Quality of CT pulmonary angiography for suspected pulmonary embolus in pregnancy

Abstract

The main objective of this study was to assess the quality of CT pulmonary angiography (CTPA) for suspected pulmonary embolus (PE) in the pregnant population. We retrospectively identified 40 consecutive pregnant patients who underwent CTPA from January 2005 to December 2006. Forty consecutive age-matched non-pregnant women were used as a control group. Studies were subjectively graded according to overall image quality by two readers in consensus, in randomised and blinded manner. Moreover, contrast enhancement of pulmonary arteries was subjectively and objectively evaluated. The proportion of sub-optimal studies was more than three times higher in the pregnant group (27.5%, n = 11) compared with the non-pregnant group (7.5%, n = 3; p = 0.015). Mean contrast enhancement was consistently higher in the non-pregnant group compared with pregnant group, both subjectively and objectively. The percentage of inadequately opacified vascular segments was more than two times higher in the pregnant group (28.7%, n = 264) than in the non-pregnant group (13.3%, n = 122; p = 0.0001). The incidence of sub-optimal CTPA studies is higher in pregnancy when compared with an age-matched non-pregnant control group. In addition to radiation issues, this should also be considered when implementing diagnostic strategies for suspected PE in pregnancy.

CTPA for the diagnosis of acute pulmonary embolism during pregnancy

“…Although the two studies differ with respect to scan speed, examination protocols and methods of image evaluation, the reduction of contrast enhancement (mean 259HU in pregnant vs 371HU in non-pregnant women [17]) and the increase in number of inadequate exams was marked and statistically significant (7.5% vs 27.5% [16]). One study even noted a higher number of segments that could not be properly evaluated (13.3% vs 28.7%, p= 0.0001 [16]), a fact that has a potential influence on the ability of CTA to rule out embolism.…”

“…In clinical practice, however, CTPA in pregnant women appears to be less robust than expected because of variable image quality. This clinical observation has been investigated by two retrospective studies published in this issue of European Radiology [16,17]. Both studies found-by subjective evaluation and objective quantification-a significantly lower enhancement of the pulmonary arteries in pregnant women than in non-pregnant women of comparable age.…”

“…One study even noted a higher number of segments that could not be properly evaluated (13.3% vs 28.7%, p= 0.0001 [16]), a fact that has a potential influence on the ability of CTA to rule out embolism. This reduced contrast enhancement in pregnant women can have a number of reasons: hyperdynamic circulation with increased cardiac output, increased plasma volume, increased body weight and more pronounced effects of a Valsalva manoeuvre.…”

“…As a consequence, contrast injection protocols for pulmonary CTA have not taken into account the physiological changes occurring during pregnancy, with the result that many routine examinations (7.5% vs 27.5% [16]) are not fully diagnostic. The authors of the two studies published in this issue [16,17] have to be congratulated for drawing attention to the need for adaptating contrast injection protocols in pregnancy. How would such an adaptation look?…”

“…Ref. [16] used the same contrast injection protocol for their 16-slice and 64-slice scanner despite the fact that the 64-slice scanner was trice as fast. Ref.…”