Percutaneous Microwave Ablation for Treatment of Retroperitoneal Tumors.

Purpose To determine if microwave ablation (MWA) of retroperitoneal tumors can safely provide high rates of local tumor control. Materials and Methods This retrospective study included 19 patients (median age, 65 years [range = 46-78 years]; 13 [68.4%] men and six [31.6%] women) with 29 retroperitoneal tumors treated over 22 MWA procedures. Hydrodissection (0.9% saline with 2% iohexol) was injected in 17 of 22 (77.3%) procedures to protect nontarget anatomy. The primary outcomes evaluated were local tumor progression (LTP) and complication rates. Oncologic outcomes, including overall survival (OS), progression-free survival (PFS), and treatment-free interval (TFI), were examined as secondary outcome measures. Results Median follow-up was 18 months (range = 0.5-113). Hydrodissection was successful in displacing nontarget anatomy in 16 of 17 (94.1%) procedures. The LTP rate was 3.4% (one of 29; 95% CI: 0.1, 17.8) per tumor and 5.3% (one of 19; 95% CI: 0.1, 26.0) per patient. The overall complication rate per patient was 15.8% (three of 19), including two minor complications and one major complication. The OS rate at 1, 2, and 3 years was 81.8%, 81.8%, and 72.7%, respectively, with a median OS estimated at greater than 7 years. There was no evidence of a difference in OS (P = .34) and PFS (P = .56) between patients with renal cell carcinoma (six of 19 [31.6%]) versus other tumors (13 of 19 [68.4%]) and patients treated with no evidence of disease (15 of 22 [68.2%]) versus patients with residual tumors (seven of 22 [31.8%]). Median TFI was 18 months (range = 0.5-108). Conclusion Treatment of retroperitoneal tumors with MWA combined with hydrodissection provided high rates of local control, prolonged systemic therapy-free intervals, and few serious complications. Keywords: Ablation Techniques (ie, Radiofrequency, Thermal, Chemical), Retroperitoneum, Microwave Ablation, Hydrodissection © RSNA, 2024.

Imaging Genomics and Multiomics: A Guide for Beginners Starting Radiomics-Based Research.

Radiomics uses advanced mathematical analysis of pixel-level information from radiologic images to extract existing information in traditional imaging algorithms. It is intended to find imaging biomarkers related to the genomics of tumors or disease patterns that improve medical care by advanced detection of tumor response patterns in tumors and to assess prognosis. Radiomics expands the paradigm of medical imaging to help with diagnosis, management of diseases and prognostication, leveraging image features by extracting information that can be used as imaging biomarkers to predict prognosis and response to treatment. Radiogenomics is an emerging area in radiomics that investigates the association between imaging characteristics and gene expression profiles. There are an increasing number of research publications using different radiomics approaches without a clear consensus on which method works best. We aim to describe the workflow of radiomics along with a guide of what to expect when starting a radiomics-based research project.

Using 18F-DCFPyL Prostate-Specific Membrane Antigen-Directed Positron Emission Tomography/Magnetic Resonance Imaging to Define Intraprostatic Boosts for Prostate Stereotactic Body Radiation Therapy.

Purpose: The recently reported FLAME trial demonstrated a biochemical disease-free survival benefit to using a focal intraprostatic boost to multiparametric magnetic resonance imaging (mpMRI)-identified lesions in men with localized prostate cancer treated with definitive radiation therapy. Prostate-specific membrane antigen (PSMA)-directed positron emission tomography (PET) may identify additional areas of disease. In this work, we investigated using both PSMA PET and mpMRI in planning focal intraprostatic boosts using stereotactic body radiation therapy (SBRT). Methods and Materials: We evaluated a cohort of patients (n = 13) with localized prostate cancer who were imaged with 2-(3-(1-carboxy-5-[(6-[18F]fluoro-pyridine-2-carbonyl)-amino]-pentyl)-ureido)-pentanedioic acid (18F-DCFPyL) PET/MRI on a prospective imaging trial before undergoing definitive therapy. The number of lesions concordant (overlapping) and discordant (no overlap) on PET and MRI was assessed. Overlap between concordant lesions was evaluated using the Dice and Jaccard similarity coefficients. Prostate SBRT plans were created fusing the PET/MRI imaging to computed tomography scans acquired the same day. Plans were created using only MRI-identified lesions, only PET-identified lesions, and the combined PET/MRI lesions. Coverage of the intraprostatic lesions and doses to the rectum and urethra were assessed for each of these plans. Results: The majority of lesions (21/39, 53.8%) were discordant between MRI and PET, with more lesions seen by PET alone (12) than MRI alone (9). Of lesions that were concordant between PET and MRI, there were still areas that did not overlap between scans (average Dice coefficient, 0.34). Prostate SBRT planning using all lesions to define a focal intraprostatic boost provided the best coverage of all lesions without compromising constraints on the rectum and urethra. Conclusions: Using both mpMRI and PSMA-directed PET may better identify all areas of gross disease within the prostate. Using both imaging modalities could improve the planning of focal intraprostatic boosts.

