Applicator reconstruction in MRI 3D image-based dose planning of brachytherapy for cervical cancer

The purpose of this study is to find the uncertainties in the reconstruction of MR compatible ring‐tandem intracavitary applicators of high‐dose rate image‐based brachytherapy treatment planning using rigid registration of 3D MR and CT image fusion. Tandem and ring reconstruction in MR image based brachytherapy planning was done using rigid registration of CT and MR applicator geometries. Verifications of registration for applicator fusion were performed in six verification steps at three different sites of tandem ring applicator set. The first site consists of three errors at the level of ring plane in (1) cranio–caudal shift (Cranial Shift) of ring plane along tandem axis, (2) antero–posterior shift (AP Shift) perpendicular to tandem axis on the plane containing the tandem, and (3) lateral shift (Lat Shift) perpendicular to the plane containing the tandem at the level of ring plane. The other two sites are the verifications at the tip of tandem and neck of the ring. The verification at the tip of tandem consists of two errors in (1) antero–posterior shift (AP Shift) perpendicular to tandem axis on the plane containing the tandem, and (2) lateral shift (Lat Shift) perpendicular to the plane containing the tandem. The third site of verification at the neck of the ring is the error due to the rotation of ring about tandem axis. The impact of translational errors from −5 mm to 5 mm in the step of 1 mm along x‐, y‐, and z‐axis and three rotational errors about these axes from −19.1° to 19.1° in the step of 3.28° on dose‐volume histogram parameters (normalD2cc,normalD1cc,normalD0.1cc, and normalD5cc of bladder, rectum, and sigmoid, and D90 and D98 of HRCTV were also analyzed. Maximum registration errors along cranio–caudal direction was 2.2 mm (1 case), whereas the errors of 31 out of 34 cases of registration were found within 1.5 mm, and those of two cases were less than 2 mm but greater than 1.5 mm. Maximum rotational error of ring about tandem axis was 3.15° (1.1 mm). In other direction and different sites of the ring applicator set, the errors were within 1.5 mm. The impacts of registration errors on DVH parameters of bladder, rectum, and sigmoid were very sensitive to antero–posterior shift. Cranio‐caudal errors of registration also largely affected the rectum DVH parameters. Largest change of 17.95% per mm and 20.65% per mm in all the DVH parameters of all OARs and HRCTV were observed for ϕ and normalΨ rotational errors as compare to other translational and rotational errors. Catheter reconstruction in MR image using rigid registration of applicator geometries of CT and MR images is a feasible technique for MR image‐based intracavitary brachytherapy planning. The applicator registration using the contours of tandem and neck of the ring of CT and MR images decreased the rotational error about tandem axis. Verification of CT MR image fusion using applicator registration which consists of six steps of verification at three different sites in ring applicator set can report all the errors due to translation and rota...

Section: Introductionmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 83%

CT and MR image fusion of tandem and ring applicator using rigid registration in intracavitary brachytherapy planning

Oinam

Tomar

Patel

et al. 2014

“…Previous studies have reported on applicator reconstruction with the use of MRI‐marker catheters and associated applicator library when a plastic applicator is reconstructed on MRI only 40 , 41 . Haack et al (42) presented applicator reconstruction accuracy for a plastic tandem‐and‐ring applicator using phantom and patient‐data studies. The GYN GEC‐ESTRO working group provided recommendations for the commissioning and applicator reconstruction of 3D BT planning, but the report lacked details describing titanium applicator commissioning and reconstruction.…”

Section: Discussionmentioning

confidence: 99%

“…The GYN GEC‐ESTRO working group provided recommendations for the commissioning and applicator reconstruction of 3D BT planning, but the report lacked details describing titanium applicator commissioning and reconstruction. Titanium applicator reconstruction accuracy validation studies on MRI are still lacking 5 , 42 , 43 . Haack et al (42) presented the pioneering results on testing titanium ring applicators by using phantom and in vivo datasets.…”

