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CC BY 4.0 · Brazilian Journal of Oncology 2025; 21: s00441790565
DOI: 10.1055/s-0044-1790565
Original Article
Radiotherapy

Prostate Cancer Stereotactic Body Radiation Therapy with Image-guided Radiation Therapy (IGRT) Technique with Three-Dimensional Transperineal Ultrasound for IGRT Tracking of the Prostate

Igor Migowski 
1   Department of Radiation Oncology, Oncologia Americas, Rio de Janeiro, RJ, Brazil
2   Professional Master's Program in Health Technology Assessment, Education and Research Coordination, Instituto Nacional de Cardiologia (INC), Rio de Janeiro, RJ, Brazil
,
Arn Migowski 
2   Professional Master's Program in Health Technology Assessment, Education and Research Coordination, Instituto Nacional de Cardiologia (INC), Rio de Janeiro, RJ, Brazil
3   Division of Clinical Research and Technological Development, Instituto Nacional de Câncer (INCA), Rio de Janeiro, RJ, Brazil
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Funding The authors have no funding information to declare. Clinical Trials None.
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Abstract

Introduction Ultrahypofractionated radical radiotherapy for prostate cancer, also known as stereotactic body radiation therapy (SBRT), is an unprecedented modality of prostate radiotherapy and is still used very sparsely in Brazil. The use of fiducial implants and spacers may make it even more difficult to implement prostate SBRT on a large scale in Brazil. We describe a completely non-invasive technique for the treatment of localized prostate cancer with stereotactic body radiotherapy.

Materials and Methods This is a case series study with 9 patients and 48 SBRT fractions analyzed. In our treatment protocol, we use the Elekta Versa-HD linear accelerator (Elekta, Stokholm, Sweden), a transperineal ultrasound (TPUS) with tracking and synchronization capabilities (Clarity 4D ultrasound system, Elekta), and the Monaco Planning System (Elekta). Displacements were measured in the three axes (lateral, longitudinal, and vertical). The discrepancy between the initial ultrasound location of the prostate and the location of the cone beam has also been documented.

Results The mean displacements were 2.02 mm, 3.12 mm, and 2.93 mm for the lateral, longitudinal, and vertical directions, respectively. The data show that treatment was interrupted in 14 of the 48 treatment fractions (29.17%), 8 (57%) with displacements greater than 5 mm and 6 (43%) with displacements between 3 and 5 mm.

The initial TPUS image-guided radiation therapy (IGRT) and its mean displacements for localization with the cone-beam computed tomography (CBCT) were 1.3 mm, 1.9 mm, and 1.5 mm, for the lateral, longitudinal, and vertical directions, respectively. Using van Herk formula, a margin of 7.3 mm in the lateral directions, 9.35 mm longitudinally, and 7.74 mm vertically, would be required

Conclusion Here we describe an SBRT technique for prostate cancer that is completely non-invasive and allows for a high level of accuracy. Transperineal 3D ultrasound provides real-time position data to the prostate that can be used to gate the SBRT treatment, allowing for smaller, more personalized planning target volume (PTV) margins even without fiducial markers or spacers, which may be more applicable for low- and middle-income countries.


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Keywords

prostatic neoplasms - radiosurgery - radiotherapy - image-guided - ultrasonography

Introduction

Prostate cancer is a highly prevalent cancer worldwide, and it also has a high incidence in Brazil. Data from the Brazilian National Cancer Institute (Instituto Nacional de Câncer [INCA], in Portuguese) estimate more than 72 thousand new cases in 2024 in this country.[1]

Radiation therapy has been used to treat prostate cancer efficiently for many decades. More recently, hypofractionated regimens have been gaining popularity due to recent studies showing efficacy, low toxicity rates, and the fact that they are 50% (or more) shorter than conventional fractionated radiotherapy.[2]

A subtype of the hypofractionated regimen is ultrahypofractionation, also known as stereotactic body radiotherapy (SBRT), which is characterized by doses equal to or greater than 5 Gy per fraction, usually with a total of 5 fractions.[3]

In many cancer centers, prostate SBRT is usually done with the use of fiducial markers and spacers.[4] [5]

Commercial fiducials are not approved by the National Health Surveillance Agency.[6] Even if they were approved, the incremental costs of using these products would likely make radiotherapy almost inaccessible in Brazil, aggravating the Brazilian bottleneck in access to cancer treatment.[7]

The current study describes a completely noninvasive prostate SBRT technique using transperineal ultrasound for intrafraction prostate screening.