Assessment of 18F-DCFPyL PSMA PET/CT and PET/MR quantitative parameters for reference standard organs: Inter-reader, inter-modality, and inter-patient variability.

Prostate specific membrane antigen (PSMA)-based radiotracers have shown promise for prostate cancer assessment. Evaluation of quantitative variability and establishment of reference standards are important for optimal clinical and research utility. This work evaluates the variability of PSMA-based [18F]DCFPyL (PyL) PET quantitative reference standards. Consecutive eligible patients with biochemically recurrent prostate cancer were recruited for study participation from August 2016-October 2017. After PyL tracer injection, whole body PET/CT (wbPET/CT) was obtained with subsequent whole body PET/MR (wbPET/MR). Two readers independently created regions of interest (ROIs) including a 40% standardized uptake value (SUV) threshold ROI of the whole right parotid gland and separate spherical ROIs in the superior, mid, and inferior gland. Additional liver (right lobe) and blood pool spherical ROIs were defined. Bland-Altman analysis, including limits of agreement (LOA), as well as interquartile range (IQR) and coefficient of variance (CoV) was used. Twelve patients with prostate cancer were recruited (mean age, 61.8 yrs; range 54-72 years). One patient did not have wbPET/MR and was excluded. There was minimal inter-reader SUVmean variability (bias±LOA) for blood pool (-0.13±0.42; 0.01±0.41), liver (-0.55±0.82; -0.22±1.3), or whole parotid gland (-0.05±0.31; 0.08±0.24) for wbPET/CT and wbPET/MR, respectively. Greater inter-reader variability for the 1-cm parotid gland ROIs was present, for both wbPET/CT and wbPET/MR. Comparing wbPET/CT to the subsequently acquired wbPET/MR, blood pool had a slight decrease in SUVmean. The liver as well as parotid gland showed a slight increase in activity although the absolute bias only ranged from 0.45-1.28. The magnitude of inter-subject variability was higher for the parotid gland regardless of modality or reader. In conclusion, liver, blood pool, and whole parotid gland quantitation show promise as reliable reference normal organs for clinical/research PET applications. Variability with 1-cm parotid ROIs may limit its use.

Reduced field-of-view and multi-shot DWI acquisition techniques: Prospective evaluation of image quality and distortion reduction in prostate cancer imaging.

OBJECTIVES: To prospectively compare image quality and apparent diffusion coefficient (ADC) quantification for reduced field-of-view (rFOV)- and multi-shot echo-planar imaging (msEPI)-based diffusion weighted imaging (DWI), using single-shot echo-planar-imaging (ssEPI) DWI as the reference. METHODS: Under IRB approval and after informed consent, msEPI, rFOV, and ssEPI DWI acquisitions were prospectively added to clinical prostate MRI exams at 3.0 T. Image distortion was quantitatively evaluated by root-mean-squared displacement (dr.m.s.). Histogram-based quantitative ADC parameters were compared in a sub-set of patients for proven sites of prostate cancer and matched non-cancerous prostate. Three radiologists also independently evaluated the DWI sequences for subjective image quality and distortion/artifact on a 5-point Likert scale. RESULTS: Twenty-five patients were included (15 with proven sites of cancer). Average dr.m.s. demonstrated a small but statistically significant reduction in distortion for both rFOV and msEPI relative to ssEPI. Quantitative ADC parameters for prostate tumors demonstrated no significant difference across the 3 DWI acquisitions and each acquisition demonstrated a statistically significant decrease in mean ADC for tumor compared to normal prostate. Qualitative reader assessment demonstrated favorable image quality for rFOV and msEPI, more notable for msEPI. CONCLUSIONS: rFOV and msEPI DWI techniques achieved reduction in image distortion, improvement in image quality, and maintained reproducible ADC quantification compared to the standard ssEPI.

Contrast-enhanced CT immediately following percutaneous microwave ablation of cT1a renal cell carcinoma: Optimizing cancer outcomes.

