Improved early outcome prediction by MRI-based 3D tumor volume assessment in patients with CNS lymphomas.

BACKGROUND: Central nervous system lymphomas (CNSL) display remarkable clinical heterogeneity, yet accurate prediction of outcomes remains challenging. The IPCG criteria are widely used in routine practice for the assessment of treatment response. However, the value of the IPCG criteria for ultimate outcome prediction is largely unclear, mainly due to the uncertainty in delineating complete from partial responses during and after treatment. METHODS: We explored various MRI features including semi-automated 3D tumor volume measurements at different disease milestones and their association with survival in 93 CNSL patients undergoing curative-intent treatment. RESULTS: At diagnosis, patients with more than 3 lymphoma lesions, periventricular involvement, and high 3D tumor volumes showed significantly unfavorable PFS and OS. At first interim MRI during treatment, the IPCG criteria failed to discriminate outcomes in responding patients. Therefore, we randomized these patients into training and validation cohorts to investigate whether 3D tumor volumetry could improve outcome prediction. We identified a 3D tumor volume reduction of ≥97% as the optimal threshold for risk stratification (=3D early response, 3D_ER). Applied to the validation cohort, patients achieving 3D_ER had significantly superior outcomes. In multivariate analyses, 3D_ER was independently prognostic of PFS and OS. Finally, we leveraged prognostic information from 3D MRI features and circulating biomarkers to build a composite metric that further improved outcome prediction in CNSL. CONCLUSIONS: We developed semi-automated 3D tumor volume measurements as strong and independent early predictors of clinical outcomes in CNSL patients. These radiologic features could help improve risk stratification and help guide future treatment approaches.

Assessment of Hepatic Perfusion Using GRASP MRI: Bringing Liver MRI on a New Level.

PURPOSE: The aim of this study was to demonstrate the feasibility of hepatic perfusion imaging using dynamic contrast-enhanced (DCE) golden-angle radial sparse parallel (GRASP) magnetic resonance imaging (MRI) for characterizing liver parenchyma and hepatocellular carcinoma (HCC) before and after transarterial chemoembolization (TACE) as a potential alternative to volume perfusion computed tomography (VPCT). METHODS AND MATERIALS: Between November 2017 and September 2018, 10 patients (male = 8; mean age, 66.5 ± 8.6 years) with HCC were included in this prospective, institutional review board-approved study. All patients underwent DCE GRASP MRI with high spatiotemporal resolution after injection of liver-specific MR contrast agent before and after TACE. In addition, VPCT was acquired before TACE serving as standard of reference. From the dynamic imaging data of DCE MRI and VPCT, perfusion maps (arterial liver perfusion [mL/100 mL/min], portal liver perfusion [mL/100 mL/min], hepatic perfusion index [%]) were calculated using a dual-input maximum slope model and compared with assess perfusion measures, lesion characteristics, and treatment response using Wilcoxon signed-rank test. To evaluate interreader agreement for measurement repeatability, the interclass correlation coefficient (ICC) was calculated. RESULTS: Perfusion maps could be successfully generated from all DCE MRI and VPCT data. The ICC was excellent for all perfusion maps (ICC ≥ 0.88; P ≤ 0.001). Image analyses revealed perfusion parameters for DCE MRI and VPCT within the same absolute range for tumor and liver tissue. Dynamic contrast-enhanced MRI further enabled quantitative assessment of treatment response showing a significant decrease (P ≤ 0.01) of arterial liver perfusion and hepatic perfusion index in the target lesion after TACE. CONCLUSIONS: Dynamic contrast-enhanced GRASP MRI allows for a reliable and robust assessment of hepatic perfusion parameters providing quantitative results comparable to VPCT and enables characterization of HCC before and after TACE, thus posing the potential to serve as an alternative to VPCT.

In vitro artifact assessment of an MR-compatible, microwave antenna device for percutaneous tumor ablation with fluoroscopic MRI-sequences.

OBJECTIVE: To evaluate artifact configuration and diameters of a magnetic resonance (MR) compatible microwave (MW) applicator using near-realtime MR-fluoroscopic sequences for percutaneous tumor ablation procedures. MATERIAL AND METHODS: Two MW applicators (14 G and 16 G) were tested in an ex-vivo phantom at 1.5 T with two 3 D fluoroscopic sequences: T1-weighted spoiled Gradient Echo (GRE) and T1/T2-weighted Steady State Free Precession (SSFP) sequence. Applicator orientation to main magnetic field (B0), slice orientation and phase encoding direction (PED) were systematically varied. The influence of these variables was assessed with ANOVA and post-hoc testing. RESULTS: The artifact was homogenous along the whole length of both antennas with all tested parameters. The tip artifact diameter of the 16 G antenna measured 6.9 ± 1.0 mm, the shaft artifact diameter 8.6 ± 1.2 mm and the Tip Location Error (TLE) was 1.5 ± 1.2 mm.The tip artifact diameter of the 14 G antenna measured 7.7 ± 1.2 mm, the shaft artifact diameter 9.6 ± 1.5 mm and TLE was 1.6 ± 1.2 mm. Orientation to B0 had no statistically significant influence on tip artifact diameters (16 G: p = .55; 14 G: p = .07) or TLE (16 G: p = .93; 14 G: p = .26). GRE sequences slightly overestimated the antenna length with TLE(16 G) = 2.6 ± 0.5 mm and TLE(14 G) = 2.7 ± 0.7 mm. CONCLUSIONS: The MR-compatible MW applicator's artifact seems adequate with an acceptable TLE for safe applicator positioning during near-realtime fluoroscopic MR-guidance.