This technique would likely make prostate SBRT more accessible to low- and middle-income countries and decrease waiting lists in radiotherapy departments by reducing the number of fractions.


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Materials and Methods

We have developed a transperineal ultrasound (TPUS)-based workflow for SBRT. Here we describe the dislocations of our first 9 patients treated with TPUS and ultrahypofractionation. It is a case series of prospective, consecutive cases. The selection criteria were patients with localized prostate cancer following hypofractionated radiotherapy for prostate cancer (hypo-RT-PC)[8] or metastatic[9] study criteria eligible for ultrahypofractionated radiotherapy. The exclusion criteria were the same as those used in these trials. The National Comprehensive Cancer Network (NCCN) risk groups were used ([Fig. 1])[10]

Zoom Image
Fig. 1 National Comprehensive Cancer Network prostate cancer risk groups.Adapted from: NCCN Prostate Cancer Guidelines.

Most patients were treated with 5 fractions. All patients underwent computed tomography simulation (CT-Sim) before treatment with a planning TPUS ([Fig. 2]), using a dedicated computed tomography, Somatom Definition AS (Siemens AG, Munich, Germany), 20-channels, large bore. During CT-SIM, a TPUS scan was generated. The CT-SIM was then fused with TPUS images and diagnostic magnetic resonance imaging (MRI) ([Fig. 3]). The clinical target volume (CTV) was contoured as the prostate with or without the proximal third of the seminal vesicles, based on CT-MRI fusion, and the final CTV count was uploaded into the Clarity 4D ultrasound system (Elekta, Stokholm, Sweden) for image-guided radiation therapy (IGRT) ([Fig. 4]). The planning target volume (PTV) is defined as the CTV plus a margin of 3 to 4 mm posteriorly and 5 mm in all other dimensions. The urethra was circumvented as an organ at risk (OAR) identified on MRI or by a pediatric relief bladder tube used during the simulation and was to receive less than 95% of the prescribed dose, but more than 35 Gy (urethra-sparing approach).[11] That means that with a prescription of 40 Gy in 5 fractions, the urethra avoidance region should receive more than 35 Gy but less than 38 Gy. The treatment planning was done by Monaco system (ELEKTA) and patients typically received two arcs with volumetric modulated arc therapy (VMAT) technique, with a flattening filter free (FFF) 6 MV photons.

Zoom Image
Fig. 2 Transperineal ultrasound image acquired during simulation.
Zoom Image
Fig. 3 Magnetic resonance imaging scan fusion with computed tomography scan.
Zoom Image
Fig. 4 Contouring.

The Monaco planning system was used to plan all patients' treatment to receive two volumetric modulated arc therapy (VMAT) arcs, with a flattening filter free (FFF) of 6 MV photons.

For treatment, the probe of the TPUS was positioned by the therapists with the aid of a physicist. The patients were positioned according to the SBRT protocol and aligned to the skin tags using lasers in the treatment room. The prostate was first located by ultrasound and then a kilovoltage (kV)-cone beam CT (CBCT) was performed to confirm the position of the prostate as well as the volumes of the rectum and bladder (preparation). The CBCT correction was the gold standard and TPUS IGRT was used for the initial localization. Once the prostate was localized by CBCT, the TPUS tracking was initiated and lasted until the end of the treatment. This whole procedure was repeated for each fraction. The displacements were recorded and are presented in [Table 1]. During intrafraction tracking by US, the beam was gated automatically if the target moved more than 3 mm for more than 5 seconds, or manually if it moved more than 5 mm, at any of the 3 orthogonal coordinates. The localization procedure would be repeated if the displacement of more than 3 mm was persistent and consistent. Between the first and second treatment arcs, an intrafraction CBCT was performed, during the first arc while the beam was on ad was used to corroborate US data and re-check bladder and rectum volumes. (Intrafraction, Elekta).

