Triphasic contrast injection improves evaluation of dual energy lung perfusion in pulmonary CT angiography.
OBJECTIVE
Lung perfusion analysis at dual energy CT (DECT) is sensitive to beam hardening artifacts from dense contrast material (CM). We compared two scan and four CM injection protocols in terms of severity of artifacts and attenuation levels in the thoracic vessels.


METHODS
Data of 120 patients who had undergone dual source dual energy CT pulmonary angiography for suspected acute pulmonary embolism were evaluated. Group 1 (n=30) was scanned in craniocaudal direction using 64×0.6 mm collimation; groups 2-4 (n=30 each) were scanned in caudocranial direction using 14×1.2 mm collimation. In groups 1-3 biphasic injection protocols with different amounts of CM and NaCl were investigated. In group 4 a split-bolus protocol with an initial CM bolus of 50 ml followed by 30 ml of a 70%:30% NaCl/CM mixture and a 50 ml NaCl chaser bolus was used. CT density values in the subclavian vein (SV), superior vena cava (SVC), pulmonary artery tree (PA), and the descending aorta (DA) were measured. Artifacts arising from the SV and SVC on DE pulmonary iodine distribution map were rated on a scale from 1 to 5 (1=fully diagnostic; 5=non-diagnostic) by two blinded readers.


RESULTS
In protocol 4 mean attenuation in the SV (645±158 HU) and SVC (389±114 HU) were significantly lower compared to groups 1-3 (p<0.002). Artifacts in group 4 (1.1±0.4 and 1.5±0.7 for the SV and SVC, respectively) were rated significantly less severe compared to group 1 (3.2±1.0 and 3.0±1.1), 2 (2.6±1.1 and 2.3±1.0) and 3 (1.9±0.9 and 1.9±0.7) (p<0.01 for all), whereas no significant difference was found between groups 1 and 2 for the subclavian vein (p=0.07). Attenuation in the PA was also significantly lower in group 4 (282±116 HU) compared to group 1 (397±137 HU), group 2 (376±115 HU) and group 3 (311±104 HU), but still on a diagnostic level.


CONCLUSIONS
Split-bolus injection provides sufficient attenuation for pulmonary DECT angiography while beam hardening artifacts arising from high density contrast material in the thoracic vessels can be reduced significantly.
Kerl
J Matthias
JM
Institute for Diagnostic and Interventional Radiology, Clinic of the Goethe University, Theodor-Stern-Kai 7, 60590 Frankfurt, Germany. matthias.kerl@gmail.com
Bauer
Ralf W
RW
Renker
Matthias
M
Weber
Eva
E
Weisser
Philipp
P
Korkusuz
Huedayi
H
Schell
Boris
B
Larson
Maya Christina
MC
Kromen
Wolfgang
W
Jacobi
Volkmar
V
Vogl
Thomas J
TJ
D000368:Aged; D000792:Angiography / Q000379:methods*; D016477:Artifacts; D003287:Contrast Media / Q000008:administration & dosage; D005260:Female; D006801:Humans; D007269:Injections, Intra-Arterial; D007479:Iopamidol / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D055420:Perfusion Imaging / Q000379:methods*; D011655:Pulmonary Embolism / Q000000981:diagnostic imaging*; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013895:Thoracic Arteries / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media; D007479:Iopamidol