Program Information
A Comparative Study to Assess Lung Function Within Each Lobe Using Dual Energy CT and SPECT/CT
A Lapointe1*, H Bahig2, D Blais2 , H Bouchard1,2,3 , E Filion2 , J Carrier1,2,3 , S Bedwani1,2,3 , (1) Universite de Montreal, Montreal, QC, (2) Centre Hospitalier de l'Universite de Montreal (CHUM), Montreal, QC, (3) Centre de Recherche du Centre Hospitalier de l'Universite de Montreal (CRCHUM), Montreal, QC
Presentations
TU-C3-GePD-JT-4 (Tuesday, August 1, 2017) 10:30 AM - 11:00 AM Room: Joint Imaging-Therapy ePoster Theater
Purpose: There is an increasing interest in the evaluation of lung function from physiological images in radiotherapy treatment planning with the aim of reducing the extent of post-radiation toxicities. The purpose of this work is to validate the functional information extracted using dual energy CT (DECT) and to compare it regionally with analogous information from single-photon emission computed tomography (SPECT) combined with CT.
Methods: Five lung cancer patients underwent a SPECT/CT scan and a contrast-enhanced DECT scan. The latter allows to measure the perfused blood volume derived from an iodine map. It is generated following a DECT stoichiometric calibration adapted to the presence of iodine with a two-material decomposition method. To regionally compare the functional information, a radiation oncologist segmented the entire lung volume into five lobes for both imaging modalities. The differential function for each subvolume (five lobes and left/right lungs) is computed relative to the whole lung volume considering the ratio of counts in SPECT/CT and the ratio of iodine concentration in DECT.
Results: Results show that the differential function per lobe derived from DECT is strongly correlated with SPECT/CT (Pearson's coefficient r = 0.90). A mean difference of 7% is observed between the differential function of the left lung using both modalities. The absence of iodine in specific locations can easily be ascribed to dysfunctional area such as emphysema or fibrosis. Two patients exhibit strong signs of emphysema in specific lobes which is manifested by a drop of the mean iodine concentration (0.85 mg/ml for patient 1; 1.0 mg/ml for patient 2) relative to most functional lobes (2.8 mg/ml; 2.1 mg/ml).
Conclusion: High iodine concentration maps provide local functional information that is in good agreement with SPECT/CT. One promising avenue in radiation therapy is to use such functional information during dose optimization to spare functional lung tissues.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by MITACS and Siemens Healthcare.
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