Effectiveness of Contrast-enhanced MR Angiography for Visualization of the Prostatic Artery prior to Prostatic Arterial Embolization

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1 ORIGINAL RESEARCH GENITOURINARY IMAGING Effectiveness of Contrast-enhanced MR Angiography for Visualization of the Prostatic Artery prior to Prostatic Arterial Embolization Jin Long Zhang, MD Mao Qiang Wang, MD, PhD Yan Guang Shen, MD Hui Yi Ye, MD Kai Yuan, MD Hai Nan Xin, MD Hong Tao Zhang, MD Jin Xin Fu, MD Jie Yu Yan, MD Yan Wang, MD From the Departments of Interventional Radiology (J.L.Z., M.Q.W., K.Y., H.N.X., J.X.F., J.Y.Y., Y.W.) and Radiology (Y.G.S., H.Y.Y., H.T.Z.), Chinese PLA General Hospital, 28 Fu-xing Rd, Beijing , PR China. Received June 28, 2018; revision requested August 17; final revision received January 7, 2019; accepted January 8. Address correspondence to M.Q.W. ( Supported by grants from the National Natural Science Foundation of China ( ), the Central Health Research Project (W2013BJ09), and the Chinese PLA Scientific Foundation of the Twelve-Five Program (BWS11J028). Conflicts of interest are listed at the end of this article. See also the editorial by Prince in this issue. Radiology 2019; 00:1 9 Content codes: Background: A major technical challenge of prostatic arterial embolization (PAE) is the identification and catheterization of the prostatic arteries (PAs). Recently, MR angiography has been shown to help visualize PAs, but the clinical utility of MR angiography for this purpose is not known. Purpose: To determine the efficacy of contrast material enhanced MR angiography in identifying the PA and to evaluate its role in PAE for benign prostatic hyperplasia (BPH). Materials and Methods: In this prospective study, 100 consecutive men who were scheduled to undergo PAE for BPH from January 2015 to May 2017 were assigned by using a randomized block design to either group A (n = 50; mean age, 71.7 years [standard deviation]) without MR angiography or group B (n = 50; mean age, 72.3 years ) with MR angiography prior to PAE. MR angiography findings of the PA anatomy were compared with those of digital subtraction angiography (DSA). The Student t test and Wilcoxon rank-sum test were used to compare the differences between the parameters indicating the performance of PAE. Results: The mean age of the 100 men in the study was 72.0 years (range, years). Compared with DSA as the reference standard, MR angiography identified PAs with a sensitivity of 91.5% (97 of 106) and a positive predictive value of 100% (97 of 97). With the knowledge of tube obliquity and anatomy, group B had lower procedure times than group A (82.3 minutes vs minutes , P,.001) and shorter fluoroscopy times (13.8 minutes vs 28.5 minutes 6 8.0, P,.001). Additionally, radiation dose was reduced for group A versus group B, from a median of 920 to 339 mgy (P =.004). Conclusion: Contrast-enhanced MR angiography can accurately show anatomy for the prostate arteries, leading to shorter prostatic artery embolization times and lower radiation dose than when preprocedural prostate MR angiography is not performed. Published under a CC BY 4.0 license. Online supplemental material is available for this article. rostatic arterial embolization (PAE) is a safe and ef- therapeutic option for symptomatic benign Pfective prostatic hyperplasia (BPH), as has been indicated by multiple studies (1 8). The major technical challenge of PAE is the identification and catheterization of the prostatic arteries (PAs), especially with regard to navigating arteries with atherosclerosis and variant prostatic vascular anatomy, leading to longer procedures and higher doses of radiation (9,10). There are many branches of the internal iliac artery (IIA) that cross over and overlap with each other, which seriously affects the judgment of the origin and trajectory of blood vessels during interventional therapy. Knowledge of the origins, trajectory, and number of PAs can help interventionists avoid the potential risk of unintentional embolization of the surrounding organs (eg, bladder, rectum, or penis), in addition to reducing the procedure time and the radiation dose. At present, identification of the PA is mainly achieved by performing multiple digital subtraction angiography (DSA) examinations or with DSA combined with conebeam CT (10,11). Maclean et al (12) assessed the value of CT angiography