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analysis of image quality will be helpful for designing ASiRTM-enhanced
paediatric CT protocols, balancing image quality and radiation dose. Catphan600
phantom studies were performed on a GE Discovery HD750 64-slice CT scanner.
Images were reconstructed with 0% - 100% ASiRTM (tube current 150 mA,
variable kVp 80 - 140) in order to determine the optimal ASiRTM-Filtered
Back Projection (FBP) blend. Images reconstructed with a 50% ASiRTM-50% FBP blend were
compared to FBP images (0% ASiRTM) over a wide range of
kVp (80 - 140) and mA (10 - 400) values. Measurements of image noise, CT number
accuracy and uniformity, spatial and contrast resolution, and low contrast
detectability were performed on axial and reformatted coronal images.
Improvements in CNR, low contrast detectability and radial uniformity were
observed in ASiRTM images compared to FBP images. 50% ASiRTM was associated with a
26% - 30% reduction in image noise. Changes in noise texture were observed at
The aim of this study was to determine whether contrast-enhanced micro-computed tomography can be used for non-invasive imaging of the early-stage changes in the vasculature of tumours that have been treated with photodynamic therapy (PDT). The subjects used were C3H mice with an RIF-1 tumour implanted subcutaneously and allowed to grow for 3 weeks prior to treatment. The experimental groups were PDT-treated (150 J/cm2 and 50 J/cm2) and control (150 J/cm2 light-only and untreated). The laser light exposure was performed at 15 - 30 minutes after the administration of the photosensitizer (BPD-MA). The contrast-enhanced micro-computed tomography imaging procedure consisted of eight-second scans taking place before treatment and up to 24 hours after treatment. The 150 J/cm2 PDT group showed a significant increase in the ratio of blood volume to tumour volume at 2, 8 and 24 hours after treatment when compared to pre-treatment measurements (p < 0.01). The observed increase in the blood volume to tumour volume at the later time points corresponds to a decrease in epithelial coverage on immunohistochemical stained (CD31) slides for the 150 J/cm2 PDT group at 24 hours after treatment. This preliminary study indicates that micro-CT can detect compromised vasculature in tumours treated with high-fluence photodynamic therapy as early as 2 hours post treatment.