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2.
J Med Radiat Sci ; 71(1): 150-155, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-37621131

RESUMO

Accurately defining gross tumour volume (GTV) and organs at risk (OAR) is key to successful radiation therapy (RT) treatment outcomes for patients with gynaecological cancers. With improved access to magnetic resonance imaging (MRI) for RT simulation and planning, the optimisation and tailoring of proven diagnostic MRI techniques towards RT specific planning goals is fast evolving. Modifying MRI techniques for radiation oncology (RO) with the priority of anatomy visualisation and spatial location over diagnosis and disease characterisation relies heavily on successful collaboration between radiology and radiation oncology staff. This 'How I Do It' paper describes a qualitative analysis of the adaptation of a diagnostic MRI vaginal opacification technique into an RT specific MRI simulation procedure using aqueous ultrasound gel for improving natural anatomical visualisation of the vaginal canal. This technique is explained and could be introduced in other RO departments for dedicated RT planning scans in MR-Sim sessions with minimal difficulty. We found 10-15 cc of aqueous gel delivered vaginally produced optimal MRI planning images for most patients. With this small amount of gel and careful application technique, the full extent of the vaginal vault and cervix can be well visualised on T2 Weighted (T2W) imaging, while tending not to unfold the natural fornices of the collapsed vagina, representing a significant improvement in image quality from the outdated tampon procedure.


Assuntos
Planejamento da Radioterapia Assistida por Computador , Vagina , Feminino , Humanos , Vagina/diagnóstico por imagem , Planejamento da Radioterapia Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Pelve , Tomografia Computadorizada por Raios X/métodos
3.
Phys Imaging Radiat Oncol ; 27: 100472, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37720461

RESUMO

Background and purpose: Magnetic Resonance Imaging (MRI)-only planning workflows offer many advantages but raises challenges regarding image guidance. The study aimed to assess the viability of MRI to Cone Beam Computed Tomography (CBCT) based image guidance for MRI-only planning treatment workflows. Materials and methods: An MRI matching training package was developed. Ten radiation therapists, with a range of clinical image guidance experience and experience with MRI, completed the training package prior to matching assessment. The matching assessment was performed on four match regions: prostate gold seed, prostate soft tissue, rectum/anal canal and gynaecological. Each match region consisted of five patients, with three CBCTs per patient, resulting in fifteen CBCTs for each match region. The ten radiation therapists performed the CBCT image matching to CT and to MRI for all regions and recorded the match values. Results: The median inter-observer variation for MRI-CBCT matching and CT-CBCT matching for all regions were within 2 mm and 1 degree. There was no statistically significant association in the inter-observer variation in mean match values and radiation therapist image guidance experience levels. There was no statistically significant association in inter-observer variation in mean match values for MRI experience levels for prostate soft tissue and gynaecological match regions, while there was a statistically significant difference for prostate gold seed and rectum match regions. Conclusion: The results of this study support the concept that with focussed training, an MRI to CBCT image guidance approach can be successfully implemented in a clinical planning workflow.

4.
J Med Radiat Sci ; 70(4): 509-517, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37421243

RESUMO

INTRODUCTION: Magnetic resonance imaging (MRI) is being increasingly used to improve radiation therapy planning by allowing visualisation of organs at risk that cannot be well-defined on computed tomography (CT). Diagnostic sequences are increasingly being adapted for radiation therapy planning, such as the use of heavily T2-weighted 3D SPACE (Sampling Perfection with Application optimised Contrasts using different flip angle Evolution) sequence for cranial nerve identification in head and neck tumour treatment planning. METHODS: A 3D isotropic T2 SPACE sequence used for cranial nerve identification was adapted for radiation therapy purposes. Distortion was minimised using a spin-echo-based sequence, 3D distortion correction, isocentre scanning and an increased readout bandwidth. Radiation therapy positioning was accounted for by utilising two small flex, 4-channel coils. The protocol was validated for cranial nerve identification in clinical applications and distortion minimisation using an MRI QA phantom. RESULTS: Normal anatomy of the cranial nerves CI-CIX, were presented, along with a selection of clinical applications and abnormal anatomy. The usefulness of cranial nerve identification is discussed for several case studies, particularly in proximity to tumours extending into the base of skull region. In-house testing validated that higher bandwidths of 600 Hz resulted in minimal displacement well below 1 mm. CONCLUSION: The use of MRI for radiation therapy planning allows for greater individualisation and prediction of patient outcomes. Dose reduction to cranial nerves can decrease late side effects such as cranial neuropathy. In addition to current applications, future directions include further applications of this technology for radiation therapy treatments.