in identifying the PAs and anastomoses and found an accuracy of 97.3% for the PA, as well as a sensitivity of 59.0% and a specificity of 94.2% for anastomoses detection. The pitfalls of CT angiography include a higher radiation dose and the risks of contrast material related renal toxicities; in addition, CT has low tissue resolution and is not suitable for the diagnosis of prostate lesions. Kim et al (9) first assessed the ability of MR angiography to identify the origins of PAs prior to embolization and demonstrated that MR angiography is useful in treatment planning. However, that study was performed in a small sample and did not include a control group. Therefore, larger and controlled clinical trials are required to confirm the value of MR angiography prior to PAE. This copy is for personal use only. To order printed copies, contact reprints@rsna.org

2 Effectiveness of MR Angiography for Visualizing Prostatic Artery before PAE Abbreviations BPH = benign prostatic hyperplasia, DAP = dose-area product, DSA = digital subtraction angiography, IIA = internal iliac artery, IPSS = International Prostate Symptom Score, PA = prostatic artery, PAE = prostatic arterial embolization, PSA = prostate-specific antigen, PV = prostate volume, PVR = post-void urine residual volume, Q max = peak urinary flow rate, QoL = quality of life, TRICKS = time-resolved imaging of contrast kinetics Summary Contrast-enhanced MR angiography showed high sensitivity and positive predictive value in detecting the origins, trajectory, and number of prostatic arteries prior to prostatic artery embolization. Key Points nn nn nn Contrast-enhanced MR angiography enables the identification of the number of prostate arteries with a sensitivity of 91.5% (97 of 106) and a positive predictive value of 100% (97 of 97). Contrast-enhanced MR angiography identification of prostatic arteries reduced the prostate artery embolization procedure time, radiation exposure, and contrast medium dose during prostate artery embolization by 33.6%, 63.2%, and 37.7%, respectively. The optimal angle for visualization of prostatic arteries was variable, between 20 and 45 in the ipsilateral anterior oblique direction; MR angiography may be useful for determining tube angles optimized for each patient. Our study objectives were to assess the effectiveness of contrast material enhanced MR angiography in depicting the PA prior to PAE and to assess its impact in terms of reduction of procedure time, fluoroscopy time, radiation dose, and contrast medium volume. Materials and Methods Study Participant Selection and Study Design This single-institution prospective randomized controlled trial was performed in accordance with the Declaration of Helsinki, with approval obtained from the institutional review board. All study participants provided written informed consent for the study prior to the procedure. One hundred consecutive men who underwent PAE for symptomatic BPH between January 2015 and May 2017 were prospectively recruited in the study and were randomly assigned in a 1:1 ratio to group A (n = 50; mean age, 71.7 years [standard deviation]; range, years) without MR angiography or to group B (n = 50; mean age, 72.3 years ; range, years) with MR angiography prior to PAE. A post-hoc power analysis proved that the sample size of 100 was adequate for this study. The baseline data of the two groups are shown in Table 1. Treatment allocation was predetermined by an independent statistician (Y.W., with 8 years of experience in statistics) using a randomized block design by computergenerated random numbers. The study participants, the radiologists responsible for follow-up imaging, and the urologists responsible for participant recruitment and assessment of clinical outcomes were blinded to the treatment groups. Study participant selection was performed in conjunction with urologists, anesthesiologists, and interventional radiologists. The inclusion criteria were as follows: men older than 50 years of age with a diagnosis of severe lower urinary tract symptoms (International Prostate Symptom Score [IPSS]. 8 points, quality of life [QoL] score [ranging from 0 {delighted} to 6 {terrible}]. 3, peak urinary flow rate [Q max ]. 