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Updated: Sep 22, 2025
Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease
Published on: December 18, 2016
Physically implausible signals as a quantitative quality assessment metric in prostate diffusion-weighted MR imaging
Teodora Szasz1, Grace Lee2, Aritrick Chatterjee2
1Research Computing Center, The University of Chicago, Chicago, IL, USA. tszasz@uchicago.edu.
Purpose:
To provide a quantitative assessment of diffusion-weighted MR images of the prostate through identification of PIDS which clearly represents artifacts in the data. We calculated the percentage and distribution of PIDS in prostate DWI and compare the amount of PIDS between mpMRI images obtained with and without an endorectal coil.
Methods:
This IRB approved retrospective study (from 03/03/2014 to 03/10/2020), included 40 patients scanned with endorectal coil (ERC) and 40 without ER coil (NERC). PIDS contains any voxel where: (1) the diffusion signal increases despite an increase in b-value; and/or (2) apparent diffusion coefficient (ADC) is more than 3.0 μm2/ms (the ADC of pure water at 37 °C and it is physically implausible for any material to have a higher ADC). PIDS for transition zone (TZ) and peripheral zone (PZ) was calculated using an in-house MATLAB program. DWI images were quantitatively inspected for noise, motion, and distortion. T-test was used to compare the difference between PIDS levels in ERC versus NERC and ANOVA to compare the PIDS levels in the anatomic zones. The images were evaluated by a fellowship-trained radiologist in Abdominal Imaging with more than 10 years of experience in reading prostate MRI. This was tested only in prostate in this study.
Results:
80 patients (58 ± 8 years old, 80 men) were evaluated. The percentage of voxels exhibiting PIDS was 17.1 ± 8.1% for the ERC cohort and 22.2 ± 15.5% for the NERC cohort. PIDS for NERC versus ERC were not significantly different (p = 0.14). The apex and base showed similar percentages of PIDS in ERC (p = 0.30) and NERC (p = 0.86). The mid (13.8 ± 8.6%) in ERC showed lower values (p = 0.02) of PIDS compared to apex (19.9 ± 11.1%) and base (17.5 ± 8.3%).
Conclusion:
PIDS maps provide a spatially resolved quantitative quality assessment for prostate DWI. Average PIDS over the entire prostate were similar for the ERC and NERC cohorts, and did not differ significantly across prostate zones. However, for many of the patients, PIDS was focally much higher in specific prostate zones. PIDS assessment can guide Radiologist's evaluation of images and the development of improved DWI sequences.
Insights
Physically implausible diffusion signal (PIDS) artifacts in prostate MRI were quantified. While overall PIDS levels were similar between scans with and without an endorectal coil, focal PIDS varied by prostate zone, aiding image quality assessment.
Area of Science:
- Radiology
- Medical Imaging
- Biophysics
Background:
- Diffusion-weighted imaging (DWI) is crucial for prostate cancer detection.
- Artifacts in DWI can compromise image interpretation and diagnostic accuracy.
- Quantifying artifacts like physically implausible diffusion signal (PIDS) is essential for quality assessment.
Purpose of the Study:
- To quantitatively assess artifacts in prostate DWI using PIDS.
- To compare PIDS levels in prostate MRI scans acquired with and without an endorectal coil (ERC).
- To evaluate the distribution of PIDS across different prostate zones.
Main Methods:
- Retrospective analysis of 80 prostate MRI scans (40 with ERC, 40 without).
- PIDS defined as voxels with signal increase vs. b-value or ADC > 3.0 μm²/ms.
- In-house MATLAB program used for PIDS calculation; statistical analysis (t-test, ANOVA) performed.
Main Results:
- Average PIDS was 17.1% with ERC and 22.2% without ERC, with no significant difference (p=0.14).
- PIDS levels did not significantly differ between ERC and NERC cohorts overall.
- The mid-prostate zone in ERC scans showed significantly lower PIDS (13.8%) compared to the apex and base.
Conclusions:
- PIDS mapping offers a quantitative, spatially resolved quality assessment for prostate DWI.
- Overall PIDS levels are comparable with or without an ERC, but focal PIDS can be high in specific zones.
- PIDS assessment can inform radiologists and guide the development of improved DWI sequences.
