Central Gland Volumes Research Articles

Prognostic Value of MRI-Assessed Central Gland Volume for Biochemical Recurrence after Prostate Cancer Radiotherapy

Introduction: Increasing central gland volume has been associated with less aggressive prostate cancer, theorized to be secondary to biomechanical stress from benign prostatic hyperplasia (BPH). The aim of this study was to evaluate pretreatment prostate magnetic resonance imaging (MRI) metrics and clinical characteristics in predicting biochemical recurrence (BCR) after definitive radiotherapy (RT) for prostate cancer. Methods: In this retrospective single institution study, we identified men in our database with prostate cancer who underwent MRI within 6 months prior to completing definitive RT from May 2011 to February 2023. Total prostate volume, central gland volume, and peripheral zone volume were measured by a radiologist using manual segmentation. The primary objective was to determine the association of central gland volume with biochemical recurrence, defined by Phoenix criteria. A multivariable Cox proportional hazards regression model was constructed and adjusted for clinical factors. Results: A total of 373 men (median age 68 years) were included, with a median follow-up of 28 months. 13 (3.5%) were low risk, 97 (26%) favorable intermediate ris, 201 (53.9%) unfavorable intermediate risk, and 62 (16.6%) high risk. 54 (14.5%) patients received conventionally fractionated RT, 105 (28.2%), moderately hypofractionated RT, 121 (32.4%), high-dose rate brachytherapy, and 93 (24.9%) stereotactic body RT. The 3 and 5 year rates of BCR were 7.8% and 18.3%, respectively. Taking into account NCCN risk group and RT type, higher central gland volume was associated with decreased risk of BCR (HR: 0.73, 95% CI: 0.55-0.98, p=0.03). No significant association was seen with peripheral zone volume, PI-RADS score, or RT type. Conclusions: Increased central gland volume on pretreatment prostate MRI is independently associated with a lower risk of biochemical recurrence after definitive radiation for prostate cancer. BPH appears to confer favorable outcomes in RT patients and represents a novel, easily quantifiable metric in risk-stratification.

Development and clinical utility analysis of a prostate zonal segmentation model on T2-weighted imaging: a multicenter study

ObjectivesTo automatically segment prostate central gland (CG) and peripheral zone (PZ) on T2-weighted imaging using deep learning and assess the model’s clinical utility by comparing it with a radiologist annotation and analyzing relevant influencing factors, especially the prostate zonal volume.MethodsA 3D U-Net-based model was trained with 223 patients from one institution and tested using one internal testing group (n = 93) and two external testing datasets, including one public dataset (ETDpub, n = 141) and one private dataset from two centers (ETDpri, n = 59). The Dice similarity coefficients (DSCs), 95th Hausdorff distance (95HD), and average boundary distance (ABD) were calculated to evaluate the model’s performance and further compared with a junior radiologist’s performance in ETDpub. To investigate factors influencing the model performance, patients’ clinical characteristics, prostate morphology, and image parameters in ETDpri were collected and analyzed using beta regression.ResultsThe DSCs in the internal testing group, ETDpub, and ETDpri were 0.909, 0.889, and 0.869 for CG, and 0.844, 0.755, and 0.764 for PZ, respectively. The mean 95HD and ABD were less than 7.0 and 1.3 for both zones. The U-Net model outperformed the junior radiologist, having a higher DSC (0.769 vs. 0.706) and higher intraclass correlation coefficient for volume estimation in PZ (0.836 vs. 0.668). CG volume and Magnetic Resonance (MR) vendor were significant influencing factors for CG and PZ segmentation.ConclusionsThe 3D U-Net model showed good performance for CG and PZ auto-segmentation in all the testing groups and outperformed the junior radiologist for PZ segmentation. The model performance was susceptible to prostate morphology and MR scanner parameters.

Impact of the bladder detrusor muscular ring on lower urinary tract symptoms due to benign prostatic hyperplasia: A quantitative MRI analysis.

