Shreyas Vasanawala, MD/ PhD
Our research interests are Novel MRI Hardware, Fast MRI Techniques & Quantitative MRI Methods
Novel MRI hardware:
Many applications of body MRI may be improved or enabled by optimization of dedicated radiofrequency receiver arrays. Thus, we are actively developing new approaches to design and construction of miniaturized radiofrequency receiver arrays for optimized and personalized MRI exams.
Fast MRI techniques:
To enable more children to undergo MRI and to enable higher resolution imaging in adults, we are developing and validating methods that combine advanced parallel imaging, compressed sensing, deep learning approaches to image reconstruction and analysis, motion correction, and higher dimensional data acquisition strategies.
Quantitative MRI methods:
Development and validation of accurate and precise cardiovascular flow and function measurements, noninvasive renal function assessment, and tumor therapy response.
Lewis Shin, MD
Dr. Shin has developed a unique Sleep MRI protocol with physiologic monitoring (oral/nasal airflow, respiratory effort monitoring, etc) to evaluate the dynamic airway collapse in Obstructive Sleep Apnea (OSA) patients. Dr. Shin research interests also includes using real-time MRI imaging for other clinical applications as evaluating Crohns disease and small bowel dysmotility.
Sleep MRI for Obstructive Sleep Apnea:
Dr. Shin has developed a unique Sleep MRI protocol with physiologic monitoring (oral/nasal airflow, respiratory effort monitoring, etc) to evaluate the dynamic airway collapse in Obstructive Sleep Apnea (OSA) patients. Utilizing custom-made MRI pulse sequences and software, continuous, multiplanar MR imaging can be performed in sleep apnea patients under natural physiologic sleep. Currently, the clinical utility of Sleep MRI is being evaluated; additional applications of sleep MRI can include further understanding the dynamics of airway collapse, development of minimally invasive OSA treatments, and evaluation/trouble shooting of existing OSA therapeutics.
Small Bowel MRI:
Bruce Daniel, MD
Dr. Daniel's research interests are Breast MRI & Interventional MRI.
At Stanford we have a large effort dedicated to improving MRI scanning techniques for breast cancer, including ultra rapid volumetric imaging of dynamic contrast enhancement, and novel diffusion weighted sequences for detecting breast cancer without contrast material.
When focal abnormalities are detected in the breast, prostate, or other organs with MRI, and these abnormalities cannot be visualized with other methods, and MRI guided biopsy may be necessary to establish a diagnosis. Current MRI scanners however provide very limited access to the body for interventional procedures. We are developing a number of flexible approaches for minimally invasive procedures under MRI guidance, including freehand breast biopsy techniques, and remote manipulators that enable transperineal access to the prostate, in conjunction with the Department of mechanical engineering.
Graham Sommer, MD
Dr. Sommer's research interests are advanced techniques of prostate MRI, focal prostate ablation under MRI guidance and focal ablation of pancreatic cancer.
Advanced techniques of prostate MRI:
Currently evaluating, along with Dr. Bruce Daniels and others, utility of advanced techniques of MRI, (DCE, reduced FOV DWI) in visualizing cancer within the gland. Goals are both to visualize tumor to permit focal ablation, and to estimate tumor size/Gleason grade as a possible factor in patient treatment decision-making.
Focal prostate ablation under MRI guidance:
The goals are the focal ablation of prostate cancer and BPH “adenoma” under MRI guidance and MRTI (thermal imaging) using specially designed high intensity ultrasound “applicators” that are put directly into the gland (interstitial) or through the urethra (transurethral).
Focal ablation of pancreatic cancer:
We have designed and are constructing 2 types of ultrasonic applicators that will be inserted endoscopically from above, designed for ablation of pancreatic CA under MRTI. Below are diagrammatic representations
Pejman Ghanouni, MD, PhD
Dr. Ghanouni's research interests include MR guided HIFU palliation of painful metastases to bone and MR guided HIFU treatment of soft tissue tumors of the extremities.
