Breathing artifacts affect 6% of CCTA images

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Breathing artifacts are common in coronary CT angiography (CCTA) with 64-slice multidetector CT (MDCT), and can adversely affect the diagnostic value of the exam, according to a retrospective review presented Tuesday at the 2009 annual meeting of the American Roentgen Ray Society (ARRS) in Boston.

Felipe Torres, MD, from the Toronto General Hospital, University of Toronto, who presented the study, said its purpose was to evaluate breathing artifacts in CCTA performed with 64-row MDCT (Toshiba America Medical Systems) and the effect of these artifacts on vessel evaluability.

The researchers reviewed 115 consecutive CTCA studies performed on a 64-slice MDCT for exclusion of native coronary artery disease during March and April, 2007 involving 63 males, with a mean age of 59.6 years

Torres and colleagues defined breathing artifacts (BA) as the occurrence of motion artifact in axial images and the presence of stair-step artifact in the thoracic wall on sagittal reformatted images. The presence of BA was graded on a three-point scale by two cardiac radiologists, as:

  1. No BA;
  2. Mild BA (blurring of vessels and bronchial walls on axial images, but stair-step artifact in the chest wall on sagittal reformations);
  3. Severe BA (stair-step artifact clearly visible on the chest wall on sagittal reformations).

    They graded the effect of BA as evaluable or unevaluable.

    Torres explained that patients at Toronto General undergo extensive breathing instructions, and practice exercised breath hold twice.

    The researchers found that BA were detected in 11.3 pecent. In 6.1 percent of these patients, respiratory motion caused at least one unevaluable coronary artery segment. For the studies affected by BA, the mean number of coronary segments affected was 2.7, and the mean number of nonevaluable segments was 2.2.

    Torres said that there was no association between the occurrence of BA and age, sex, body mass index, history of asthma or chronic obstructive pulmonary disease, use of beta-blocker and scan duration. Patients experiencing BA had a higher median heart rate (84.8 bpm), compared with those who did not (58.1 bpm). He added that they administered beta blockers for patients whose heart rate was higher than 65 bpm.

    Overall, the researchers found that BA adversely affected the diagnostic value of the examination in 6.1 percent of patients.

    However, Torres said that "the decision to rescan is a complicated question, and needs to be judged on an individual basis, taking into consideration the effects of the stress test."