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Diagnostic Radiology Department
Genetic Imaging
The imaging of genetic syndromes is of critical importance to the understanding of genotype-phenotype correlations. Moreover, noninvasive imaging techniques now permit accurate descriptions of the natural history of many of these disorders, which have been previously followed clinically. There are many examples of genetic imaging in the DRD. For instance, Dr. Nilo Avila has focused on the natural history of Lymphangiomatosis (LAM), Hermansky Pudlak Syndrome, and Congenital Adrenal Hyperplasia. Drs. Nicholas Patronas and Azar Dagher are describing imaging findings and the natural history of Mucolipidosis Type IV and Pallister Hall syndromes. Dr. Nicholas Patronas is also conducting a phenotype-genotype study in Neurofibromatosis 2. Dr. Suvimol Hill is evaluating the response of Gaucher's disease to enzyme replacement therapy and the natural history of Job's (Hyper IgE) syndrome and Proteus syndrome. Dr. Azar Dagher is also evaluating Osteogenesis Imperfecta basilar invagination with computer tomography (CT) and magnetic resonance imaging (MRI). Dr. Peter Choyke performs genotype-phenotype correlations and natural history studies of hereditary renal tumors including Beckwith-Wiedemann syndrome, Von Hippel Lindau Syndrome, hereditary renal oncocytomas, and hereditary papillary renal carcinomas.
In addition to these clinical genetic studies, a new animal imaging program is under development to investigate various genetic animal models including knock-out, knock-in, and mice with tumor and nonneoplastic allografts. The goal of these studies is to provide an objective and non-invasive method of correlating genotype and phenotype in well-characterized genetic models. In addition, imaging permits the testing of novel therapies in genetic disease.
Image Processing
Image processing and data analysis is becoming an increasingly important part of the Imaging Sciences and DRD research portfolio. Examples of the use of image processing include Dr. Ronald Summers' work on virtual bronchoscopy in which fly throughs of the tracheo-bronchial tree can be performed using only data from CT. Dr. Ronald Summers and Dr. Peter Yim are developing image processing algorithms to improve the diagnostic utility of magnetic resonance angiography (MRA) studies. Dr. Ronald Summers is also working on semiautomatic detection methods of identifying and determining the size of lesions and characterizing them as solid or cystic. Dr. Alexander Ling is studying the effects of lossy wavelet compression on the diagnostic accuracy of images. This could have profound implications for the storage, transfer, and interpretation of image data in the future. Dr. Azar Dagher is using Medx, Vortex, and BrainMap applications for neuroradiologic image processing. Dr. Azar Dagher is also evaluating Bayesian decision support for radiology and has developed Java-based applets for use on the World Wide Web. Dr. Alan Liu is developing methods of computationally comparing images derived from a normal atlas with abnormal images in the brain.
Noninvasive Vascular Imaging
Noninvasive vascular imaging is a fast growing area of imaging research. Coronary arterial calcification, for instance, is considered a strong predictor of coronary artery disease. Drs. Nilo Avila and Alexander Ling are comparing electron beam CT (EBCT) and sub-second helical CT, using a prototype CT scanner, for detecting coronary calcifications. If successful, coronary screening will be more widely available since the number of EBCT machines is limited. Dr. Ronald Summers is evaluating MRA in characterizing atherosclerosis in familial hypercholesterolemics. Drs. Peter Choyke, Vincent Ho, and Thomas Foo are developing advanced techniques for MRA including table motion studies to permit angiography of the entire lower extremity and abdomen. Prototype software is being developed to improve the speed and image quality of MRAs. Drs. Peter Choyke and Elizabeth Jones are also involved in sonographic studies of the carotid to determine intimal-medial wall thickness as a predictor of cardiovascular disease in studies of frequent vs. infrequent blood donors and in HIV-infected patients on triple antiviral therapies.
