Analysis of patient's X-ray exposure in hepatic chemosaturation procedures: a single center experience.

BACKGROUND: Hepatic chemosaturation is a technique in which a high dose of the chemotherapeutic agent melphalan is administered directly into the liver while limiting systemic side effects. We reviewed our institutional experience regarding patient's X-ray exposure caused by the procedure. METHODS: Fifty-five procedures, performed between 2016 and 2020 in 18 patients by three interventional radiologists (radiologist), were analyzed regarding the patient's exposure to radiation. Dose-area-product (DAP) and fluoroscopy time (FT) were correlated with the experience of the radiologist and whether the preprocedural evaluation (CS-EVA) and the procedure were performed by the same radiologist. Additionally, the impact of previous liver surgery on DAP/FT was analyzed. RESULTS: Experienced radiologist require less DAP/FT (50 ± 18 Gy*cm2/13.2 ± 3.84 min vs. 69 ± 20 Gy*cm2/15.77 ± 7.82 min; p < 0.001). Chemosaturations performed by the same radiologist who performed CS-EVA required less DAP/FT (41 ± 12 Gy*cm2/11.46 ± 4.41 min vs. 62 ± 11 Gy*cm2/15.55 ± 7.91 min; p < 0.001). Chemosaturations in patients with prior liver surgery with involvement of the inferior cava vein required significantly higher DAP/FT (153 ± 27 Gy*cm2/25.43 ± 4.57 min vs. 56 ± 25 Gy*cm2/14.44 ± 7.55 min; p < 0.001). CONCLUSION: There is a significant learning curve regarding the procedure of hepatic chemosaturation. Due to dose reduction the evaluation and chemosaturation therapy should be performed by the same radiologist. Procedures in patients with previous liver surgery require higher DAP/FT.

Clinical evaluation of in silico planning and real-time simulation of hepatic radiofrequency ablation (ClinicIMPPACT Trial).

OBJECTIVES: To evaluate the accuracy and clinical integrability of a comprehensive simulation tool to plan and predict radiofrequency ablation (RFA) zones in liver tumors. METHODS: Forty-five patients with 51 malignant hepatic lesions of different origins were included in a prospective multicenter trial. Prior to CT-guided RFA, all patients underwent multiphase CT which included acquisitions for the assessment of liver perfusion. These data were used to generate a 3D model of the liver. The intra-procedural position of the RFA probe was determined by CT and semi-automatically registered to the 3D model. Size and shape of the simulated ablation zones were compared with those of the thermal ablation zones segmented in contrast-enhanced CT images 1 month after RFA; procedure time was compared with a historical control group. RESULTS: Simulated and segmented ablation zone volumes showed a significant correlation (ρ = 0.59, p < 0.0001) and no significant bias (Wilcoxon's Z = 0.68, p = 0.25). Representative measures of ablation zone comparison were as follows: average surface deviation (absolute average error, AAE) with 3.4 ± 1.7 mm, Dice similarity coefficient 0.62 ± 0.14, sensitivity 0.70 ± 0.21, and positive predictive value 0.66 ± 0. There was a moderate positive correlation between AAE and duration of the ablation (∆t; r = 0.37, p = 0.008). After adjustments for inter-individual differences in ∆t, liver perfusion, and prior transarterial chemoembolization procedures, ∆t was an independent predictor of AAE (ß = 0.03 mm/min, p = 0.01). Compared with a historical control group, the simulation added 3.5 ± 1.9 min to the procedure. CONCLUSION: The validated simulation tool showed acceptable speed and accuracy in predicting the size and shape of hepatic RFA ablation zones. Further randomized controlled trials are needed to evaluate to what extent this tool might improve patient outcomes. KEY POINTS: • More reliable, patient-specific intra-procedural estimation of the induced RFA ablation zones in the liver may lead to better planning of the safety margins around tumors. • Dedicated real-time simulation software to predict RFA-induced ablation zones in patients with liver malignancies has shown acceptable agreement with the follow-up results in a first prospective multicenter trial suggesting a randomized controlled clinical trial to evaluate potential outcome benefit for patients.

In-bore biopsies of the prostate assisted by a remote-controlled manipulator at 1.5 T.

PURPOSE: To evaluate the technical and clinical utility of a fully MRI-compatible, pneumatically driven remote-controlled manipulator (RCM) for targeted biopsies of the prostate at 1.5 T. MATERIALS AND METHODS: The data of the first 22 patients that were biopsied under robotic assistance were analyzed. Interventional planning relied on T2-weighted (T2w) turbo spin-echo (TSE) images (axial and sagittal) with a high-b-value diffusion-weighted acquisition added in selected cases. Alignment of the needle guide was controlled with a short balanced SSFP sequence in two oblique planes along the MR-visible sheath. Signals were acquired with a combination of elements from a 30-channel body and a 32-channel spine coil. Biopsy samples were taken with a fully automatic 18-G biopsy gun with a length of 150 or 175 mm. RESULTS: Mean age was 66.6 years and average PSA level was 11.5 ng/ml. Fourteen out of 22 patients (63%) had received prior biopsies under transrectal ultrasound guidance. Diagnostic MRI reports (before biopsy) involved 17 cases with a single suspicious finding (four PI-RADS 3, one PI-RADS 3-4, eight PI-RADS 4 and nine PI-RADS 5 cases). The median effective procedure time was 33.9 (range 25.0-55.9) min for 16 cases with one CSR and 63.4 (52.7-81.8) min for 5 cases with two CSRs. The biopsy with three CSRs took 74.0 min. Histopathologic examination revealed prostate cancer in 14 of 22 cases. CONCLUSION: MR-targeted, transrectal biopsy of the prostate could be reliably performed with a robotic manipulator at a field strength of 1.5 T. Balanced SSFP imaging is considered a viable option for fast procedural control. Follow-up work needs to evaluate to what extent in-bore adjustments and workflow enhancements will contribute to shorter procedure times or higher patient comfort.

Navigated MRI-guided liver biopsies in a closed-bore scanner: experience in 52 patients.

OBJECTIVES: To evaluate clinical effectiveness and diagnostic efficiency of a navigation device for MR-guided biopsies of focal liver lesions in a closed-bore scanner. METHODS: In 52 patients, 55 biopsies were performed. An add-on MR navigation system with optical instrument tracking was used for image guidance and biopsy device insertion outside the bore. Fast control imaging allowed visualization of the true needle position at any time. The biopsy workflow and procedure duration were recorded. Histological analysis and clinical course/outcome were used to calculate sensitivity, specificity and diagnostic accuracy. RESULTS: Fifty-four of 55 liver biopsies were performed successfully with the system. No major and four minor complications occurred. Mean tumour size was 23 ± 14 mm and the skin-to-target length ranged from 22 to 177 mm. In 39 cases, access path was double oblique. Sensitivity, specificity and diagnostic accuracy were 88 %, 100 % and 92 %, respectively. The mean procedure time was 51 ± 12 min, whereas the puncture itself lasted 16 ± 6 min. On average, four control scans were taken. CONCLUSIONS: Using this navigation device, biopsies of poorly visible and difficult accessible liver lesions could be performed safely and reliably in a closed-bore MRI scanner. The system can be easily implemented in clinical routine workflow. KEY POINTS: • Targeted liver biopsies could be reliably performed in a closed-bore MRI. • The navigation system allows for image guidance outside of the scanner bore. • Assisted MRI-guided biopsies are helpful for focal lesions with a difficult access. • Successful integration of the method in clinical workflow was shown. • Subsequent system installation in an existing MRI environment is feasible.

Alternative treatment of symptomatic pancreatic fistula.

BACKGROUND: The management of symptomatic pancreatic fistula after pancreaticoduodenectomy is complex and associated with increased morbidity and mortality. We here report continuous irrigation and drainage of the pancreatic remnant to be a feasible and safe alternative to total pancreatectomy. MATERIALS AND METHODS: Between 2005 and 2011, patients were analyzed, in which pancreaticojejunal anastomosis was disconnected because of grade C fistula, and catheters for continuous irrigation and drainage were placed close to the pancreatic remnant. Clinical data were monitored and quality of life was evaluated. RESULTS: A total of 13 of 202 patients undergoing pancreaticoduodenectomy required reoperation due to symptomatic pancreatic fistula. Ninety-day mortality of these patients was 15.3%. Median length of stay on the intensive care unit and total length of stay was 18 d (range 3-45) and 46 d (range 33-96), respectively. Patients with early reoperation (<10 d) had significantly decreased length of stay on the intensive care unit and operation time (P < 0.05). Global health status after a median time of 22 mo (range 6-66) was nearly identical, when compared with that of a healthy control group. Mean follow-up was 44.4 mo (±27.2). Four patients (36.6 %) died during the follow-up period; two patients from tumor recurrence, one patient from pneumonia, and one patient for unknown reasons. CONCLUSIONS: Treatment of pancreatic fistula by continuous irrigation and drainage of the preserved pancreatic remnant is a simple and feasible alternative to total pancreatectomy. This technique maintains a sufficient endocrine function and is associated with low mortality and reasonable quality of life.

Non-invasive estimation of prostate cancer aggressiveness using diffusion-weighted MRI and 3D proton MR spectroscopy at 3.0 T.

BACKGROUND: Clinical management of prostate cancer increasingly aims to distinguish aggressive types that require immediate and radical treatment from indolent tumors that are candidates for watchful waiting. This requires reliable and reproducible parameters to effectively control potential cancer progression. Magnetic resonance imaging (MRI) may provide a non-invasive means for this purpose. PURPOSE: To assess the value of diffusion-weighted imaging and proton MR spectroscopy for the prediction of prostate cancer (PCa) aggressiveness. MATERIAL AND METHODS: In 39 of 64 consecutive patients who underwent endorectal 3-T MRI prior to radical prostatectomy, prostate specimens were analyzed as whole-mount step sections. Apparent diffusion coefficient (ADC), normalized ADC (nADC: tumor/healthy tissue), choline/citrate (CC), and (choline + creatine)/citrate (CCC) ratios were correlated with Gleason scores (GS) from histopathological results. The power to discriminate low (GS ≤ 6) from higher-risk (GS ≥ 7) tumors was assessed with receiver operating characteristics (area under the curve [AUC]). Resulting threshold values were used by a blinded reader to distinguish between aggressive and indolent tumors. RESULTS: Ninety lesions (1 × GS = 5, 41 × GS = 6, 36 × GS = 7, 12 × GS = 8) were considered. nADC (AUC = 0.90) showed a higher discriminatory power than ADC (AUC = 0.79). AUC for CC and CCC were 0.73 and 0.82, respectively. Using either nADC < 0.46 or CCC > 1.3, as well as both criteria for aggressive PCa, the reader correctly identified aggressive and indolent tumors in 31 (79%), 28 (72%), and 33 of 39 patients (85%), respectively. Predictions of tumor aggressiveness from TRUS-guided biopsies were correct in 27 of 36 patients (75%). CONCLUSION: The combination of a highly sensitive normalized ADC with a highly specific CCC was found to be well suited to prospectively estimate PCa aggressiveness with a similar diagnostic accuracy as biopsy results.

Careful treatment planning enables safe ablation of liver tumors adjacent to major blood vessels by percutaneous irreversible electroporation (IRE).

BACKGROUND: Irreversible electroporation (IRE) is a tissue ablation method, which relies on the phenomenon of electroporation. When cells are exposed to a sufficiently electric field, the plasma membrane is disrupted and cells undergo an apoptotic or necrotic cell death. Although heating effects are known IRE is considered as non-thermal ablation technique and is currently applied to treat tumors in locations where thermal ablation techniques are contraindicated. MATERIALS AND METHODS: The manufacturer of the only commercially available pulse generator for IRE recommends a voltage-to-distance ratio of 1500 to 1700 V/cm for treating tumors in the liver. However, major blood vessels can influence the electric field distribution. We present a method for treatment planning of IRE which takes the influence of blood vessels on the electric field into account; this is illustrated on a treatment of 48-year-old patient with a metastasis near the remaining hepatic vein after a right side hemi-hepatectomy. RESULTS: Output of the numerical treatment planning method shows that a 19.9 cm3 irreversible electroporation lesion was generated and the whole tumor was covered with at least 900 V/cm. This compares well with the volume of the hypodense lesion seen in contrast enhanced CT images taken after the IRE treatment. A significant temperature raise occurs near the electrodes. However, the hepatic vein remains open after the treatment without evidence of tumor recurrence after 6 months. CONCLUSIONS: Treatment planning using accurate computer models was recognized as important for electrochemotherapy and irreversible electroporation. An important finding of this study was, that the surface of the electrodes heat up significantly. Therefore the clinical user should generally avoid placing the electrodes less than 4 mm away from risk structures when following recommendations of the manufacturer.

In vivo revascularization and tissue effects of uterine artery embolization with starch microspheres in sheep.

OBJECTIVE: In uterine artery embolization (UAE) for the treatment of fibroids, nondegradable particles permanently occlude the uterine artery (UA). These particles remain in the vessels and can cause secondary undesirable effects, such as severe pain after embolization and fertility issues. In this prospective experimental study, we aimed to evaluate the angiographic recanalization, local and systemic reactions, and uterine damage occurring after performing UAE with newly developed degradable starch microspheres (DSMs) in sheep. MATERIALS AND METHODS: Under general anesthesia, eight nonpregnant sheep underwent bilateral UAE using DSMs to achieve stasis. Angiographic evaluation was performed on days 1, 3 and 7 after embolization to assess in vivo recanalization. In addition, the angiographic series were scored via a modified embolization score. A postmortem tissue examination was performed to determine whether DSMs and foreign body inflammatory reactions were present and to assess uterine necrosis. RESULTS: Complete bilateral embolization of the UA and cervicovaginal branches was achieved in all treated animals. Recanalization of the occluded arteries was evident in 25 of 27 arteries during the angiographic evaluation. In all sheep, there were multifocal areas of uterine necrosis, and some uterine vessels contained intraluminal material consistent with DSMs. The average weight of both uterine horns was significantly correlated with both the number of microspheres needed for complete embolization (r = 0.69, ρ<0.01) and the average percentage of necrosis in both uterine horns (r = 0.64, ρ<0.05). CONCLUSIONS: Our findings demonstrated the efficacy of vascular embolization with DSM by inducing ischemic changes in the uterus and subsequent recanalization of previously occluded arteries.

Novel technique for MR elastography of the prostate using a modified standard endorectal coil as actuator.

PURPOSE: To present a novel method for MR elastography (MRE) of the prostate at 3 Tesla using a modified endorectal imaging coil. MATERIALS AND METHODS: A commercial endorectal coil was modified to dynamically generate mechanical stress (contraction and dilation) in a prostate phantom with embedded phantom "lesions" (6 mm diameter) and in a porcine model. Resulting tissue displacements were measured with a motion-sensitive EPI sequence at actuation frequencies of 50-200 Hz. Maps of shear modulus G were calculated from the measured phase-difference shear-wave patterns. RESULTS: In the G maps of the phantom, "lesions" were easily discernible against the background. The average G values of regions of interest placed in the "lesion" (8.2 ± 1.9 kPa) were much higher than those in the background (3.6 ± 1.4 kPa) but systematically lower than values reported by the vendor (13.0 ± 1.0 and 6.7 ± 0.7 kPa, respectively). In the porcine model, shear waves could be generated and measured shear moduli were substantially different for muscle (7.1 ± 2.0 kPa), prostate (3.0 ± 1.4 kPa), and bulbourethral gland (5.6 ± 1.9 kPa). CONCLUSION: An endorectal MRE concept is technically feasible. The presented technique will allow for simultaneous MRE and MRI acquisitions using a commercial base device with minor, MR-conditional modifications. The diagnostic value needs to be determined in further trials.

Outcome after open surgery repair in endovascular-suitable patients with ruptured abdominal aortic aneurysms.

BACKGROUND: Endovascular aneurysm repair (EVAR) has been suggested in several studies to be superior to open surgery repair (OSR) for the treatment of ruptured abdominal aortic aneurysms (rAAAs), but this finding might be affected by selection bias based on aneurysm morphology and patient characteristics. We tested rAAA anatomy according to EVAR suitability in patients undergoing OSR to assess the impact on mortality. PATIENTS AND METHODS: This retrospective analysis reports on 83 patients with rAAAs treated between November 2002 and July 2013. Pre-operative computed tomography (CT) scans were evaluated based on EVAR suitability and were determined by blinded independent reviewers. CT scans were lacking due to acquisition in an external institution with no availability (n = 9) or solely ultrasound evaluations (n = 8). In addition patient characteristics and outcomes were assessed. RESULTS: All patients who underwent OSR and who had available preoperative CT scans were included in the study (n = 66). In summary, 42 % of the patients (28/66; 95 % confidence interval [CI], 30.5 - 54.4) were considered eligible for EVAR according to pre-operative CT scans and 58 % of the patients (38/66; 95 % CI, 45.6 - 69.5) were categorized as unsuitable for endovascular repair. Patients suitable for EVAR had a significantly lower prevalence of in-hospital deaths (25 % [7/28]; 95 % CI, 9 - 41) in contrast to patients unsuitable for EVAR (53 % [20/38]; 95 % CI, 36.8 - 68.5; p = 0.02). CONCLUSIONS: EVAR-suitable patients had a highly significant mortality reduction undergoing OSR. Thus, the present study proposes that EVAR suitability is a positive predictor for survival after open repair of rAAA.

Diagnostic value of ADC in patients with prostate cancer: influence of the choice of b values.

OBJECTIVES: To evaluate the influence of the choice of b values on the diagnostic value of the apparent diffusion coefficient (ADC) for detection and grading of prostate cancer (PCa). METHODS: Forty-one patients with biopsy-proven PCa underwent endorectal 3-T MRI before prostatectomy. Different combinations of b values (0-800 s/mm(2)) were used to calculate four representative ADC maps. Mean ADCs of tumours and non-malignant tissue were determined. Tumour appearance on different ADC maps was rated by three radiologists as good, fair or poor by assigning a visual score (VS) of 2, 1 or 0, respectively. Differences in the ADC values with the choice of b values were analysed using one-way ANOVA. RESULTS: Choice of b values had a highly (P < 0.001) significant influence on the absolute ADC in each tissue. Maps using b = [50, 800] and [0, 800] were rated best (VS= 1.6 ± 0.3) and second best (1.1 ± 0.3, P < 0.001), respectively. For low-grade carcinomas (Gleason score ≤ 6, 13/41 patients), only the former choice received scores better than fair (VS = 1.4 ± 0.3). Mean tumour ADCs showed significant negative correlation (Spearman's ρ -0.38 to -0.46, P < 0.05) with Gleason score. CONCLUSIONS: Absolute ADC values strongly depend on the choice of b values and therefore should be used with caution for diagnostic purposes. A minimum b value greater than zero is recommended for ADC calculation to improve the visual assessment of PCa in ADC maps. KEY POINTS: • Absolute ADC values are highly dependent on the choice of b values. • Absolute ADC thresholds should be used carefully to predict tumour aggressiveness. • Subjective ratings of ADC maps involving b = 0 s/mm ( 2 ) are poor to fair. • Minimum b value greater than 0 s/mm ( 2 ) is recommended for ADC calculation.

Body fat composition determines outcomes before and after liver transplantation in patients with cirrhosis.

Cachexia occurs in late stages of liver cirrhosis, and a low-fat mass is potentially associated with poor outcome. This study compared different computed tomography (CT)-derived fat parameters with respect to its prognostic impact on the development of complications and death before and after liver transplantation. Between 2001 and 2014, 612 patients with liver cirrhosis without hepatocellular carcinoma listed for liver transplantation met the inclusion criteria, including abdominal CT scan (±200 days to listing). A total of 109 patients without cirrhosis served as controls. The subcutaneous fat index (SCFI), the paraspinal muscle fat index, and the visceral fat index were assessed at L3/L4 level and normalized to the height (cm2 /m2 ). Data were collected and analyzed retrospectively. Low SCFI was associated with a higher rate of ascites and increased C-reactive protein levels (p < 0.001). In addition, multivariate Cox regression analysis adjusting for sex, age, body mass index (BMI), and Model for End-Stage Liver Disease showed that decreasing SCFI was also associated with an increased risk of cirrhosis-related complications (p = 0.003) and death on the transplant wait list (p = 0.013). Increased paraspinal and visceral fat were not only positively correlated with creatinine levels (p < 0.001), BMI, and metabolic comorbidities (all p < 0.001) before transplantation, but also predictive for 1-year mortality after transplantation. Conclusion: The distribution of body fat is a major determinant for complications and outcome in cirrhosis before and after liver transplantation.

Repeated percutaneous hepatic perfusion with melphalan can maintain long-term response in patients with liver cancers.

Chemosaturation (CS; CHEMOSAT®, Delcath Systems Inc.) temporarily administers melphalan into the liver by percutaneous hepatic perfusion (PHP). CS-PHP can effectively control growth in liver tumors, but efficacy and tolerability of sequential treatments are unclear. We analyzed outcomes of sequential CS-PHP treatment. Patients with either unresectable intrahepatic metastases of ocular melanoma (OM, n = 9), cholangiocarcinoma (CCA, n = 3), or hepatocellular carcinoma (HCC, n = 1) were recruited retrospectively. Response was assessed by tomography imaging. Ten patients (mean age 60 years) with more than one CS-PHP treatment were included. CS-PHP was administered 2-6 times in the OM patients, 3 times in the CCA, and the HCC patient received 6 treatments. Overall response rate (ORR) to CS-PHP was 80%, and stable disease was achieved in one patient. Median hepatic progression-free survival (hPFS) was 336 days (range 0-354) for OM, 251 days for the CCA patient, and 256 days for the HCC patient. At the end of observation (153-701 days after first CS-PHP), 6/10 patients were still alive (5/9 with OM, 0 with CCA, and 1 with HCC). Death cases were not related to CS-PHP. Adverse events were mostly hematologic, grade I-IV, and self-resolving. The liver function was not deteriorated by CS-PHP. We conclude that repeated CS-PHP treatments were effective and well tolerated in the long term.

Suitability of miniature inductively coupled RF coils as MR-visible markers for clinical purposes.

PURPOSE: MR-visible markers have already been used for various purposes such as image registration, motion detection, and device tracking. Inductively coupled RF (ICRF) coils, in particular, provide a high contrast and do not require connecting wires to the scanner, which makes their application highly flexible and safe. This work aims to thoroughly characterize the MR signals of such ICRF markers under various conditions with a special emphasis on fully automatic detection. METHODS: The small markers consisted of a solenoid coil that was wound around a glass tube containing the MR signal source and tuned to the resonance frequency of a 1.5 T MRI. Marker imaging was performed with a spoiled gradient echo sequence (FLASH) and a balanced steady-state free precession (SSFP) sequence (TrueFISP) in three standard projections. The signal intensities of the markers were recorded for both pulse sequences, three source materials (tap water, distilled water, and contrast agent solution), different flip angles and coil alignments with respect to the B(0) direction as well as for different marker positions in the entire imaging volume (field of view, FOV). Heating of the ICRF coils was measured during 10-min RF expositions to three conventional pulse sequences. Clinical utility of the markers was assessed from their performance in computer-aided detection and in defining double oblique scan planes. RESULTS: For almost the entire FOV (±215 mm) and an estimated 82% of all possible RF coil alignments with respect to B(0), the ICRF markers generated clearly visible MR signals and could be reliably localized over a large range of flip angles, in particular with the TrueFISP sequence (0.3°-4.0°). Generally, TrueFISP provided a higher marker contrast than FLASH. RF exposition caused a moderate heating (≤5 °C) of the ICRF coils only. CONCLUSIONS: Small ICRF coils, imaged at low flip angles with a balanced SSFP sequence showed an excellent performance under a variety of experimental conditions and therefore make for a reliable, compact, flexible, and relatively safe marker for clinical use.

Retrospective Study for Validation and Improvement of Numerical Treatment Planning of Irreversible Electroporation Ablation for Treatment of Liver Tumors.

OBJECTIVE: The aims of this study were to determine the electric field threshold that best fits the local response to irreversible electroporation (IRE) ablation of hepatic tumors as seen in follow-up MRI; to numerically evaluate the heat generating effect of IRE; and to demonstrate the utility of treatment planning to improve procedures in the future. METHODS: 18 cases of hepatic tumors treated with IRE ablation were numerically reconstructed and treatment outcome was computed with a numerical treatment planning framework. Simulated ablation volumes were compared to ablation volumes segmented from 6-week follow-up MRI. Two cases with a high thermal component were selected for numerical optimization. RESULTS: The best fit between segmented and simulated ablation zones was obtained at 900 V/cm threshold with the average absolute error of 5.6 ± 1.5 mm. Considerable heating was observed in 7/18 cases, where >50% of tumor volume experienced heating likely to cause thermal damage. In the selected two cases, thermal damage was eliminated with adjustment of applied voltages. CONCLUSION: Lesions visible on MRI 6 weeks post IRE represent areas that experienced an electric field of 900 V/cm or higher. This threshold is higher than previously reported for IRE of hepatic tumors. It is likely the 6-week follow-up period was too long and the ablation zone has already shrunk considerably, resulting in overestimation of the threshold. SIGNIFICANCE: We developed a sophisticated method for validation of the numerical treatment planning framework. A future prospective study can be effectively designed based on the findings of this study.

Flexible add-on solution for MR image-guided interventions in a closed-bore scanner environment.

MRI is of great clinical utility for the guidance of various diagnostic and therapeutic procedures. In a standard closed-bore scanner, the simplest approach is to manipulate the instrument outside the bore and move the patient into the bore for reference and control imaging only. Without navigational assistance, however, such an approach can be difficult, inaccurate, and time consuming. Therefore, an add-on navigation solution is described that addresses these limitations. Patient registration is established by an automatic, robust, and fast (<30 sec) localization of table-mounted MR reference markers and the instrument is tracked optically. Good hand-eye coordination is provided by following the virtual instrument on MR images that are reconstructed in real time from the reference data. Needle displacements of 2.2 +/- 0.6 mm and 3.9 +/- 2.4 mm were determined in a phantom (P < 0.05), depending on whether the reference markers were placed at smaller (98-139 mm) or larger (147-188 mm) distances from the isocenter. Clinical functionality of the navigation concept is demonstrated by a double oblique, subscapular hook-wire insertion in a patient with a body mass index of 30.1 kg/m(2). Ease of use, compactness, and flexibility of this technique suggest that it can be used for many other procedures in different body regions. More patient cases are needed to evaluate clinical performance and workflow.

MRI-guided procedures in various regions of the body using a robotic assistance system in a closed-bore scanner: preliminary clinical experience and limitations.

PURPOSE: To present the clinical setup and workflow of a robotic assistance system for image-guided interventions in a conventional magnetic resonance imaging (MRI) environment and to report our preliminary clinical experience with percutaneous biopsies in various body regions. MATERIALS AND METHODS: The MR-compatible, servo-pneumatically driven, robotic device (Innomotion) fits into the 60-cm bore of a standard MR scanner. The needle placement (n = 25) accuracy was estimated by measuring the 3D deviation between needle tip and prescribed target point in a phantom. Percutaneous biopsies in six patients and different body regions were planned by graphically selecting entry and target points on intraoperatively acquired roadmap MR data. RESULTS: For insertion depths between 29 and 95 mm, the average 3D needle deviation was 2.2 +/- 0.7 mm (range 0.9-3.8 mm). Patients with a body mass index of up to approximately 30 kg/m(2) fitted into the bore with the device. Clinical work steps and limitations are reported for the various applications. All biopsies were diagnostic and could be completed without any major complications. Median planning and intervention times were 25 (range 20-36) and 44 (36-68) minutes, respectively. CONCLUSION: Preliminary clinical results in a standard MRI environment suggest that the presented robotic device provides accurate guidance for percutaneous procedures in various body regions. Shorter procedure times may be achievable by optimizing technical and workflow aspects.

Validation of a Web-Based Planning Tool for Percutaneous Cryoablation of Renal Tumors.

PURPOSE: To validate a simulation environment for virtual planning of percutaneous cryoablation of renal tumors. MATERIALS AND METHODS: Prospectively collected data from 19 MR-guided procedures were used for validation of the simulation model. Volumetric overlap of the simulated ablation zone volume (Σ) and the segmented ablation zone volume (S; assessed on 1-month follow-up scan) was quantified. Validation metrics were DICE Similarity Coefficient (DSC; the ratio between twice the overlapping volume of both ablation zones divided by the sum of both ablation zone volumes), target overlap (the ratio between the overlapping volume of both ablation zones to the volume of S; low ratio means S is underestimated), and positive predictive value (the ratio between the overlapping volume of both ablation zones to the volume of Σ; low ratio means S is overestimated). Values were between 0 (no alignment) and 1 (perfect alignment), a value > 0.7 is considered good. RESULTS: Mean volumes of S and Σ were 14.8 cm3 (± 9.9) and 26.7 cm3 (± 15.0), respectively. Mean DSC value was 0.63 (± 0.2), and ≥ 0.7 in 9 cases (47%). Mean target overlap and positive predictive value were 0.88 (± 0.11) and 0.53 (± 0.24), respectively. In 17 cases (89%), target overlap was ≥ 0.7; positive predictive value was ≥ 0.7 in 4 cases (21%) and < 0.6 in 13 cases (68%). This indicates S is overestimated in the majority of cases. CONCLUSION: The validation results showed a tendency of the simulation model to overestimate the ablation effect. Model adjustments are necessary to make it suitable for clinical use.

Position Paper of the German Society for Interventional Radiology (DeGIR) on Prostatic Artery Embolization. / Positionspapier der Deutschen Gesellschaft für Interventionsradiologie (DeGIR) zur Prostataarterienembolisation.

BACKGROUND: In recent years prostate artery embolization (PAE) evolved into a clinically established minimally invasive endovascular treatment option for lower urinary tract symptoms caused by benign prostate syndrome (BPS). METHODS: In this interdisciplinary position paper, initiated by the steering group for research of the German Society for Interventional Radiology (IR), the method of PAE is presented and discussed in the context of current evidence. RESULTS: PAE is a safe IR procedure for the treatment of BPS. In terms of symptom relief, measured with the IPSS (International Prostate Symptom Score), the PAE has comparable effect, similar to the historic gold standard, transurethral resection (TUR) of the prostate. With regard to reducing subvesical obstruction PAE is inferior to TUR, but does not limit subsequent surgery. Based on current evidence, PAE is recommended by the British National Institute for Health and Care Excellence as an alternative therapy. The feasibility under local anaesthesia and the preservation of sexual function are important arguments for patients in favour of interventional therapy. Patient selection and therapy concepts require close interdisciplinary collaboration between urologists and radiologists. CONCLUSION: Effectiveness and safety of PAE for the treatment of BPS are proven. Further randomized trials should focus on long term outcome and help to identify most suitable indications for PAE. KEY POINTS: · PAE, an endovascular procedure, is a patient-friendly, minimally invasive, alternative therapy option of the BPS. · PAE can reduce the symptoms of the lower urinary tract (LUTS), comparable to transurethral resection (TUR). The deobstructive and volume-reducing potential of the PAE is inferior to that of the TUR. · The main advantages of PAE are use of local anesthesia (no general anesthesia required), short patient recovery and maintenance of sexual function, including antegrade ejaculation.. · Based on current evidence PAE should be considered after conservative drug therapy and before TUR.. · The role of PAE in the context of other minimally invasive procedures (MIST) requires further evaluation with an open minded approach towards PAE.. · PAE is carried out by interventional radiologists, usually on a referral basis from urologists, and requires close interdisciplinary cooperation.. CITATION FORMAT: · Kovacs A, Bücker A, Grimm M et al. Position Paper of the German Society for Interventional Radiology (DeGIR) on Prostatic Artery Embolization. Fortschr Röntgenstr 2020; 192: 835 - 846.