Heminder Kaur Sokhi MBBCh, Abstract Co-Author: Nothing to Disclose

Arjun Nair MBCHB, FRCR, Presenter: Nothing to Disclose

Seyed Mohammad Mehdi Ameli Renani MBBS, Abstract Co-Author: Nothing to Disclose

Farzana Mehzabin Rahman MBBS, Abstract Co-Author: Nothing to Disclose

Kate Baskerville, Abstract Co-Author: Nothing to Disclose

Ioannis Vlahos MBBS, Abstract Co-Author: Researcher, Siemens AG Consultant, Siemens AG Consultant, General Electric Company Consultant, Medicsight, Inc

Danielle Clark, Abstract Co-Author: Nothing to Disclose

PBV is a DECT metric of pulmonary enhancement difficult to corroborate in vivo in humans. No human dual energy phantoms exist and paired pre/post contrast lung imaging is limited by variations in phase of inspiration and co-registration. To overcome this, an incremental tiered contrast volume study to evaluate effect on PBV was undertaken.

88 patients (47 female, 41 male) with a variety of thoracic indications were prospectively recruited during a 12 month period for DECT imaging using a dual source CT system (100/Sn140kVp, refmAs 150/128, Definition FLASH, Siemens Medical Systems). Patients were randomised to 80 (n=26), 100 (n=30) or 120mls (n=30) contrast medium (Iohexol 300mgI/ml, 5ml/s).  Main pulmonary artery (PA) enhancement was calculated from post-contrast and single pre-contrast sections through the main PA. Volumetric analysis of PBV, volumetric lung density (LD) and volumetric thresholded lung density (TLD) to match PBV thresholds (-960HU to -200HU) were calculated on a 3-D workstation (Syngo). Multiple 2-D standardized measurements evaluated regional lung density (anterior, mid and posterior lung at the level of superior aortic arch, PA and 2cm above diaphragm) and corresponding PBV measurements. The correlation of PBV measures to lung density and PA enhancement was calculated.  

PA enhancement demonstrated a stepwise trend of progressive enhancement with increasing contrast levels (mean 119, 136, 147 HU) with a comparable stepwise increase in PBV measurements (mean 19, 22, 24 HU). Global volumetric PBV measurements were strongly correlated with LD and TLD ( r=0.64,0.67, p<0.001). However, global PBV correlation was more strongly correlated to post-contrast PA density and PA enhancement (r=0.74,0.75, p<0.001). A significant but weaker correlation was present between individual regional PBV measurements (n=1538) and corresponding lung HU measurements (r=0.27, p<0.001).

PBV measurements demonstrate a stepwise increase with contrast administration suggesting these accurately reflect progressive enhancement. Volumetric PBV measurements strongly correlate to lung density, however, regional correlation is weaker. PBV is most closely related to vascular enhancement.

PBV analysis on DECT appears to accurately reflect pulmonary vascular enhancement rather than lung density justifying its use as a surrogate measure of pulmonary perfusion.

Sokhi, H, Nair, A, Ameli Renani, S, Rahman, F, Baskerville, K, Vlahos, I, Clark, D, Quantitative Evaluation of Dual-Energy CT (DECT) Perfused Blood Volume (PBV) Measurements in a Tiered Contrast Volume Cohort.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11010610.html