The etiology of lower urinary tract symptoms secondary to benign prostatic hyperplasia (LUTS/BPH) remains uncertain. The purpose of our study was to quantitatively analyze anatomic characteristics on magnetic resonance imaging (MRI) to assess novel independent factors for symptoms. This retrospective single-institution study evaluated treatment-naïve men who underwent prostate MRI within 3 months of international prostate symptom score (IPSS) scoring from June 2021 to February 2022. Factors measured on MRI included: size of the detrusor muscular ring (DMR) surrounding the bladder outlet, central gland (CG) mean apparent diffusion coefficient (ADC), levator hiatus (LH) volume, intrapelvic volume, intravesicular prostate protrusion (IPP) volume, CG volume, peripheral zone (PZ) volume, prostate urethra angle (PUA), and PZ background ordinal score. Multivariable logistic regression and receiver operating characteristic analysis were used to analyze factors for moderate/severe (IPSS ≥ 8) and severe LUTS/BPH (IPSS ≥ 20). A total of 303 men (mean age: 66.1 [SD: 8.1]) were included: 154 demonstrated moderate or severe symptoms with 28 severe and 149 with asymptomatic/mild symptoms. Increasing age [p = 0.02; odds ratio (OR): 1.05 (1.01-1.08)], PUA [p = 0.02; OR: 1.05 (1.01-1.09)], LHvolume [p = 0.04; OR: 1.02 (1.00-1.05)], and DMR size measured as diameter [p < 0.001; OR: 5.0 (3.01-8.38)] or area [p < 0.001; OR: 1.92 (1.47-2.49)] were significantly independently associated with moderate/severe symptoms, with BMI [p = 0.02; OR: 0.93 (0.88-0.99)] inversely related. For every one cm increase in DMR diameter, patients had approximately five times the odds for moderate/severe symptoms. Increasing DMR size [diameter p < 0.001; OR: 2.74 (1.76-4.27) or area p < 0.001; OR: 1.37 (1.18-1.58)] was independently associated with severe symptoms. Optimal criterion cutoff of DMR diameter for moderate/severe symptoms was 1.2 cm [sensitivity: 77.3; specificity: 71.8; AUC: 0.80 (0.75-0.84)]. Inter-reader reliability was excellent for DMR diameter [ICC = 0.92 (0.90-0.94)]. Expansion of the DMR surrounding the bladder outlet is a novel anatomic factor independently associated with moderate and severe LUTS/BPH, taking into account prostate volumes, including quantified IPP volume, which were unrelated. Detrusor ring diameter, easily and reliably measured on routine prostate MRI, may relate to detrusor dysfunction from chronic stretching of this histologically distinct smooth muscle around the bladder neck.

Benign prostate hyperplasia as a potential protective factor against prostate cancer: Insights from a magnetic resonance imaging study of compositional characteristics.

The structural relationship between benign prostate hyperplasia (BPH) and prostate cancer (Pca) is controversial. The purpose of our study was to examine the association between quantitative prostate compositional metrics by magnetic resonance imaging (MRI) and Pca. We identified 405 patients who underwent prostate MRI and biopsy and/or prostatectomy from January 2019 to January 2021 at our institution. Segmentation volumetric methods were used to assess central gland (CG) and peripheral zone (PZ) volume. PZ mean thickness and mean apparent diffusion coefficient (ADC), marker of underlying histologic components, were measured. Multivariable logistic regression was performed with outcomes of ≥Grade Group (GG) 2 Pca and for multifocal disease. On multivariable analysis, higher CG volumes were at lower odds of ≥GG2 disease (n = 227) (OR: 0.97, 95% CI 0.96-0.98, p < 0.0001), taking into account PZ volume (p = 0.18) and thickness (p = 0.70). For every one cc increase in CG volume, there was an approximately 3% decrease in odds of ≥GG2 disease. Similar findings were noted for multifocal disease (n = 180) (OR: 0.97, 95% CI 0.96-0.98, p < 0.0001). Notably, ADC of the normal PZ was not significantly associated with CG volume (p = 0.21) nor a predictor of disease (p = 0.49). Increasing central gland volume, driven by BPH, is associated with lower odds of significant Pca, including multifocal disease, while PZ anatomic and histologic surrogate changes were noncontributory. Findings support BPH impediment of global tumor growth predicted by theoretical mechanobiological model. This potential stabilizing factor should be further studied for risk stratification and in consideration for BPH therapy.

Outcome prediction of prostatic artery embolization: post hoc analysis of a randomized, open-label, non-inferiority trial.

