Effect of neoadjuvant endocrine therapy on the acoustic environment in tissue of prostate cancer: a study of histopathological characteristics

Introduction

As one of the most common malignant tumors among elderly males, the number of new cases and deaths related to prostate cancer (PCa) was estimated to be 1.41 million in 2020, which has a serious impact on the health of middle-aged and elderly men (1,2). The standard treatment methods for early PCa include prostatectomy and radiotherapy. Prostatectomy consists of removing the lesion in its entirety, but it is a major surgical procedure that causes significant surgical trauma. Complications may occur after surgery, including severe intraoperative bleeding, which affects the patient’s quality of life adversely (3). Radiotherapy can have the same clinical effects as radical resection for those who have contraindications of surgery, but it can also have severe side effects, such as radiation rectal injury or bone marrow suppression (4). Some local methods of treatment have emerged in recent years as an alternative to traditional treatments, including high intensity focused ultrasound (HIFU), cryotherapy, laser ablation, photodynamic therapy, and irreversible electroporation. It has been shown that HIFU has the potential advantage of better safety with fewer complications when compared with other local treatment methods (5).

A wide variety of clinical trials using HIFU to treat early PCa have been reported, with positive short- and mid-term results, but there was a controversy about the long-term effects (6). There are several reasons for this controversy, including the fact that local therapy only treats lesions that can be seen on imaging and be proved PCa by puncture biopsy. In addition, it is not easy to treat lesions that are not visible on imaging/puncture biopsy, and since most PCa manifests pathologically as multiple lesions, residual lesions may cause local progression or distant metastasis if they persist after surgery. The problems mentioned above make it necessary to identify other treatments that can be combined with HIFU to deal with lesions that are not visible on imaging or on punch biopsy. One of these therapies is neoadjuvant endocrine therapy (NET), which can serve as an effective tool for slowing down and even stopping the progression of PCa, improving tumor control, and treating lesions that cannot be seen on conventional imaging. NET is a systemic treatment that can potentially treat not only the invisible lesions, etc. but also the potential early distant metastases (7). It is therefore possible that NET could be administered before HIFU treatment for a better effect on the patient.

There have been a number of previous studies that investigated NET in conjunction with radical prostatectomy (RP). A retrospective study conducted by Hu et al. (8) found that PCa patients’ operation time, blood loss, and positive surgical margin rate decreased significantly after NET. In a study by Ma et al. (9), patients with radical PCa who received NET before surgery had less surgical difficulty, reduced operation time, and improved postoperative recovery. It seems likely that the combination of NET and HIFU therapy may have a more beneficial therapeutic effect than HIFU alone at the time of treatment; however, one question that needs to be considered is: does endocrine therapy prior to the HIFU adversely affect the subsequent HIFU itself?

HIFU treatment involves the use of high frequency ultrasound beams that can be focused on precisely defined target areas, causing localized temperature elevation and coagulative necrosis in these targets—as a result of thermal and cavitation effects—with no damage to surrounding viable tissue (10,11). From the physical process of HIFU, it can be inferred that the tissue structure in the target area is an important factor affecting the efficiency of HIFU treatment.

The tissue acoustic environment (AET) can affect ultrasound transmission and energy deposition manifested by the unique structure, density, blood supply, and functional status of tissues during HIFU treatment (12). Previous studies have shown that altering the tissue structure means changing the tissue structure, density, blood supply, and functional state of the tissue in a particular way, thereby altering the inherent acoustic properties of the tissue, so as to increase the deposition of ultrasound energy. The aim is to increase the treatment efficiency by reducing the total dose of ultrasound energy and to decrease the incidence of complications by shortening the sonication time and total treatment time (13). For PCa, the types of tumors, the number of calcifications, the proportion of smooth muscle cells and vascular perfusion might interfere with the tissue structure of the tumor. There has been no comparative study of AET changes after NET for PCa. Therefore, this retrospective study aimed to analysis of the pathological changes in tissue components and structures, focusing on the calcifications, smooth muscle cells and blood vessels which are important factors affecting AET. We present this article in accordance with the MDAR reporting checklist (available at https://tcr.amegroups.com/article/view/10.21037/tcr-23-1224/rc).