Assuntos
Nervos Cranianos , Imageamento por Ressonância Magnética , Humanos , Nervos Cranianos/diagnóstico por imagem , Nervos Cranianos/anatomia & histologia , Imageamento por Ressonância Magnética/métodos , Tomografia Computadorizada por Raios X , Planejamento da Radioterapia Assistida por Computador/métodos , Imagens de Fantasmas
5.
Radiat Oncol ; 17(1): 55, 2022 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-35303919

RESUMO

PURPOSE: Previous work on Magnetic Resonance Imaging (MRI) only planning has been applied to limited treatment regions with a focus on male anatomy. This research aimed to validate the use of a hybrid multi-atlas synthetic computed tomography (sCT) generation technique from a MRI, using a female and male atlas, for MRI only radiation therapy treatment planning of rectum, anal canal, cervix and endometrial malignancies. PATIENTS AND METHODS: Forty patients receiving radiation treatment for a range of pelvic malignancies, were separated into male (n = 20) and female (n = 20) cohorts for the creation of gender specific atlases. A multi-atlas local weighted voting method was used to generate a sCT from a T1-weighted VIBE DIXON MRI sequence. The original treatment plans were copied from the CT scan to the corresponding sCT for dosimetric validation. RESULTS: The median percentage dose difference between the treatment plan on the CT and sCT at the ICRU reference point for the male cohort was - 0.4% (IQR of 0 to - 0.6), and - 0.3% (IQR of 0 to - 0.6) for the female cohort. The mean gamma agreement for both cohorts was > 99% for criteria of 3%/2 mm and 2%/2 mm. With dose criteria of 1%/1 mm, the pass rate was higher for the male cohort at 96.3% than the female cohort at 93.4%. MRI to sCT anatomical agreement for bone and body delineated contours was assessed, with a resulting Dice score of 0.91 ± 0.2 (mean ± 1 SD) and 0.97 ± 0.0 for the male cohort respectively; and 0.96 ± 0.0 and 0.98 ± 0.0 for the female cohort respectively. The mean absolute error in Hounsfield units (HUs) within the entire body for the male and female cohorts was 59.1 HU ± 7.2 HU and 53.3 HU ± 8.9 HU respectively. CONCLUSIONS: A multi-atlas based method for sCT generation can be applied to a standard T1-weighted MRI sequence for male and female pelvic patients. The implications of this study support MRI only planning being applied more broadly for both male and female pelvic sites. Trial registration This trial was registered in the Australian New Zealand Clinical Trials Registry (ANZCTR) ( www.anzctr.org.au ) on 04/10/2017. Trial identifier ACTRN12617001406392.


Assuntos
Imageamento por Ressonância Magnética , Planejamento da Radioterapia Assistida por Computador , Doenças Retais/radioterapia , Tomografia Computadorizada por Raios X , Neoplasias Uterinas/radioterapia , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Dosagem Radioterapêutica
6.
Front Oncol ; 12: 822687, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35211413

RESUMO

PURPOSE: There are several means of synthetic computed tomography (sCT) generation for magnetic resonance imaging (MRI)-only planning; however, much of the research omits large pelvic treatment regions and female anatomical specific methods. This research aimed to apply four of the most popular methods of sCT creation to facilitate MRI-only radiotherapy treatment planning for male and female anorectal and gynecological neoplasms. sCT methods were validated against conventional computed tomography (CT), with regard to Hounsfield unit (HU) estimation and plan dosimetry. METHODS AND MATERIALS: Paired MRI and CT scans of 40 patients were used for sCT generation and validation. Bulk density assignment, tissue class density assignment, hybrid atlas, and deep learning sCT generation methods were applied to all 40 patients. Dosimetric accuracy was assessed by dose difference at reference point, dose volume histogram (DVH) parameters, and 3D gamma dose comparison. HU estimation was assessed by mean error and mean absolute error in HU value between each sCT and CT. RESULTS: The median percentage dose difference between the CT and sCT was <1.0% for all sCT methods. The deep learning method resulted in the lowest median percentage dose difference to CT at -0.03% (IQR 0.13, -0.31) and bulk density assignment resulted in the greatest difference at -0.73% (IQR -0.10, -1.01). The mean 3D gamma dose agreement at 3%/2 mm among all sCT methods was 99.8%. The highest agreement at 1%/1 mm was 97.3% for the deep learning method and the lowest was 93.6% for the bulk density method. Deep learning and hybrid atlas techniques gave the lowest difference to CT in mean error and mean absolute error in HU estimation. CONCLUSIONS: All methods of sCT generation used in this study resulted in similarly high dosimetric agreement for MRI-only planning of male and female cancer pelvic regions. The choice of the sCT generation technique can be guided by department resources available and image guidance considerations, with minimal impact on dosimetric accuracy.

