Efficacy of fine focal spot computed tomography of pulmonary arteries in image quality improvement compared to faster temporal resolution.

Abstract

Purpose: Computed tomography of pulmonary arteries (CTPA) has become the imaging modality of choice for diagnosing pulmonary embolism (PE). The diagnostic confidence of PE is influenced by the image quality of the CTPA. Faster temporal resolution (FTR) has been employed as a CTPA technique which helps correcting some motion artefacts and enables better definition of vessel luminal details. The recent use of fine focal spot (FFS) in CT scanning may improve vessel and emboli margin clarity. The aim of this retrospective study of CTPA was to evaluate the efficacy of FFS compared to FTR in CTPA. Material(s) and Method(s): 50 consecutive adult CTPA who were routinely scanned with FTR at 0.275 second rotation time and standard focal spot were included. FFS scanning was implemented recently but could only be performed at slower (0.33 second) rotation time. 50 adult consecutive CTPA who had this FFS were included. All other scanning parameters were similar. Patients who had suboptimal contrast enhancement of pulmonary arteries were excluded. The CTPA images from both groups were blindly, randomly and independently reviewed by 2 radiologists. Qualitative review on the clarities of pulmonary vessels, lung, aortas, heart, ribs and liver using 5 point ranking method was performed. Results from 2 groups were compared. Result(s): 50 FFS CTPA (19male:31female, mean age of 62) and 50 FTR (23male: 27female, mean age of 65) were included. 4 patients in FFS group and 5 patients in FTR were excluded due to suboptimal contrast opacification. The image qualities of pulmonary arteries, lungs, aorta, liver and ribs were significantly better in FFS than FTR (Mann-Whitney U test). The cardiac motion artefacts were similar with both FFS and FTR. Conclusion(s): CTPA image quality improves with FFS scanning, despite the CT rotation time is slowed by 0.055 second as compared to the conventional faster temporal resolution scanning. FFS may become an important imaging tool in future that may improve the diagnostic confidence in PE detection on CTPA.