Cardiophile MD Archive » Cardiac MRI (CMR) http://www.cardiophile.net Archive of Cardiophile MD Wed, 16 Jun 2010 00:06:48 +0000 en hourly 1 http://wordpress.org/?v=3.0 Blood-oxygen-level dependent (BOLD) MRI for myocardial ischemia evaluation http://www.cardiophile.net/2010/03/blood-oxygen-level-dependent-bold-mri-for-myocardial-ischemia-evaluation.html http://www.cardiophile.net/2010/03/blood-oxygen-level-dependent-bold-mri-for-myocardial-ischemia-evaluation.html#comments Fri, 12 Mar 2010 10:58:44 +0000 Johnson Francis http://cardiophile.org/?p=4197 Blood-oxygen-level dependent (BOLD) magnetic resonance imaging (MRI) is technique useful in detecting myocardial ischemia. Oxyhaemoglobin and deoxyhaemoglobin differ in their magnetic properties – the former in diamagnetic while the latter is paramagnetic. This difference in magnetic properties can be used as an endogenous contrast to visualize tissue oxygenation. This technique has been termed BOLD MRI. Deoxygenation of hemoglobin causes inhomogeneity in the local magnetic field and hence a change in T2 weighted MRI images. BOLD MRI can detect changes in deoxyhemoglobin levels as a result of changes in blood flow and oxygen consumption. When coronary vasodilation is induced by giving dipyridamole, the levels of deoxyhemoglobin in the coronary venous blood falls as the blood flow increase is disproportionate to the oxygen demand. Occlusion of a coronary artery on the other hand increases the myocardial venous blood deoxyhemoglobin concentration due to myocardial ischemia. In areas supplied by a stenotic coronary artery, there will be no vasodilatory reserve as the capillaries are already maximally dilated. Hence dipyridamole can be used to identify ischemic myocardium by BOLD MRI as these regions will show decreased signal on MRI suggesting hypoperfusion.

]]> http://www.cardiophile.net/2010/03/blood-oxygen-level-dependent-bold-mri-for-myocardial-ischemia-evaluation.html/feed 0 Dark blood imaging http://www.cardiophile.net/2009/09/dark-blood-imaging.html http://www.cardiophile.net/2009/09/dark-blood-imaging.html#comments Fri, 25 Sep 2009 10:07:09 +0000 Johnson Francis http://www.cardiophile.net/?p=3448 Dark blood imaging and bright blood imaging are terminologies usually used in:

a. Cardiac magnetic resonance imaging
b. Echocardiography
c. Coronary angiography
d. Multi slice CT

Answer: a

Dark blood imaging and bright blood imaging are terminologies usually used in cardiac magnetic resonance imaging. Generally, in spin echo imaging flowing blood appears dark and in gradient echo imaging, flowing blood appears bright.

]]> http://www.cardiophile.net/2009/09/dark-blood-imaging.html/feed 0 Magnetic resonance imaging in congenital heart disease (CHD) http://www.cardiophile.net/2009/07/magnetic-resonance-imaging-in-congenital-heart-disease-chd.html http://www.cardiophile.net/2009/07/magnetic-resonance-imaging-in-congenital-heart-disease-chd.html#comments Thu, 16 Jul 2009 15:18:02 +0000 Johnson Francis http://cardiophile.org/?p=1340 Advantages of MRI in congenital heart disease imaging 

  1. No ionizing radiation
  2. 3D anatomy can be visualised
  3. Blood flow analysis is possible - black blood and white blood imaging > flowing blood is seen as white in white blood imaging.

Indications for cardiac magnetic resonance (CMR) imaging in CHD

  1. Repaired tetralogy of Fallot – Right ventricular outflow tract aneurysm  has to be looked fo in cases in which a trans annular patch has been used.
  2. Evaulation of Aorti acrch pathology like coarctation and double aortic arch
  3. Transposition of great arteries
  4. Evaluation of vascular rings
  5. Evaluation of regional funciton by CMR
  6. Imaging of pulmonary veins
  7. Evaluation of endo grafts
  8. Coronary imaging by MR  – Anomalous origin right coronary artery from RCA from left sinus can cause sudden cardiac death (SCD) during exercise, because the artery courses between the aorta and the pulmonary trunk.

Special modalities in CMR

  1. Phase contrast MR
  2. MR tagging for asssessment of regional function by MR
  3. CMR overlay over live fluro has been evaluated experimentally
]]> http://www.cardiophile.net/2009/07/magnetic-resonance-imaging-in-congenital-heart-disease-chd.html/feed 0 MRI in persons with coronary stents http://www.cardiophile.net/2009/05/mri-in-persons-with-coronary-stents.html http://www.cardiophile.net/2009/05/mri-in-persons-with-coronary-stents.html#comments Thu, 07 May 2009 03:53:18 +0000 Johnson Francis http://cardiophile.org/?p=1217 Coronary stents can get heated up during magnetic resonance imaging (MRI). Hence MRI is better avoided within the first month after bare metal stent and three months of drug eluting stent implantation. This is the usual time period for endothelisation of these stents.

]]> http://www.cardiophile.net/2009/05/mri-in-persons-with-coronary-stents.html/feed 0 Cardiac magnetic resonance imaging (CMR) http://www.cardiophile.net/2009/04/cardiac-magnetic-resonance-imaging-cmr.html http://www.cardiophile.net/2009/04/cardiac-magnetic-resonance-imaging-cmr.html#comments Mon, 13 Apr 2009 03:39:00 +0000 Johnson Francis http://cardiophile.org/?p=1140  Most accurate and reproducible technique for imaging the heart

Outstanding image resolution and intrinsic tissue contrast

Safe, non-invasive and does not expose the subject to ionizing radiation

White blood and dark blood imaging in CMR:

For functional imaging white blood imaging is used while dark blood imaging is used for morphological evaluation.

Delayed enhancement with gadolinium:

Delayed enhancement is seen in myocardial infarction and is due to relative excess of gadolinium in pathological tissues compared to normal tissue. Transmural delayed enhancement indicates poor prospects of revascularisation. Delayed enhancement is not specific for ischemic injury and can occur with acute myocarditis, hypertrophic cardiomyopathy with fibrosis and dilated cardiomyopathy with fibrosis. Delayed enhancement indicates more of interstitial tissue into which gadolinium is concentrated.

Dobutamine stress MRI:

Dobutamine stress MRI has high specificity and low sensitivity. Increased systolic wall thickening of more than 2 mm is indicative of viability.

MRI for coronary evaluation:

MRI is useful for evaluation of coronary anomalies. But it is not an ideal modality for assessment of coronary stenosis.

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