OBJECTIVE: To evaluate the effect of intra-procedural contrast-enhanced CT (CECT) and same-session repeat ablation (SSRA) on primary efficacy, the complete eradication of tumor after the first ablation session as confirmed on first imaging follow-up, of clinically localized T1a (cT1a) renal cell carcinoma (RCC). METHODS: 398 consecutive patients with cT1a RCC were treated with cryoablation between 10/2003 and 12/2017, radiofrequency (RFA) or microwave ablation (MWA) between 1/2010 and 12/2017. SSRA was performed for residual tumor identified on intra-procedural CECT. Kruskal-Wallis and Pearson's chi-squared tests were performed to assess differences in continuous and categorical variables, respectively. Multivariate linear regression was used to determine predictors for primary efficacy and decline in estimated glomerular filtration rate. RESULTS: 347 consecutive patients (231 M, mean age 67.5 ± 9.1 years) were included. Median tumor diameter was smaller [2.5 vs 2.7 vs 2.6 (p = 0.03)] and RENAL Nephrometry Score (NS) was lower [6 vs 7 vs 7 (p = 0.009] for MWA compared to the RFA and cryoablation cohorts, respectively. Primary efficacy was higher in the MWA cohort [99.4% (170/171)] compared to the RFA [91.4% (85/93)] and cryoablation [92.8% (77/83)] cohorts (p = 0.001). Microwave ablation and SSRA was associated with higher primary efficacy on multivariate linear regression (p = 0.01-0.03). CONCLUSION: MWA augmented by SSRA, when residual tumor is identified on intra-procedural CECT, may improve primary efficacy for cT1a RCC.

Split-bolus CT urography after microwave ablation of renal cell carcinoma improves image quality and reduces radiation exposure.

OBJECTIVE: To compare image quality and radiation dose between single-bolus 2-phase and split-bolus 1-phase CT Urography (CTU) performed immediately after microwave ablation (MWA) of clinically localized T1 (cT1) RCC. METHODS: Forty-two consecutive patients (30 M, mean age 67.5 ± 9.0) with cT1 RCC were treated with MWA from 7/2013 to 12/2013 at two academic quaternary-care institutions. Renal parenchymal enhancement, collecting system opacification and distention and size-specific dose estimate (SSDE) were quantified and image quality subjectively assessed on single-bolus 2-phase versus split-bolus 1-phase CTU. Kruskal-Wallis and Pearson's Chi-squared tests were performed to assess differences in continuous and categorical variables, respectively. Two-sample T test with equal variances was used to determine differences in quantitative and qualitative image data. RESULTS: Median tumor diameter was larger [2.9 cm (IQR 1.7-5.3) vs 3.6 cm (IQR 1.7-5.7), p = 0.01] in the split-bolus cohort. Mean abdominal girth (p = 0.20) was similar. Number of antennas used and unenhanced CTs obtained before and during MWA were similar (p = 0.11-0.32). Renal pelvis opacification (2.5 vs 3.5, p < 0.001) and distention (4 mm vs 8 mm, p < 0.001) were improved and renal enhancement (Right: 127 HU vs 177 HU, p = 0.001; Left: 124 HU vs 185 HU, p < 0.001) was higher for the split-bolus CTU. Image quality was superior for split-bolus CTU (3.2 vs 4.0, p = 0.004). Mean SSDE for the split-bolus CTU was significantly lower [163.9 mGy (SD ± 73.9) vs 36.3 mGy (SD ± 7.7), p < 0.001]. CONCLUSION: Split-bolus CTU immediately after MWA of cT1 RCC offers higher image quality, improved opacification/distention of the collecting system and renal parenchymal enhancement at a lower radiation dose.

Improved free-breathing liver fat and iron quantification using a 2D chemical shift-encoded MRI with flip angle modulation and motion-corrected averaging.