Methods

Patients

This retrospective study was approved by the Ethics Committee of Zigong Fourth People’s Hospital (No. 2022-123) and informed consent was obtained from all individual participants. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). A total of 40 patients with pathologically confirmed PCa were included in this study. The inclusion criteria were as follows: age 60−80 years; Gleason score of 7−8 points; No calcification was observed in magnetic resonance imaging (MRI) before endocrine therapy and before RP; the tumor node metastasis (TNM) stage was lower than or equal to the T2aN0M0; no contraindications of RP; no contraindications of endocrine therapy. The exclusion criteria were as follows: Gleason scored less than 7 points or more than 8 points; the TNM stage was greater than the T2aN0M0, and thus RP was not possible; reflex therapy had been done; accompanied with other tumors. In this study, after daily oral endocrine therapy of bicalutamide 50 mg and subcutaneous injection of goserelin 3.6 grams at different times had been administered, patients who received endocrine therapy before RP were assigned as test group (n=20), and patients without endocrine therapy were treated as control group (n=20).

Specimen processing

A 12-hour fixation in neutral formaldehyde was conducted on all specimens to qualitatively analyze smooth muscle, calcification, and vascular changes. The samples were collected, dehydrated, transparented, embedded in paraffin, sliced at a 4-µm thickness, and sealed after hematoxylin-eosin (HE) staining. Van Gieson (VG)-special staining (MXB biotechnologies, Fuzhou, China) was used to measure smooth muscle cell changes quantitatively. Three wax blocks were randomly selected from each case, and then each specimen was cut into four 1-mm thick sections and sealed. Yellow staining was applied to smooth muscle cells.

Quantitative analysis

Image analyses were performed separately by two pathologists who were blinded to the other’s test results. The two pathologists checked each other’s results when the analysis was completed. If the results of the two pathologists were inconsistent, both pathologists repeated the measurements separately until the results were consistent with each other. If there were still inconsistencies, a senior pathologist was asked to give suggestions and make the final decision. The results of the three fields were averaged.

Calcifications

Pathologists examined three randomly selected HE-stained pathological sections in each case under an optical microscope. The total number of calcifications was counted by randomly selecting ten fields of view from each section under 100-fold magnification. To quantify calcification, statistical analysis was performed on the diameters of the maximum and minimum calcifications, the number of calcifications, and the area of calcifications in both groups.

Smooth muscle cells

A pathological section of smooth muscle tissue was randomly selected from each case to examine under an optical microscope the qualitative changes that occurred within the cells. The microscope and camera (Olympus, Tokyo, Japan) were used to obtain five images (400-fold field-of-view) for each VG-special stained section. To calculate the proportion of smooth muscle cells, the 2021 version of Photoshop (Adobe Systems Inc, San Jose, CA, USA) was used. The pixel value of the yellow area of each image was quantitatively measured by opening the image in the software, selecting color areas, extracting the color, recording the measured pixel values, and performing statistical analysis on the total value of the pixel values.

Blood vessels

Pathologists examined three HE-stained pathological sections from each case under an optical microscope. To count the total number of blood vessels, ten images with a 100-fold field-of-view were randomly selected from each section. We classified blood vessels based on histological and embryological grading standards in our analysis of quantitative changes in blood vessels. Veins smaller than 200 microns in diameter were considered micro-veins. Those smaller than 1 millimeter and larger than 200 microns were classified as small veins. Arterial vessels smaller than 300 microns were considered micro-arteries. The term “small artery” referred to arteries with a diameter of 300 microns or less and a diameter of 1 millimeter or less.

Statistical analyses

Statistical Product and Service Solutions (SPSS) version 22.0 software was used to analyze all experimental data [International Business Machine (IBM) Corp, Armonk, NY, USA]. The data were expressed as median and interquartile range (IQR). Two independent sample t-tests were used to compare the two groups when the data were normally distributed. For comparisons between the two groups, two independent sample t-tests were used for normally distributed data, whereas for comparisons between the two groups, two independent sample t-tests were used for normally distributed data, and a non-parametric independent sample test (Mann-Whitney U test) was used for non-normally distributed data. The statistical significance was determined by a P value of less than 0.05.

Results

Basic characteristics

A total of 40 patients were screened from October 2020 to December 2022, with 20 cases in the endocrine therapy group and 20 cases in the control group. The baseline parameters of both groups showed no significant difference. All the baseline data are summarized in Table 1.

