Faculty Bibliography

Positron emission tomography (PET) and magnetic resonance (MR) imaging until recently has been performed by separate PET and MR devices with temporal delay between these two acquisitions. However, various recent hardware solutions have been developed by different vendors which permit simultaneous or near simultaneous PET and MR acquisition. However, the clinical translation of this modality for oncologic imaging requires not only identifying the appropriate clinical indications, but also understanding various components involved in establishing a PET/ MR service which include physical installation of the system, equipment safety, clinical workflow, technician and physician training, and monetary reimbursement. The current and potential clinical indications for imaging of metastatic disease can be broadly classified as follows: (1). Simultaneous local and distant staging of cancers such as rectal cancer and gynecologic malignancies. Here high spatial resolution of MRI provides information about local extent of the disease and PET is used predominantly for distant staging. (2). Problem solving for potential metastatic disease such as for small liver lesions, small lymph nodes, or bone marrow involvement. Additional information provided by MRI and PET can better characterize lesions and improve confidence in diagnosing presence or absence of metastatic disease. (3). Assessment of treatment response. Use of quantitative MR and PET information can potentially provide synergistic information in assessing treatment response. To address these clinical need there are number of operational considerations such as: (1). Protocol optimisation. (2). Workflow in scanning and interpretation of studies. Some of the technical challenges and limitations that need to be considered include: (1). Limitation of MRI for lung lesion detection. (2). Attenuation correction. (3). Registration of free-breathing PET and breath-hold thoacoabdominal MR data. While FDG PET/CT remains the workhorse for diagnosis and management of oncologic diseases, early experience shows that PET/MR may have a complementary role. PET/MR could potentially play a significant role in diagnosis and management algorithms of several malignancies

Dynamic contrast enhanced (DCE) MRI has emerged as a reliable and diagnostically useful functional imaging technique. DCE protocol typically lasts 3-15 minutes and results in a time series of N volumes. For automated analysis, it is important that volumes acquired at different times be spatially coregistered. We have recently introduced a novel 4D, or volume time series, coregistration tool based on a user-specified target volume of interest (VOI). However, the relationship between coregistration accuracy and target VOI size has not been investigated. In this study, coregistration accuracy was quantitatively measured using various sized target VOIs. Coregistration of 10 DCE-MRI mouse head image sets were performed with various sized VOIs targeting the mouse brain. Accuracy was quantified by measures based on the union and standard deviation of the coregistered volume time series. Coregistration accuracy was determined to improve rapidly as the size of the VOI increased and approached the approximate volume of the target (mouse brain). Further inflation of the VOI beyond the volume of the target (mouse brain) only marginally improved coregistration accuracy. The CPU time needed to accomplish coregistration is a linear function of N that varied gradually with VOI size. From the results of this study, we recommend the optimal size of the VOI to be slightly overinclusive, approximately by 5 voxels, of the target for computationally efficient and accurate coregistration.

Purpose Pre-operative three-dimensional (3D) printed renal malignancy models are tools with potential benefits in surgical training and patient education [1,2]. Most importantly, 3D models may facilitate surgical planning by allowing surgeons to assess tumor complexity as well as the relationship of the tumor to major anatomic structures [3]. The objective of this study was to evaluate this impact. Methods Imaging was obtained from an IRB approved, prospectively collected database of multiparametric magnetic resonance imaging (MRI) of renal masses. Ten cases eligible for elective partial nephrectomy were retrospectively selected. High-fidelity models were 3D printed in multiple colors based on T1 images (Fig. 1). Cases were reviewed by three attending surgeons and six senior residents with imaging alone and in addition to the 3D model. A standardized questionnaire was developed to capture the planned surgical approach and intraoperative technique in both sessions. Results Surgical approach was changed in 20 % of decisions, intraoperative considerations were changed in 40 % (Fig. 2). Thirty percent and 23 % of decisions in the attending and resident groups, respectively, were altered by the 3D model. Overall, every case was modified with this additional information. All participants reported that the models helped plan the surgical approach for partial nephrectomy. Most reported improved comprehension of anatomy and confidence in surgical plan. Half reported that the 3D printed model altered their surgical plan significantly. Due to use of T1 images, reconstruction of calyces and tertiary blood vessels were limited: 8 of the 9 participants desired more information regarding these structures. (Figure presented) Conclusion Utilization of 3D modeling may aid in pre-operative and intra-operative planning for both attending and resident surgeons. While 3D models with MR imaging is feasible, computed tomography (CT) imaging may provide additional anatomical information. Future study is required to prospectively assess the utility of models and pre-operative planning and intra-operative guidance

von Hippel-Lindau (VHL) disease is an autosomal-dominant, hereditary, multisystem neoplasia syndrome with increased susceptibility to several benign and malignant tumors. VHL occurs in about 1 in 36,000 live births and is associated with germline mutation of the VHL tumor suppressor gene on the short arm of chromosome 3. VHL disease exhibits diverse genotype and phenotype correlations, exhibits variable intrafamilial and interfamilial expressivity, and can manifest with benign and malignant tumors of the central nervous system, kidneys, adrenals, pancreas, and reproductive organs. Imaging and management of this entity are therefore multidisciplinary. An overview of VHL disease is presented.

