestinal stromal tumor liver metastases undergoing treatment with tyrosine kinase inhibitors.

PURPOSE Gastrointestinal stromal tumors (GISTs) spread frequently to the peritoneum and the liver. If metastasectomy or tyrosine kinase inhibitors (TKIs) fail, interventional ablation techniques are considered. The purpose of this study is to assess the progression-free interval (PFI) of GIST liver metastases after radioembolization (RE). MATERIALS AND METHODS Eleven patients with progressive GIST liver metastases undergoing TKI therapy were referred for RE; one was excluded because of a large hepatopulmonary shunt, and one was lost to follow-up. Depending on intrahepatic tumor distribution, one or both liver lobes were treated with RE. Contrast-enhanced magnetic resonance imaging, contrast-enhanced computed tomography (CT), and [(18)F]fluorodeoxyglucose positron-emission tomography/CT were used for follow-up. RESULTS In all, 16 liver lobes were treated with a mean activity of 1.06 GBq ± 0.37 (range, 0.55-1.88) per lobe. Three patients showed complete response, five showed partial response, and one showed stable disease. No patient showed progressive disease after RE. Median PFI was 15.9 months (range, 4-29 mo). Median survival was 29.8 months (range, 10-72 mo). No radiation-induced liver disease developed; however, one patient required surgery for persistent stomach ulcer. CONCLUSIONS RE offers a safe and effective treatment for patients with GIST liver metastases who do not show a response to TKIs. RE could be an option for earlier phases of therapy in patients with mutational status. The results might also challenge the notion that GISTs are resistant to radiation therapy.

Evaluation of Radiation Exposure of Medical Staff During CT-Guided Interventions

PURPOSE The purpose of this prospective study was to investigate absolute radiation exposure values and factors that influence radiation exposure of interventionists during CT-guided interventions (CTGIs). To our knowledge, no data exist regarding the radiation dose to which the interventionist is exposed during these procedures. METHODS Absolute radiation dose values from a total of 131 CTGIs were analyzed. Radiation dose values were collected by thermoluminescent dosimeters that were positioned above the lead protection being worn, on the forehead, thyroid, chest, gonads, and right and left hand and foot. The radiation doses were analyzed with respect to the experience level of the person performing the procedure, the degree of difficulty measured on a 4-point Likert scale, the lesion size measured on a 3-point Likert scale, and the CT system used. RESULTS Median whole-body dose was 12 μSv. With the exception of the forehead, all whole-body radiation doses were statistically significantly lower in CTGIs performed using the modern dual-source CT system compared with the 16-slice multi-detector CT. For CTGIs rated as more complex, the radiation exposure of the radiologist performing the procedure was statistically significantly higher, with the exception of the left hand. A statistically significantly lower median whole-body dose was measured for inexperienced compared with experienced radiologists. However, a few dose measurements of more than 1 mSv were found at the right hand. CONCLUSIONS Radiation exposure measured during CTGIs is low (<50 μSv). Because the radiation dose was higher in more-complex interventions and for 16-slice multi-detector row CT, inexperienced radiologists should focus on less-complex procedures.

Computed Tomography–Assisted Thoracoscopic Surgery: A Novel, Innovative Approach in Patients With Deep Intrapulmonary Lesions of Unknown Malignant Status

Objectives Minimally invasive resection of small, deep intrapulmonary lesions can be challenging due to the difficulty of localizing them during video-assisted thoracoscopic surgery (VATS). We report our preliminary results evaluating the feasibility of an image-guided, minimally invasive, 1-stop-shop approach for the resection of small, deep intrapulmonary lesions in a hybrid operating room (OR). Materials and Methods Fifteen patients (5 men, 10 women; mean age, 63 years) with a total of 16 solitary, deep intrapulmonary nodules of unknown malignant status were identified for intraoperative wire marking. Patients were placed on the operating table for resection by VATS. A marking wire was placed within the lesion under 3D laser and fluoroscopic guidance using a cone beam computed tomography system. Then, wedge resection by VATS was performed in the same setting without repositioning the patient. Results Complete resection with adequate safety margins was confirmed for all lesions. Marking wire placement facilitated resection in 15 of 16 lesions. Eleven lesions proved to be malignant, either primary or secondary; 5 were benign. Mean lesion size was 7.7 mm; mean distance to the pleural surface was 15.1 mm (mean lesion depth–diameter ratio, 2.2). Mean procedural time for marking wire placement was 35 minutes; mean VATS duration was 36 minutes. Conclusions Computed tomography–assisted thoracoscopic surgery is a new, safe, and effective procedure for minimally invasive resection of small, deeply localized intrapulmonary lesions. The benefits of computed tomography–assisted thoracoscopic surgery are 1. One-stop-shop procedure, 2. Lower risk for the patient (no patient relocation, no marking wire loss), and 3. No need to coordinate scheduling between the CT room and OR.

Accuracy of percutaneous soft-tissue interventions using a multi-axis, C-arm CT system and 3D laser guidance.