Calcification changes

A majority of the calcifications were found in the normal tissues surrounding the cancer. Based on the 30 images of the HE-stained pathological sections under 100-fold field-of-view, the largest diameter of calcification in the control group was 0.30 (0.16–0.48) millimeters while the smallest diameter was 0.03 (0.02–0.05) millimeters. The number of calcifications in the control group was 7.00 (3.00–20.50), and the total calcification area was 0.14 (0.02–0.37) mm² (Figure 1A-1C). In the test group, the largest diameter of calcification was 0.60 (0.50–0.86) millimeters, and the smallest diameter of calcification was 0.05 (0.02–0.10) millimeters. There were 21.00 (17.25–39.25) calcifications and 1.23 (0.82–1.56) mm² of calcifications in the test group (Figure 1D-1F). Compared with the control group, the maximum diameter of calcifications (P<0.001), the total number of calcifications (P=0.001), and the total area of calcification (P<0.001) were a little greater in the test group (Table 2).

Figure 1 Distribution of calcification in normal tissues after neoadjuvant endocrine therapy for prostate cancer (HE-stained pathological sections). Control group: A, ×40; B, ×100; C, ×200; test group: D, ×40; E, ×100; F, ×200. The yellow box represented the magnified observation area. The calcifications were significantly more abundant in the test group than in the control group. HE, hematoxylin-eosin.

Changes in smooth muscle cells

NET significantly increased the density of smooth muscle cells and resulted in smooth muscle cells belonging to the proliferative state in the PCa tissue. Observing HE-stained pathological sections in both groups, there was an orderly arrangement of smooth muscle cells in the control group (Figure 2A-2C), while the arrangement of smooth muscle cells in the test group was disordered (Figure 2D-2F). VG-special staining revealed that smooth muscle cells were yellow after quantitative analysis (Figure 3). In the 15 images of the VG-special stained sections under 400-fold field-of-view, the smooth muscle cell proportion pixel value of 2.00×10⁷ (1.69×10⁷–2.47×10⁷) pixels in the test group was significantly higher than that in the control group [1.12×10⁷ (0.99×10⁷–1.40×10⁷) pixels, P<0.001] (Figures 4,5).

Figure 2 Changes in smooth muscle cells in tissues after neoadjuvant endocrine therapy for prostate cancer (HE-stained pathological sections). In the control group, the smooth muscle cells were arranged in an orderly manner (A, ×40; B, ×100; C, ×200). In the test group, the smooth muscle cells were obviously proliferated and arranged in disorder (D, ×40; E, ×100; F, ×200). The yellow box represented the enlarged observation area. The smooth muscle in the test group showed significantly more hyperplasic changes than in the control group. HE, hematoxylin-eosin.

Figure 3 Changes in smooth muscle cells in tissues after neoadjuvant endocrine therapy for prostate cancer (VG-special stained sections). Control group: A, ×40; B, ×100; C, ×200; test group: D, ×40; E, ×100; F, ×200. The yellow box represented the enlarged observation area. The results were consistent with Figure 2. VG, Van Gieson.

Figure 4 Changes of smooth muscle cells calculated in Photoshop after neoadjuvant endocrine therapy for prostate cancer (VG-special stained sections). (A,B) Control group (VG-special stained sections, ×400); the pixel value was 1.12×10⁷ pixels. (C,D) Test group (VG-special stained sections, ×400); the pixel value measured by Photoshop software was 2.00×10⁷ pixels. The results were consistent with Figure 2. VG, Van Gieson.

Figure 5 Smooth muscle cell pixel values in prostate cancer tissue after neoadjuvant endocrine therapy.