7.
Phys Imaging Radiat Oncol ; 20: 34-39, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34901474

RESUMO

BACKGROUND AND PURPOSE: Magnetic resonance imaging (MRI)-only treatment planning is gaining in popularity in radiation oncology, with various methods available to generate a synthetic computed tomography (sCT) for this purpose. The aim of this study was to validate a sCT generation software for MRI-only radiotherapy planning of male and female pelvic cancers. The secondary aim of this study was to improve dose agreement by applying a derived relative electron and mass density (RED) curve to the sCT. METHOD AND MATERIALS: Computed tomography (CT) and MRI scans of forty patients with pelvic neoplasms were used in the study. Treatment plans were copied from the CT scan to the sCT scan for dose comparison. Dose difference at reference point, 3D gamma comparison and dose volume histogram analysis was used to validate the dose impact of the sCT. The RED values were optimised to improve dose agreement by using a linear plot. RESULTS: The average percentage dose difference at isocentre was 1.2% and the mean 3D gamma comparison with a criteria of 1%/1 mm was 84.0% ± 9.7%. The results indicate an inherent systematic difference in the dosimetry of the sCT plans, deriving from the tissue densities. With the adapted REDmod table, the average percentage dose difference was reduced to -0.1% and the mean 3D gamma analysis improved to 92.9% ± 5.7% at 1%/1 mm. CONCLUSIONS: CT generation software is a viable solution for MRI-only radiotherapy planning. The option makes it relatively easy for departments to implement a MRI-only planning workflow for cancers of male and female pelvic anatomy.

8.
J Med Radiat Sci ; 67(4): 257-259, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33104276

RESUMO

Deformable image registration is an increasingly important method to account for soft tissue deformation between image acquisitions. This editorial discusses the clinical need and current status of deformable image registration.


Assuntos
Processamento de Imagem Assistida por Computador , Planejamento da Radioterapia Assistida por Computador , Algoritmos , Humanos , Imagens de Fantasmas
9.
Biochem Biophys Res Commun ; 310(2): 391-7, 2003 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-14521923

RESUMO

Transforming growth factor beta (TGFbeta) can signal through a variety of Smad-independent pathways, including the p38 MAPK pathway. Recent work has shown that inhibitors of p38 MAPK, such as SB203580 and SB202190, can inhibit signaling induced by TGFbeta. Here we show that another p38 MAPK inhibitor, PD169316, abrogates signaling initiated by both TGFbeta and Activin A, but not bone morphogenetic protein (BMP) 4. Inhibition of TGFbeta signaling is dose dependent and results in reduced Smad2 and Smad3 phosphorylation, nuclear translocation, and up-regulation of the TGFbeta target gene Smad7. Reduced TGFbeta signaling is not due to abrogation of p38 MAPK activity, since blocking p38 MAPK activity with a dominant negative form of p38 MAPK has no effect on TGFbeta/Smad signaling. Our results show that use of PD169316 at 5 MICROM or higher can block TGFbeta signaling activity and thus caution must be used when attributing cellular activities exclusively to p38 MAPK signaling when these inhibitors are used experimentally.


Assuntos
Proteínas de Ligação a DNA/antagonistas & inibidores , Inibidores Enzimáticos/farmacologia , Imidazóis/farmacologia , Proteínas Quinases Ativadas por Mitógeno/antagonistas & inibidores , Transdução de Sinais/efeitos dos fármacos , Transativadores/antagonistas & inibidores , Fator de Crescimento Transformador beta/antagonistas & inibidores , Ativinas/antagonistas & inibidores , Linhagem Celular Tumoral , Proteínas de Ligação a DNA/metabolismo , Relação Dose-Resposta a Droga , Feminino , Humanos , Subunidades beta de Inibinas/antagonistas & inibidores , Proteínas Quinases Ativadas por Mitógeno/genética , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Mutação , Neoplasias Ovarianas , Proteínas Smad , Transativadores/metabolismo , Fator de Crescimento Transformador beta1 , Proteínas Quinases p38 Ativadas por Mitógeno
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