INTRODUCTION Purpose of this phantom study was to compare the accuracy of needle placement using a multi-axis, C-arm-based, flat-panel, cone-beam computed tomography system (CBCT guidance) with that under multi-detector computed tomography guidance (MDCT guidance). MATERIALS AND METHODS In an abdominal phantom, eight lesions (six lesions in the liver and two in the renal pelvises, respectively) were each punctured in-plane and off-plane with a 20G needle under CBCT and MDCT guidance. Access paths were initially defined and reproduced identically on the two systems. In total, 32 interventions were conducted. CBCT and MDCT guidance was compared prospectively with respect to technical success, accuracy, and overall procedural time. RESULTS All 32 interventions were technically successful in that it was possible to hit the respective lesion in each procedure. When comparing the accuracy of MDCT to CBCT guidance there was no significant difference in absolute, angular, and longitudinal deviation for either in- or off-plane interventions. Overall procedural duration was significantly longer under CBCT guidance for in-plane interventions (888 vs 527s, p=0.00005), whereas, for off-plane procedures there was no significant difference between CBCT and MDCT guidance (920 vs 701s, p=0.08). Off-plane interventions took significantly longer than in-plane interventions under MDCT guidance (701 vs 527s, p=0.03), whereas under CBCT guidance no significant difference could be found between off- and in-plane procedures (920 vs. 888s, p=0.2). CONCLUSIONS In this phantom study, we could show that percutaneous soft-tissue interventions under CBCT guidance can be conducted with an accuracy comparable to that under MDCT guidance. Although overall procedural duration is in general shorter using MDCT guidance, CBCT-guided interventions offer the advantage of more degrees of freedom, which is of particular importance for off-plane procedures.

Radiation exposure of the interventional radiologist during percutaneous biopsy using a multiaxis interventional C-arm CT system with 3D laser guidance: a phantom study

OBJECTIVE Evaluation of absolute radiation exposure values for interventional radiologists (IRs) using a multiaxis interventional flat-panel C-arm cone beam CT (CBCT) system with three-dimensional laser guidance for biopsy in a triple-modality, abdominal phantom. METHODS In the phantom, eight lesions were punctured in two different angles (in- and out-of-plane) using CBCT. One C-arm CT scan was performed to plan the intervention and one for post-procedural evaluation. Thermoluminescent dosemeters (TLDs) were used for dose measurement at the level of the eye lens, umbilicus and ankles on a pole representing the IRs. All measurements were performed without any lead protection. In addition, the dose-area product (DAP) and air kerma at the skin entrance point was documented. RESULTS Mean radiation values of all TLDs were 190 µSv for CBCT (eye lens: 180 µS, umbilicus: 230 µSv, ankle: 150 µSv) without a significant difference (p > 0.005) between in- and out-of-plane biopsies. In terms of radiation exposure of the phantom, the mean DAP was not statistically significantly different (p > 0.05) for in- and out-of-plane biopsies. Fluoroscopy showed a mean DAP of 7 or 6 μGym(2), respectively. C-arm CT showed a mean DAP of 5150 or 5130 μGym(2), respectively. CONCLUSION In our setting, the radiation dose to the IR was distinctly high using CBCT. For dose reduction, it is advisable to pay attention to lead shielding, to increase the distance to the X-ray source and to leave the intervention suite for C-arm CT scans. ADVANCES IN KNOWLEDGE The results indicate that using modern navigation tools and CBCT can be accompanied with a relative high radiation dose for the IRs since detector angulation can make the use of proper lead shielding difficult.

Cardiac impact of R-wave triggered irreversible electroporation therapy

BACKGROUND Irreversible electroporation (IRE) is a novel tumor ablative therapy technique, using electric fields to induce apoptosis in target tissues. Whether these electric pulses of high field strength can cause cardiac damage and/or ablation-induced arrhythmias is unclear. OBJECTIVE The purpose of this study was to systematically evaluate the safety of electrocardiogram (ECG)-gated IRE with regard to cardiac side effects. METHODS In all patients, 12-lead ECG and signal-averaged ECG (SAECG) recordings were performed before and after IRE and 24-hour Holter recording on the day of the IRE procedure. Venous blood samples (N-terminal pro-brain-type natriuretic peptide [NT-proBNP], high-sensitive troponin I [hsTnI]) were obtained before and 4 and 16 hours after the procedure. Patients with abnormal findings were reevaluated after 3 months. RESULTS In total, 26 patients with an oncologic indication for IRE (11 females, mean age 62.9 years) were prospectively enrolled. Nine patients (34.6%) showed an increase in hsTnI and 21 patients (80.8%) an increase in NT-proBNP after ablation. Fifteen patients (57%) developed arrhythmias related to the procedure. One patient, in whom hsTnI and NT-proBNP had increased, developed multiple, nonsustained ventricular tachycardia events. In another patient, atrial fibrillation was triggered twice in 2 separate procedures. Twelve patients had clinically benign arrhythmias. SAECG was negative in all patients. CONCLUSION Subclinical myocardial injury and nonfatal cardiac arrhythmias can occur in the context of IRE treatment. Although no sustained cardiac injuries could be found at 3-month follow-up, we propose implementation of a cardiac safety algorithm consisting of cardiac biomarkers and ECG monitoring when IRE is conducted.

Management of Progressive Pulmonary Nodules Found during and outside of CT Lung Cancer Screening Studies

ABSTRACT Although the effectiveness of screening for lung cancer remains controversial, it is a fact that most lung cancers are diagnosed at an advanced stage outside of lung cancer screening programs. In 2013, the U.S. Preventive Services Task Force revised its lung cancer screening recommendation, now supporting lung cancer screening by low‐dose computed tomography in patients at high risk. This is also endorsed by many major medical societies and advocacy group stakeholders, albeit with different eligibility criteria. In Europe, population‐based lung cancer screening has so far not been recommended or implemented, as some important issues remain unresolved. Among them is the open question of how enlarging pulmonary nodules detected in lung cancer screening should be managed. This article comprises two parts: a review of the current lung cancer screening approaches and the potential therapeutic options for enlarging pulmonary nodules, followed by a meeting report including consensus statements of an interdisciplinary expert panel that discussed the potential of the different therapeutic options.