12 ml/ sec) due to BPH that was refractory to medical treatment and prostate volume (PV) greater than 40 ml (Appendix E1 [online]). Prostate biopsy was performed in men with prostatespecific antigen (PSA) levels greater than 4.0 ng/ml to exclude malignancy. Exclusion criteria were as follows: suspicion of prostate cancer; large (.5 cm) bladder diverticula; large (.2 cm) bladder stones; chronic renal failure; active prostatitis or urinary tract infection; neurogenic bladder or detrusor failure; urethral stricture; coagulopathies; contraindications to angiography; and the presence of a cardiac pacemaker, a nerve stimulator, or other metal implants (Fig 1). MRI and Image Reconstruction Technique All MRI studies were performed with a 3.0-T MRI system (Discovery 750; GE Healthcare, Milwaukee, Wis) by using a surface phased array coil. The enhanced MRI examination involved three-dimensional time-resolved imaging of contrast kinetics (TRICKS) acquisitions that included the following sequences: (a) axial, coronal, and sagittal fast spinecho T2-weighted imaging (repetition time msec/echo time msec, 6728/114, 7340/115, and /108, respectively; section thickness, 3 mm; intersection gap, 0, 0.5, and 0.5 mm, respectively; field of view, , , and cm, respectively; matrix, ; bandwidth, 62.5, 62.5, and Hz, respectively). The imaging range involved the bladder, prostate, and seminal vesicle. (b) Axial two-dimensional time-of-flight MRI, for which the parameters were as follows: 3.7/1.2; section thickness, 6 mm; intersection gap, 0 mm; field of view, cm; matrix, ; flip angle, 50, bandwidth, 62.5 Hz; and time of acquisition, 20 seconds. The imaging range involved the lower abdominal aorta, the common iliac artery, and the IIA Table 1: Baseline Characteristics of All 100 Men in Both Groups Characteristic Group A (n = 50) Group B (n = 50) P Value Age (y) (51 87) (53 88).91 IPSS QoL score Prostate volume (ml) Q max (ml/sec) PVR (ml) PSA level (ng/ml) IIEF-5 score Note. Data are means 6 standard deviations, with ranges in parentheses. IIEF-5 = International Index of Erectile Function, IPSS = International Prostate Symptom Score, PSA = prostate-specific antigen, PVR = post-void urine residual volume, QoL = quality of life (scores range from 0 [delighted] to 6 [terrible]), Q max = peak urinary flow rate. 2 radiology.rsna.org n Radiology: Volume 00: Number

3 Figure 1: Flowchart shows study population and groups. MRA = MR angiography, PAE = prostatic artery embolization, PSA = prostate-specific antigen. Table 2: Comparison of DSA and MR Angiography for Defining the Prostatic Artery Origin Prostatic Artery Origin and Carnevale Type (14) DSA MR Angiography Superior vesicular (type I) Anterior division of IIA (type II) Obturator (type III) Internal pudendal (type IV) Other (type V) 3 2 Total Note. Data are numbers of prostatic arteries. DSA = digital subtraction angiography, IIA = internal iliac artery. and its branches. (c) Three-dimensional TRICKS imaging, for which the parameters were as follows: 3.9/1.3; field of view, cm; section thickness, 1.2 mm; sections, 84 94; matrix, ; number of signals acquired, one; flip angle, 20 ; bandwidth, khz; and each phase of 8 10 phases in seconds. The mask was first imaged for seconds; then, a total of ml (0.15 mmol per kilogram of body weight) gadobenate dimeglumine (MultiHance; Bracco Sine, Shanghai, China) was used for rapid intravenous injection at a rate of 3 ml/sec using a power injector (Spectris; Medrad, Warrendale, Pa) through the A1 channel. Subsequently, 10 ml (0.075 mmol/kg) was injected Zhang et al at a rate of 0.5 ml/sec through the A2 channel, followed by a 30-mL saline flush at the rate of 2 ml/sec through the B channel. When imaging was complete, subtracted images in the arterial phase were loaded into a postprocessing workstation (Advantage Workstation, version 4.6; GE Healthcare, Buc, France). Rotational maximum intensity projections of the IIA and its branches were reconstructed from axial and coronal multiplanar (MPR) images, and curved planar reformats of the PA were derived from axial and MPR images and were traced backward to the origin of the PA from the prostate. Then, 5 -interval images along the head-end axis were generated that could be rotated in all directions. MR Angiography Evaluation and X-ray Tube Angle Prediction Two radiologists (H.Y.Y. and Y.G.S., with 25 and 10 years of experience in pelvic MRI, respectively) assessed all the MR angiography images independently, and decisions were made by consensus in case of discrepant readings. Both radiologists performed