OBJECTIVES: 3D chemical shift-encoded (CSE) MRI enables accurate and precise quantification of proton density fat fraction (PDFF) and R2*, biomarkers of hepatic fat and iron deposition. Unfortunately, 3D CSE-MRI requires reliable breath-holding. Free-breathing 2D CSE-MRI with sequential radiofrequency excitation is a motion-robust alternative but suffers from low signal-to-noise-ratio (SNR). To overcome this limitation, this work explores the combination of flip angle-modulated (FAM) 2D CSE imaging with a non-local means (NLM) motion-corrected averaging technique. METHODS: In this prospective study, 35 healthy subjects (27 children/8 adults) were imaged on a 3T MRI-system. Multi-echo 3D CSE ("3D") and 2D CSE FAM ("FAM") images were acquired during breath-hold and free-breathing, respectively, to obtain PDFF and R2* maps of the liver. Multi-repetition FAM was postprocessed with direct averaging (DA)- and NLM-based averaging and compared to 3D CSE using Bland-Altmann and regression analysis. Image qualities of PDFF and R2* maps were reviewed by two radiologists using a Likert-like scale (score 1-5, 5 = best). RESULTS: Compared to 3D CSE, multi-repetition FAM-NLM showed excellent agreement (regression slope = 1.0, R2 = 0.996) for PDFF and good agreement (regression slope 1.08-1.15, R2 ≥ 0.899) for R2*. Further, multi-repetition FAM-NLM PDFF and R2* maps had fewer artifacts (score 3.8 vs. 3.2, p < 0.0001 for PDFF; score 3.2 vs. 2.6, p < 0.001 for R2*) and better overall image quality (score 4.0 vs. 3.5, p < 0.0001 for PDFF; score 3.4 vs. 2.7, p < 0.0001 for R2*). CONCLUSIONS: Free-breathing FAM-NLM provides superior image quality of the liver compared to the conventional breath-hold 3D CSE-MRI, while minimizing bias for PDFF and R2* quantification. KEY POINTS: • 2D CSE FAM-NLM is a free-breathing method for liver fat and iron quantification and viable alternative for patients unable to hold their breath. • 2D CSE FAM-NLM is a feasible alternative to breath-hold 3D CSE methods, with low bias in proton density fat fraction (PDFF) and no clinically significant bias in R2*. • Quantitatively, multiple repetitions in 2D CSE FAM-NLM lead to improved SNR.

Advanced CT techniques for hepatic microwave ablation zone monitoring and follow-up.

PURPOSE: To evaluate utility of advanced CT techniques including HighlY constrained back-projection and dual-energy CT for intra- and post-procedure hepatic microwave ablation zone monitoring. METHODS: 8 hepatic microwave ablations were performed in 4 adult swine (5 min/65 W). Low-dose routine CECT and dual-energy CT images were obtained every 1 min during ablation. Images were reconstructed ± HYPR. Image quality and dose metrics were collected. 21 MWA were performed in 4 adult swine. Immediate post-procedure CECT was performed in the arterial, portal venous, and delayed phases using both routine and DECT imaging with full-dose weight-based IV contrast dosing. An additional 16 MWA were subsequently performed in 2 adult swine. Immediate post-procedure CT was performed with half-dose IV contrast using routine and DECT. 12 patients (10 M/2F, mean age 62.4 yrs) with 14 hepatic tumors (4 HCC, 10 metastatic lesions) treated with MWA were prospectively imaged with DECT 1 month post-procedure. 120 kV equivalent images were compared to DECT [51 keV, iodine material density]. Image quality and dose metrics were collected. RESULTS: Gas created during MWA led to high CNR in all intraprocedural CT datasets. Optimal CNRs were noted at 4 min with CNR 6.7, 15.5,15.9, and 21.5 on LD-CECT, LD-CECT + HYPR, DECT, and DECT + HYPR, respectively (p < 0.001). Image quality scores at 4 min were 1.8, 2.8, 2.4, and 3, respectively (p < 0.001). Mean radiation dose (CTDIvol) was eightfold higher for the DECT series. For swine, post-procedural DECT images (IMD/51 keV) showed improved CNR compared to routine CT at all time points with full and with reduced dose contrast (CNR 4.6, 3.2, and 1.5, respectively, at half-contrast dose, p < 0.001). For human subjects, the 51 keV and IMD images showed higher CNRs (5.8, 4.8 vs 4.0, p < 0.001) and SNRs (3.7, 5.9 vs 2.8). Ablation zone sharpness was improved with DECT (routine 3.0 ± 0.7, DECT 3.5 ± 0.5). Diagnostic confidence was higher with DECT (routine 2.3 ± 0.9, DECT 2.6 ± 0.8). Mean DLP for DECT was 905.7 ± 606 mGy-cm, CTDIvol 37.5 ± 21.2 mGy, and effective dose 13.6 ± 9.1 mSv, slightly higher than conventional CT series. CONCLUSION: Advanced CT techniques can improve CT image quality in peri-procedural hepatic microwave ablation zone evaluation.

Efficacy of percutaneous image-guided biopsy for diagnosis of intrahepatic cholangiocarcinoma.

