SYNCHROTRON RADIATION INLINE PROPAGATION BASED PHASE CONTRAST COMPUTERIZED TOMOGRAPHY (PC-CT) OF HUMAN PROSTATE SAMPLE

Abstract

The human prostate is an accessory male reproductive gland located below the neck of the urinary bladder. Benign prostatic hyperplasia (BPH) and prostate cancer are the frequently encountered pathological conditions of the prostate. It is estimated that 50% of men will develop BPH by age 50 with the incidence increasing to 90% by age 90. Prostate cancer is the second most common cause of cancer in men worldwide after lung cancer. In this study, we examined the ability of synchrotron radiation propagation phase-contrast computerized tomography (PC-CT) in comparison to ultrasound (US), magnetic resonance imaging (MRI) and histology, to characterize and differentiate various structural features and pathological lesions in 61 prostate tissues from 13 human patients collected during trans-urethral resection of the prostate. We compared the PC-CT, MRI, US and histology images of the same tissues from the same plane to determine if different structures like blood vessels, dilated acini etc. could be observed with each modality. The PC-CT was found to be a powerful imaging technique compared to MRI and US in identifying and resolving small structures located near each other. With PC-CT imaging, the same structures could be correctly identified almost 4 times and 15 times more often than MRI and US respectively. While comparing the ability to identify and resolve the nearby structures in PC-CT images reconstructed from 100%, 50% and 25% of the number of total projections collected (i.e. 2250 projections over 180 degree rotation of a sample on imaging stage), the ranking was as follows: 100% PC-CT>50% PC-CT>25% PC-CT (p<0.05). Radiation data recorded during a previous study while imaging dog cadavers with PC-CT were also analyzed. It was found that the average effective radiation dose imparted in a medium-sized dog during PC-CT imaging of one view of 7.8 mm height with 2000 projections in the biomedical imaging and therapy – insertion device (BMIT-ID) beamline of Canadian light source (CLS) beamline was 1,481.7 mSv, which is very high compared to the standard clinical CT examination deposits in human clinical medicine. The dose could be reduced by performing sparse view imaging i.e. 50% projection PC-CT or 25% projection PC-CT, but these amounts are still hazardous, such that a similar protocol used in human would have the potential to induce cancer later in life in approximately 0.5 % of the patients. For PC-CT imaging of human prostate in situ, a human positioning device was also designed. Due to the limitation in the weight-bearing capacity of the stage in the beamline, the positioning device was designed to be able to hold only a human pelvis or pelvis phantom up to 50 kg of weight in an upright position. The results from this work demonstrate that the synchrotron radiation-based inline PC-CT is a promising technique that offers closer-to-histology grade non-invasive diagnostic imaging of prostate tissue. Further study in conducting in-vivo prostate imaging to reduce the radiation dose is the next step to move forward in this direction.