Vascular changes

HE-stained pathological sections were analyzed to determine if changes in vascular characteristics occurred. According to the 30 images of the HE-stained pathological sections under 100-fold field-of-view, there were 446.00 (369.00–489.75) micro-veins, 111.00 (90.50–138.75) small veins, 20.00 (13.50–22.00) micro-arteries, 6.50 (5.00–14.00) small arteries, 554.50 (468.25–622.00) veins (the sum of micro-veins and small veins), 28.00 (18.50–34.75) arteries (the total number of micro-arteries and small arteries), and 570.00 (484.50–645.00) total blood vessels (the sum of all veins and arteries) in the control group. In the test group, there were 275.00 (262.00–303.75) micro-veins, 71.00 (58.75–79.00) small veins, 36.50 (21.75–43.75) micro-arteries, 11.00 (7.00–15.75) small arteries, 353.00 (324.50–381.25) veins in total, 44.50 (40.0–52.50) arteries in total, and 399.50 (375.75–426.75) blood vessels in total. Based on the comparison of the two groups, the number of micro-veins (P<0.001), small veins (P<0.001), veins (P<0.001) and sum of blood vessels (P<0.001) in the test group were significantly lower than those in the control group. The number of veins decreased [201.00 (143.75–240.75)] significantly more than the number of arteries increased [16.50 (21.50–17.75)]. There was a significant increase in micro-arteries in the test group (P<0.001) and in the total number of arteries in the test group (P=0.001). The differences of the small arteries (P=0.301) were not statistically significant (Figures 6-8).

Figure 6 Arterial distribution within the tissue after neoadjuvant endocrine therapy for prostate cancer (HE-stained pathological sections). Control group: A, ×40; B, ×100; C, ×200; test group: D, ×40; E, ×100; F, ×200. The yellow box represented the magnified observation area. The vascular arteries in the test group were increased when compared with the control group. HE, hematoxylin-eosin.

Figure 7 Venous distribution in the tissues after neoadjuvant endocrine therapy for prostate cancer (HE-stained pathological sections). Control group: A, ×40; B, ×100; C, ×200; test group: D, ×40; E, ×100; F, ×200. The yellow box represented the magnified observation area. The number of venous vessels in the test group decreased significantly when compared with the control group. HE, hematoxylin-eosin.

Figure 8 Changes in blood vessels of prostate cancer after neoadjuvant endocrine therapy.

Discussion

It has been reported that different structures, densities, blood supply, and functional statuses of tissues would affect ultrasound transmission and energy deposition during HIFU treatment (12). From the perspective of acoustic properties, changes in the tissue structure are mainly reflected by the speed and attenuation of sound propagation in tissues, and these two factors are closely related to the structure and composition of the local tissue. Thus, the change in the tissue structure could result in increasing the ultrasonic energy deposition (12,13). Therefore, we observed the pathological changes in tissue components and structures, which may affect the AET of PCa after NET.

The reflection of the ultrasound beam by highly dense materials such as calcification will decrease the focal intensity and focal volume, resulting in a decrease in ultrasound energy concentration (14). Suomi et al. (15) found that prostate tissue and the surrounding calcifications have very different acoustic impedances (1.63 vs. 3.20 MRayl) and attenuation coefficients (0.78 vs. 2.64 dB/MHz1.1/cm). As a result, therapeutic ultrasound treatment range and heating efficiency may be limited as a result of ultrasound energy loss, reflection, and attenuation. In this study, a majority of calcifications were found in normal tissues near PCa. The quantitative analysis demonstrated that after NET, the number of calcifications and the area of calcifications increased. Calibrations will distort the ultrasonic field due to their irregular shapes and different locations. Additionally, calcium causes strong reflections of ultrasound and affects the focus of ultrasound energy. It is possible for some of the heat energy around the calcification to dissipate into the tissue surrounding the calcification, thus reducing its efficacy. Furthermore, calcification has a higher attenuation coefficient than surrounding tissue, so ultrasonic energy will be attenuated, which may hinder the deposition of the focused ultrasonic energy to the targeted tumor (15). However, none of the calcifications found on MRI was seen before endocrine therapy or before RP, the number of increased calcifications found in our study was very small and manifested only at the microscopic level of the pathology. According to our results, the increase of the total number and area of calcification after NET might result in a very small reduction in the ultrasonic energy deposition.