PURPOSE: To evaluate the efficacy of percutaneous biopsy for diagnosing intrahepatic cholangiocarcinoma (IHCCA). METHODS: Retrospective review of biopsy and pathology databases from 2006 to 2019 yielded 112 patients (54F/58 M; mean age, 62.9 years; 27 cirrhotic) with IHCCA who underwent percutaneous biopsy. Data regarding the lesion, biopsy procedure technique, and diagnostic yield were collected. If biopsy was non-diagnostic or discordant with imaging, details of repeat biopsy or resection/explant were gathered. A control group of 100 consecutive patients (56F/44 M; mean age, 63 years, 5 cirrhotic) with focal liver lesions > 1 cm was similarly assessed. RESULTS: Mean IHCCA lesion size was 6.1 ± 3.6 cm, with dominant lesion sampled in 78% (vs. satellite in 22%). 95% (n = 106) were US guided and 96% were core biopsies (n = 108), typically 18G (n = 102, 91%), median 2 passes. 18 patients (16%) had discordant/ambiguous pathology results requiring repeat biopsy, with two patients requiring 3-4 total attempts. A 4.4% minor complication rate was seen. Mean time from initial biopsy to final diagnosis was 60 ± 120 days. Control group had mean lesion size of 2.9 ± 2.5 cm and showed a non-diagnostic rate of 3.3%, both significantly lower than that seen with CCA, with average time to diagnosis of 21 ± 28.8 days (p = 0.002, p = 0.001). CONCLUSION: IHCCA is associated with lower diagnostic yield at initial percutaneous biopsy, despite larger target lesion size. If a suspicious lesion yields a biopsy result discordant with imaging, the radiologist should recommend prompt repeat biopsy to prevent delay in diagnosis.

Effect of Metabolic Syndrome on Anatomy and Function of the Lower Urinary Tract Assessed on MRI.

OBJECTIVE: To investigate the relationship between metabolic syndrome (MetS) and lower urinary tract symptoms (LUTS) with functional and anatomic changes of the lower urinary tract with MRI. MATERIALS AND METHODS: The bladder and prostate of 95 subjects (56M, 39F) were segmented on T2-weighted pelvic MRI using Materialize Mimics 3D software. Bladder wall volume (BWV), post-void residual (PVR) and prostate volume (PV) were quantified from the 3D renderings. LUTS were quantified using validated questionnaires administered at the time of MRI. Wilcoxin rank sum, win ratio and chi-square tests were used to correlate symptom scores, BWV, PVR and PV in patients 1) without vs with MetS, 2) with mild (IPSS or UDI-6: 0-7) vs moderate-severe (IPSS: 8-35 or UDI-6: ≥8) and 3) normal vs enlarged prostates (>40cm3). Multivariate linear regression was used to determine predictors for BWV, PVR and PV. RESULTS: Men with MetS had increased BWV (66.8 vs 51.1cm3, P = .003), higher PVR (69.1 vs 50.5cc, P= .05) and increased PV (67.2 vs 40.1cm3, P= .01). Women without and with MetS had similar BWV, PVR and LUTS (P= .3-.78). There was no difference in prevalence of MetS, BWV, PVR or PV in men or women with mild vs moderate-severe LUTS (P = .26-.97). Men with enlarged prostates were more likely to have MetS (P = .003). There was no difference in BWV, PVR and LUTS for men with normal vs enlarged prostates (P= .44-.94). In men, BWV was highly correlated with MetS (P = .005) on regression analysis. CONCLUSION: MetS leads to detrusor hypertrophy and may contribute to impaired bladder function, likely related to the effect on the prostate.

Combined mpMRI/US fusion targeted and concurrent standard biopsies in the detection of prostate cancer: a retrospective study.

In this retrospective study we compared the PCa detection rates between combined (combined MRI/US fusion targeted biopsy with concurrent standard biopsy) and standard systemic, combined and targeted (component), and targeted (component) and concurrent standard (component) biopsies. DESIGN: Two cohorts, totaling 735 cases, were selected from the University of Wisconsin Pathology archive. 390 cases (cohort 1) were combined biopsies from 2017-2020 and 345 cases (cohort 2) were part of the standard US-guided systematic biopsies from the same period. PCa was stratified into three categories: low, intermediate, and high risks. RESULTS: We found that combined biopsy was significantly better than the standard biopsy in detection of PCa (65.4% vs. 51.6%, P<0.01) and intermediate-risk PCa (18.7% vs. 10.4%, P=0.05) but only slightly better at detecting high-risk PCa (26.7% vs. 23.5%, P=0.32). Further examining the biopsy results in cohort 1, we found that combined biopsy was superior to targeted biopsy (65.4% vs. 56.9%, P=0.02) or concurrent standard biopsy (65.4% vs. 52.1%, P=0.0002) in PCa detection. Combined biopsy detected significantly more high-risk PCa than concurrent standard biopsy (26.7% vs. 17.4, P=0.002), but the difference in detecting high-risk PCa between combined and targeted biopsies was not significant (26.7% vs. 22.1%, P=0.133). Similarly, the differences in detecting PCa and high-risk PCa between targeted and concurrent standard biopsies were not significant (56.9% vs. 52.1%, P=0.172 and 22.1% vs. 17.4, P=0.133, respectively). Both targeted and concurrent standard biopsies missed PCa of each risk level. CONCLUSION: Combined MRI/US fusion targeted plus standard prostate biopsy is a superior technique for the detection of PCa and clinically significant PCa.

