CTA method lowers radiation exposure, maintains image quality for suspected stroke patients

A CT angiography (CTA) approach with drastically lowered tube currents combined with iterative construction reduced radiation exposure and maintained image quality in patients with suspected acute stroke, reported authors of a recent study published in the American Journal of Roentgenology.

Cerebral unenhanced CT and head and neck CTA—usually combined with perfusion CT—are the “imaging workhorse” at most institutions when evaluating patients with suspected acute stroke, wrote Nico Sollmann, of the department of diagnostic and interventional neuroradiology at Technische Universität München in Munich, and colleagues.

But due to the radiation exposure involved, the researchers sought a way to make such imaging safer for patients.

“The aim of this study was to systematically evaluate image quality and diagnostic accuracy of head and neck CTA with two levels of IR and virtually lowered tube currents in patients with suspected acute stroke,” Sollmann et al. wrote.

To do this, 30 patients (15 with large-vessel occlusion or dissection) underwent CTA of the supraaortal up to the intracranial arterial vessels. The scans were simulated at 50% (D50), 25% (D25) and 10% (D10) of the original tube current. Two different iterative construction methods were tested: “similar to clinical reconstructions” (level A) and “two times stronger regularization” (level B). Two readers evaluated overall image quality, artifacts, vessel contrast, detection of vessel abnormalities and diagnostic confidence.

CTA scans at D25 combined with both iterative reconstruction methods showed good vessel contrast with clear visibility of the peripheral arterial branches of anterior, middle and posterior cerebral arteries.

At D10, iterative reconstruction at level B was favorable for image quality and artifacts, while level A was preferred for D100 and D50. CTA at D25 and level A had an “adequate” level of diagnostic confidence, both readers noted.

“Head and neck CTA with tube currents drastically lowered and combined with IR is feasible and does not compromise detection of vessel abnormalities in patients with suspected acute stroke," the researchers concluded. Thus, our approach entails marked decreases in radiation exposure for patients undergoing such examinations."

The authors cited the simulation of tube current reductions as a limitation of their study.

Sollmann and colleagues also suggested their results may be improved upon in future research.

“To further decrease radiation exposure, sparse sampling might be evaluated in the context of head and neck CTA as the next step because it has potential for enabling even more drastic dose reductions with preserved image quality and accuracy for other purposes”