Table 1

Maximum (max) prostate displacements during transperineal ultrasound tracking (mm)

Patient

Direction

Day 1

Day 2

Day 3

Day 4

Day 5

Day 6

A

Xmax

2.12

2.83

1.64

2.12

2.36

Ymax

2.87

2.64

10.45

3.08

1.41

Zmax

1.58

1.79

1.11

2.75

1.44

B

Xmax

1.66

1.68

1.22

1.03

1.56

1.45

Ymax

5.65

12.27

3.69

1.37

2.28

1.82

Zmax

2.59

2.52

1.38

0.83

1.12

1.25

C

Xmax

3.70

1.12

1.38

1.09

1.52

Ymax

2.57

1.59

7.57

2.17

3.05

Zmax

0.30

0.97

1.03

0.73

1.39

D

Xmax

7.38

2.42

2.23

5.49

2.16

Ymax

2.90

2.48

2.68

5.28

2.67

Zmax

3.33

0.96

2.02

2.57

2.58

E

Xmax

2.47

0.71

3.62

1.41

0.77

Ymax

2.27

3.55

1.85

6.04

1.17

Zmax

1.64

1.34

1.58

2.57

0.57

F

Xmax

0.61

0.61

0.89

0.86

0.77

Ymax

0.89

0.43

0.80

2.00

0.51

Zmax

0.38

0.53

0.72

0.83

0.97

G

Xmax

0.87

1.84

1.23

0.95

0.52

0.55

Ymax

0.98

1.74

2.28

1.06

1.04

0.94

Zmax

1.01

0.92

1.37

0.73

1.66

0.67

H

Xmax

1.09

0.69

0.74

1.22

0.95

Ymax

0.96

0.69

1.07

0.90

0.72

Zmax

0.51

0.53

0.70

0.67

0.32

I

Xmax

1.73

0.56

1.24

2.10

2.19

0.78

Ymax

2.38

2.43

2.34

2.80

6.32

2.40

Zmax

2.07

1.77

2.35

2.18

3.49

1.59

In our study, we considered a displacement of 3 mm to be significant, since our lowest margin could be 3 mm, but any displacement of more than 5 mm was considered unacceptable.

To calculate the PTV using the Van Herk formula (M = 2.5Σ + 0.7σ),[12] a delineation error of 2.5 mm was considered as systematic,[13] and the set-up error was obtained by the standard deviation of the means of the displacements obtained in the cone beams performed before the beginning of the treatment. To calculate the random error, the standard deviation of the means of the intrafraction displacements was obtained.

This study respected the ethical principles contained in the Declaration of Helsinki.

This project was approved by a research ethics committee and registered in Plataforma Brasil under CAAE number. 64273317.9.0000.5533


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Results

The mean displacements were 2.02 mm, 3.12 mm, and 2.93 mm in the lateral, longitudinal, and vertical directions, respectively.

Treatment was interrupted in 14 of the 48 treatment fractions (29.17%), 8 with displacements greater than 5 mm and 6 with displacements between 3 and 5 mm. The largest displacement observed was 12.27 mm. In other words, in 16.66% of the fractions, the target would have exceeded the PTV margin, causing some loss of coverage.

Analyzing the directions, 11 of the 17 displacements (64.7%) capable of interrupting the treatment (> 3 mm) occurred in the vertical direction, 4 in the lateral direction, and another 2 in the longitudinal direction. Not all dislocations > 3 mm resulted in interruption as long as they lasted less than 5 seconds.

