Multidetector computed tomography pulmonary angiography: does arm position affect pulmonary artery enhancement?
OBJECTIVE
To evaluate whether arm position affects pulmonary artery enhancement in computed tomographic pulmonary angiography (CTPA).


METHODS
Study protocol had local ethics committee approval. Eighty-six patients who received 16 detector row CTPA for suspected pulmonary embolism were scanned with their contrast-injected arm resting at their side and compared with 94 patients who were scanned with both arms resting above their head. Two radiologists assessed pulmonary artery enhancement with a region-of-interest measurement of the main pulmonary artery density, scored the degree of beam-hardening artifact arising from the superior vena cava (SVC) and from the dependent arm that crossed the pulmonary arteries (1 = no artifact, 5 = artery obscured), and measured the degree of central venous compression of the injected veins at the thoracic inlet. A 2-tailed t test was performed to compare pulmonary artery density and central venous compression.


RESULTS
There was no difference in pulmonary artery enhancement between the 2 arm positions. Mean density of contrast in the main pulmonary artery was 329 Hounsfield units (HU) (95% confidence interval (CI), 310-350) in the arm-down group, compared with 325 HU (95% CI, 306-346) in the arm-up group (P = 0.65). Greater compression of the central veins occurred in the arm-up group (48.5%; 95% CI, 42.3%-54.8%) than in the arm-down group (22.3%; 95% CI, 16.8%-27.8%) (P < 0.05). There was also more beam hardening arising from contrast in the SVC in the arm-up group (P < 0.0001).


CONCLUSIONS
Arm position does not affect pulmonary arterial enhancement during CTPA. There was greater central venous compression and more beam-hardening artifact arising from the SVC when the arm was held above the head.
Gunn
Martin L D
ML
Department of Radiology, Waitemata District Health Board, Auckland, New Zealand. marting@u.washington.edu
Worthington
Adam
A
Hoon
Damien
D
Barnett
John Mark
JM
Blackmore
C Craig
CC
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography / Q000379:methods; D001132:Arm; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D011187:Posture; D011446:Prospective Studies; D011651:Pulmonary Artery / Q000000981:diagnostic imaging*; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*