To identify predictors for different treatment outcomes after prostatic artery embolization (PAE) in the treatment of lower urinary tract symptoms secondary to benign prostatic hyperplasia. A post hoc analysis of data derived from the 48 patients undergoing PAE in a randomized, open-label, non-inferiority trial was performed. Relative changes in the International Prostate Symptoms Score (IPSS), absolute changes in maximum urinary flow rate (Qmax ), and relative changes in magnetic resonance imaging-assessed prostate volume from baseline to 12 weeks were defined as the outcomes measures of interest. Their association with various baseline characteristics and measures, technical details of PAE, and early postoperative measures were analysed using Spearman rank correlations and Wilcoxon rank-sum tests. The most promising predictors were further evaluated in receiver-operating characteristic (ROC) curve analyses. Higher total prostate and central gland (i.e. central plus transitional zone) volumes were associated with more pronounced improvements in the IPSS (Spearman rank correlation [rs]: -0.35 and -0.34; P = 0.01 and P = 0.02, respectively) and the Qmax (rs: 0.31 and 0.39; P = 0.05 and P = 0.01, respectively). ROC curve analyses suggested that volumes of 39 and 38 mL for total prostate and central gland volume, respectively, would be the optimal thresholds with which to predict PAE success as measured by the IPSS. Other anatomical characteristics of the prostate, such as the central gland index, also showed an even more distinct correlation to the improvement in Qmax (rs: 0.46, P = 0.003). The relative changes in prostate volume were clearly dependent on the technical performance of PAE. Occurrence of postoperative pain and blood levels of prostate-specific antigen and C-reactive protein emerged as potential early-stage outcome predictors after PAE. Baseline and peri-operative findings might help to guide patient selection and outcome prediction for PAE. Patients with larger prostates have a higher chance of success with PAE. Larger-scale clinical trials including a longer follow-up are warranted to further elucidate the most suitable patients for PAE.

Prostate Artery Embolization for Lower Urinary Tract Symptoms Secondary to Benign Prostatic Hyperplasia: Results From a Prospective FDA-Approved Investigational Device Exemption Study

ObjectiveTo evaluate the safety and efficacy of prostate artery embolization (PAE) for lower urinary tract symptoms (LUTS) attributed to benign prostatic hyperplasia (BPH). MethodsA prospective, single-center, open-label FDA-approved study was conducted to evaluate the safety and efficacy of PAE for LUTS secondary to BPH. We enrolled men ≥ 45, prostate volume > 40 g, International prostate symptom score (IPSS) > 13, peak flow rate (Qmax) ≤ 12 mL/s, and voided volume ≥ 125 mL. Patients were evaluated with questionnaires (IPSS, quality-of-life [QoL], International index of erectile function, and male sexual health questionnaire for ejaculatory dysfunction) and clinical measures (postvoid residual volume and Qmax at baseline 1, 3, and 12 months) after PAE. Baseline and 6-month total prostate (TV) and central gland (CG) volumes were obtained. Results45 patients (mean volume: 99 cc, range: 30-214 g) were treated over the course of the 3-year study. At 1 month, there were improvements in IPSS (23.6 ± 6.1 to 12.0 ± 5.9, P < .0001), QoL (4.8 ± 0.9 to 2.6 ± 1.6, P < .0001), Qmax (5.8 ± 1.0 to 12.4 ± 6.8,P < .0001). At 3 months, there were improvements in IPSS (10.2 ± 6.0, P < .0001), QoL (2.4 ± 1.6, P < .0001) and Qmax (15.3 ± 12.3, P < .0001). At 6 months, there were improvements in IPSS (11.0 ± 7.6, P < .0001) and QoL (2.3 ± 1.7, P < .0001). At 1 year, there were improvements in IPSS (12.4 ± 8.4,P < .0001) and QoL (2.6 ± 1.6, P < .0001). There were reductions in postvoid volume residues: baseline 157 ± 45, 1 month 123 ± 47, P = .057, 3 months 127 ± 114, P = .34, 6 months 112±116, P = .002 and 1 year 109±116 P = .025. Median decreases in TV and CG were 18% (CI: 13-27) (P = 0.0001) and 27% (CI: 20-36)(P = 0.0001), respectively. Self-limited adverse events included dysuria (n = 13), hematuria (n = 6), hematospermia (n = 2), urinary frequency (n = 3) and retention (n = 2). No severe adverse events, nontarget embolization, or adverse effects on erectile function or sexual health. ConclusionThis prospective clinical trial demonstrates that PAE is safe and efficacious for BPH, with significant improvement in LUTS and reduction in TV and CG volumes.