We compared the location of the TPUS with the CBCT and the complete data are shown in [Table 2]. The percentage of CBCT displacement above 7 mm was only 7.6%, meaning that a 7 mm PTV for a treatment with TPUS IGRT alone would be adequate for 92.4% of all treatment fractions.

Table 2

Values for displacement discrepancy between the transperineal ultrasound and the kilovoltage cone beam (mm)

Patients

Direction

Day 1

Day 2

Day 3

Day 4

Day 5

Day 6

A

Lateral

3.10

2.50

1.80

0.10

3.50

Longitudinal

0.70

6.20

2.10

3.30

8.20

Vertical

2.00

5.20

3.80

5.10

3.70

B

Lateral

3.00

0.80

5.00

0.80

2.90

3.80

Longitudinal

1.20

3.70

1.80

0.20

1.60

0.00

Vertical

6.00

7.40

0.00

0.40

0.90

0.00

C

Lateral

NI

NI

0.60

1.10

2.1

Longitudinal

NI

NI

0.90

2.30

0.8

Vertical

NI

NI

0.40

1.60

3.3

D

Lateral

3.40

5.00

1.5

1.4

1.50

Longitudinal

1.00

11.20

1.5

3.2

0.20

Vertical

0.10

4.40

4

4

3.20

E

Lateral

0.1

0

1.90

4.90

3.80

Longitudinal

1.9

0

0.90

0.60

7.40

Vertical

0.9

0

8.90

8.60

3.30

F

Lateral

1.1

4.5

1.90

1.40

2.90

Longitudinal

3.9

7.8

1.90

3.60

0.10

Vertical

0.5

6.2

3.50

5.60

0.60

G

Lateral

2.2

0.2

0.90

3.90

0.80

3.00

Longitudinal

6.6

2

8.20

6.20

6.30

9.60

Vertical

5.4

8.5

1.10

0.00

3.10

0.70

H

Lateral

2.90

2.30

0.30

1.20

3.80

Longitudinal

2.40

4.70

2.60

4.20

2.90

Vertical

3.90

2.50

2.50

0.30

0.90

I

Lateral

0.30

1.80

2.90

1.90

1.00

1.90

Longitudinal

0.10

0.30

1.30

0.30

2.60

3.50

Vertical

8.30

4.70

2.30

7.10

0.50

3.00

Using Van Herk formula (M = 2.5Σ + 0.7σ), a margin of 7.3 mm would be required in the lateral directions, 9.35 mm in the longitudinal direction, and 7.74 mm in the vertical direction, respectively, where Σ represents the systematic uncertainty and σ the random uncertainty.


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Discussion

Stereotactic body radiation therapy is a fractionation modality that has been gaining more and more acceptance in the treatment of prostate cancer.

Several approaches can be taken to reduce the possibility of acute and late toxicity, such as spacers, urethral preservation techniques, and reduced PMTC margins. Whenever the margins of the PTV are reduced, the possibility of geographical missing increases. An alternative to mitigate this risk is to apply intrafraction monitoring, and here we describe our protocol with the TPUS Clarity 4D system, which allows intrafraction monitoring and gating.[14]

A PTV of 7 mm would likely be suitable for a TPUS IGRT without CBCT, since the discrepancy between initial localization in TPUS and correction by CBCT was below 2 mm on average. In the lateral, longitudinal, and vertical axes, the mean displacements were 2.02 mm, 3.12 mm, and 2.93 mm, respectively, but some displacements were greater, with a maximum of 11.2 mm in the longitudinal direction in only 1 patient and in only 1 day of treatment. The percentage of displacement above 7 mm was only 7.6%.

The outliers must have other reasons for a discrepant movement, other than change in volume of bladder and rectum. One of those was discomfort in set-up positioning or a full bladder eliciting muscular contraction. Particularly obese patients could press the TPUS probe between their legs, thus provoking false prostate movements in the system.