Section: Discussionmentioning

confidence: 99%

“…Titanium applicator reconstruction accuracy validation studies on MRI are still lacking 5 , 42 , 43 . Haack et al (42) presented the pioneering results on testing titanium ring applicators by using phantom and in vivo datasets. They recommended using titanium susceptibility artifacts as an applicator reconstruction landmark, but the susceptibility artifacts are inherently uncertain in terms of its location and magnitude due to its very nature.…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Commissioning of a 3D image‐based treatment planning system for high‐dose‐rate brachytherapy of cervical cancer

Kim

Modrick

Pennington

et al. 2016

The objective of this work is to present commissioning procedures to clinically implement a three‐dimensional (3D), image‐based, treatment‐planning system (TPS) for high‐dose‐rate (HDR) brachytherapy (BT) for gynecological (GYN) cancer. The physical dimensions of the GYN applicators and their values in the virtual applicator library were varied by 0.4 mm of their nominal values. Reconstruction uncertainties of the titanium tandem and ovoids (T&O) were less than 0.4 mm on CT phantom studies and on average between 0.8‐1.0 mm on MRI when compared with X‐rays. In‐house software, HDRCalculator, was developed to check HDR plan parameters such as independently verifying active tandem or cylinder probe length and ovoid or cylinder size, source calibration and treatment date, and differences between average Point A dose and prescription dose. Dose‐volume histograms were validated using another independent TPS. Comprehensive procedures to commission volume optimization algorithms and process in 3D image‐based planning were presented. For the difference between line and volume optimizations, the average absolute differences as a percentage were 1.4% for total reference air KERMA (TRAK) and 1.1% for Point A dose. Volume optimization consistency tests between versions resulted in average absolute differences in 0.2% for TRAK and 0.9 s (0.2%) for total treatment time. The data revealed that the optimizer should run for at least 1 min in order to avoid more than 0.6% dwell time changes. For clinical GYN T&O cases, three different volume optimization techniques (graphical optimization, pure inverse planning, and hybrid inverse optimization) were investigated by comparing them against a conventional Point A technique. End‐to‐end testing was performed using a T&O phantom to ensure no errors or inconsistencies occurred from imaging through to planning and delivery. The proposed commissioning procedures provide a clinically safe implementation technique for 3D image‐based TPS for HDR BT for GYN cancer.PACS number(s): 87.55.D‐

Clinical implementation, logistics and workflow guide for MRI image based interstitial HDR brachytherapy for gynecological cancers

Zhang

Donnelly

Strauss

et al. 2019

Interstitial brachytherapy (IBT) is often utilized to treat women with bulky endometrial or cervical cancers not amendable to intracavitary treatments. A modern trend in IBT is the utilization of magnetic resonance imaging (MRI) with a high dose rate (HDR) afterloader for conformal 3D image‐based treatments. The challenging part of this procedure is to properly complete many sequenced and co‐related physics preparations. We presented the physics preparations and clinical workflow required for implementing MRI‐based HDR IBT (MRI‐HDR‐IBT) of gynecologic cancer patients in a high‐volume brachytherapy center. The present document is designed to focus on the clinical steps required from a physicist’s standpoint. Those steps include: (a) testing IBT equipment with MRI scanner, (b) preparation of templates and catheters, (c) preparation of MRI line markers, (d) acquisition, importation and registration of MRI images, (e) development of treatment plans and (f) treatment evaluation and documentation. The checklists of imaging acquisition, registration and plan development are also presented. Based on the TG‐100 recommendations, a workflow chart, a fault tree analysis and an error‐solution table listing the speculated errors and solutions of each step are provided. Our workflow and practice indicated the MRI‐HDR‐IBT is achievable in most radiation oncology clinics if the following equipment is available: MRI scanner, CT (computed tomography) scanner, MRI/CT compatible templates and applicators, MRI line markers, HDR afterloader and a brachytherapy treatment planning system capable of utilizing MRI images. The OR/procedure room availability and anesthesiology support are also important. The techniques and approaches adopted from the GEC‐ESTRO (Groupe Européen de Curiethérapie ‐ European Society for Therapeutic Radiology and Oncology) recommendations and other publications are proven to be feasible. The MRI‐HDR‐IBT program can be developed over time and progressively validated through clinical experience, this document is expected to serve as a reference workflow guideline for implementing and performing the procedure.