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15 Employing aQuality Improvement Program toOptimize mpMRI-Directed Fusion Biopsy
161
algorithms is possible by retrospective assess­ment of the procedure based on the biopsy results and trajectory of each needle relative to the tar­get, which will be discussed below.

Patient Factors During FB

Noise-canceling headphones and relaxing music have been suggested to alleviate anxiety and, according to certain studies, can positively impact (decrease) the perceived pain level [25, 26]. The application of intrarectal topical anesthesia is advantageous for pain management, although it is less effective than periprostatic nerve block while combining both modalities yields superior outcomes in terms of pain control [27]. Apical lesion targeting is challenging, and the operator should maneuver the probe to ensure that the needle insertion site is above the dentate line to prevent patient movement due to pain. Familiarizing the patient with the “snap” sound of the biopsy device can prevent the startle move­ment of the patient during the procedure. Our institutional study showed that the anxiety from FB plus systematic biopsy is higher than the sys­tematic biopsy alone, which could be attributed to the relatively longer duration of FB or/and the patient’s perceived knowledge of higher chances of the csPCa detection by FB [28]. Thus, explain­ing what to expect on the biopsy date and con­tinuous communication with the patient during the procedure can minimize patient movements and increase the chances of successful FB.
single-bevel needle tip gives a longer length of tissue but has higher deection, the multi-bevel design helps to balance bending moments but decreases the length of the tissue sampling [29]. The operator must be familiar with the character­istics of the needle in use and make appropriate adjustments to account for deection during the targeting and ring processes.
Congurations of US probes, such as side-
ring or end-ring, exhibit comparable PCa detection rates and are selected based on the operator’s preference and target location [30, 31]. Based on our experience, using a side-ring con­guration for apical lesions can spare the sphinc­ter bers (which are located immediately anterior to the apex) and avoid pain and the resultant patient movement. Conversely, end-re needles are more helpful when seminal vesicle FB is indi­cated (the following ndings increase the odds of detection of seminal vesicle invasion on pathol­ogy: mpMRI suspicion for seminal vesicle involvement, prostate base lesions with moderate suspicion of extra-prostatic extension, post­biopsy high GG lesion at prostate base [32]).
Ideally, biopsy cores should be handled in a
separate container for each site. Submitting more than two cores in a single container increases the probability of tissue core fragmentation [33]. More details on biopsy core optimization are dis­cussed in Chap. 22 of this textbook by Iczkowski.
Reverse Fusion Workow: TheCrucial Element ofQI inFB
Obtaining theBiopsy
Precise navigation toward MRI targets involves utilizing fusion software as a guiding tool, cou­pled with the simultaneous correlation of land­marks through real-time ultrasound. Following successful fusion, rapid completion of the proce­dure is imperative to minimize patient discom­fort. One of the factors that can alter FB precision in hitting the target is the geometry of the biopsy needle tip, which inuences both needle deec­tion and the length of tissue sampling. While a
While reverse fusion serves as the concluding sec­tion of this chapter, it is the initiation of the learn­ing process. In the case of a discordant biopsy, it is not acceptable for the clinician to solely convey a negative result to the patient without gaining a deeper understanding of the potential factors con­tributing to the discordance. For proper patient counseling, QI, and research purposes, it is crucial to compare pre-biopsy imaging ndings with his­topathological results, ensuring accurate diagno­ses and facilitating learning from any potential errors. As mentioned before, reverse fusion refers to the multidisciplinary review of discordant
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pathology results of FB by re-evaluation of imag­ing and lesion sampling. Namely, uncertainty arises when the biopsy of PI-RADS 4/5 lesions results in grade group (GG) 1 disease or benign prostate instead of the expected diagnosis of csPCa.
Our institutional ow of the reverse fusion starts with a re-evaluation of the original mpMRI by a fellowship-trained prostate radiologist with over 13years of experience (the corresponding author of the present chapter). This step aims to afrm or downgrade the assigned PI-RADS score. If the second radiologist conrms the ini­tial PI-RADS score, the discordant results are considered unresolved. Discordance is consid­ered resolved if the imaging review conrms a PI-RADS of 3 or lower. The second step involves an assessment of sufcient sampling by a mini­mum of two cores per target. As mentioned before, several fusion platforms can record ultra­sound segmentation, US-MRI registration and fusion, and needle trajectories. Reviewing these steps is essential to detect any procedural error
that could potentially cause discordant results. Such multidisciplinary meetings also provide a QI opportunity to evaluate radiology and pathol­ogy structured reports and facilitate the harmoni­zation of terminology between different disciplines [34]. An illustration of the approach to discordant biopsy results is shown in Fig.15.4.
As a practical example, we used the presented workow to assess discordant results of PI-RADS 4 lesions in our institution. After re-evaluation through the motioned algorithm, we sub­categorized those lesions based on the ADC maps. From a total of 286 lesions, the subcatego­rization of lesions into higher suspicion (4-plus) and lower suspicion (4-minus) yielded 158 and 117 lesions, respectively [35]. Reverse fusion analysis demonstrated that 61% of 4-plus lesions and 17% of 4-minus lesions contained csPCa with signicantly different PSAD [median (IQR):
0.16 (0.1–0.2) versus 0.13 (0.08–0.2), respec­tively]. In another institutional example of 121 PI-RADS 5 lesions, we detected 45 discordant results, out of which 27 were unresolved [5]. The
Fig. 15.4 Our institutional reverse fusion algorithm for discordant pathology results. GGG: Gleason grade group; PSA: prostate-specic antigen. (Reprinted from Kotamarti
S, Gupta RT, Wang B, Séguier D, Michael Z, Zhang D, Abern MR, Huang J, Polascik TJ.Reconciling Discordance
Between Prostate Biopsy Histology and Magnetic Resonance Imaging Suspicion - Implementation of a Quality Improvement Protocol of Imaging Re-review and Reverse fusion Target Analysis. Eur Urol Oncol. 2022 Oct;5(5):483–493 with permission from Elsevier)
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positive predictive value of PI-RADS 5 lesion in detecting csPCa increased from 0.63 to 0.74 before and after adjusting for unresolved discor­dant results. To provide more detailed examples of our QI protocol, a case series by Kotamarti etal. discusses several examples from our institu­tional multidisciplinary experience of the reverse fusion [36].