Previous studies have also reported the effects of smooth muscle hyperplasia on HIFU ablation. In a study of 14 patients with uterine fibroids, Dillon et al. (16) analyzed 22 leiomyoma specimens and found that fibroid tissue had a higher acoustic attenuation than myometrium. The pathomorphology of uterine leiomyomas revealed that they were hyperplastic smooth muscle tissue and increased density of smooth muscle cells, while normal myometrium was normal smooth muscle tissue. Another study conducted by Keshavarzi et al. (17) compared the sound attenuation of normal uterine muscle walls and uterine fibroids and found that fibroids were more attenuative than normal uterine muscle walls. Based on these two studies, it appeared that hyperplastic smooth muscle tissue had a higher acoustic attenuation rate compared to non-hyperplastic smooth muscle tissue. There are three types of attenuation of sound in tissue: diffusion attenuation, absorption attenuation, and scattering attenuation. With greater ultrasonic attenuation, there might be greater acoustic absorption in the corresponding target tissue and more acoustic energy could be converted into heat energy when the focused ultrasound passes through, allowing the target tissue to be ablated quickly (18). Despite the absolute number of proliferations of smooth muscle cells after endocrine treatment for PCa did not change significantly, the increased smooth muscle cells density leads to the proliferation of smooth muscle cells. Therefore, sound attenuation may increase after AET compared to normal prostate tissue.

It is also important to consider the blood perfusion of the local tissue when considering HIFU therapy. Coagulation necrosis in the tissue is formed when enough heat accumulates at the focal point in the target area. The blood flow will take away part of the heat, resulting in a cooling effect and a lower local tissue temperature, hindering the heat deposition (19). According to Keserci et al. (20), the number of blood vessels and the amount of blood perfusion may be the main factor influencing the temperature rise of HIFU treatment in the focus. Studies on uterine fibroids have found that fibroid tissue proliferated and blood flow decreased when compared to normal myometrial smooth muscle cells, which made it relatively easy to ablate fibroids while keeping the safety of the surrounding normal myometrium. Our findings indicated significant differences in PCa tissues after NET. Specifically, there was a slight increase in the number of different types of arteries. Micro-arteries and small arteries were observed to contain a substantial amount of smooth muscle tissue, which could potentially affect the blood flow through the tissues and suggested that the tissue blood perfusion was slightly increased. Conversely, there was a significant decrease in the number of veins of all sizes after NET. Veins are considered volume vessels due to their thin walls and high expandability. With fewer veins present in PCa after NET, the blood vessel volume decreased significantly, which suggested that the blood reflux within the tissue was significantly reduced. Previous research has demonstrated that the change in blood flow was more pronounced by a decrease in veins than by an increase in arteries. Thus, in our study, it could be demonstrated that after NET, the overall change of blood supply in the whole organs of the prostate was significantly reduced. As a result of these changes, the reduction of blood in the AET supply would result in more heat deposition in the PCa after AET.

Our study has a relatively small sample size, which cannot fully explain our research findings. Therefore, we must enlarge the sample size to consolidate the existing discoveries or obtain new findings. Additionally, we can continue researching the acoustic characteristic changes in PCa tissues after NET. By analyzing changes in tissue velocity, acoustic impedance, acoustic attenuation, and other factors, we can further validate our research findings.

Conclusions

According to the changes of AET in PCa after NET with very small increasing number and area of calcifications, multiplying smooth muscle cells and significantly decreasing numbers of venous vessels and overall blood vessels. The pathological changes may have an impact on the local AET.

Acknowledgments

Funding: This work was supported by the Foundation of State Key Laboratory of Ultrasound in Medicine and Engineering (grant No. 2021KFKT019); and Key Project of Zigong Science and Technology (No. 2022ZCYGY06).

Footnote

Reporting Checklist: The authors have completed the MDAR reporting checklist. Available at https://tcr.amegroups.com/article/view/10.21037/tcr-23-1224/rc

Data Sharing Statement: Available at https://tcr.amegroups.com/article/view/10.21037/tcr-23-1224/dss