all the three-dimensional reconstructions and slowly rotated the pelvic arterial tree in both directions to identify the best angle obliquity that clearly depicted the origin of the PA. Obliquity of the angles clearly demonstrated the origin of the PA without the need for caudal or cephalic angulations. The best angle obliquity was provided to the interventionists to set the tube angle obliquity during the procedure for better visualization of the origin of the PA. However, the interventionists were blinded to the patient s identity and clinical history and the purpose of the study. PAE Procedure All PAE procedures were performed by the same interventionists (M.Q.W. and J.L.Z., with 28 and 12 years of experience in vascular and interventional radiology, respectively) using a therapeutic angiographic unit equipped with a digital flatpanel detector system (Innova 4100 IQ; GE Healthcare, Milwaukee, Wis) and nonionic contrast medium (Visipaque, 320 mg/ml of iodine; GE Healthcare, Princeton, NJ). After local anesthesia was administered, a 4-F vascular sheath (Radifocus; Terumo, Tokyo, Japan) was inserted into the right femoral artery by using the Seldinger technique. For group A, initial pelvic angiography was performed to evaluate the iliac vessels with a 4-F pigtail-type catheter (Cordis, Miami, Fla) and injection of 30 ml of contrast material at a rate of 15 ml/sec (4 frames per second). Next, to evaluate the branches of the IIA, DSA (4 frames per second) was performed by using a 4-F Simmons I catheter (Cordis) at the main IIA by using ipsilateral anterior oblique projection at 30, with injection of 9 18 ml of contrast medium at a rate of 3 6 ml/sec. Repeat DSA was performed if the origin and Radiology: Volume 00: Number n radiology.rsna.org 3

4 Effectiveness of MR Angiography for Visualizing Prostatic Artery before PAE Figure 2: Images in 75-year-old man with symptomatic benign prostatic hyperplasia (prostate volume, 93 ml). (a) Targeted maximum intensity projection image reconstructed from contrast-enhanced MR angiography data prior to prostate artery embolization in a 35 ipsilateral anterior oblique direction shows the left prostatic artery (white arrow) arising from the internal pudendal artery (black arrow). = Prostate region. (b) Image from digital subtraction angiography (performed in a 35 ipsilateral anterior oblique direction with the injection of 12 ml of contrast medium at a rate of 4 ml/sec [4 frames per second]) shows the origin of the prostatic artery (white arrow) arising from the internal pudendal artery (black arrow), in accordance with the contrast-enhanced MR angiographic findings. (c) Selective angiography of the left prostatic artery (arrow) performed with 3 ml of contrast medium at a rate of 1 ml/sec (4 frames per second) shows contrast medium staining in the prostate ( ). Figure 3: Images in a 65-year-old man with symptomatic benign prostatic hyperplasia (prostate volume, 78 ml). (a) Three-dimensionally reconstructed maximum intensity projection image from contrast-enhanced MR angiography in a 30 ipsilateral anterior oblique direction shows the origin of the right prostatic artery (white arrow) originating from the anterior division of the internal iliac artery, in common with the internal pudendal artery (black arrow). = Prostate region. (b) Discontinuous digital subtraction angiography image in a 30 ipsilateral anterior oblique direction shows the origin of the prostatic artery (white arrow), in common with the internal pudendal artery (black arrow), in accordance with the MR angiography findings. = Contrast medium staining in the prostate. trajectory of the PA were not displayed well. Then, superselective PA angiography was performed by using a coaxial 2.7-F microcatheter (Progreat; Terumo, Tokyo, Japan) with injection of 3 6 ml of contrast medium at a rate of ml/sec. If necessary, cone-beam CT was then performed, with a 5-second delay after injection of 4 6 ml of contrast medium at a rate of ml/sec. In group B, PAE was performed within 3 days after MR angiography. DSA was performed with the injection of contrast medium in the IIA immediately distal to the origin of the superior gluteal artery in the anterior oblique projection at the best angle demonstrated at MR angiography. Conebeam CT was avoided, if possible; alternatively, the temporarily recorded fluoroscopy image was used for selective catheterization. Next, prostate artery DSA was performed with the injection of contrast medium at a rate of 1 2 ml/ sec for a total volume of 3 6 ml. Embolization was performed with 100-mm nonspherical polyvinyl alcohol particles ( mm, PVA; Cook, Bloomington, Ind). Each vial of polyvinyl alcohol (1 ml) was diluted 4 radiology.rsna.org n Radiology: Volume 00: Number

