Computed tomographic pulmonary angiography using low tube voltage and slow contrast medium injection

The diagnosis of acute pulmonary thromboembolism (PTE) is often performed by computed tomographic pulmonary angiography (CTPA). This study investigated the effects of a CTPA protocol combining slow contrast medium injection and low tube voltage on radiation exposure and image quality.

We retrospectively analyzed 82 patients undergoing CT scans for cancer treatment efficacy or follow-up, and simultaneous PTE exclusion. Patients were divided into two groups. Those in Group A (n = 43) received slow contrast injection (0.7-1.5 mL/s), and those in Group B (n = 39) received rapid injection (2.6-4.2 mL/s). All CT scans were performed using a multi-detector row CT scanner with optimized tube voltage and current settings. Contrast medium doses were adjusted based on the patient's body weight.

Group A had significantly lower radiation exposure compared with Group B. PTE was diagnosed in eight patients in Group A and seven in Group B, with no significant difference in prevalence rates. While Group B indicated higher mean CT values in the CTPA phase, the difference in the mean CT value of the pulmonary artery was only 29.6 Hounsfield units. Group A demonstrated superior contrast enhancement in parenchymal organs during the second phase.

The slow-injection CTPA method proved effective for simultaneous PTE exclusion and cancer treatment evaluation, maintaining diagnostic accuracy with reduced risks associated with rapid injection.