Discussion

Learning Curve
Although we present our institutional workow, there are numerous potential areas for QI research in optimizing FB.Commonly used types of MRI­directed prostate sampling are cognitive biopsy, MRI-ultrasound software-fusion targeted biopsy (FB), and in-bore MRI-guided biopsy; each tech­nique possesses specic advantages and disad­vantages in terms of cost, availability, required equipment, learning curve, biopsy site recording, operative time, the possibility of simultaneous systematic biopsy, etc. The approach of these biopsy techniques could be transrectal or trans­perineal [37]. The increased diagnostic quality of prostate mpMRI has made targeted biopsy pos­sible. Compared to standard systematic biopsy, several well-designed studies have shown that FB enables the detection of a greater number of clini­cally signicant PCa (csPCa) with fewer non­csPCa diagnoses [38, 39]. Following the increasing adoption of FB, reports from pio­neered centers with experienced urologists high­lighted a signicant learning curve. One report mentioned that after 1300 consecutive cases in a 4-year period, cancer detection rates continued to increase, especially for lesions with PI-RADS ≥4 (with a detection rate of 50% in 2012 rising to 76% in 2016) [40, 41]. A recent study demon­strated that when a facility begins to adopt FB, a prociency threshold to reach consistent, high performance in csPCa detection rate was observed after approximately 50 cases, indicat­ing the learning curve for optimal implementa­tion [41]. In addition to improved urologists’ technical skills, such increases in detection rate
likely reect institutional improvements in differ­ent disciplines like mpMRI interpretation and reporting, MR-US co-registration, pathology reporting, and interdisciplinary communication.
Core Number Optimization
The optimal number of targeted biopsy cores has remained controversial. Based on the results of the PRECISION trial, four cores per target are superior to a 10–12 core TRUS-guided system­atic biopsy [38]. In 2023, European Urological Association [42] and American Urological Association [43] guidelines advised combining targeted biopsy with systematic biopsy for biopsy-naïve patients with mpMRI-visible lesions, necessitating greater numbers of biopsy cores. This increases the complication rate (i.e., infection, bleeding, discomfort, and urinary issues) as well as the time and expenses related to the procedure and pathology study. Several stud­ies tried to optimize MRI-FTB core numbers by obtaining 1–5 cores from the target [4446]. Although the rst two cores obtained from the target diagnose the majority (75–89%) of the csPCa, it has been shown to miss csPCa in 11–25% of cases, and additional cores up to 4–5 transrectal samples from the target could benet this proportion of cases [47, 48].
Besides targeting the lesion or so-called umbra, sampling of the 10-mm shadow or “pen­umbra” could improve the detection rate of csPCa and decrease the detection of non-csPCa [49]. A meta-analysis comparing the effective- ness of MRI-FTB plus regional biopsy to MRI­FTB plus systematic biopsy found signicant heterogeneity in denitions for regional sam­pling, highlighting a lack of consensus for this core number optimization efforts. Examples of such denitions proposed for sampling the rest of the prostate tissue are ipsilateral systematic biopsy, regional saturation or targeted sampling (cores taken in the 5-mm interval, along the lon­gest axis of ROIs plus the adjacent cross-hair pattern), focal saturation biopsy (cores taken from the target sector and an adjacent sector), and targeted sector sampling (cores taken from
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the target sector) [50]. This meta-analysis study, with overall 2600 MRI-positive cases, con­cluded that regional sampling (considering the mentioned heterogeneity) could decrease the number of cores by a median of 6.5 [IQR 4–16], and cumulative detection rates of csPCa (GG>1) were not inferior to FB plus systematic biopsy [50].