Microwave Ablation of Renal Cell Carcinoma.

Management options for small renal masses include active surveillance, partial nephrectomy, radical nephrectomy, and thermal ablation. For tumors typically ≤3 cm in size, thermal ablation is a good option for those desiring an alternative to surgery or active surveillance, especially in patients who are considered high surgical risk. We favor microwave ablation because of the more rapid heating, higher temperatures that overcome the heat sink effect of vessels, reproducible cell kill, and a highly visible ablation zone formed by water vapor that corresponds well to the zone of necrosis. For central tumors, we favor cryoablation because of the slower formation of the ablation zone and less likelihood of damage to the collecting system. With microwaves, it is important to monitor the ablation zone in real time (ultrasound is the best modality for this purpose), avoid direct punctures of the collecting system, and to place probes tangential to the collecting system to avoid burning open a persistent tract between the urothelium and extrarenal spaces or causing strictures. The surgical steps described in this video cover our use of high-frequency jet ventilation with general anesthesia to minimize organ motion, initial imaging and targeting, probe insertion, hydrodissection (a technique that enables displacement of adjacent structures), the ablation itself, and finally our dressing. Postoperative cares typically consist of observation with a same-day discharge or an overnight stay. Follow-up includes a magnetic resonance imaging abdomen with and without contrast, chest X-ray, and laboratories (basic metabolic panel, complete blood count, and C-reactive protein) 6 months postablation. Overall, percutaneous microwave ablation is an effective and safe treatment option for renal cell carcinoma in both T1a and T1b tumors in selected patients with multiple studies showing excellent oncologic outcomes when compared with partial and radical nephrectomy.

Microwave ablation for colorectal cancer metastasis to the liver: a single-center retrospective analysis.

BACKGROUND: The purpose of this study is to evaluate the safety and intermediate-term efficacy of percutaneous microwave (MW) ablation for the treatment of colorectal liver metastases (CRLM) at a single institution. METHODS: A retrospective review was performed of all CRLM treated with MW ablation from 3/2011 to 7/2020 (102 tumors; 72 procedures; 57 patients). Mean age was 60 years (range, 36-88) and mean tumor size was 1.8 cm (range, 0.5-5.0 cm). The patient population included 19 patients with extra-hepatic disease. Chemotherapy (pre- and/or post-ablation) was given in 98% of patients. Forty-five sessions were preceded by other focal CRLM treatments including resection, ablation, radiation, and radioembolization. Kaplan-Meier curves were used to estimate local tumor progression-free survival (LTPFS), disease-free survival (DFS), and overall survival (OS) and multivariate analysis (Cox Proportional Hazards model) was used to test predictors of OS. RESULTS: Technical success (complete ablation) was 100% and median follow-up was 42 months (range, 1-112). There was a 4% major complication rate and an overall complication rate of 8%. Local tumor progression (LTP) rate during the entire study period was 4/98 (4%), in which 2 were retreated with MW ablation for a secondary LTP-rate of 2%. LTP-free survival at 1, 3, and 5 years was 93%, 58%, and 39% and median LTP-free survival was 48 months. OS at 1, 3, and 5 years was 96%, 66%, 47% and median OS was 52 months. There were no statistically significant predictors of OS. CONCLUSIONS: MW ablation of hepatic colorectal liver metastases appears safe with excellent local tumor control and prolonged survival compared to historical controls in selected patients. Further comparative studies with other local treatment strategies appear indicated.

Differential Imaging of Liver Tumors before and after Microwave Ablation with Electrode Displacement Elastography.

Liver cancer is a leading cause of cancer-related deaths; however, primary treatment options such as surgical resection and liver transplant may not be viable for many patients. Minimally invasive image-guided microwave ablation (MWA) provides a locally effective treatment option for these patients with an impact comparable to that of surgery for both cancer-specific and overall survival. MWA efficacy is correlated with accurate image guidance; however, conventional modalities such as B-mode ultrasound and computed tomography have limitations. Alternatively, ultrasound elastography has been used to demarcate post-ablation zones, yet has limitations for pre-ablation visualization because of variability in strain contrast between cancer types. This study attempted to characterize both pre-ablation tumors and post-ablation zones using electrode displacement elastography (EDE) for 13 patients with hepatocellular carcinoma or liver metastasis. Typically, MWA ablation margins of 0.5-1.0 cm are desired, which are strongly correlated with treatment efficacy. Our results revealed an average estimated ablation margin inner quartile range of 0.54-1.21 cm with a median value of 0.84 cm. These treatment margins lie within or above the targeted ablative margin, indicating the potential to use EDE for differentiating index tumors and ablated zones during clinical ablations. We also obtained a high correlation between corresponding segmented cross-sectional areas from contrast-enhanced computed tomography, the current clinical gold standard, when compared with EDE strain images, with r2 values of 0.97 and 0.98 for pre- and post-ablation regions.

