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Is the Ellipsoid Formula Reliable in Prostate MRI?
Rossy Vlăduț Teică1, Cristina Mihaela Ciofiac1, Lucian Mihai Florescu2
1Doctoral School, University of Medicine and Pharmacy of Craiova, 200349 Craiova, Romania.
Abstract:
Our study seeks to study the accuracy of the ellipsoidal formula in prostate MRI of different sizes and to establish the limits of its use. The study included 31 patients with a well-visualized, intact prostatic capsule, excluding malignantly transformed prostates, as well as treated prostates, in which the contrast between the prostatic capsule and parenchyma is reduced. Each patient's prostatic volume was recalculated according to the ellipsoidal formula, and then it was compared with the prostatic volume calculated by the segmentation method. The two calculated volumes were similar, in some cases almost identical, with a slight tendency to underestimate prostate volume below 100cm3, in total in 18 cases, on average by 7.6% (+/-6%), overestimation of those with a volume over 100cm3, a total of 13 cases, on average by 3.2% (+/-2.5%), and of all, in 4 cases the difference between the two formulas was below 1%. There was no statistical difference between the two variables, Student's t-test p-value=0.039. With a precision of 92% (+/-6%), the ellipsoidal formula can be considered accurate when it is correctly performed, but if we take into account the importance that PSA density is starting to have in diagnosis, treatment and follow-up, the calculation of a secondary value through the segmentation method or high-precision software can be motivated when the ellipsoidal formula returns a value close to a threshold.
Insights
The ellipsoidal formula accurately estimates prostate MRI volume, though it may slightly underestimate smaller prostates. For critical PSA density calculations, consider high-precision segmentation methods near threshold values.
Area of Science:
- Radiology
- Medical Imaging
- Urology
Background:
- Prostate MRI is crucial for diagnosis and management.
- Accurate prostate volume measurement is vital for PSA density calculations.
- The ellipsoidal formula is a common method for estimating prostate volume.
Purpose of the Study:
- To evaluate the accuracy of the ellipsoidal formula for prostate MRI volume.
- To determine the limits of its clinical application.
- To compare ellipsoidal formula results with segmentation-based volume calculations.
Main Methods:
- Included 31 patients with intact prostate capsules, excluding treated or malignant prostates.
- Calculated prostate volume using both the ellipsoidal formula and 3D segmentation.
- Compared the two volume measurements and analyzed discrepancies.
Main Results:
- Ellipsoidal formula volumes closely matched segmentation volumes (92% accuracy).
- Underestimation occurred in 18 prostates <100cm³ (avg. 7.6%); overestimation in 13 prostates >100cm³ (avg. 3.2%).
- No statistically significant difference between methods (p=0.039), but 4 cases had <1% difference.
Conclusions:
- The ellipsoidal formula is accurate for prostate MRI volume estimation when performed correctly.
- Segmentation or high-precision software may be beneficial for PSA density near critical thresholds.
- Refined volume calculation is important for accurate prostate cancer diagnosis, treatment, and follow-up.
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