MR guided HIFU palliation of painful metastases to bone: Bones are the third most common site of metastasis, and pain from these metastases is the most common cause of cancer-related pain. External beam radiotherapy (EBRT) is the standard of care, with > 40% of patients experiencing at least a 50% reduction in pain at 1 month. However, approximately one-third of patients do not have pain relief after radiation, and retreatment with EBRT is limited by toxicity to normal tissue. MRgHIFU has recently completed a phase 3 trial assessing the effectiveness and safety of this method for palliation of pain in patients with bone metastases.
Figure 6: Images from the pre-treatment PET-CT and MR demonstrate a metabolically active, enhancing expansile mass in the right ischial tuberosity. The patient was unable to sit on his right buttock because of 8 out of 10 pain from this lesion. The MR-HIFU images demonstrate thermal dose, in blue, deposited on the posterior aspect of the right ischial tuberosity. Post-treatment PET-CT and MR images demonstrate diminished metabolic activity and enhancement in a distribution that matches the region of the thermal deposition from the HIFU treatment. More importantly, this patient was able to sit normally within one week, with a pain score of between 0 - 1 out of 10 at 12 weeks.
MR guided HIFU treatment of soft tissue tumors of the extremities: Soft tissue tumors of the extremity occur in people of all ages. The standard of care is complete surgical resection of the tumor, and, in the case of malignant tumors, an additional margin of healthy tissue. Despite advances in surgical techniques, imaging technologies, chemotherapy regimens and radiotherapy, the morbidity associated with treating these tumors and the survival of patients with malignant tumors has not significantly improved in the past 20 years. We are adapting MRgHIFU techniques to the treatment of benign and malignant soft tissue tumors of the extremities, culminating in a Phase 1 clinical trial.
Figure 7: A photo of the right thigh of a patient with recurrent desmoid tumors, requiring three surgeries and multiple treatments with radiation, which are current standards of care. Despite the treatment, the patient is disfigured, had a pathologic fracture of the femur, and poor wound healing. Patients such as this would benefit greatly from a non-invasive therapy such as MRgHIFU. Images in the top right represent T1 weighted MR images of a human cadaveric lower leg undergoing HIFU planning. The yellow cylinders represent planned areas of sonication, and the blue areas are the treated areas with thermal dose deposited. The bottom right photo is of the tissue specimen showing the coagulated treatment area.
Andreas Loening, MD/PhD
Dr Loening’s research interests include improving imaging quality and diagnostic capabilities of MRI in genitourinary disease via the application of advanced pulse sequences and new imaging protocols.
Variable Refocusing Flip Angle Single Shot Fast Spin Echo Imaging
The most time consuming portion of most pelvic imaging protocols is the acquisition of T2-weighted imaging utilizing 2D fast-spin echo (FSE) sequences; this often requires 20-30 minutes of scanner time. Additionally, these 2D fast-spin echo sequences are often compromised by artifacts arising from respiratory motion and bowel peristalsis. Due to their greatly increased speed single shot fast spin echo (SSFSE) sequences have been proposed as a replacement for FSE as they essentially eliminate artifacts from motion, albeit at a cost of reduced signal-to-noise (SNR) and image blurring arising from T2-decay occurring during signal acquisition. We have incorporated variable refocusing flip angles into SSFSE (vrfSSFSE) in order to improve its image quality compared to conventional SSFSE as well as to further decrease imaging time via reductions in radiofrequency energy deposition (SAR constraints).
High-Resolution Post-Contrast Imaging for Tumor Staging in the Pelvis:
As another approach to move away from the use of time-consuming and artifact-prone 2D fast-spin echo sequences in the pelvis, we have been exploring the relative diagnostic capability of a single high-resolution
3D post-contrast T1-weighted acquisition versus conventional multi-planar 2D FSE based imaging protocols. This high-resolution T1-weighted sequence allows reformation of arbitrary imaging planes retrospectively, removing the need for the acquisition of multiple separate planes of imaging as well as eliminating errors in acquisition plane prescription.