5 Zhang et al Figure 4: Images in an 85-year-old man with symptomatic benign prostatic hyperplasia (prostate volume, 102 ml). (a) Maximum intensity projection of the left internal iliac artery (IIA) and its branches from contrast-enhanced MR angiographic data in a 30 ipsilateral anterior oblique direction shows two prostatic arteries (PAs) (white arrow and black arrow) arising from the anterior division of the IIA common trunk with the superior vesical artery (black arrowhead) and the distal part of the obturator artery (white arrowhead), respectively. = Prostate region. (b) IIA angiography performed with injection of 12 ml of contrast medium at a rate of 4 ml/sec (4 frames per second) in a 30 ipsilateral anterior oblique direction; visualization of the IIA braches is unsatisfactory. One PA (arrow) arises from the distal part of the obturator artery (white arrowhead). (c) Superselective angiography of the first PA (arrow) performed with injection of 3 ml of contrast medium at a rate of 1 ml/sec (4 frames per second). = Prostate region. (d) Superselective angiography of the anterior division performed by injecting the contrast medium by hand shows another PA (arrow) in common with the superior vesical artery (arrowhead). (e) Superselective angiography of the second PA (arrow) performed with injection of 3.6 ml of contrast medium at a rate of 1.2 ml/sec (4 frames per second). = Prostate region. in a 50-mL solution of nonionic contrast medium. The particles were slowly injected with fluoroscopic guidance until the end point (occlusion of the identifiable vessels supplying the prostate) was reached. Postprocedural Treatment The study participants stayed in the hospital for 1 3 days for observation and were then discharged if no complications occurred. Appropriate hydration was administered for 2 or 3 days after PAE. If necessary, patients were given nonsteroidal anti-inflammatory medications or non-opioid analgesics during and after PAE. Angiographic Imaging Evaluation The DSA, rotational angiography, and cone-beam CT images were evaluated independently by the two interventional radiologists (M.Q.W. and J.L.Z.) who performed the PAE; in cases of discrepant interpretations, the radiologists achieved consensus. The number of PAs on each side of the pelvis and their origins, Radiology: Volume 00: Number n radiology.rsna.org 5

6 Effectiveness of MR Angiography for Visualizing Prostatic Artery before PAE distribution, and termination were recorded and taken as the reference for MR angiography. Evaluation of the Performance of PAE So that we could compare the performance of the two groups, the procedure time, fluoroscopy time, number of DSA acquisitions, total number of frames acquired at DSA, radiation dose, dose-area product (DAP), and contrast medium volume were retrieved from the equipment records and surgical reports immediately after the procedure. Follow-up Follow-up was performed at 1, 3, 6, and 12 months by the interventionalists and the urologists. The overall results of embolization (IPSS, QoL score, IIEF-5 score, PSA level, Q max, post-void urine residual volume [PVR], and PV at MRI) were compared between both groups. Technical success was defined as bilateral embolization or as successful embolization of all angiographically visible arteries supplying the prostate. Postembolization symptoms and complications were registered and classified according to the Quality Improvement Guidelines for Percutaneous Transcatheter Embolization (13). Complications were considered minor if they could be addressed with ambulatory medical treatment and major if they resulted in prolonged hospitalization, hospital readmission, or surgery. Statistical Analysis All statistical analyses were performed by using commercial software (SPSS Statistics for Windows, version 20.0; IBM, Armonk, Table 3: Optimum Angle of Prostatic Arteries Provided by Contrast-enhanced MR Angiography Ipsilateral Anterior Oblique Angle (degrees) Left Pelvis Right Pelvis Total Total Note. Data are numbers of prostatic