Pulmonary CTA in sickle cell patients: quantitative assessment of enhancement quality

The purpose of this study was to validate the observation that pulmonary artery (PA) enhancement is often decreased in sickle cell disease (SCD) patients imaged with MDCT for suspected pulmonary embolism and determine whether contrast infusion parameters are accountable for lower enhancement levels.

Retrospective comparison of 35 adult SCD patients imaged for suspected pulmonary embolism (PE) in our emergency department using 128-slice dual source MDCT scanner to 34 age and weight matched adult controls. Bolus tracking data was recorded, and enhancement levels of the main PA and descending aorta were measured. Electronic records were reviewed for demographics, imaging and lab correlation, and infusion parameters.

Age, weight, contrast infusion rate, and contrast volume were similar for both SCD and control patients. SCD patients had significantly lower main PA enhancement (mean 233 HU, range 151-361 HU) than the control subjects (mean 290 HU, range 138-487 HU) (p < 0.001). Most (74%) SCD subjects had PA enhancement that was <250 HU, while most (68%) control patients had PA enhancement ≥250 HU. Change in PA enhancement per second during bolus tracking was lower in SCD patients (12 HU/s, range -24 to 91 HU/s) than control patients (mean 30 HU/s, range -37 to 138 HU/s), although the difference was not statistically significant (p = 0.08). Hemoglobin levels were significantly lower in the SCD cohort (p < 0.001).

In this series of adult SCD patients with suspected PE imaged with MDCT, main PA enhancement level was lower than controls. Quality improvement investigations should focus on protocol optimization to improve enhancement quality and likelihood of a definitive diagnosis.