Faculty Bibliography

OBJECTIVE: To determine whether patient-specific 3D printed renal tumor models change pre-operative planning decisions made by urological surgeons in preparation for complex renal mass surgical procedures. MATERIALS AND METHODS: From our ongoing IRB approved study on renal neoplasms, ten renal mass cases were retrospectively selected based on Nephrometry Score greater than 5 (range 6-10). A 3D post-contrast fat-suppressed gradient-echo T1-weighted sequence was used to generate 3D printed models. The cases were evaluated by three experienced urologic oncology surgeons in a randomized fashion using (1) imaging data on PACS alone and (2) 3D printed model in addition to the imaging data. A questionnaire regarding surgical approach and planning was administered. The presumed pre-operative approaches with and without the model were compared. Any change between the presumed approaches and the actual surgical intervention was recorded. RESULTS: There was a change in planned approach with the 3D printed model for all ten cases with the largest impact seen regarding decisions on transperitoneal or retroperitoneal approach and clamping, with changes seen in 30%-50% of cases. Mean parenchymal volume loss for the operated kidney was 21.4%. Volume losses >20% were associated with increased ischemia times and surgeons tended to report a different approach with the use of the 3D model compared to that with imaging alone in these cases. The 3D printed models helped increase confidence regarding the chosen operative procedure in all cases. CONCLUSIONS: Pre-operative physical 3D models created from MRI data may influence surgical planning for complex kidney cancer.

Magnetic resonance (MR)/PET scanners provide an imaging platform that enables simultaneous acquisition of MR and PET data in perfect spatial and temporal registration. This feature allows improving image quality for the MR and PET images obtained during the course of an examination. In this work the authors demonstrate the use of prospective MR-based motion tracking information for removing motion blur in MR/PET images of small pulmonary nodules. The theoretical basis for the algorithms is presented alongside clinical examples of its use.

PURPOSE: To define important elements of a structured radiology report of a CT or MRI performed to evaluate an indeterminate renal mass. METHODS: IRB approval was waived for this multi-site prospective quality improvement study. A 35-question survey investigating elements of a CT or MRI report describing a renal mass was created through an iterative process by the Society of Abdominal Radiology Disease-Focused Panel on renal cell carcinoma. Surveys were distributed to consenting abdominal radiologists and urologists at nine academic institutions. Consensus within and between specialties was defined as >/=70% agreement. Respondent rates were compared with Chi Square test. RESULTS: The response rate was 68% (117/171; 55% [39/71] urologists, 78% [78/100] radiologists). Inter-specialty consensus was that the following were essential: mass size with comparison to prior imaging, mass type (cystic vs. solid), presence of fat, presence of enhancement, and radiologic stage. Urologists were more likely to prefer the Nephrometry score (75% [27/36] vs. 22% [17/76], p < 0.0001), quantitative reporting of enhancement on CT (85% [32/38] vs. 46% [36/77], p < 0.0001), and mass position with respect to the renal polar lines (67% [24/36] vs. 36% [27/76], p = 0.002). There was inter-specialty consensus that the Bosniak classification for cystic masses was preferred. Most urologists (60% [21/35]) preferred management recommendations be omitted for solid masses or Bosniak III-IV cystic masses. CONCLUSIONS: Important elements to include in a CT or MRI report of an indeterminate renal mass are critical diagnostic features, the Bosniak classification if relevant, and the most likely specific diagnosis when feasible; including management recommendations is controversial.

The introduction of compressed sensing for increasing imaging speed in magnetic resonance imaging (MRI) has raised significant interest among researchers and clinicians, and has initiated a large body of research across multiple clinical applications over the last decade. Compressed sensing aims to reconstruct unaliased images from fewer measurements than are traditionally required in MRI by exploiting image compressibility or sparsity. Moreover, appropriate combinations of compressed sensing with previously introduced fast imaging approaches, such as parallel imaging, have demonstrated further improved performance. The advent of compressed sensing marks the prelude to a new era of rapid MRI, where the focus of data acquisition has changed from sampling based on the nominal number of voxels and/or frames to sampling based on the desired information content. This article presents a brief overview of the application of compressed sensing techniques in body MRI, where imaging speed is crucial due to the presence of respiratory motion along with stringent constraints on spatial and temporal resolution. The first section provides an overview of the basic compressed sensing methodology, including the notion of sparsity, incoherence, and nonlinear reconstruction. The second section reviews state-of-the-art compressed sensing techniques that have been demonstrated for various clinical body MRI applications. In the final section, the article discusses current challenges and future opportunities. LEVEL OF EVIDENCE: 5 J. Magn. Reson. Imaging 2016.

Incidental detection of renal mass results in management dilemma. Historically all enhancing renal tumours without imaging evidence of bulk fat were considered surgical. However, it is clear that many of these small renal masses are either benign such as angiomyolipoma (AML) or oncocytoma, or are neoplasms with indolent behavior [1]. Surgical resection of these benign or indolent tumours, especially in patients with decreased renal function or other co-morbidities, results in increased cost without improvement in survival or mortality [2]. Use of advance imaging, such as diffusion weighted imaging (DWI) and perfusion weighted imaging (PWI), to non-invasively investigate renal tumour histopathology and aggressiveness can impact treatment decision and lower treatment cost. Number of key observations highlighting the role of MR including advance imaging techniques in evaluation of renal masses is as listed below: 1. Differentiating benign renal masses from malignant tumours.-Certain MRI features such as homogenous T2 signal, uniform enhancement, restricted diffusion with low ADC, and without evidence for necrosis and calcification can differentiate lipid poor AML from clear cell and papillary subtype of kidney cancers [3, 4].-It is nearly impossible to discriminate benign oncocytoma from chromophobe and clear cell subtypes of kidney cancers on conventional imaging [5]. However, DWI and PWI have shown some promise in small studies. 2. Tumour aggressiveness of solid RCC-Kidney cancers with different histologic subtypes differ in aggressiveness. Conventional MR imaging has shown some promise in differentiating papillary subtype of RCC from other subtypes based on hypovascularity, homogenous low T2 signal, T1 hyperintensity, and low ADC values. Advance DWI and PWI may further improve accuracy of MRI in discriminating papillary subtype from other types of kidney cancers.-Clear cell subtype of kidney cancers is hypervascular with heterogeneous T2 and diffusion signal [6]. 3. Tumour aggressiveness/outcome of cystic RCC-Cystic RCC with less than 25% solid enhancing component tend to be less aggressive than solid RCC [7]

Positron Emission Tomography and Compute Tomography (PET/CT) is routinely used in evaluation for cancer staging and assessment of metastatic disease. In addition, MRI is used as a problem solving tool. Until recently PET and MR examinations have been performed by separate PET and MR devices with temporal delay between these two types of acquisitions. However, recent introduction of hybrid PET/MR systems has made it possible to acquire PET and MRI data either simultaneously or near simultaneously. PET/MR is a powerful tool that provides opportunity for multiparametric PET and MR imaging. This has tremendous potential in cancer staging, detection of metastatic disease, and assessment of treatment response. However, to take advantage of this powerful tool and implement it in clinical practice requires understanding of various components of the system, what the system can and can't do, and how to optimize protocols to answer clinically relevant questions. Some of these areas of opportunities and challenges include: (1) PET/MR: System and workflow considerations such as-Attenuation correction with MRI-Validation of PET/MR with respect to PET/CT-Whole body and targeted organ protocol (2) Current and potential clinical indications for oncologic imaging such as-Lymphoma Imaging-Simultaneous locodistant staging for cancers-Assessment of treatment response (3) Limitations of PET/MR such as-Lung imaging-Osseous lesions

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.

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