Transrectal Versus Transperineal
A paradigm shift has been initiated in recent years toward the TP approach, mainly with the rationale of lower infectious complications and better anterior PCa detection. In a multicenter, randomized trial, Hu et al. allocated biopsy­naïve participants to either undergo TP (287 cases) biopsy without antibiotic prophylaxis or TR (280 cases) biopsy with targeted prophy­laxis [51]. The latter involved rectal culture screening for uoroquinolone- resistant bacteria, with antibiotic administration tailored to the culture and sensitivity results. Infectious and non-infectious complications and csPCa detec­tion rates were comparable. Mian etal. showed the same infectious complications for the TP approach without prophylaxis and the TR approach with prophylaxis [52]. Although the TP approach is preferred in terms of lower anti­biotic use, antimicrobial resistance rates, and urosepsis admissions, it is usually more time­consuming and requires more staff, while the physician’s reimbursement is not proportional in the US health system. Additionally, based on a survey in 2023, less than 50% of urology resi­dents were exposed to TP biopsy, and lower exposure inherently translates to lower intent to adoption of TP biopsy post- training [53]. Some argue that the increased infection from the TR approach, although a higher form than that of TP, is clinically low in experienced centers. However, probably more detailed studies on cost-effectiveness and the added benet of omit­ting antibiotic prophylaxis in this specic patient population are needed for a more con­dent conclusion.
Future Directions
The most important requirement of an ideal FB is accurate localization with an imaging modality that is reproducible and has less operator­dependent variation. This rapid and widespread adoption of mpMRI for PCa management has resulted in large volumes of mpMRI but not all of this MRI demonstrates high image quality or highly accurate image interpretation [54]. This variability of quality poses a signicant risk as producing diagnostic images of suboptimal qual­ity could lead to downstream challenges in image­directed biopsy or even biopsy being not performed in cases where it should be performed. Even when the quality is deemed acceptable, the variety in equipment, practices, and image inter­pretation can complicate mpMRI standardization. Studies have demonstrated that the PPVs for a given PI-RADS score can vary not only among different institutions but also among individual radiologists [9, 55]. Some of these variations can be attributed to factors such as the pretest proba­bility of patients undergoing mpMRI and the expertise of the radiologist. However, it should be mentioned that protocols to obtain prostate MRI can be heterogeneous worldwide and mostly set based on each institution’s radiologists and physi­cists. Although PI-RADS v2.1 has provided the minimum technical requirements for performing prostate mpMRI (which are important to follow) and systems such as Prostate Imaging Quality (PI-QUAL) have attempted to standardize assess­ment of MR image quality, it is evident that even adherence to these technical standards does not ensure high quality, as certain MRI machines may achieve better results with technical parameters beyond the recommended guidelines [56]. This is a huge opportunity for QI in imaging and, conse­quently, in FB to move toward a more standard­ized mpMRI where new technology such as deep learning could be used to improve image quality, reduce image acquisition time, and help to stan­dardize the appearance of prostate MR images. This will undoubtedly help in rectifying inter­reader discrepancies pave the way for articial intelligence aided detection to become a reality.
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Conclusion

