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Updated: Jan 12, 2026
Quantitative Magnetic Resonance Imaging of Skeletal Muscle Disease
Published on: December 18, 2016
Diffusion-weighted Imaging Distortion in Prostate MRI: A Cross-sectional Study Comparing Supine and Prone Positioning
Objectives:
Diffusion weighted imaging (DWI) is a key component of multiparametric (mp) prostate MRI. DWI using echo-planar techniques is susceptible to distortion at the recto-prostatic air-tissue interface. This study was to determine whether prone patient positioning reduces adjacent rectal air and DW image distortion when compared with standard-of-care supine positioning.
Materials And Methods:
This prospective study included consecutive patients undergoing mpMRI for suspected PCa between 2023 and 2024. Prostate segmentation was performed on DW and contrast-enhanced images. DWI distortion was measured quantitatively. Qualitative image quality of DWI and T2-weighted imaging (T2WI) was evaluated using PI-QUAL version 2; a separate 5-point clinically based Likert scale was employed to evaluate the volume of rectal air adjacent to the prostate.
Results:
Fifty-two patients were enrolled. In total, 58% of patients expressed a preference for supine imaging versus 20% for prone imaging. Qualitative DWI image quality improved significantly in the prone position [median: 4 (3 to 4)] versus supine [3 (1 to 4)]; P < 0.001. In contrast, prone T2WI quality [1 (1 to 1)] was significantly inferior than supine T2WI [3 (3-4)]; P < 0.001. Quantitative measures of rectal air were significantly lower for prone [1.13 cm 3 (0.34-2.43)] compared with supine imaging [1.96 cm 3 (0.47 to 5.81); P = 0.005]. There was no significant difference in distortion between prone [3.21 mm (2.42 to 3.82) and supine [2.95 mm (2.25 to 4.21)] positioning across all patients ( P = 0.80); however, in patients with >4 cm 3 of supine rectal air (n = 19), distortion was significantly reduced by prone imaging [3.49 mm (2.84 to 4.03)] compared with supine [4.60 mm (3.17 to 5.95)]; P = 0.02. The mean additional scanning time for the necessary prone imaging was 8 minutes 18 seconds.
Conclusions:
Prone positioning significantly reduces DWI distortion artefact when rectal air is present, but consistently results in degraded T2WI quality.
Insights
Prone positioning in prostate MRI reduces rectal air and diffusion-weighted imaging (DWI) distortion, particularly when air is present. However, it degrades T2-weighted imaging (T2WI) quality, impacting diagnostic accuracy.
Area of Science:
- Radiology
- Medical Imaging
- Prostate Cancer Diagnostics
Background:
- Diffusion-weighted imaging (DWI) is crucial for multiparametric (mp) prostate MRI.
- Echo-planar DWI techniques are prone to distortion near the recto-prostatic air-tissue interface.
Purpose of the Study:
- To evaluate if prone patient positioning minimizes rectal air and DWI distortion compared to supine positioning.
- To assess the impact of prone positioning on overall image quality.
Main Methods:
- Prospective study of patients undergoing mpMRI for suspected prostate cancer.
- Quantitative measurement of DWI distortion and rectal air volume.
- Qualitative assessment of DWI and T2-weighted imaging (T2WI) using PI-QUAL and Likert scales.
Main Results:
- Prone positioning significantly reduced rectal air volume and improved qualitative DWI quality.
- T2WI quality was significantly inferior in the prone position.
- DWI distortion was reduced in prone positioning for patients with significant rectal air (>4 cm³).
- Prone imaging added an average of 8 minutes 18 seconds to scan time.
Conclusions:
- Prone positioning effectively reduces DWI distortion and rectal air in prostate MRI.
- The benefit of reduced DWI distortion must be weighed against the degradation of T2WI quality.
- Prone positioning is beneficial for DWI quality when rectal air is a concern, but may compromise T2WI assessment.
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