Imaging response assessment of immunotherapy in patients with renal cell and urothelial carcinoma.

PURPOSE OF REVIEW: Recent advances in anticancer immunotherapy have revolutionized the treatment of metastatic renal cell (RCC) and urothelial carcinoma. In this review, we discuss the mechanisms of action of these new therapeutic approaches, explicate the common adverse events, and highlight different imaging-based response criteria. RECENT FINDINGS: The recent introduction of immune-checkpoint inhibitors led to substantial advances in therapy of metastatic RCC and urothelial carcinoma. Because of the distinct effector mechanisms of these new substances, atypical response patterns such as transient enlargements of tumor lesions, appearance of new lesions after therapy, no measurable decrease in tumor size, or delayed responses are observed in medical imaging studies. This indicates that the established imaging-based response assessment according to the Response Evaluation Criteria in Solid Tumors (RECIST) guidelines has shortcomings to comprehensively evaluate treatment effects. SUMMARY: While monitoring response to immunotherapy still relies on RECIST criteria, immune-related response criteria have been established to better address the imaging changes occurring under immunotherapy. Further studies with long-term follow-up are needed to properly identify and predict response after treatment beyond progression. Because of the expanding clinical use of immune checkpoint inhibitors, radiologists, urologist, and oncologists should be familiar with common imaging findings under this respective therapy.

Feasibility of low-dose digital pulsed video-fluoroscopic swallow exams (VFSE): effects on radiation dose and image quality.

Background Fluoroscopy is a frequently used examination in clinical routine without appropriate research evaluation latest hardware and software equipment. Purpose To evaluate the feasibility of low-dose pulsed video-fluoroscopic swallowing exams (pVFSE) to reduce dose exposure in patients with swallowing disorders compared to high-resolution radiograph examinations (hrVFSE) serving as standard of reference. Material and Methods A phantom study (Alderson-Rando Phantom, 60 thermoluminescent dosimeters [TLD]) was performed for dose measurements. Acquisition parameters were as follows: (i) pVFSE: 76.7 kV, 57 mA, 0.9 Cu mm, pulse rate/s 30; (ii) hrVFSE: 68.0 kV, 362 mA, 0.2 Cu mm, pictures 30/s. The dose area product (DAP) indicated by the detector system and the radiation dose derived from the TLD measurements were analyzed. In a patient study, image quality was assessed qualitatively (5-point Likert scale, 5 = hrVFSE; two independent readers) and quantitatively (SNR) in 35 patients who subsequently underwent contrast-enhanced pVFSE and hrVFSE. Results Phantom measurements showed a dose reduction per picture of factor 25 for pVFSE versus hrVFSE images (0.0025 mGy versus 0.062 mGy). The DAP (µGym2) was 28.0 versus 810.5 (pVFSE versus hrVFSE) for an average examination time of 30 s. Direct and scattered organ doses were significantly lower for pVFSE as compared to hrVFSE ( P < 0.05). Image quality was rated 3.9 ± 0.5 for pVFSE versus the hrVFSE standard; depiction of the contrast agent 4.8 ± 0.3; noise 3.6 ± 0.5 ( P < 0.05); SNR calculations revealed a relative decreased of 43.9% for pVFSE as compared to hrVFSE. Conclusion Pulsed VFSE is feasible, providing diagnostic image quality at a significant dose reduction as compared to hrVFSE.

In vitro artefact assessment of a new MR-compatible microwave antenna and a standard MR-compatible radiofrequency ablation electrode for tumour ablation.

OBJECTIVE: To evaluate and compare artefact configuration and diameters in a magnetic resonance (MR)-compatible prototype microwave (MW) applicator and a standard MR-compatible radiofrequency (RF) applicator for MR-guided tumour ablation. METHODS: Both applicators were tested in a phantom study at 1.5T with three sequences: T1-weighted three-dimensional volume interpolated breath-hold examination (VIBE), T1-weighted fast low angle shot (FLASH), T2-weighted turbo spin echo (TSE). Applicator orientation to main magnetic field (B0) and slice orientation were varied. Needle tip location error (TLE) was assessed, and artefact diameters were calculated. Influence of imaging parameters on artefacts was assessed with analysis of variance (ANOVA) and post hoc testing. RESULTS: MW applicator: the shaft artefact diameter measured 2.3 +/- 0.8 mm. Tip artefact diameter and length measured 2.2 ± 0.8 mm and 2.4 ± 1.3 mm, respectively. A prominent oval artefact (diameter: 16.5 +/- 1.8 mm, length: 19.1 +/- 2.5 mm) appeared close to the tip. TLE: - .3 +/- 0.6 mm. RF applicator: shaft and tip diameter measured 8.9 +/- 4.7 mm and 9.0 +/- .0 mm, respectively. TLE: -0.1 +/- 0.8 mm. Minimal artefacts were measured with RF applicator orientation parallel to B0 (P < 0.0001), whereas no such influence was found for MW applicator. For both applicators, significantly large artefacts were measured with T1 FLASH (P = 0.03). CONCLUSION: The MW applicator's artefact is satisfactory and seems useable for MR-guided ablation procedures. KEY POINTS: MW applicator's artefact appearance is independent of angulation to main magnetic field. MW applicator's prominent distal artefact may increase visibility under MR-guidance. RF and MW applicator's artefacts are precise concerning tip depiction. Largest artefact diameters are measured with T1-weighted fast low angle shot sequence.