One strategy implemented later on was to make the patient comfortable before initiating prostate tracking and starting the simulation with an intermediate bladder volume.

Inserting fiducials and spacers is time-consuming and expensive.

Implementing TPUS tracking has its own challenges but once your team gains expertise, the process is fast, accurate, non-invasive, and probably cheaper than inserting fiducials and/or spacers. Overall, the TPUS probe was an easy and intuitive tool to use compared to other IGRT systems. When using TPUS as IGRT the accuracy increases with the learning curve.[15] [16] [17] [18]

The main limitation of our study is our low number of patients.


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Conclusion

In the present study, we describe our completely non-invasive technique for prostate SBRT using TPUS as tracking system without fiducials or spacers, which may be more affordable for developing countries. The average changes are small, although some individual changes are big enough to warrant a screening system if the PTV margins are small, which is typically the case in prostate SBRT planning.


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Conflict of Interests

The authors have no conflict of interests to declare.

Authors' Contribution

IM: collection and assembly of data, conception and study design, data analysis and interpretation, manuscript writing, provision of study materials or patient, final approval of the manuscript; AM: conception and study design, data analysis and interpretation, manuscript review and editing and final approval of the manuscript.


  • References

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    Search in Google Scholar
  • 2 Lehrer EJ, Kishan AU, Yu JB. et al. Ultrahypofractionated versus hypofractionated and conventionally fractionated radiation therapy for localized prostate cancer: A systematic review and meta-analysis of phase III randomized trials. Radiother Oncol 2020; 148: 235-242
    Search in Google Scholar
  • 3 Morgan SC, Hoffman K, Loblaw A. et al. ASTRO guideline. Pract Radiat Oncol 2018; 8: 354-360
    Search in Google Scholar
  • 4 Holmes OE, Gratton J, Szanto J. et al. Reducing errors in prostate tracking with an improved fiducial implantation protocol for CyberKnife based stereotactic body radiotherapy (SBRT). J Radiosurg SBRT 2018; 5 (03) 217-227
    Search in Google Scholar
  • 5 Mariados N, Sylvester J, Shah D. et al. Hydrogel Spacer Prospective Multicenter Randomized Controlled Pivotal Trial: Dosimetric and Clinical Effects of Perirectal Spacer Application in Men Undergoing Prostate Image Guided Intensity Modulated Radiation Therapy. Int J Radiat Oncol Biol Phys 2015; 92 (05) 971-977
    Search in Google Scholar
  • 6 ANVISA [homepage na internet] [acessado em 10 de abril de 2021]. Disponível em: https://www.gov.br/anvisa/pt-br/sistemas/consulta-a-registro
  • 7 Mendez LC, Moraes FY, Fernandes GDS, Weltman E. Cancer Deaths due to Lack of Universal Access to Radiotherapy in the Brazilian Public Health System. Clin Oncol (R Coll Radiol) 2018; 30 (01) e29-e36
    Search in Google Scholar
  • 8 Widmark A, Gunnlaugsson A, Beckman L. et al. Ultra-hypofractionated versus conventionally fractionated radiotherapy for prostate cancer: 5-year outcomes of the HYPO-RT-PC randomised, non-inferiority, phase 3 trial. Lancet 2020
    Search in Google Scholar
  • 9 Parker CC, James ND, Brawley CD. et al; Systemic Therapy for Advanced or Metastatic Prostate cancer: Evaluation of Drug Efficacy (STAMPEDE) investigators. Radiotherapy to the primary tumour for newly diagnosed, metastatic prostate cancer (STAMPEDE): a randomised controlled phase 3 trial. Lancet 2018; 392 (10162): 2353-2366
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  • 10 National Comprehensive Cancer Network (NCCN) [internet homepage] [Accessed in March 14, 2021]. Available in https://www.nccn.org/professionals/physician_gls/pdf/prostate.pdf
  • 11 Repka MC, Guleria S, Cyr RA. et al. Acute Urinary Morbidity Following Stereotactic Body Radiation Therapy for Prostate Cancer with Prophylactic Alpha-Adrenergic Antagonist and Urethral Dose Reduction. Front Oncol 2016; 6: 122
    Search in Google Scholar
  • 12 van Herk M. Errors and margins in radiotherapy. Semin Radiat Oncol 2004; 14 (01) 52-64
    Search in Google Scholar
  • 13 Rasch C, Steenbakkers R, van Herk M. Target definition in prostate, head, and neck. Semin Radiat Oncol 2005; 15 (03) 136-145
    Search in Google Scholar
  • 14 Smith AL, Stephans KL, Kolar MD. et al. Prostate SBRT IntrafractionMonitoring with Transperineal Ultrasound, IJROBP 2017)
  • 15 Yu AS, Najafi M, Hristov DH, Phillips T. Intrafractional tracking accuracy of a transperineal ultrasound image guidance system for prostate radiotherapy. Technol Cancer Res Treat 2017; 16 (06) 1067-1078
    Search in Google Scholar
  • 16 Han B, Najafi M, Cooper DT. et al. Evaluation of transperineal ultrasound imaging as a potential solution for target tracking during hypofractionated radiotherapy for prostate cancer. Radiat Oncol 2018; 13 (01) 151
    Search in Google Scholar
  • 17 Salter BJ, Szegedi M, Tward J. et al. 3D transperineal ultrasound image guidance methods for prostate SBRT radiotherapy treatment. ESTRO; 2015
    Search in Google Scholar
  • 18 Robinson D, Liu D, Steciw S. et al. An evaluation of the Clarity 3D ultrasound system for prostate localization. J Appl Clin Med Phys 2012; 13 (04) 3753
    Search in Google Scholar