Peer Review File: Available at https://tcr.amegroups.com/article/view/10.21037/tcr-23-1224/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tcr.amegroups.com/article/view/10.21037/tcr-23-1224/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the ethics committee of Zigong Fourth People’s Hospital (No. 2022-123), and informed consent was obtained from all individual participants.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Mattiuzzi C, Lippi G. Current Cancer Epidemiology. J Epidemiol Glob Health 2019;9:217-22. [Crossref] [PubMed]
2. Sung H, Ferlay J, Siegel RL, et al. Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries. CA Cancer J Clin 2021;71:209-49. [Crossref] [PubMed]
3. Mathieu R, Doizi S, Bensalah K, et al. Complications in urological surgery: Prostate surgery. Prog Urol 2022;32:953-65. [Crossref] [PubMed]
4. Henderson RH, Bryant C, Nichols RC Jr, et al. Local salvage of radiorecurrent prostate cancer. Prostate 2023;83:1001-10. [Crossref] [PubMed]
5. Fujihara A, Ukimura O. Focal therapy of localized prostate cancer. Int J Urol 2022;29:1254-63. [Crossref] [PubMed]
6. Westhoff N, Ernst R, Kowalewski KF, et al. Medium-term Oncological Efficacy and Patient-reported Outcomes After Focal High-intensity Focused Ultrasound: The FOXPRO Trial. Eur Urol Focus 2023;9:283-90. [Crossref] [PubMed]
7. Gómez Rivas J, Fernandez L, Abad-Lopez P, et al. Androgen deprivation therapy in localized prostate cancer. Current status and future trends. Actas Urol Esp 2023;47:398-407. (Engl Ed). [PubMed]
8. Hu JC, Hung SC, Ou YC. Assessments of Neoadjuvant Hormone Therapy Followed by Robotic-Assisted Radical Prostatectomy for Intermediate- and High-Risk Prostate Cancer. Anticancer Res 2017;37:3143-50. [PubMed]
9. Ma BL, Yao L, Fan Y, et al. Short-term benefit of neoadjuvant hormone therapy in patients with localized high-risk or limited progressive prostate cancer. Cancer Manag Res 2019;11:4143-51. [Crossref] [PubMed]
10. Chu KF, Dupuy DE. Thermal ablation of tumours: biological mechanisms and advances in therapy. Nat Rev Cancer 2014;14:199-208. [Crossref] [PubMed]
11. Elhelf IAS, Albahar H, Shah U, et al. High intensity focused ultrasound: The fundamentals, clinical applications and research trends. Diagn Interv Imaging 2018;99:349-59. [Crossref] [PubMed]
12. Wang Zhibiao, Bai Jin, Li Faqi, et al. A study of acoustic environment in tissue of high intensity focused ultrasound. 3rd International Symposium on Therapeutic Ultrasound; 22-25 June 2003; Lyon, France. International Society for Therapeutic Ultrasound (ISTU); 2003:68.
13. Connor CW, Hynynen K. Bio-acoustic thermal lensing and nonlinear propagation in focused ultrasound surgery using large focal spots: a parametric study. Phys Med Biol 2002;47:1911-28. [Crossref] [PubMed]
14. Collins Fekete CA, Plamondon M, Martin AG, et al. Calcifications in low-dose rate prostate seed brachytherapy treatment: post-planning dosimetry and predictive factors. Radiother Oncol 2015;114:339-44. [Crossref] [PubMed]
15. Suomi V, Treeby B, Jaros J, et al. Transurethral ultrasound therapy of the prostate in the presence of calcifications: A simulation study. Med Phys 2018;45:4793-805. [Crossref] [PubMed]
16. Dillon C, Rezvani M, McLean H, et al. A tissue preparation to characterize uterine fibroid tissue properties for thermal therapies. Med Phys 2019;46:3344-55. [Crossref] [PubMed]
17. Keshavarzi A, Vaezy S, Kaczkowski PJ, et al. Attenuation coefficient and sound speed in human myometrium and uterine fibroid tumors. J Ultrasound Med 2001;20:473-80. [Crossref] [PubMed]
18. Yang R, Sanghvi NT, Rescorla FJ, et al. Liver cancer ablation with extracorporeal high-intensity focused ultrasound. Eur Urol 1993;23:17-22. [Crossref] [PubMed]
19. Goldberg SN, Gazelle GS, Mueller PR. Thermal ablation therapy for focal malignancy: a unified approach to underlying principles, techniques, and diagnostic imaging guidance. AJR Am J Roentgenol 2000;174:323-31. [Crossref] [PubMed]
20. Keserci B, Duc NM. The role of T1 perfusion-based classification in predicting the outcome of magnetic resonance-guided high-intensity focused ultrasound treatment of adenomyosis. Int J Hyperthermia 2018;34:306-14. [Crossref] [PubMed]