Evolution of the Interventional Radiology (IR) Pathway-Various Changes and Interrelation to Diagnostic Radiology (DR).

Interventional radiology continues to evolve into a more robust and clinically dynamic specialty underpinned by significant advancements in training, education, and practice. This article, prepared by members of the 2020-2021 Association of University Radiologists' task force of the Radiology Research Alliance, will review these developments, highlighting the evolution of interventional radiology pathways with attention to growing educational differences, interrelation to diagnostic radiology training, post-training practice patterns, distribution of procedures and future trends, amongst other key features important to those pursuing a career in interventional radiology as well as those in practice.

Effect of iodinated contrast material on post-operative eGFR when administered during renal mass ablation.

OBJECTIVE: To evaluate the effect of intravenous iodinated contrast on estimated glomerular filtration rate (eGFR) when administered immediately after thermal ablation of clinically localized T1a (cT1a) renal cell carcinoma (RCC). METHODS: This HIPAA-compliant, dual-center retrospective study was performed under a waiver of informed consent. Three hundred forty-two consecutive patients with cT1a biopsy-proven RCC were treated with percutaneous ablation between January 2010 and December 2017. Immediate post-ablation contrast-enhanced CT was the routine standard of care at one institution (contrast group), but not the other (control group). One-month pre- and 6-month post-ablation eGFR were compared using the Wilcoxon signed-rank test or the Kruskal-Wallis test. Multivariate linear regression was used to determine the effect of contrast on eGFR. A 1:1 propensity score matching was performed for all patients with a logistic model using patient, tumor, and procedural covariates. RESULTS: In total, 246 patients (158 M; median age 69 years, IQR 62-74) were included. Median tumor diameter (2.4 vs 2.5, p = 0.23) and RENAL nephrometry scores (6 vs 6, p = 0.92), surrogates for ablation zone size, were similar. Baseline kidney function was similar for the control and contrast groups, respectively (median eGFR: 70 vs 74 mL/min/1.73 m2, p = 0.29). There was an expected mild decline in eGFR after ablation (control: 70 vs 60 mL/min/1.73 m2, p < 0.001; contrast: 75 vs 71 mL/min/1.73 m2, p = 0.001). Intravenous iodinated contrast was not associated with a decline in eGFR on multivariate linear regression (1.91, 95% CI - 3.43-7.24, p = 0.46) or 1:1 propensity score-matched model (- 0.33, 95% CI - 6.81-6.15, p = 0.92). CONCLUSION: Intravenous iodinated contrast administered during ablation of cT1a RCC has no effect on eGFR. KEY POINTS: • Intravenous iodinated contrast administered during thermal ablation of clinically localized T1a renal cell carcinoma has no effect on kidney function. • Thermal ablation of clinically localized T1a renal cell carcinoma results in a mild decline in kidney function. • A decline in kidney function is similar for radiofrequency and microwave ablation of clinically localized T1a renal cell carcinoma.

Long-Term Outcomes and Prognostic Factors in Kidney Transplant Recipients with Polycystic Kidney Disease.