Oncologic Imaging
Oncologic imaging comprises a significant part of the department's workload and many projects derive from this patient population. Drs. Peter Choyke and Ronald Summers are investigating the imaging of angiogenesis using MRI in conjunction with an antiangiogenesis clinical and animal study. Dr. Peter Choyke and Dr. Jorge Carrasquillo are studying patients with rising CEA levels after colon cancer surgery with CT, MRI, and positron emission tomography and reexploration to determine which technique is most sensitive for detecting recurrences. Drs. Suvimol Hill and Peter Choyke are studying the early effects of treatment using MRI and Doppler US in osteosarcomas of the extremities. Drs. Catherine Chow and Elizabeth Jones are investigating the role of MRI in detecting and staging breast cancers in high-risk women using a prototype biopsy/imaging surface coil. Drs. Ahalya Premkumar and Nilo Avila are examining the effects of Raloxifene and tamoxifen on uterine endometrial hyperplasia and ovarian hyperstimulation using transvaginal ultrasound with color Doppler and sonohysterography in a population of women at high risk for breast cancer. Radiation therapy is often delivered to patients with head and neck cancers and results in the troublesome side effect of very dry mouth, which is very uncomfortable. Drs. Nicholas Patronas and Azar Dagher are using MRI to study early radiation effects on the parotid gland in order to better understand the pathophysiology of changes in the parotid gland after radiation.
Neuroradiologic Imaging
The diversity of neurologic investigation at NIH has given rise to a wide range of imaging projects. Drs. Azar Dagher, Nicholas Patronas, and Nick Bryan are investigating acute stroke image analysis using high-speed MRI studies, which will allow early intervention with thrombolytics. Dr. Nick Bryan is studying methods of mapping abnormal images onto normal images from an atlas. This will permit automated lesion detection in the future. Dr. Nicholas Patronas has an ongoing study on the pathophysiology of syrinx formation using MR, CT, and intraoperative ultrasound. Drs. Azar Dagher and Greg Katzman are using fMRI techniques to evaluate taste and smell in normal subjects. Dr. Azar Dagher is also investigating the role of magnetization transfer effects in the brain and elsewhere in the body (Magnetization Transfer quantitation study protocol # 98-CC-0084).
Endocrine Imaging
The localization of parathyroid adenomas remains problematic especially in patients with recurrent disease. Dr. John Doppman and Dr. Lynne Pusanik have been involved in the assessment of "fast" parathyroid hormone assays during venous sampling to help guide the interventionalist to the site of the tumor. Additionally, hypocalcemic stimuli, such as contrast media itself and other calcium-lowering agents are being tested to ascertain whether this will improve the sensitivity of venous sampling for parathyroid adenomas. In Cushing's disease, localization of the pituitary adenoma remains problematic. Venous sampling of ACTH levels from the petrosal veins remains the gold standard test. A comparison with jugular venous sampling is under way since this could greatly simplify the examination. Drs. John Doppman, Thomas Shawker, and Nicholas Patronas also have been successfully testing transsphenoidal sonography with a prototype transducer to localize pituitary adenomas during surgery and compare this new approach to MRI. Dr. Thomas Shawker has extensive experience in localizing neuroendocrine tumors in the operating room using color Doppler ultrasound.
Thrombolysis
Dr. Lynne Pusanik is evaluating the role of thrombolytic therapy in deep venous thrombosis using tissue plasminogen activator. She is also developing microspheres that could deliver therapeutic agents (e.g., chemotherapy) into vascular malformations to treat them with interventional techniques.
Musculoskeletal Imaging
A variety of musculoskeletal imaging projects are under way. Dr. Ahalya Premkumar is comparing the role of ultrasound and MRI in the evaluation of posterior tibialis tendon rupture in conjunction with Dr. Lynn Gerber from Rehabilitation Medicine. Dr. Peter Choyke is evaluating psoriatic arthritis response to therapy with contrast enhanced three-dimensional MRI. Dr. Ronald Summers participates in studies of polymyositis of the lower extremities. Dr. Suvimol Hill is investigating the role of MRI in assessing the thickness of the Achilles tendon in familial homozygous hypercholesterolemia.
Imaging of Immunodeficiency Syndromes
AIDS is an important clinical focus in the Clinical Center. Drs. Azar Dagher and Nicholas Patronas are investigating the vascular manifestations of human immunodeficiency virus in the pediatric brain. Dr. Elizabeth Jones is investigating the imaging findings of side effects of triple antiviral therapy such as indinovar including fat redistribution and premature atherosclerotic changes.