Prostate Zonal Volumetry as a Predictor of Clinical Outcomes for Prostate Artery Embolization.

To determine prostate baseline zonal volumetry and correlate these findings with clinical outcomes for patients who underwent prostate artery embolization (PAE) for lowerurinary tract symptoms (LUTS)due to benign prostatic hyperplasia(BPH). This is aretrospective study that included patients treated by PAE from 2010 to 2014. Baseline and 6-month follow-up evaluations included prostate MRI with whole prostate (WP) and central gland (CG) volume measurements-as well as prostate zonal volumetry index (ZVi) calculation, defined as the CG/WP volumes relation-the International Prostate Symptom Score (IPSS), and the Quality of life (QoL) index. Baseline WP, CG, and ZVi were statistical compared to IPSS and QoL values at 6months. A total of 93 consecutive patients were included, with mean age of 63.4years (range, 51-86). Clinical failure, defined as IPSS>7 or QoL>2, was seen in four cases (4.3%). Mean reductions in prostate volumes after PAE were of 30.6% and 31.2% for WP and CG, respectively (p<0.0001). Clinical parameters had mean decrease from 21 to 3.3 points for IPSS, and from 4.7 to 1.2 points for QoL (p<0.0001). Baseline WP, CG, and ZVi correlated to the degree of clinical improvement (p<0.05 for all). The baseline ZVi cut-off calculated for better clinical outcomes was>0.45, with 85% sensitivity and 75% specificity. Baseline CG and WP volumes as well as ZVi presented strong correlation with clinical outcomes in patients undergoing PAE, and its assessment should be considered in pre-treatment evaluation whenever possible. Both patients and medical team should be aware of the possibility of less favorable outcomes when ZVi<0.45.

Can prostatic arterial embolisation (PAE) reduce the volume of the peripheral zone? MRI evaluation of zonal anatomy and infarction after PAE.

To assess the impact of prostatic arterial embolisation (PAE) on various prostate gland anatomical zones. We retrospectively reviewed paired MRI scans obtained before and after PAE for 25 patients and evaluated changes in volumes of the median lobe (ML), central gland (CG), peripheral zone (PZ) and whole prostate gland (WPV) following PAE. We used manual segmentation to calculate volume on axial view T2-weighted images for ML, CG and WPV. We calculated PZ volume by subtracting CG volume from WPV. Enhanced phase on dynamic contrasted-enhanced MRI was used to evaluate the infarction areas after PAE. Clinical results of International Prostate Symptom Score and International Index of Erectile Function questionnaires and the urodynamic study were evaluated before and after PAE. Significant reductions in volume were observed after PAE for ML (26.2% decrease), CG (18.8%), PZ (16.4%) and WPV (19.1%; p < 0.001 for all these volumes). Patients with clinical failure had smaller volume reductions for WPV, ML and CG (all p < 0.05). Patients with significant CG infarction after PAE displayed larger WPV, ML and CG volume reductions (all p < 0.01). PAE can significantly decrease WPV, ML, CG and PZ volumes, and poor clinical outcomes are associated with smaller volume reductions. • The MRI segmentation method provides detailed comparisons of prostate volume change. • Prostatic arterial embolisation (PAE) decreased central gland and peripheral zone volumes. • Prostates with infarction after PAE showed larger decreases in volume. • A larger decrease in prostate volume is associated with clinical success.

Prostate Volumes Derived From MRI and Volume-Adjusted Serum Prostate-Specific Antigen: Correlation With Gleason Score of Prostate Cancer

