Clinical value of prostate segmentation and volume determination on MRI in benign prostatic hyperplasia

Abstract

Benign prostatic hyperplasia (BPH) is a nonmalignant pathological enlargement of the prostate, which occurs primarily in the transitional zone. BPH is highly prevalent and is a major cause of lower urinary tract symptoms in aging males, although there is no direct relationship between prostate volume and symptom severity. The progression of BPH can be quantified by measuring the volumes of the whole prostate and its zones, based on image segmentation on magnetic resonance imaging. Prostate volume determination via segmentation is a useful measure for patients undergoing therapy for BPH. However, prostate segmentation is not widely used due to the excessive time required for even experts to manually map the margins of the prostate. Here, we review and compare new methods of prostate volume segmentation using both manual and automated methods, including the ellipsoid formula, manual planimetry, and semiautomated and fully automated segmentation approaches. We highlight the utility of prostate segmentation in the clinical context of assessing BPH. Benign prostatic hyperplasia (BPH) can result in lower urinary tract symptoms, and is one of the most common diseases affecting aging men. BPH can compromise quality of life and is a major healthcare cost. Despite the high prevalence of BPH, few methods of accurately assessing prostate volume are actually used in clinical practice. While patient assessment of urinary symptoms dictates the need for treatment, it is highly subjective, whereas prostate volume change is a more objective measure of treatment response. The most common clinical model for approximating the prostate gland size is the ellipsoid model from transrectal ultrasonography (TRUS) imaging, which has been shown to underestimate prostate volume for prostates larger than 50 mL and to overestimate prostate volume for glands smaller than 30 mL (1). Despite its limitations, the TRUS method of prostate volume assessment is preferred in current clinical practice due to its availability and cost and time efficiency (2). More accurate prostate volume measurement with magnetic resonance (MR) planimetry is time-intensive and, thus, rarely performed.Prostate segmentation is an accurate technique for prostate volume determination that can be used in coregistration with various imaging modalities, such as magnetic resonance imaging (MRI) with positron emission tomography and MRI with ultrasonography. Segmentation can be used for both diagnostic and interventional procedures, including guided biopsies and focal ablation. Newly developed methods of automated prostate segmentation allow for efficient prostate volume determination, thereby enhancing decision support systems and computer-aided diagnosis tools.This article reviews the major methods of prostate volume determination currently in use, including the ellipsoid formula, manual planimetry, and semiautomated and fully automated segmentation. A clinical overview of BPH is also provided to highlight the utility of prostate segmentation in the clinical management...

Peripheral zone volume ratio (PZ-ratio) is relevant with biopsy results and can increase the accuracy of current diagnostic modality

“…This contributes, at various extents, to the enlargement of the prostate, and almost exclusively, of TZ [27]. Thus, one may hypothesize that the elevation of PSA in biopsy-negative cases is likely to be contributed by BPH in otherwise healthy males [28].…”

Prostate volume estimations using magnetic resonance imaging and transrectal ultrasound compared to radical prostatectomy specimens

“…11 Other established methods of estimating prostate volume on MRI that take into account non-uniform shapes include: stepwise planimetry, semi-automated and fully automated segmentation. 12 While methods such as planimetry may be more accurate at estimating prostate volume, the significant time and cost burden associated with manually outlining the prostate on each slice means it is rarely performed in practice. 9,11,12 There are several potential limitations to our study.…”

“…12 While methods such as planimetry may be more accurate at estimating prostate volume, the significant time and cost burden associated with manually outlining the prostate on each slice means it is rarely performed in practice. 9,11,12 There are several potential limitations to our study. Only one measurement was available for both TRUS and pathological volumes, compared to two raters for MRI images, which may have resulted in less accurate TRUS or pathological measurements.…”

“…The prolate ellipsoid formula may also be less accurate compared to stepwise planimetry or other modalities. 9,12 Finally, the association between errors in volume estimates and clinical outcomes were not assessed.…”

Measurement of Prostate Volume with MRI (A Guide for the Perplexed): Biproximate Method with Analysis of Precision and Accuracy

“…Accurate measurement may affect cancer treatment strategies 1,2 . However, the ability to make consistent and accurate measurement of the prostate is also useful in the diagnosis and management of BPH 3,4 .…”