Advanced MR Imaging Techniques in the Characterization of Renal Cell Carcinoma: Correlation with Pathology and Gene Expression Profiles
After obtaining IRB approval, patients with known renal masses that are scheduled for a partial or radical nephrectomy at our institution as part of their standard of care will be offered to participate in this study. Study subjects will be adult (i.e. and amp;gt;18 years) male and female patients with confined renal masses (stage 1-3) as well as those with stage 4 disease in whom a debulking nephrectomy is chosen as the initial treatment. A research assistant will be responsible for patient recruitment and obtaining informed consent. MR examinations will be performed on a 1.5T or 3T MRI Scanner located within the department of Radiology at UT Southwestern Medical Center.
Exclusion criteria will include, similar to our routine clinical practice, any contraindication for MRI: 1) medically unstable, 2) cardiac pacemaker, 3) intracranial clips, metal implants, or external clips within 10 mm of the head, 4) metal in the eyes, 5) pregnant or nursing, and 6) claustrophobia. In addition, patients with a biopsy-proven benign renal mass or suspected to have an angiomyolipoma based on imaging will be excluded.
The research MRI protocol of this proposal includes 2D ASL acquisitions acquired in two orthogonal planes (i.e. axial, coronal, and/or sagittal) selected depending on the tumor location, and axial DWI images to cover the renal mass. A 3D ASL acquisition is under development at UTSW and will be added to the imaging protocol once it becomes available. ASL and DWI acquisitions will be obtained in approximately 15-20 minutes. 2D ASL acquisitions will be obtained with a single-shot fast spin echo sequence modified with pulsed-continuous ASL preparation (67) using approximately the following parameters: TR= 6000, TE= 50 ms, flip angle= 130, matrix= 128x128, thickness 10 mm. Sixteen spin-labeled-controls are acquired over 3.5 minutes (67). DWI acquisition will be obtained in approximately 3 minutes using an echo planar sequence using respiratory-triggering (with the use of abdominal wall bellows) and approximately the following parameters: TR= 4000-6000 (depending on respiratory cycle), TE= 70 ms, matrix= 96x96, thickness= 5 mm, NEX=4, and b values of 0 and 850 s⋅mm-2.
Dynamic contrast-enhanced (DCE) MRI is a key component of the standard clinical protocol and allows for accurate delineation of the anatomy as well as characterization of renal masses and prediction of their histologic subtypes (65). High temporal resolution DCE T1-weighted MR images will be acquired in this research protocol before, during, and up to 2 minutes after the administration of a single dose of the gadolinium-based contrast agent (Gadavist 0.1 mmol/kg body weight x similar dose than that of clinical MRI examinations). The overall scan time for the MRI examination will be under 1 hour. DCE MRI data will be exported to a separate password-protected workstation in the Rogers MRI reading room equipped with the kinetic analysis software Omnilook (iCAD Inc. Nashua, NH). Estimates of tumor perfusion will be then calculated from the DCE MRI data including the rate constant for the transfer of Gd-DTPA from the plasma into the extracellular space (transfer constant Ktrans), blood plasma volume fraction (Vp), area under the contrast concentration versus time curve for 90 seconds after contrast injection (IAUC90). These parameters will be compared to perfusion values obtained with ASL MRI.
Quantitative MRI measures of blood flow (ASL, DCE-MRI) and diffusion (DWI) will be obtained in up to 3 renal tumors per patient, and correlated to histopathology and immunohistochemical evaluations, clinical outcomes, and gene expression profiles as proposed in A1-4.
* Males or females, age of 18-99
* Patient has a known confined renal mass
* Patient is scheudled for a partial or radical nephrectomy at UT Southwestern Medical Center