Address for correspondence

Igor Migowski, MSc
Oncologia Americas Departamento de Oncologia de Radiação
Av. Jorge Cury, 550, Bloco C, Rio de Janeiro, RJ
Brazil   

Publication History

Received: 17 February 2024

Accepted: 28 June 2024

Article published online:
05 February 2025

© 2025. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution 4.0 International License, permitting copying and reproduction so long as the original work is given appropriate credit (https://creativecommons.org/licenses/by/4.0/)

Thieme Revinter Publicações Ltda.
Rua do Matoso 170, Rio de Janeiro, RJ, CEP 20270-135, Brazil

Bibliographical Record
Igor Migowski, Arn Migowski. Prostate Cancer Stereotactic Body Radiation Therapy with Image-guided Radiation Therapy (IGRT) Technique with Three-Dimensional Transperineal Ultrasound for IGRT Tracking of the Prostate. Brazilian Journal of Oncology 2025; 21: s00441790565.
DOI: 10.1055/s-0044-1790565

  • References

  • 1 Instituto Nacional de Câncer. Estimativa 2023: incidência de câncer no Brasil. INCA; 2022
    Search in Google Scholar
  • 2 Lehrer EJ, Kishan AU, Yu JB. et al. Ultrahypofractionated versus hypofractionated and conventionally fractionated radiation therapy for localized prostate cancer: A systematic review and meta-analysis of phase III randomized trials. Radiother Oncol 2020; 148: 235-242
    Search in Google Scholar
  • 3 Morgan SC, Hoffman K, Loblaw A. et al. ASTRO guideline. Pract Radiat Oncol 2018; 8: 354-360
    Search in Google Scholar
  • 4 Holmes OE, Gratton J, Szanto J. et al. Reducing errors in prostate tracking with an improved fiducial implantation protocol for CyberKnife based stereotactic body radiotherapy (SBRT). J Radiosurg SBRT 2018; 5 (03) 217-227
    Search in Google Scholar
  • 5 Mariados N, Sylvester J, Shah D. et al. Hydrogel Spacer Prospective Multicenter Randomized Controlled Pivotal Trial: Dosimetric and Clinical Effects of Perirectal Spacer Application in Men Undergoing Prostate Image Guided Intensity Modulated Radiation Therapy. Int J Radiat Oncol Biol Phys 2015; 92 (05) 971-977
    Search in Google Scholar
  • 6 ANVISA [homepage na internet] [acessado em 10 de abril de 2021]. Disponível em: https://www.gov.br/anvisa/pt-br/sistemas/consulta-a-registro
  • 7 Mendez LC, Moraes FY, Fernandes GDS, Weltman E. Cancer Deaths due to Lack of Universal Access to Radiotherapy in the Brazilian Public Health System. Clin Oncol (R Coll Radiol) 2018; 30 (01) e29-e36
    Search in Google Scholar
