Diagnostic Accuracy of Cardiac CT Perfusion Compared to PET Imaging
Condition: Myocardial Ischemia; Coronary Artery Disease; Myocardial Infarction
MeSH terms: Coronary Artery Disease; Myocardial Ischemia; Myocardial Infarction; Infarction; Ischemia
Study type: Observational

Summary: 
      This purpose of this research project is to test the diagnostic accuracy (i.e., sensitivity,
      specificity, positive and negative predictive value, and receiver operator curve area under
      the curve) of cardiac computed tomography (CT) perfusion as compared to the best non-invasive
      test of blood flow -- cardiac positron emission transmission (PET) perfusion imaging.

      The primary outcome of the study is to determine the CT perfusion technique with the highest
      overall diagnostic accuracy measured by the highest area under the receiver operator curve.

      The investigators will test 4 different CT perfusion techniques. (A) Qualitative, visual
      inspection of the contrast-enhanced CT images (B) Enhanced voxel distribution analysis (C)
      Rate of myocardial contrast enhancement analysis (D) Quantitative heart blood flow using a
      distributed 2-region analysis

      A second aim is to reduce the radiation dose needed to maintain CT perfusion diagnostic
      accuracy. Using the CT perfusion data, the investigators will model the minimal number of
      cardiac cycle radiation exposures needed to keep the diagnostic accuracy similar to the full
      data set.

      A third aim is to test the incremental diagnostic accuracy of CT angiography plus CT
      perfusion to identify regions of low blood flow as compared to PET perfusion alone.
    

Detailed description: 
      Chest pain and other symptoms can occur as a result of blockages in the arteries that supply
      the heart; these arteries are called the "coronary arteries". Blockages in the coronary
      arteries may decrease blood flow and oxygen delivery to the heart muscle, causing chest pain
      or other "anginal" symptoms. Coronary angiography is a commonly used test to visualize
      coronary artery disease or blockages but may not provide all the answers physicians need to
      assess patients with symptoms like chest pain. Two options for coronary angiography exist,
      invasive angiography and cardiac computed tomography angiography (CCTA). CCTA is completed by
      injecting contrast into a peripheral vein (not an artery) and then imaging when the coronary
      arteries fill with contrast. The imaged coronary arteries may be blocked partially,
      completely or not at all. While a blockage that occludes greater than 70% of an artery is
      highly correlated with chest pain or other anginal symptoms, occlusions of 40% or more may or
      may not decrease heart blood flow. Often multiple imaging studies are needed to evaluate
      whether blood flow is decreased in the setting of partial coronary artery blockages including
      non-invasive heart imaging to assess heart blood flow.

      One type of nuclear imaging is termed positron emission tomography (PET). In order to
      differentiate blockages that have poor heart perfusion with activity, nuclear PET images are
      taken at rest, when flow should be normal, and then repeated after the investigators "stress"
      the heart with medications. If blood flow is decreased during stress, a "defect" on the PET
      images is seen.

      An alternative, non-invasive technique to test for heart blood flow/perfusion to to measure
      heart blood flow as computed tomography (CT) contrast goes in and comes out. Preliminary
      studies in animals and humans to assess heart blood flow/perfusion using contrast-enhanced
      cardiac CT have been promising, but further work is needed. Combining CCTA with CT blood
      flow/perfusion measurements in the same setting could lead to a single, accurate diagnostic
      test that measures coronary artery blockage as well as blood flow.

      One limitation of CT imaging is the amount of radiation that can be given. The CCTA radiation
      dose is currently less than both nuclear PET imaging and invasive coronary angiography.
      However, if CT blood flow imaging is added to routine CCTA to assess heart perfusion and
      coronary blockages in one test, the radiation dose may be higher.

      The primary purpose of this research project is to test the diagnostic accuracy of various
      cardiac CT perfusion techniques as compared to the best non-invasive test of blood flow,
      cardiac PET perfusion imaging. The investigators goal is to use the least amount of radiation
      to achieve a high diagnostic accuracy for CCTA as well as CT blood flow/perfusion. The
      investigators goal is to have CT heart blood flow/perfusion radiation doses that are the same
      or less than nuclear blood flow imaging. The investigators have estimated that they need as
      few as 4 low radiation dose images of the heart to allow accurate heart blood flow
      measurement.
    

Observational model: Case-Only
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        Adults with suspected or known myocardial ischemia
      
Keywords: Cardiac CT perfusion; Positron emission tomography perfusion; Quantitative perfusion