arteries. NY). Interobserver variability regarding the visualization of the PA origins with MR angiography was assessed by using k statistics. k Values of were considered to indicate slight agreement; k values of , fair agreement; k values of , moderate agreement; k values of , substantial agreement; and k values of , almost perfect agreement. Age, IPSS, QoL score, PV, PVR, IIEF-5 score, PSA level, procedure time, total number of frames acquired at DSA, fluoroscopy time, and contrast medium volume were recorded as means 6 standard deviations, and the differences between the two groups were tested by using the Student t test. Number of DSA acquisitions, radiation dose, and DAP were recorded as medians (with interquartile ranges), and the differences between the two groups were tested by using the Wilcoxon rank-sum test. The differences in minor complications after PAE between the two groups were tested by using the two-tailed Fisher exact test. P,.05 was considered to indicate a statistically significant difference. Results Baseline Characteristics Baseline demographic and clinical data of the study participants are listed in Table 1. A total of 100 men (mean age, 72.0 years ; range, years) were recruited. There were no significant differences (P =.94,.54,.71,.71,.66,.48, and.70, respectively) in preprocedure IPSS, QoL score, PV, Q max, PVR, PSA level, and IIEF-5 score between the two groups. Three and four patients in groups A and B, respectively, underwent biopsy, and no malignant lesion was detected. Bilateral PAE was successful in 96.0% (48 of 50) and 100% (50 of 50) of men in groups A and B, respectively; the difference was not statistically significant (P =.16). Two men in group A underwent unilateral PAE only because of technical failure owing to severe tortuosity and atherosclerotic changes of the IIAs. Evaluation of the PAs at MR Angiography before PAE Agreement with regard to the PA between the two radiologists was almost perfect (k = 0.92). In group B, 50 men (100 pelvic sides) with 106 PAs (mean diameter, 1.4 mm 6 0.4) had their anatomy confirmed with intraprocedural DSA or DSA combined with cone-beam CT. There was one PA in 94% (94 of 100) of pelvic sides and two independent PAs in the other 6% (six of 100) of pelvic sides. MR angiography successfully revealed 97 PAs and their origins in 95 pelvic sides; all of these findings were in accordance Table 4: Differences in Procedural Parameters of Prostatic Artery Embolization between the Groups A and B Parameter Group A Group B Reduction Rate (%) P Value Procedure time (min) ,.001 Fluoroscopy time (min) ,.001 No. of frames acquired with DSA Contrast medium volume (ml) ,.001 No. of DSA acquisitions 7 (6 7) 4 (4 5) 42.9,.001 Radiation dose (mgy) 920 ( ) 339 ( ) Dose-area product (cgy cm 2 ) ( ) ( ) Note. Data are means 6 standard deviations or medians with interquartile ranges in parentheses. DSA = digital subtraction angiography. 6 radiology.rsna.org n Radiology: Volume 00: Number

7 Figure 5: Graphs show clinical outcomes after treatment with prostatic artery embolization in groups A and B measured in terms of (a) International Prostate Symptom Score (IPSS), (b) quality of life (QoL) score, (Fig 5 continues) with the angiographic findings. MR angiography identified PAs with a sensitivity of 91.5% (97 of 106) (95% confidence interval [CI]: 86.1%, 96.9%) and a positive predictive value of 100% (97 of 97) (95% CI: 100%, 100%). In 43 men, bilateral PAs were visualized at MR angiography before PAE. MR angiography did not reveal nine of 106 PAs (of which four pelvic sides had two PAs); these were PAs with small diameters (,5 mm). PA Anatomy at MR Angiography According to the standard Carnevale classification (14), types of PA origin according to MR angiography findings were divided into types I IV. The most frequent PA origin was the anterior division of the IIA (29%; 28 of 97), followed by the internal pudendal artery (27%; 26 of 97), the common trunk with the superior vesical artery (23%; 22 of 97), the obturator artery (20%; 19 of 97), and, rarely, the accessory pudendal artery (2%; two of 97) (Table 2). The predicted angle of tube obliquity provided to the interventionists prior to PAE was the same as the actual angle used during PAE for visualization of the origin of the PA. The preprocedural predicted optimal angle for both sides was between 20 and 45 in the ipsilateral anterior oblique