Treatment planning methodology for the Miami Multichannel Applicator following the American Brachytherapy Society recently published guidelines: the Lahey Clinic experience

Abstract

The objective of this study was to develop a standardized procedure from simulation to treatment delivery for the multichannel Miami applicator, in order to increase planning consistency and reduce errors. A plan is generated prior to the 1st treatment using the CT images acquired with the applicator in place, and used for all 3 fractions. To confirm the application placement before each treatment fraction, an AP image is acquired and compared with the AP baseline image taken at simulation. A preplanning table is generated using the EBRT doses and is used to compute the maximum allowable D2cc for bladder, rectum, and sigmoid, and the mean allowable dose for the upper vaginal wall per HDR brachytherapy fraction. These data are used to establish the criteria for treatment planning dose optimization. A step‐by‐step treatment planning approach was developed to ensure appropriate coverage for the tumor (D90>100% prescribed dose of 700 cGy/fraction) and the uninvolved vaginal surface (dose for the entire treatment length > 600 cGy/fraction), while keeping the organs at risk below the tolerance doses. The equivalent dose 2 Gy (EQD2) tolerances for the critical structures are based on the American Brachytherapy Society (ABS) recently published guidelines. An independent second check is performed before the 1st treatment using an in‐house Excel spreadsheet. This methodology was successfully applied for our first few cases. For these patients: the cumulative tumor dose was 74–79 EQD2 Gy10 (ABS recommended range 70–85); tumor D90 was >100% of prescribed dose (range 101%–105%); cumulative D2cc for bladder, rectum, and sigmoid were lower than the tolerances of 90, 75, and 75 EQD2 Gy3, respectively; cumulative upper vaginal wall mean dose was below the tolerance of 120 EQD2 Gy3; the second check agreement was within 5%. By using a standardized procedure the planning consistency was increased and all dosimetric criteria were met.PACS numbers: 87.55‐x, 87.56 bg

3D printer-based novel intensity-modulated vaginal brachytherapy applicator: feasibility study

“…It is becoming increasingly important to reduce the treatment-related side effects in these patients with long survival expectancy. Rectum, bladder and sigmoid are the major dose-limiting organs in the treatment of gyneco-logic malignancies [2,12,15,18], particularly in patients with locally advanced disease when there is a need for combining intracavitary BRT with EBRT due to the large tumor volume. In order to overcome the problems in gynecological BRT, MC applicators with different designs and trademarks, such as Capri, which is a trademark of Varian Medical Systems, Inc. have been introduced by the manufacturers.…”

“…In order to overcome the problems in gynecological BRT, MC applicators with different designs and trademarks, such as Capri, which is a trademark of Varian Medical Systems, Inc. have been introduced by the manufacturers. Iftimia et al [12], Demanes et al [13] and Tanderup et al [14] reported that MC applicators had dosimetric advantages in terms of target coverage and critical organ doses compared with CSC applicators. Additionally, Iftimia et al [12], