MR imaging-guided interventions in the genitourinary tract: an evolving concept

Effect of lipiodol marking before CT-guided cryoablation on the outcome of sporadic renal cell carcinoma

PURPOSE

This retrospective study evaluates the impact of preoperative lipiodol marking on the outcomes of computed tomography (CT)-guided cryoablation for histologically diagnosed sporadic renal cell carcinoma (RCC).

METHODS

This study analyzed the data of 173 patients who underwent CT-guided cryoablation for histologically proven sporadic RCC at a single institution between April 2014 and December 2020. The local control rate (LCR), recurrence-free survival rate (RFSR), overall survival rate (OSR), changes in renal function, and complications in patients with (n = 85) and without (n = 88) preoperative lipiodol marking were compared.

RESULTS

The 5-year LCR and 5-year RFSR were significantly higher in patients with lipiodol marking (97.51% and 93.84%, respectively) than in those without (72.38% and 68.10%, respectively) (P value <0.01, log-rank test). There were no significant differences between the two groups regarding the 5-year OSR (97.50% vs. 86.82%) or the deterioration in chronic kidney disease stage (12.70% vs. 16.43%). Grade ≥3 complications occurred in patients with lipiodol marking (n = 2, retroperitoneal hematoma and cerebral infarction in 1 patient each) and without (n = 5; urinary fistula in 2, colonic perforation in 2, urinary infection in 1).

CONCLUSION

Lipiodol marking before CT-guided cryoablation for sporadic RCC is a feasible approach to improving local control and RFS while mitigating the decline in renal function. Additionally, it may help reduce complications.

MRI-guided percutaneous transhepatic cholangiodrainage: feasibility study in a porcine model

BACKGROUND AND STUDY AIMS

MRI-guided procedures combine high-quality imaging with lack of radiation. Percutaneous transhepatic cholangiodrainage under real-time MRI guidance (MRI-PTCD) seems promising, allowing targeted puncture and avoiding multiple blind passes and use of contrast, which are associated with standard PTCD's heaviest complications.

PATIENTS AND METHODS

Aim of this study was to investigate the feasibility of MRI-PTCD in three outbred piglets. Obstructive cholestasis was induced by common bile duct ligation. Two days later, MRI-PTCD was performed (open MRI, 1.0 Tesla) with prototype MRI-compatible accessories. Visualization was achieved with a balanced steady-state free precession real-time sequence (bSSFP: 0.75 frames/s, TR/TE [ms]: 7.2/3.6; flip angle: 45°; 200 × 200 matrix size; resolution: 1.3 × 1.3 mm(2), slice thickness: 7 mm). Cannulation of the bile ducts was followed by placement of Yamakawa drainages.

RESULTS

Twelve punctures were performed (four per animal, 10/12 successful); in 2/10 the bile ducts could not be cannulated. Animal survival was 100% and no significant complications occurred.

CONCLUSIONS

Initial data show that MRI-PTCD can be successfully performed. This may lead to establishment of a new optimized PTCD technique compared to the standard approach under fluoroscopy.

Automatic iceball segmentation with adapted shape priors for MRI-guided cryoablation

PURPOSE

To develop and evaluate an automatic segmentation method that extracts the 3D configuration of the ablation zone, the iceball, from images acquired during the freezing phase of MRI-guided cryoablation.

MATERIALS AND METHODS

Intraprocedural images at 63 timepoints from 13 kidney tumor cryoablation procedures were examined retrospectively. The images were obtained using a 3 Tesla wide-bore MRI scanner and axial HASTE sequence. Initialized with semiautomatically localized cryoprobes, the iceball was segmented automatically at each timepoint using the graph cut (GC) technique with adapted shape priors.

RESULTS

The average Dice Similarity Coefficients (DSC), compared with manual segmentations, were 0.88, 0.92, 0.92, 0.93, and 0.93 at 3, 6, 9, 12, and 15 min timepoints, respectively, and the average DSC of the total 63 segmentations was 0.92 ± 0.03. The proposed method improved the accuracy significantly compared with the approach without shape prior adaptation (P = 0.026). The number of probes involved in the procedure had no apparent influence on the segmentation results using our technique. The average computation time was 20 s, which was compatible with an intraprocedural setting.

CONCLUSION

Our automatic iceball segmentation method demonstrated high accuracy and robustness for practical use in monitoring the progress of MRI-guided cryoablation.

Percutaneous transhepatic cholangiodrainage under real-time MRI guidance: initial experience in an animal model

AIMS

To assess percutaneous transhepatic cholangiodrainage (PTCD) under real-time MRI-guidance and compare it to procedures performed under fluoroscopy.

METHODS

We developed an in vitro model for MRI-guided and conventional PTCD, using an animal organ set including liver and bile ducts placed in an MRI-compatible box and tested it in a 1.0-Tesla open MRI-scanner. Prototype 18G needles and guide wires, standard guide wires, dilatation bougies, and drainages were used (MRI-compatible). MRI-visualization was by means of a bFFE real-time sequence using a surface coil (Flex-L). Outcome measurements were success rates and time needed for bile duct puncture using real-time MRI-guidance versus conventional radiologic methods in the model. Cannulation and drainage placement were also analysed.

RESULTS

Fifty MRI-guided experiments were performed, leading to rapid (mean: 43s, range: 15-72s) and successful puncture and cannulation in 96% of procedures. Median drainage placement time was 321.5s (range: 241-411s). In 35 control experiments under fluoroscopy, puncture success was 69%, whereas times were significantly longer (mean 273s, range 45-631s).

CONCLUSIONS

Initial in vitro experience shows that PTCD can be successfully and rapidly performed under real-time MRI-guidance and demonstrates improved performance compared to the conventional radiologic approach.