Diffusion anisotropy in fresh and fixed prostate tissue ex vivo

Abstract

Purpose: To investigate diffusion anisotropy in whole human prostate specimens Methods: Seven whole radical prostatectomy specimens were obtained with informed patient consent and institutional ethics approval. Diffusion tensor imaging was performed at 9.4 Tesla. Diffusion tensors were calculated from the native acquired data and after progressive downsampling

Measurement and modeling of diffusion time dependence of apparent diffusion coefficient and fractional anisotropy in prostate tissue ex vivo

“…Three radical prostatectomy specimens were collected immediately after surgery with institutional ethics approval and written informed consent from patients (Specimen 1, 50 g, 62 years old, PSA 8.3 ng/mL; Specimen 2, 44 g, 62 years old, PSA 5.0 ng/mL; Specimen 3, 89 g, PSA 6.5 ng/mL, 60 years old). Specimens were fixed overnight in 10% neutral buffered formalin and then immersed in 1 L 0.5% ( w / v ) saline overnight to remove formalin prior to imaging . The prostate was imaged suspended on a 5 mm saline‐filled NMR tube inserted through the urethra and mounted in brackets in a plastic casing that maintained the tube axis parallel to and approximately 5 mm above the magnet z ‐axis.…”

“…In this study we treat the mean diffusivity (MD) of the calculated DTI tensor as the ADC that would be obtained from a conventional three‐direction clinical DWI scan. The typically very low FA observed in prostate tissue at the voxel volumes used in this study indicates there would be very little orientation dependence of the ADC derived from a three‐direction DWI measurement . To estimate the effect of an isotropic restricted signal component on the ADC and FA at each measured diffusion time the zeppelin‐sphere model was fitted to the combined three‐direction data (Table ) and Δ = 20 ms six‐direction data for each voxel.…”

“…A summary parameter, fractional anisotropy (FA), describes the degree of diffusion anisotropy but has not yet been demonstrated to have any clinical value in prostate disease assessment. Despite high microscopic anisotropy in the fibromuscular stroma, ex vivo whole organ studies show generally low anisotropy at clinical voxel volumes and wide FA differences between prostates . It has been argued that the relatively low signal‐to‐noise ratio (SNR) of clinical DWI measurements leads to artifactually high FA estimates …”

Comparison between 3-Scan Trace and Diagonal Body Diffusion-Weighted Imaging Acquisitions: A Phantom and Volunteer Study

“…In the prostate, low CV values were observed, indicative of the absence of the effects of anisotropy, motion, and pulsatile flow, unlike the kidney and spleen. Indeed, FA is shown to be lower in the prostate than in the liver (average FA values of ~ 0.17 in the peripheral zone and 0.24 in the transitional zone) (24, 25), indicative of relatively low diffusion anisotropy, and therefore, dDWI is likely more applicable in the prostate than in the abdominal organs. According to our initial results, we observed better image quality at b1000 and b1600 in the prostate at 1.5 T using dDWI; however, better image quality was not observed at 3.0 T. The latter finding could be explained by the fact that 1.5 T DWI MRI examinations in the pelvis generally suffer from low SNR, and therefore, the lower TE in dDWI than in tDWI likely has a more substantial effect on the image quality at 1.5 T compared with that at 3.0 T.…”

Apparatus for Histological Validation of In Vivo and Ex Vivo Magnetic Resonance Imaging of the Human Prostate

“…Formalin fixation leads to tissue shrinkage (17) and shape changes (18). Fixation of the prostate in the mold constrains any shape changes.…”