direction, without the need for caudal or cephalic angulations (Figs 2 4). For optimal visualization of the PA origin, the most frequent ipsilateral anterior oblique angle Zhang et al was (42%; 41 of 97), followed by (30%; 29 of 97), (11%; 11 of 97), and (9%; nine of 97), and the most rare angle was (7%; seven of 97) (Table 3). Bilateral oblique angle symmetry was observed in 21 men (42%; 21 of 50). Evaluation of the Performance of PAE for Groups A and B Compared with group A, in group B, preprocedural prediction of the best tube angle obliquity resulted in a 33.6% reduction (P,.001) in procedure time, from a mean of minutes (range, minutes) to 82.3 minutes (range, minutes). The fluoroscopy time was reduced by 51.6% (P,.001), from a mean of 28.5 minutes (range, minutes) to 13.8 minutes (range, minutes). The radiation dose was reduced by 63.2% (P =.004), from a median of 920 mgy (range, mgy) to 339 mgy (range, mgy). The DAP was reduced by 35.3% (P =.04), from a median of cgy cm 2 (range, cgy cm 2 ) to cgy cm 2 (range, cgy cm 2 ). The number of DSA acquisitions was reduced (P,.001), from a median of seven (range, five to nine) to four (range, four to six), which resulted in a significant reduction (P =.003) in the total number of frames acquired at DSA (32.4%). In addition, the contrast medium volume decreased by 37.7% (P,.001), from a mean of ml (range, ml) to ml (range, ml) (Table 4). Clinical Outcomes The follow-up period was 15 months 6 4 (range, months). Compared with baseline values, the IPSS, QoL score, Q max, PV, and PVR improved significantly at 1, 3, 6, and 12 months for group A and group B (P,.001 for all). There were significant differences in the mean total PSA level at 24 hours and 1 week for group A (P,.001 for both) and group B (P,.001 and P =.001, respectively) after PAE compared with the baseline levels. The level then reduced with no significant difference at 1, 3, 6, and 12 months compared with baseline for group A (P =.08,.15,.20, and.68, respectively) and group B (P =.12,.70,.80, and.61, respectively). Compared with baseline, the mean IIEF-5 score was not significantly different at 1, 3, 6, and 12 months for group A (P =.63,.35,.87, and.19, respectively) or group B (P =.79,.06,.07, and.09, respectively). Additionally, there was no significant difference in IPSS (P =.87,.44,.56, and.56, respectively), QoL score (P =.48,.06,.84, and.82, respectively), Q max (P =.42,.37,.06, and.22, Radiology: Volume 00: Number n radiology.rsna.org 7

8 Effectiveness of MR Angiography for Visualizing Prostatic Artery before PAE respectively), PV (P =.76,.18,.29, and.21, respectively), PVR (P =.68,.63,.14, and.19, respectively), PSA level (P =.97,.76,.75, and.78, respectively), or IIEF-5 score (P =.71,.38,.36, and.90, respectively) at the 1-, 3-, 6-, and 12-month follow-ups between the two groups after PAE. No procedurerelated complications were noted during the follow-up period (Fig 5; Fig E1 [online]). There were no major complications in either group. Minor complications included acute urinary retention, urethral burning, transient hematuria, hematospermia, lowgrade fever, and small inguinal hematoma (Table 5), and there were no significant differences between the groups with regard to these minor symptoms (P =.77,.80,.72,.44,.58, and P..99, respectively). The symptoms were treated only if necessary; these minor complications resolved during the 1st postoperative week. Glans penis ischemia, retrograde ejaculation, or erectile dysfunction was not observed. Discussion We assessed the effectiveness of MR angiography in depicting the prostatic artery (PA) prior to prostatic arterial embolization (PAE) and its impact on procedure time, fluoroscopy time, radiation dose, and contrast medium volume. We found that use of time-resolved MR angiography had a sensitivity of 91.5% (97 of 106) and a positive predictive value of 100% (97 of 97) in revealing the origins, trajectory, and number of PAs and resulted in significant reductions in procedure time, fluoroscopy time, radiation dose, and contrast medium volume during PAE (by 33.6%, 51.6%, 63.2%, and 37.7%, respectively). Recently, Kim et al (9) assessed the utility of MR angiography in identifying the origin of the PA prior to PAE and identified 26 (76.5%) of 34 PAs in 17 patients (34 pelvic sides). Their study was useful in treatment planning, with reduced radiation dose and procedure