Dose reduction of 69% for computed tomography pulmonary angiography: reduced z-axis computed tomography pulmonary angiography retains accuracy in those younger than 40 years.

OBJECTIVE

We sought to determine whether reduced scan range (z axis) computed tomography pulmonary angiography (CTPA) technique in 18- to 40-year age group can accurately detect pulmonary embolism (PE) and other important conditions and to quantify the resulting dose reduction.

METHODS

We retrospectively identified 200 patients in the age group of 18 to 40 years who underwent CTPA over a period of 3 years. These included 86 patients with PEs and 114 randomly selected patients negative for PE (control subjects). The scans were modified by reducing the scan coverage by eliminating images above the aortic arch and below the base of the heart. Two blinded experienced radiologists rescored them for PE and incidental and pertinent non-PE findings. Discrepancies between these and the original report were assessed by a third experienced radiologist. Separately, a departmental quality-control project was conducted in 15 patients to assess the dose length product along the z axis across the 3 zones of thorax.

RESULTS

Pulmonary embolism was diagnosed in all 86 patients. No pertinent additional findings were missed. Only 7 incidental findings were missed (eg, benign thyroid nodules [n = 4], benign adrenal adenoma [n = 1], gallstones [n = 1], and hepatic hemangioma [n = 1]). None affected clinical outcome or management. Dose length product was reduced by a mean of 69% (60%-79%).

CONCLUSIONS

Reduced z-axis CTPA for PE is definitely feasible in 18- to 40-year age group. There is a significant radiation reduction (69%) and hence should be considered in selected subgroups of patients.