Background: Polycystic kidney disease (PKD) accounts for approximately 15% of kidney transplants, but long-term outcomes in patients with PKD who have received a kidney transplant are not well understood. Methods: In primary recipients of kidney transplants at our center (1994-2014), we compared outcomes of underlying PKD (N=619) with other native diseases (non-PKD, N=4312). Potential factors influencing outcomes in PKD were evaluated using Cox proportional-hazards regression and a rigorous multivariable model. Results: Patients with PKD were older and were less likely to be sensitized or to experience delayed graft function (DGF). Over a median follow-up of 5.6 years, 1256 of all recipients experienced death-censored graft failure (DCGF; 115 patients with PKD) and 1617 died (154 patients with PKD). After adjustment for demographic, dialysis, comorbid disease, surgical, and immunologic variables, patients with PKD had a lower risk of DCGF (adjusted hazard ratio [aHR], 0.73; 95% CI, 0.57 to 0.93; P=0.01) and death (aHR, 0.62; 95% CI, 0.51 to 0.75; P<0.001). In our multiadjusted model, calcineurin-inhibitor (CNI) use was associated with lower risk of DCGF (aHR, 0.45; 95% CI, 0.26 to 0.76; P=0.003), whereas HLA mismatch of five to six antigens (aHR, 2.1; 95% CI, 1.2 to 3.64; P=0.009) was associated with higher likelihood of DCGF. Notably, both pretransplant coronary artery disease (CAD) and higher BMI were associated with increased risk of death (CAD, aHR, 2.5; 95% CI, 1.69 to 3.71; P<0.001; per 1 kg/m2 higher BMI, aHR, 1.07; 95% CI, 1.04 to 1.11; P<0.001), DCGF, and acute rejection. Nephrectomy at time of transplant and polycystic liver disease were not associated with DCGF/death. Incidence of post-transplant diabetes mellitus was similar between PKD and non-PKD cohorts. Conclusions: Recipients with PKD have better long-term graft and patient survival than those with non-PKD. Standard practices of CNI use and promoting HLA match are beneficial in PKD and should continue to be promoted. Further prospective studies investigating the potential benefits of CNI use and medical/surgical interventions to address CAD and the immunologic challenges of obesity are needed. Podcast: This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/K360/2021_02_25_KID0001182019.mp3.

Comprehensive non-invasive analysis of lower urinary tract anatomy using MRI.

PURPOSE: Anatomic changes that coincide with aging including benign prostatic hyperplasia (BPH) and lower urinary tract symptoms (LUTS) negatively impact quality of life. Use of MRI with its exquisite soft tissue contrast, full field-of-view capabilities, and lack of radiation is uniquely suited for quantifying specific lower urinary tract features and providing comprehensive measurements such as total bladder wall volume (BWV), bladder wall thickness (BWT), and prostate volume (PV). We present a technique for generating 3D anatomical renderings from MRI to perform quantitative analysis of lower urinary tract anatomy. METHODS: T2-weighted fast-spin echo MRI of the pelvis in 117 subjects (59F;58 M) aged 30-69 (49.5 ± 11.3) without known lower urinary tract symptoms was retrospectively segmented using Materialise software. Virtual 3D models were used to measure BWV, BWT, and PV. RESULTS: BWV increased significantly between the 30-39 and 60-69 year age group in women (p = 0.01), but not men (p = 0.32). BWV was higher in men than women aged 30-39 and 40-49 (p = 0.02, 0.05, respectively) ,but not 50-59 or 60-69 (p = 0.18, 0.16, respectively). BWT was thicker in men than women across all age groups. Regional differences in BWT were observed both between men and women and between opposing bladder wall halves (anterior/posterior, dome/base, left/right) within each sex in the 50-59 and 60-69 year groups. PV increased from the 30-39 to 60-69 year groups (p = 0.05). BWT was higher in subjects with enlarged prostates (> 40cm3) (p = 0.05). CONCLUSION: Virtual 3D MRI models of the lower urinary tract reliably quantify sex-specific and age-associated changes of the bladder wall and prostate.

Patterns of Initial Metastatic Recurrence After Surgery for High-Risk Nonmetastatic Renal Cell Carcinoma.

OBJECTIVE: To evaluate postoperative recurrence patterns for high-risk nonmetastatic renal cell carcinoma (RCC) and to identify prognostic factors associated with site-specific metastatic recurrence using a multi-institutional contemporary cohort. METHODS: Data for nonmetastatic ≥pT3a RCC patients treated with surgery at 4 independent centers was analyzed. Initial recurrence locations were identified, and imaging templates were defined by anatomic landmarks using radiologic definitions. Prognostic factors for site specific recurrence were evaluated with univariate and multivariable analyses. RESULTS: A total of 1057 patients were treated surgically for ≥pT3a RCC. Initial recurrence location was in a single site for 160 (59.3%) patients and at multiple locations in 110 (41.7%) patients. The most common sites of metastatic recurrence were lung (144/270, 53.3%), liver (54/270, 20.0%), and bone (48/270, 17.8%). Recurrence was identified in 52 of 270 (19.3%) patients outside the chest/abdomen template, most commonly in the pelvis (25/270, 9.3%). Bone and brain metastases were the most common organs for metastases outside chest/abdomen. Patients with tumor diameter >10 cm and grade 4 were more likely to recur in the bone (HR 3.61, P <.001) and brain (HR 16.5, P <.001). CONCLUSION: Metastatic progression outside chest/abdomen imaging templates was present in 1 of 5 high risk patients at initial metastatic RCC diagnosis, most commonly in the pelvis. Patients with large (>10 cm) tumors and grade 4 histology are at highest risk for bone and brain metastases.