time. However, that study Table 5: Complications after Prostate Artery Embolization in the DSAonly and MR Angiography Groups Characteristic had some technical defects that reduced the identification rate of PAs, such as a low dose of contrast medium (0.1 ml/kg of Gadovist), a slow intravenous injection rate of contrast medium (1.5 ml/sec), and low image resolution (matrix, ). Our objective was also to reduce the radiation dose and contrast medium volume needed during PAE. Providing the interventionist with the optimal visualization angle of tube obliquity of the origin and trajectory of the PA without using ionizing radiation helped fulfill these objectives. The preprocedural predicted optimal angle for both sides was between 20 Figure 5 (continued): (c) peak urinary flow rate (Q max ) and (d) prostate volume (PV). There were no significant differences (P..05 for all) between the two groups at every follow-up time point. Vertical lines = standard deviations. Group A (DSA Only) (n = 50) Group B (MR Angiography) (n = 50) P Value* Acute urinary retention 6 (12) 8 (16).77 Urethral burning 10 (20) 8 (16).80 Low-grade fever 6 (12) 9 (18).58 Transient hematuria 3 (6) 5 (10).72 Hematospermia 5 (10) 2 (4).44 Small inguinal hematoma 2 (4) 1 (2)..99 Note. Data are numbers of patients, with percentages in parentheses. DSA = digital subtraction angiography. * P values were obtained with the Fisher exact test. and 45 in the ipsilateral anterior oblique direction, without the need for caudal or cephalic angulations; the most frequent ipsilateral anterior angle was In addition, there was bilateral oblique angle symmetry only in 42% (21 of 50) of the cohort. Therefore, no standard angle can be recommended for all individuals, similar to uterine artery embolization (UAE) (15), and the angle should be tailored for each patient, similar to the prediction of UAE. DSA with high spatial resolution ( 0.3 mm) is the reference standard for identification of vascular structures, especially 8 radiology.rsna.org n Radiology: Volume 00: Number

9 Zhang et al small arteries, collateral branches, and anastomoses. In our study, nine PAs could not be identified at MR angiography, and their diameter was less than 0.5 mm, as confirmed at DSA combined with cone-beam CT. This demonstrated that MR angiography has limitations in the identification of small arteries (,5 mm in diameter). There may be two reasons for this. First, MR angiography is not a dynamic imaging modality like DSA, and its resolution is lower than that of DSA. In addition, in TRICKS MR angiography with high temporal resolution, the spatial resolution is lower, and thus it is not effective in depicting small arteries. Our study had some limitations. First, this study included only a small number of men, with limited follow-up. Second, we did not assess the anastomoses between the PAs and the adjacent arteries. We conclude that preprocedure time-resolved gadolinium MR angiography provides useful information for PAE planning and could significantly reduce the procedure time, fluoroscopy time, radiation dose, and contrast medium volume needed during PAE. However, a large cohort is necessary to confirm our findings. Acknowledgments: We thank Xiao Jing Zhang, MD, from the Department of Radiology, Chinese PLA General Hospital, for her technical support. We also thank Xin Ma, MD, and Xu Zhang, MD, from the Department of Urology, Chinese PLA General Hospital, and Dan Feng, PhD, from the Department of Medical Statistics, Chinese PLA General Hospital, for their consultations. Author contributions: Guarantors of integrity of entire study, J.L.Z., M.Q.W., Y.G.S., H.Y.Y., K.Y., H.N.X., H.T.Z., Y.W.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; agrees to ensure any questions related to the work are appropriately resolved, all authors; literature research, J.L.Z., H.T.Z., J.X.F.; clinical studies, all authors; experimental studies, H.T.Z.; statistical analysis, H.T.Z., Y.W.; and manuscript editing, J.L.Z., H.T.Z., J.Y.Y. Disclosures of Conflicts of Interest: J.L.Z. disclosed no relevant relationships. M.Q.W. disclosed no relevant relationships. Y.G.S. disclosed no relevant relationships. H.Y.Y. disclosed no relevant relationships. K.Y. disclosed no relevant relationships. H.N.X. disclosed no relevant relationships. H.T.Z. disclosed no relevant relationships. 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