Validation of automatic target volume definition as demonstrated for 11C-choline PET/CT of human prostate cancer using multi-modality fusion techniques.
OBJECTIVE
Positron emission tomography (PET) is actively investigated to aid in target volume definition for radiation therapy. The objectives of this study were to apply an automatic computer algorithm to compute target volumes and to validate the algorithm using histologic data from real human prostate cancer.


METHODS
Various modalities for prostate imaging were performed. In vivo imaging included T2 3-T magnetic resonance imaging and (11)C-choline PET. Ex vivo imaging included 3-T magnetic resonance imaging, histology, and block face photos of the prostate specimen. A novel registration method based on mutual information and thin-plate splines was applied to all modalities. Once PET is registered with histology, a voxel-by-voxel comparison between PET and histology is possible. A thresholding technique based on various fractions of the maximum standardized uptake value in the tumor was applied, and the respective computed threshold volume on PET was compared with histologic truth.


RESULTS
Sixteen patients whose primary tumor volumes ranged from 1.2 to 12.6 cm(3) were tested. PET has low spatial resolution, so only tumors > 4 cm(3) were considered. Four cases met this criterion. A threshold value of 60% of the (11)C-choline maximum standardized uptake value resulted in the highest volume overlap between threshold volume on PET and histology. Medial axis distances between threshold volume on PET and histology showed a mean error of 7.7 +/- 5.2 mm.


CONCLUSIONS
This is a proof-of-concept study demonstrating for the first time that histology-guided thresholding on PET can delineate tumor volumes in real human prostate cancer.
Park
Hyunjin
H
Department of Biomedical Engineering, Gachon University of Medicine and Science, Incheon, South Korea. hyunjinp@gachon.ac.kr
Meyer
Charles R
CR
Wood
David
D
Khan
Asra
A
Shah
Rajal
R
Hussain
Hero
H
Siddiqui
Javed
J
Seo
Jongbum
J
Chenevert
Thomas
T
Piert
Morand
M
D000465:Algorithms; D001185:Artificial Intelligence; D002250:Carbon Radioisotopes; D002794:Choline; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D010363:Pattern Recognition, Automated / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D011471:Prostatic Neoplasms / Q000175:diagnosis*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique; D014057:Tomography, X-Ray Computed / Q000379:methods*
D002250:Carbon Radioisotopes; D019275:Radiopharmaceuticals; D002794:Choline