The purpose of this article is to study relationships between MRI-based prostate volume and volume-adjusted serum prostate-specific antigen (PSA) concentration estimates and prostate cancer Gleason score. The study included 61 patients with prostate cancer (average age, 63.3 years; range 52-75 years) who underwent MRI before prostatectomy. A semiautomated and MRI-based technique was used to estimate total and central gland prostate volumes, central gland volume fraction (central gland volume divided by total prostate volume), PSA density (PSAD; PSA divided by total prostate volume), and PSAD for the central gland (PSA divided by central gland volume). These MRI-based volume and volume-adjusted PSA estimates were compared with prostatectomy specimen weight and Gleason score by using Pearson (r) or Spearman (ρ) correlation coefficients. The estimated total prostate volume showed a high correlation with reference standard volume (r = 0.94). Of the 61 patients, eight (13.1%) had a Gleason score of 6, 40 (65.6%) had a Gleason score of 7, seven (11.5%) had a Gleason score of 8, and six (9.8%) had a Gleason score of 9 for prostate cancer. The Gleason score was significantly correlated with central gland volume fraction (ρ = -0.42; p = 0.0007), PSAD (ρ = 0.46; p = 0.0002), and PSAD for the central gland (ρ = 0.55; p = 0.00001). Central gland volume fraction, PSAD, and PSAD for the central gland estimated from MRI examinations show a modest but significant correlation with Gleason score and have the potential to contribute to personalized risk assessment for significant prostate cancer.

Age‐related changes in prostate zonal volumes as measured by high‐resolution magnetic resonance imaging (MRI): a cross‐sectional study in over 500 patients

Study Type--Diagnosis (case series) Level of Evidence 4. What's known on the subject? and What does the study add? Benign prostatic hyperplasia is the most common symptomatic disorder of the prostate and its severity varies greatly in the population. Various methods have been used to estimate prostate volumes in the past including the digital rectal examination and ultrasound measurements. High-resolution T2 weighted MRI can provide accurate measurements of zonal volumes and total volumes, which can be used to better understand the etiology of lower urinary tract symptoms of men. • To use ability of magnetic resonance imaging (MRI) to investigate age-related changes in zonal prostate volumes. • This Institutional Review Board approved, Health Insurance Portability and Accountability Act-compliant study consisted of 503 patients who underwent 3 T prostate MRI before any treatment for prostate cancer. • Whole prostate (WP) and central gland (CG) volumes were manually contoured on T2-weighted MRI using a semi-automated segmentation tool. WP, CG, peripheral zone (PZ) volumes were measured for each patient. • WP, CG, PZ volumes were correlated with age, serum prostate-specific antigen (PSA) level, International Prostate Symptom Score (IPSS), Sexual Health Inventory for Men (SHIM) scores. • Linear regression analysis showed positive correlations between WP, CG volumes and patient age (P < 0.001); there was no correlation between age and PZ volume (P= 0.173). • There was a positive correlation between WP, CG volumes and serum PSA level (P < 0.001), as well as between PZ volume and serum PSA level (P= 0.002). • At logistic regression analysis, IPSS positively correlated with WP, CG volumes (P < 0.001). • SHIM positively correlated with WP (P= 0.015) and CG (P= 0.023) volumes. • As expected, the IPSS of patients with prostate volumes (WP, CG) in first decile for age were significantly lower than those in tenth decile. • Prostate MRI is able to document age-related changes in prostate zonal volumes. • Changes in WP and CG volumes correlated inversely with changes in lower urinary tract symptoms. • These findings suggest a role for MRI in measuring accurate prostate zonal volumes; have interesting implications for study of age-related changes in the prostate.

Comparison of Peripheral Zone and Central Gland Volume in Patients Undergoing Intensity-Modulated Radiotherapy

The shrinking effect of androgen deprivation therapy (ADT) and radiotherapy (RT) on prostate gland volume is a known clinical finding. Until now, it is not known which part of the prostate shrinks more. We examined patients with and without ADT undergoing intensity-modulated RT (IMRT) and performed 3-dimensional measurements of the peripheral zone (PZ) and central gland (CG) with magnetic resonance imaging (MRI). Prostate gland volumes of PZ and CG between planning MRI and first available follow-up MRI were retrospectively determined in 44 patients with localized prostate carcinoma. A total of 24 patients had ADT with a median time interval of 5 months (range, 1.5-24 months). Median time interval between both MRI time points was 132 days (range, 104-224 days). Two observers performed PZ and CG delineation in consensus using planimetry. Volume changes over time were determined and compared. Patients who had ADT showed smaller prostate volume in the first MRI (mean [SD], 32 [16.7] mL), which was still present after IMRT (28.1 [16.7] mL). Patients who had no ADT started with 44.6 (16.9) mL and showed 37.5 (13.9) mL after IMRT. Shrinking effect in PZ was significantly larger than in CG for all patients (-18.3% vs -6.3%, P < 0.05). Because, typically, most tumors are located in PZ and this area also shows the largest shrinkage effect after IMRT, this should be taken into account for planning purposes. Notably, there are only minor differences in the relative shrinking effects between patients with and without ADT, although they start with different volumes.