Purpose To develop a three-dimensional breath-hold (BH) magnetic resonance (MR) cholangiopancreatographic protocol with sampling perfection with application-optimized contrast using different flip-angle evolutions (SPACE) acquisition and sparsity-based iterative reconstruction (SPARSE) of prospectively sampled 5% k-space data and to compare the results with conventional respiratory-triggered (RT) acquisition. Materials and Methods This HIPAA-compliant prospective study was institutional review board approved. Twenty-nine patients underwent conventional RT SPACE and BH-accelerated SPACE acquisition with 5% k-space sampling at 3 T. Spatial resolution and other parameters were matched when possible. BH SPACE images were reconstructed by enforcing joint multicoil sparsity in the wavelet domain (SPARSE-SPACE). Two board-certified radiologists independently evaluated BH SPARSE-SPACE and RT SPACE images for image quality parameters in the pancreatic duct and common bile duct by using a five-point scale. The Wilcoxon signed-rank test was used to compare BH SPARSE-SPACE and RT SPACE images. Results Acquisition time for BH SPARSE-SPACE was 20 seconds, which was significantly (P < .001) shorter than that for RT SPACE (mean +/- standard deviation, 338.8 sec +/- 69.1). Overall image quality scores were higher for BH SPARSE-SPACE than for RT SPACE images for both readers for the proximal, middle, and distal pancreatic duct, but the difference was not statistically significant (P > .05). For reader 1, distal common bile duct scores were significantly higher with BH SPARSE-SPACE acquisition (P = .036). More patients had acceptable or better overall image quality (scores >/= 3) with BH SPARSE-SPACE than with RT SPACE acquisition, respectively, for the proximal (23 of 29 [79%] vs 22 of 29 [76%]), middle (22 of 29 [76%] vs 18 of 29 [62%]), and distal (20 of 29 [69%] vs 13 of 29 [45%]) pancreatic duct and the proximal (25 of 28 [89%] vs 22 of 28 [79%]) and distal (25 of 28 [89%] vs 24 of 28 [86%]) common bile duct. Conclusion BH SPARSE-SPACE showed similar or superior image quality for the pancreatic and common duct compared with that of RT SPACE despite 17-fold shorter acquisition time. (c) RSNA, 2016.

OBJECTIVE: The purpose of this study was to determine whether qualitative and quantitative MRI feature analysis is useful for differentiating type 1 from type 2 papillary renal cell carcinoma (PRCC). MATERIALS AND METHODS: This retrospective study included 21 type 1 and 17 type 2 PRCCs evaluated with preoperative MRI. Two radiologists independently evaluated various qualitative features, including signal intensity, heterogeneity, and margin. For the quantitative analysis, a radiology fellow and a medical student independently drew 3D volumes of interest over the entire tumor on T2-weighted HASTE images, apparent diffusion coefficient parametric maps, and nephrographic phase contrast-enhanced MR images to derive first-order texture metrics. Qualitative and quantitative features were compared between the groups. RESULTS: For both readers, qualitative features with greater frequency in type 2 PRCC included heterogeneous enhancement, indistinct margin, and T2 heterogeneity (all, p < 0.035). Indistinct margins and heterogeneous enhancement were independent predictors (AUC, 0.822). Quantitative analysis revealed that apparent diffusion coefficient, HASTE, and contrast-enhanced entropy were greater in type 2 PRCC (p < 0.05; AUC, 0.682-0.716). A combined quantitative and qualitative model had an AUC of 0.859. Qualitative features within the model had interreader concordance of 84-95%, and the quantitative data had intraclass coefficients of 0.873-0.961. CONCLUSION: Qualitative and quantitative features can help discriminate between type 1 and type 2 PRCC. Quantitative analysis may capture useful information that complements the qualitative appearance while benefiting from high interobserver agreement.

PURPOSE: To investigate the feasibility of high temporal resolution quantitative perfusion imaging of bladder tumors performed simultaneously with conventional multi-phase MR urography (MRU) using a novel free-breathing continuously acquired radial MRI sequence with compressed-sensing reconstruction. METHODS: 22 patients with bladder lesions underwent MRU using GRASP (Golden-angle RAdial Sparse Parallel) acquisition. Multi-phase contrast-enhanced abdominopelvic GRASP was performed during free-breathing (1.4x1.4x3.0mm3 voxel size; 3:44min acquisition). Two dynamic datasets were retrospectively reconstructed by combining different numbers of sequentially acquired spokes into each dynamic frame: 110 spokes per frame for 25-second temporal resolution (serving as conventional MRU for clinical interpretation) and 8 spokes per frame for 1.7-second resolution. Using 1.7-second resolution images, ROIs were placed within bladder lesions and normal bladder wall, a femoral artery arterial input function was generated, and the Generalized Kinetic Model was applied. RESULTS: Biopsy/cystectomy demonstrated 16 bladder tumors (13 stage>/=T2, 3 stage/=T2 than stage