Detailed distribution of acute pulmonary thromboemboli: Direct evidence for reduction of acquisition length and radiation dose for triple rule-out CT angiography

PurposeTo reduce the redundant acquisition range and total radiation dose for planning appropriate “triple rule-out” CT angiography (CTA) for acute chest pain, we evaluated the detailed distribution of pulmonary thromboemboli (PTE) in subjects with acute PTE.Materials and methodsRetrospective review of CTA n 75-subjects (48-females; 57 ± 16 years) with proven acute PTE was performed to determine whether PTE was present solely above the aortic arch or below the heart.Results77% had PTE in the right upper lobe but none had PTE that were solely located higher than the aortic arch; 73% had PTE in the right middle lobe; 80% had PTE in the right lower lobe, but none had PTE that were solely located lower than the heart. 81% had PTE in the left upper lobe and 3% of them had PTE solely located higher than the aortic arch; both had PTE in the right upper, middle, and lower, and the left lower lobes. 75% had PTE in the left lower lobe, but none had PTE that were solely located lower than the heart. The acquisition length in limited CTPA in this population was reduced on average by 21.9% compared with full CTPA.ConclusionsIn subjects with acute PTE, there were none whose PTE was located solely in the upper lobes which were higher than the aortic arch, nor solely in the lower lobes which were lower than the heart. A limited range triple rule-out CTA protocol would decrease effective doses approximately 22% relative to full chest CTA and may help the physician find all PE present.