Changes in Prostate Shape and Volume and Their Implications for Radiotherapy After Introduction of Endorectal Balloon as Determined by MRI at 3T

To determine the changes in prostate shape and volume after the introduction of an endorectal coil (ERC) by means of magnetic resonance imaging (MRI) at 3T. A total of 44 consecutive patients with biopsy-proven prostate cancer underwent separate MRI examinations at 3T with a body array coil and subsequently with an ERC inflated with 50 mL of fluid. Prospectively, two experienced readers independently evaluated all data sets in random order. The maximal anteroposterior, right-to-left, and craniocaudal prostate diameters, as well as the total prostate and peripheral zone and central gland volumes were measured before and after ERC introduction. The changes in prostate shape and volume were analyzed using Wilcoxon's test for paired samples. The introduction of the ERC significantly changed the prostate shape in all three directions, with mean changes in the anteroposterior, right-to-left, and craniocaudal diameters of 15.7% (5.5 mm), 7.7% (3.5 mm), and 6.3% (2.2 mm), respectively. The mean total prostate, peripheral zone, and central gland volume decreased significantly after ERC introduction by 17.9% (8.3 cm(3)), 21.6% (4.8 cm(3)), and 14.2% (3.4 cm(3)), respectively. ERC introduction as observed by 3T MRI changed the prostate shape and volume significantly. The mean anteroposterior diameter was reduced by nearly one-sixth of its original diameter, and the mean total prostate volume was decreased by approximately 18%. This could cause difficulties and should be considered when using ERC-based MRI for MRI-computed tomography fusion and radiotherapy planning.

Validity of prostate‐specific antigen as a tumour marker in men with prostate cancer managed by watchful‐waiting: correlation with findings at serial endorectal magnetic resonance imaging and spectroscopic imaging

To investigate the validity of prostate-specific antigen (PSA) as a tumour marker in men with clinically localized prostate cancer who have selected watchful waiting, by determining if serial PSA level measurements are correlated with findings of malignancy or benign prostatic hyperplasia (BPH) at serial endorectal magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI). We retrospectively identified 69 men with biopsy-proven prostate cancer being managed by watchful waiting, who underwent serial endorectal MRI/MRSI and who had contemporaneous serial PSA measurements. The mean (range) follow-up was 392 (294-571) days. A panel of three experienced readers reviewed the initial and follow-up MRI/MRSI studies, and classified findings of prostate cancer as stable or progressive. Another reader assessed BPH by calculating total gland and central gland volumes on all studies. At the follow-up MRI/MRSI, 51, 17 and one patient had stable, progressive, or unevaluable prostate cancer, respectively. The mean PSA velocity was significantly greater in patients with radiologically progressive disease (1.42 vs 0.42 ng/mL/year, P = 0.04). A PSA velocity of >0.75 ng/mL/year identified those with radiologically progressive disease with a true-positive fraction of 0.71 and a false-positive fraction of 0.39. PSA levels were not correlated with changes in total or central gland volumes (P > 0.05). In men with clinically localized prostate cancer who select watchful waiting, serial PSA levels are correlated with findings of malignancy but not BPH at serial endorectal MRI/MRSI, suggesting that PSA is a useful longitudinal tumour marker in this population.

Quantitative MR Imaging Assessment of Prostate Gland Deformation before and During MR Imaging–Guided Brachytherapy

Rationale and Objectives The authors performed this study to document the deformations that occur between pretreatment magnetic resonance (MR) imaging and intraoperative MR imaging during brachytherapy. Materials and Methods MR images obtained at 1.5 and 0.5 T in 10 patients with prostate cancer were analyzed for changes in the shape and substructure of the prostate. Three-dimensional models of the prostate were obtained. The authors measured anteroposterior dimension; total gland, peripheral zone, and central gland volumes; transverse dimension; and superoinferior height. Results Gland deformations were seen at visual inspection of the three-dimensional models. The anteroposterior dimension of the total gland, central gland, and peripheral zone increased from 1.5- to 0.5-T imaging (median dimension, 4.9, 1.5, and 1.8 mm, respectively), and the increase was greatest in the peripheral zone ( P < .05, all comparisons). There was a decrease in the transverse dimension from 1.5- to 0.5-T imaging (median, 4.5 mm; P < .005). The total gland volume and the superoinferior height did not show a statistically significant change. Conclusion There were significant deformations in the shape of the prostate, especially in the peripheral zone, between the two imaging studies. The likely causes of the shape change are differences in rectal filling (endorectal coil used in 1.5-T studies vs obturator in 0.5-T studies) and/or changes in patient position (supine vs lithotomy). These findings suggest that pretreatment images alone may not be reliable for accurate therapy planning. It may be useful to integrate pre- and intraoperative data.

