Perfusion scintigraphy safer for pregnant women with pulmonary embolism

In a comparison safety study between scintigraphy and 256-slice angiography for pregnant women suspected of having a pulmonary embolism, scintigraphy was found to be the safest choice for moms and their unborn babies, according to a study published May 29 in the Journal of Nuclear Medicine.

The phantom study was designed to model the average pregnant women at the third, sixth, and ninth months of gestation to determine normalized dose between the two imaging modalities. The research was conducted by a team of scientists including Kostas Perisinakis, MD, from the department of medical physics at the Medical School of the University of Crete, Heraklion, in Crete, Greece.

“Despite being a rather rare complication, occurring in only one in 1,000 pregnancies, pulmonary embolism (PE) is the leading nonobstetric cause of maternal death," wrote Perisinakis et al. "About one in 100 pregnant patients diagnosed with PE die from this complication. Evaluation of suspected PE during pregnancy is quite challenging since clinical symptoms may be nonspecific. Despite having been proposed as a first-line imaging modality, lower limb ultrasonography has much lower sensitivity than chest radiography, lung perfusion scintigraphy (LPS), and CT pulmonary angiography (CTPA). However, those three imaging approaches use ionizing radiation and, therefore, are associated with a certain radiation dose burden for both the expectant mother and the embryo/fetus. The significance of early diagnosis and treatment of PE during pregnancy and concerns about radiation from the available imaging tests have enhanced debate on which diagnostic strategy to follow.”

As a result of their research, Perisinakis and his team have determined that an average-sized expectant mother in her first trimester would receive a 1 mSv dose and her baby a 0.05 mGy dose from 256-slice CTPA. Dose increased significantly with larger body size and later gestational phase. When compared to lung perfusion scintigraphy, CTPA resulted in 30 percent higher maternal effective dose, but a 3.4 to 6 times lower fetal/embryonic dose. Nevertheless, lung perfusion scintigraphy was deemed to have less aggregated radiation risk for the average pregnant patient based on the absorbed dose of 16 phantom models of varying sizes.

“Compared with CTPA performed with a modern wide-area CT scanner, [lung perfusion scintigraphy] remains comparatively more dose-efficient,” concluded the authors.