Optimization of image quality in pulmonary CT angiography with low dose of contrast material

Aim: The aim of this study was to compare objective image quality data for patient pulmonary embolism between a
conventional pulmonary CTA protocol with respect to a novel acquisition protocol performed with optimize radiation
dose and less amount of iodinated contrast medium injected to the patients during PE scanning.
Materials and Methods: Sixty- four patients with Pulmonary Embolism (PE) possibility, were examined using angio-CT
protocol. Patients were randomly assigned to two groups: A (16 women and 16 men, with age ranging from 19-89
years) mean age, 62 years with standard deviation 16; range, 19-89 years) - injected contrast agent: 35-40 ml. B (16
women and 16 men, with age ranging from 28-86 years) - injected contrast agent: 70-80 ml. Other scanning parameters
were kept constant. Pulmonary vessel enhancement and image noise were quantified; signal-to-noise ratio (SNR) and
contrast-to-noise ratio (CNR) were calculated. Subjective vessel contrast was assessed by two radiologists in consensus.
Result: A total of 14 cases of PE (22 %) were found in the evaluated of subjects (nine in group A, and five in group B).
All PE cases were detected by the two readers. There was no significant difference in the size or location of the PEs
between the two groups, the average image noise was 14 HU for group A and 19 HU for group B. The difference was
not statistically significant (p = 0.09). Overall, the SNR and CNR were slightly higher on group B (24.4 and 22.5
respectively) compared with group A (19.4 and 16.4 respectively), but those differences were not statistically
significant (p = 0.71 and p = 0.35, respectively).
Conclusion and Discussion: Both groups that had been evaluated by pulmonary CTA protocol allow similar image
quality to be achieved as compared with each other's, with optimize care dose for both protocol and contrast volume
were reduced by 50 % in new protocol comparing to the conventional protocol.