Evaluation of three-dimensional finite element-based deformable registration of pre- and intraoperative prostate imaging.

In this report we evaluate an image registration technique that can improve the information content of intraoperative image data by deformable matching of preoperative images. In this study, pretreatment 1.5 tesla (T) magnetic resonance (MR) images of the prostate are registered with 0.5 T intraoperative images. The method involves rigid and nonrigid registration using biomechanical finite element modeling. Preoperative 1.5 T MR imaging is conducted with the patient supine, using an endorectal coil, while intraoperatively, the patient is in the lithotomy position with a rectal obturator in place. We have previously observed that these changes in patient position and rectal filling produce a shape change in the prostate. The registration of 1.5 T preoperative images depicting the prostate substructure [namely central gland (CG) and peripheral zone (PZ)] to 0.5 T intraoperative MR images using this method can facilitate the segmentation of the substructure of the gland for radiation treatment planning. After creating and validating a dataset of manually segmented glands from images obtained in ten sequential MR-guided brachytherapy cases, we conducted a set of experiments to assess our hypothesis that the proposed registration system can significantly improve the quality of matching of the total gland (TG), CG, and PZ. The results showed that the method statistically-significantly improves the quality of match (compared to rigid registration), raising the Dice similarity coefficient (DSC) from prematched coefficients of 0.81, 0.78, and 0.59 for TG, CG, and PZ, respectively, to 0.94, 0.86, and 0.76. A point-based measure of registration agreement was also improved by the deformable registration. CG and PZ volumes are not changed by the registration, indicating that the method maintains the biomechanical topology of the prostate. Although this strategy was tested for MRI-guided brachytherapy, the preliminary results from these experiments suggest that it may be applied to other settings such as transrectal ultrasound-guided therapy, where the integration of preoperative MRI may have a significant impact upon treatment planning and guidance.

Prostatic growth rate determined from MRI data: age-related longitudinal changes.

Men with prostatic enlargement are at highest risk of developing symptomatic lower urinary tract symptoms (LUTS) and related outcomes, such as acute urinary retention. The study of prostatic growth rate can identify the age range at which prostate growth peaks. Evaluation of the natural course of prostate growth requires repeated intraindividual volume measurements at time intervals sufficient to document growth. Our objective was to examine age-stratified prostate growth rates from men taking part in a longitudinal study of aging using magnetic resonance imaging (MRI) of the prostate. Sixty-four men (ages 30-71 years) enrolled in the Baltimore Longitudinal Study of Aging (BLSA) who had T2 pelvic MRIs taken approximately every 2 years were studied. Men were age stratified into four groups: <45, 45-55, 56-65, and >65 years old. Whole prostate and central gland (anatomically referred to as the transition zone) volumes were determined from the MRI images by a semi-automated image analysis program. Peripheral gland volumes were calculated as the difference between whole prostate and central gland volumes. Growth rates (cc per year) were calculated as change in volume divided by the time interval. On the basis of measurements from the T2 images (n = 128), we observed a linear trend between prostate volume and age. The overall prostate growth rate was 2.36 +/- 3.52 cc per year. Age-stratified growth rates revealed that prostate growth increased with age, peaked at 4.15 +/- 4.98 cc/year for the 56-65-year-old age group and then declined rapidly for the older-aged men. The central gland growth rates followed a trend similar to total prostate volume. These data suggest that there is an age-related increase in prostate growth rate that peaks in men ages 56-65 and then declines. Identification of this trend in prostate growth may aid physicians in targeting men for early diagnosis of LUTS and for possible early intervention. Future studies with a larger sample size are necessary to substantiate these findings.