Assistant Professor of Radiology
Stanford University School of Medicine
Department of Radiology
Richard M. Lucas Center for Imaging
1201 Welch Road, Room P269
Stanford, CA 94305-5488
(o) 650-498-4485
(f) 650-723-5795

 


 

Clinical Overview:

  • Abdominal and pelvic MRI: Application of fast volumetric imaging to MR arteriography and venography, solid organ transplants, and gynecologic tumors.
  • MR guided high intensity focused ultrasound: Clinical applications for treatment of uterine leiomyomata (fibroids) and palliation of pain from metastases to bone.

 

Clinical Interests

MR angiography: MR provides an high-resolution, radiation-free means of evaluating vessel number, size, course, and patency. For example, in patients with acute or chronic leg swelling, MR may be used to identify the presence and extent of venous thrombosis, as well as any anatomic cause predisposing a patient to forming a venous clot. For those with venous stents, MR may be used to confirm continued patency of the stent. MR may also be used to thoroughly evaluate patients prior to planned surgery. For example, MR imaging of patients being considered for renal donation for transplant reveals the presence of accessory renal arteries, variant venous anatomy, unsuspected renal masses, or hydronephrosis.

Figure 1: High resolution post-contrast axial MR image of the legs demonstrates swelling of the left leg, and an expansile filling defect in the left popliteal vein, indicating an acute thrombus.

Figure 2: Curved planar reformatted image from post-contrast MR images demonstrates anatomy consistent with May-Thurner syndrome, with narrowing of the left common iliac vein between the crossing right common iliac artery and the spine. This compression predisposes patients to thrombosis within the left lower extremity.

Figure 3: Coronal post-contrast MR image demonstrates homogeneous opacification of a stent in the left common iliac vein, indicating stent patency. 

Figure 4: Volume rendered images generated from multiphasic MR images of a potential renal donor demonstrate prehilar branching of the renal arteries, and a circumaortic left renal vein. 

Interventional MR: Approximately 600,000 hysterectomies are performed every year, with more than 30% of these surgeries done to address the symptoms of uterine fibroids. While surgery and minimally invasive methods such as uterine artery embolization (UAE) have important roles in the management of patients with uterine fibroids, MR guided high intensity focused ultrasound (MRgHIFU) is an entirely non-invasive method that may be used to treat a subset of these patients.

Figure 5: Sagittal T2 weighted MR image shows an enlarged uterus with several hypointense uterine fibroids. Fibroids may cause excessive menstrual bleeding, and/or pain from mass effect on adjacent pelvic organs such as the bladder or rectum.

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 extremitiesSoft 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.

Collaborators: Kim Butts Pauly, David Hovsepian, Raffi Avedian, Garry Gold, Bertha Chen, Paul Blumenthal, Hong Yu, George Segall, Shreyas Vasanawala, Bruce Daniel, Graham Sommer.

Last modified Fri, 19 Oct, 2012 at 14:50