Comparison of enhancement quantification from virtual unenhanced images to true unenhanced images in multiphase renal Dual-Energy computed tomography: A phantom study.

Multiphase computed tomography (CT) exams are a commonly used imaging technique for the diagnosis of renal lesions and involve the acquisition of a true unenhanced (TUE) series followed by one or more postcontrast series. The difference in CT number of the mass in pre- and postcontrast images is used to quantify enhancement, which is an important criterion used for diagnosis. This study sought to assess the feasibility of replacing TUE images with virtual unenhanced (VUE) images derived from Dual-Energy CT datasets in renal CT exams. Eliminating TUE image acquisition could reduce patient dose and improve clinical efficiency. A rapid kVp-switching CT scanner was used to assess enhancement accuracy when using VUE compared to TUE images as the baseline for enhancement calculations across a wide range of clinical scenarios simulated in a phantom study. Three phantoms were constructed to simulate small, medium, and large patients, each with varying lesion size and location. Nonenhancing cystic lesions were simulated using distilled water. Intermediate (10-20 HU [Hounsfield units]) and positively enhancing masses (≥20 HU) were simulated by filling the spherical inserts in each phantom with varied levels of iodinated contrast mixed with a blood surrogate. The results were analyzed using Bayesian hierarchical models. Posterior probabilities were used to classify enhancement measured using VUE compared to TUE images as significantly less, not significantly different, or significantly higher. Enhancement measured using TUE images was considered the ground truth in this study. For simulation of nonenhancing renal lesions, enhancement values were not significantly different when using VUE versus TUE images, with posterior probabilities ranging from 0.23-0.56 across all phantom sizes and an associated specificity of 100%. However, for simulation of intermediate and positively enhancing lesions significant differences were observed, with posterior probabilities < 0.05, indicating significantly lower measured enhancement when using VUE versus TUE images. Positively enhancing masses were categorized accurately, with a sensitivity of 91.2%, when using VUE images as the baseline. For all scenarios where iodine was present, VUE-based enhancement measurements classified lesions with a sensitivity of 43.2%, a specificity of 100%, and an accuracy of 78.1%. Enhancement calculated using VUE images proved to be feasible for classifying nonenhancing and highly enhancing lesions. However, differences in measured enhancement for simulation of intermediately enhancing lesions demonstrated that replacement of TUE with VUE images may not be advisable for renal CT exams.

Pre-procedural and intra-procedural computerized tomography: providing a roadmap for successful adrenal venous sampling procedures.

BACKGROUND AND PURPOSE: Adrenal venous sampling (AVS) is used for the diagnosis of primary hyperaldosteronism. Technical difficulties with right adrenal vein (RAV) catheterization can lead to erroneous results. Our purpose was to delineate the location of the RAV on pre-procedural CT imaging in relation to the location identified during AVS and to report on the impact of successful RAV cannulation with and without the use of intra-procedural CT scanning. METHODS: Retrospective case series including patients who underwent AVS from October 2000 to September 2022. Clinical and laboratory values were abstracted from the electronic medical record. Successful cannulation of the RAV was defined as a selectivity index > 3. RESULTS: 110 patients underwent 124 AVS procedures. Pre-AVS CT imaging was available for 118 AVS procedures. The RAV was identified in 61 (51.7%) CT datasets. Biochemical confirmation of successful RAV cannulation occurred in 98 (79.0%) of 124 AVS procedures. There were 52 (85.2%) procedures in which the RAV was identified on pre-AVS CT and there was biochemical confirmation of successful RAV sampling. Among these 52 procedures, the RAV was localized during AVS at the same anatomic level or within 1 vertebral body level cranial to the level identified on pre-AVS CT in 98.1% of cases. The rate of successful RAV cannulation was higher in patients who underwent intra-procedural CT (93.8% versus 63.9%), P < 0.01. CONCLUSIONS: Pre-AVS and intra-procedural CT images provide an invaluable roadmap that resulted in a higher rate of accurate identification of the RAV and successful AVS procedures; in particular, search for the RAV orifice during AVS can be limited to 1 vertebral body cranial to the level identified on pre-AVS CT imaging and successful cannulation can be confidently verified with intra-procedural CT.

A novel use of biomechanical model-based deformable image registration (DIR) for assessing colorectal liver metastases ablation outcomes.

PURPOSE: Colorectal cancer is the third most common form of cancer in the United States, and up to 60% of these patients develop liver metastasis. While hepatic resection is the curative treatment of choice, only 20% of patients are candidates at the time of diagnosis. While percutaneous thermal ablation (PTA) has demonstrated 24%-51% overall 5-year survival rates, assurance of sufficient ablation margin delivery (5 mm) can be challenging, with current methods of 2D distance measurement not ensuring 3D minimum margin. We hypothesized that biomechanical model-based deformable image registration (DIR) can reduce spatial uncertainties and differentiate local tumor progression (LTP) patients from LTP-free patients. METHODS: We retrospectively acquired 30 patients (16 LTP and 14 LTP-free) at our institution who had undergone PTA and had a contrast-enhanced pre-treatment and post-ablation CT scan. Liver, disease, and ablation zone were manually segmented. Biomechanical model-based DIR between the pre-treatment and post-ablation CT mapped the gross tumor volume onto the ablation zone and measured 3D minimum delivered margin (MDM). An in-house cone-tracing algorithm determined if progression qualitatively collocated with insufficient 5 mm margin achieved. RESULTS: Mann-Whitney U test showed a significant difference (p < 0.01) in MDM from the LTP and LTP-free groups. A total of 93% (13/14) of patients with LTP had a correlation between progression and missing 5 mm of margin volume. CONCLUSIONS: Biomechanical DIR is able to reduce spatial uncertainty and allow measurement of delivered 3D MDM. This minimum margin can help ensure sufficient ablation delivery, and our workflow can provide valuable information in a clinically useful timeframe.