The workow for QI in FB underscores the criti­cal importance of interdisciplinary communica­tion among radiologists, urologists, and pathologists. Inaccuracies in FB can stem from the operator’s experience, inaccurate segmenta­tion of the mpMRI and/or US, registration/fusion errors, variations in prostate deformation due to factors like the TRUS probe, patient positioning, endorectal coil, rectal stool/gas content, bladder fullness, errors in handling biopsy cores, etc. The workow, as exemplied, follows a meticulous process from MRI acquisition to biopsy, planning sessions for mutual understanding, and continu­ous learning through routine reviews. Regular in­person multidisciplinary meetings enhance the planning phase, aiming to establish consensus on MRI targets and address discordant biopsy results. In essence, the outlined institutional example reects a commitment to QI at every stage of the FB process, promoting effective communication, learning, and adaptability for better patient care.

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Multiparametric Ultrasound forProstate Imaging andTargeting
DerekChan andKathrynNightingale
16

Introduction

Ultrasound is a fast, safe, and portable modality for imaging the prostate. Conventional B-mode ultrasound images are formed by using a trans­ducer to transmit ultrasound into the tissue and then tracking the backscattered signal as it is reected toward the transducer. These images visualize differences in acoustic impedance, which is affected by tissue’s density and speed of sound [1]. However, B-mode ultrasound often has low sensitivity and specicity for prostate lesions, which can appear isoechoic with healthy tissue [2]. Because of this, many ultrasound­based imaging modalities have been developed based on differences in tissue characteristics between prostate cancer and benign tissue to image and target prostate cancer more effectively.
Multiparametric ultrasound (mpUS) com­bines different ultrasound modalities to improve imaging performance. Because each modality has distinct advantages and challenges, and dif­ferent ultrasound modalities may capture differ­ent characteristics of prostate cancer, it can be benecial to combine information from multiple modalities [3]. There have been many studies
D. Chan · K. Nightingale (*) Department of Biomedical Engineering, Duke University, Durham, NC, USA e-mail: derek.chan@duke.edu; Kathy.nightingale@
duke.edu
investigating various combinations of ultrasound imaging techniques [38].
The following sections include overviews of ultrasound elastography (strain elastography, shear wave elastography, and acoustic radiation force impulse imaging), quantitative ultrasound, Doppler and contrast-enhanced ultrasound, and micro-ultrasound imaging, any of which can be combined to generate multiparametric prostate ultrasound images providing enhanced lesion contrast.

Ultrasound Elastography

Elastography is the generation of images that enable the assessment of tissue stiffness. It is used in many clinical applications because tissue elasticity often changes with disease state [9]. Elasticity has been studied as a biomarker in the prostate because prostate cancer has been shown to be stiffer than healthy tissue, possibly due to an increase in collagen deposition and/or an increase in cellular density and connectivity [9,
10]. This section contains an overview of three
elastography methods that have been applied in the prostate: strain elastography, shear wave elas­tography, and acoustic radiation force impulse (ARFI) imaging.
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2024 T. J. Polascik et al. (eds.), Imaging and Focal Therapy of Early Prostate Cancer,
https://doi.org/10.1007/978-3-031-66754-1_16
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D. Chan and K. Nightingale
Strain Elastography
In strain elastography, the clinician applies slight compression to the prostate using the ultrasound transducer, and imaging data are acquired before and during the compression [11]. A motion­tracking algorithm is used to track the strain induced in different regions of the prostate; stiffer tissue will exhibit smaller displacement and lower strains than softer tissue [12].
Figure16.1, reproduced from Yoo etal. (2012), shows a strain elastography image and a gray­scale B-mode image of the prostate, with the let­ter “A” in each image indicating a lesion with increased stiffness [13].
Kanagaraju et al. (2020) conducted a study with 60 patients. They found that strain elastogra­phy increased sensitivity to prostate cancer com­pared to B-mode ultrasound (89% vs. 79%), though it was less specic than B-mode (56% vs.
Fig. 16.1 Strain elastography of the prostate, depicting the strain ratio metric. (Reproduced from [13]: Yo o etal. (2012), “Role of the elastography strain ratio using tran­srectal ultrasonography in the diagnosis of prostate cancer
and clinically signicant prostate cancer,” published in Scientic Reports under a Creative Commons Attribution
4.0 International license)
16 Multiparametric Ultrasound forProstate Imaging andTargeting
171
81%) [11]. Yo o etal. (2022) investigated the use of the elastography strain ratio for predicting prostate cancer. They reported an area under the receiver operative curve (AUC) of 0.845 when the strain ratio was combined with variables such as prostate-specic antigen (PSA) level and pros­tate volume [13].
Challenges with strain elastography include imaging artifacts resulting from uneven compres­sion or calcications, difculty quantifying the elastic modulus because the applied stress is generally unknown, and susceptibility to tissue slip boundaries [14].
Shear Wave Elastography
Shear wave elastography is a quantitative imag­ing technique in which a focused ultrasound exci­tation is used to displace the tissue by several microns, and the speed of the resulting shear
waves is estimated. If the tissue is assumed to be linear, elastic, isotropic, and incompressible, then the shear wave speed can be related to Young’s modulus and shear modulus of the tissue, which are elastic material constants related to tissue stiffness [15]. A higher shear wave speed corre­sponds to stiffer tissue [16].
Because the elastic modulus obtained with shear wave elastography is a quantitative metric of tissue stiffness, it can be used to characterize prostate tissue and establish a threshold to distin­guish cancer from healthy tissue [16]. Figure16.2, reproduced from Secasan etal. (2022), shows the application of shear wave elastography in the prostate; the shear modulus values are shown as a color overlay on the grayscale B-mode image. In the gure, the red region of the prostate is a region with increased stiffness that was con­rmed to be cancer after a biopsy [17].
A 2019 meta-analysis of shear wave elastog­raphy for detecting prostate cancer reported a
Fig. 16.2 Shear wave elastography in the prostate, shown as the color overlay on the grayscale B-mode image. A stiffer region of the prostate is shown in red. (Reproduced from [17]: Secasan et al. (2022), “Articial Intelligence
System for Predicting Prostate Cancer Lesions from Shear Wave Elastography Measurements,” published in Current Oncology under a Creative Commons Attribution 4.0 license)