  • 8 Widmark A, Gunnlaugsson A, Beckman L. et al. Ultra-hypofractionated versus conventionally fractionated radiotherapy for prostate cancer: 5-year outcomes of the HYPO-RT-PC randomised, non-inferiority, phase 3 trial. Lancet 2020
    Search in Google Scholar
  • 9 Parker CC, James ND, Brawley CD. et al; Systemic Therapy for Advanced or Metastatic Prostate cancer: Evaluation of Drug Efficacy (STAMPEDE) investigators. Radiotherapy to the primary tumour for newly diagnosed, metastatic prostate cancer (STAMPEDE): a randomised controlled phase 3 trial. Lancet 2018; 392 (10162): 2353-2366
    Search in Google Scholar
  • 10 National Comprehensive Cancer Network (NCCN) [internet homepage] [Accessed in March 14, 2021]. Available in https://www.nccn.org/professionals/physician_gls/pdf/prostate.pdf
  • 11 Repka MC, Guleria S, Cyr RA. et al. Acute Urinary Morbidity Following Stereotactic Body Radiation Therapy for Prostate Cancer with Prophylactic Alpha-Adrenergic Antagonist and Urethral Dose Reduction. Front Oncol 2016; 6: 122
    Search in Google Scholar
  • 12 van Herk M. Errors and margins in radiotherapy. Semin Radiat Oncol 2004; 14 (01) 52-64
    Search in Google Scholar
  • 13 Rasch C, Steenbakkers R, van Herk M. Target definition in prostate, head, and neck. Semin Radiat Oncol 2005; 15 (03) 136-145
    Search in Google Scholar
  • 14 Smith AL, Stephans KL, Kolar MD. et al. Prostate SBRT IntrafractionMonitoring with Transperineal Ultrasound, IJROBP 2017)
  • 15 Yu AS, Najafi M, Hristov DH, Phillips T. Intrafractional tracking accuracy of a transperineal ultrasound image guidance system for prostate radiotherapy. Technol Cancer Res Treat 2017; 16 (06) 1067-1078
    Search in Google Scholar
  • 16 Han B, Najafi M, Cooper DT. et al. Evaluation of transperineal ultrasound imaging as a potential solution for target tracking during hypofractionated radiotherapy for prostate cancer. Radiat Oncol 2018; 13 (01) 151
    Search in Google Scholar
  • 17 Salter BJ, Szegedi M, Tward J. et al. 3D transperineal ultrasound image guidance methods for prostate SBRT radiotherapy treatment. ESTRO; 2015
    Search in Google Scholar
  • 18 Robinson D, Liu D, Steciw S. et al. An evaluation of the Clarity 3D ultrasound system for prostate localization. J Appl Clin Med Phys 2012; 13 (04) 3753
    Search in Google Scholar

  Permissions and Reprints All articles of this category
Zoom Image
Fig. 1 National Comprehensive Cancer Network prostate cancer risk groups.Adapted from: NCCN Prostate Cancer Guidelines.
Zoom Image
Fig. 2 Transperineal ultrasound image acquired during simulation.
Zoom Image
Fig. 3 Magnetic resonance imaging scan fusion with computed tomography scan.
Zoom Image
Fig. 4 Contouring.