Year : 2005 | Volume
: 15 | Issue : 1 | Page : 11--12
Total body MR Screening a new concept and protocol
Shrinivas B Desai
Shrinivas B Desai
|How to cite this article:|
Desai SB. Total body MR Screening a new concept and protocol.Indian J Radiol Imaging 2005;15:11-12
|How to cite this URL:|
Desai SB. Total body MR Screening a new concept and protocol. Indian J Radiol Imaging [serial online] 2005 [cited 2020 Feb 18 ];15:11-12
Available from: http://www.ijri.org/text.asp?2005/15/1/11/28734
For long, mass miniature radiography of the chest and mammography were considered as useful radiological screening tests. Probably the extent of radiation prohibited regular screening of rest of the body organs. MRI with its high spatial and temporal resolution, excellent soft tissue contrast and absence of radiation probably is emerging as an alterative screening modality MR screening protocol is capable of evaluating CNS, peripheral and cardiovascular system, as well as prostate and colonic cancers.
OMR appears best suited for total body screening simply because of its high diagnostic accuracy. Even MR contrast agents are for safer and void of any significant nephrotoxocity. New MR breath hold sequences, navigator assisted newer imaging techniques and excellent quality body images have made MR almost equivalent to CT Scan, making it an ideal modality for screening. MR has already been used for breast cancer screening to detect early malignancy especially in patients with dense breasts. MR has been found very sensitive and highly specific in detecting the lesions in the breast not seen on conventional Mammography or other imaging modalities. As we know in most of the western countries, and the rule is no different for our countries, women above the age of 50 and in some countries above the age of 40 are advised to undergo routine early mammography. Kuhl CK et al have discussed the role of breast MR imaging in women suspected to be carriers of breast cancer susceptibility gene. In the western world colorectal cancer is 2nd most common cause of cancer mortality. With changing dietary habits and life style, there is an increase in the incidence of this disease in our country also. Fenlon et al and Pappalardo et al found virtual MR colonoscopy or CT colonoscopy highly sensitive in detecting clinically relevant colorectal polyps of more than 8mm size. MR colonoscopy consistently detected polyps larger than 10mm, identifying the risk for malignant degeneration. MR colonoscopy combined with fecal tagging enhances the detectability of polyps larger than 8mm with specificity almost equaling to 100%.
Contrast enhanced 3D MR angiography, with a capability of screening a large field of view from head to toe, has been a boon in evaluating the entire vascular system in the study of atherosclerosis. The availability of bolus - chase technique, faster gradient systems have resulted in considerably decreasing the scanning time for complete evaluation of vascular system. The coverage of carotid arteries to popliteal trifurcation can be done merely in 64 to 72 seconds. It is normally done by obtaining 5 overlapping 3D data sets. Use of TIM technology has further resulted in higher signal to noise ratio, contrast to noise value with considerable increase in sensitivity and specificity upto 95 to 97% for detection of significant arterial stenosis. Goyen M et al, in their series of 100 consecutive patients with PVD, studied with 3D MRA, found additionally clinically relevant disease in 25 patients (33 segments), including renal artery stenosis, carotid artery narrowing, abdominal aortic aneurysm, not suspected earlier. Today it is possible to obtain total body 3D data set with moving the MR table with cranio caudal coverage of upto almost 40cm. The data for the entire body can be collected without patient movement outside the magnet even once. Usually contrast is injected twice, once for mapping the vascular tree and then for MR colonography. The total body screening can be obtained by
Brain studied with T1 and T2 SE and DW imaging 3D TOF (time of flight) MR Angiography is obtained • Whole body MR angiography is obtained with FLASH 3D technique with overlapping of 5 data sets in approximately 60 secondsThe heart morphology and lung parenchyma are studied with axial HASTE images. Subsequent assessment of cardiac function is done with TRUE-FISP imaging along the 2 chamber, 4 chamber and short axis. Late enhancement of myocardial infarction and myocardial viability study is obtained with 3D segmental IR turbo gradient sequence.MR colonography is obtained following filling up of colon with water with T1 W1 3D gradient echo sequence. Colonic wall is studied following IV contrast injection with 3D breath hold sequence.Total body imaging for metastatic detection is obtained with T1 TSE coronal and T1 IRM coronal sequences Initial experience of different authors reveal high detection rate for vascular diseases, colonic malignancy, pulmonary.
Initial experience of different authors reveal high detection rate for vascular diseases, colonic malignancy, pulmonary nodules, heart and brain pathologies with this simple technique. The sensitivity and specificity of detecting metastasis was found higher than conventional nuclear bone scan and even PET scan MR based screening protocols are a reality and are likely to emerge as routine radiological practice for total body screening.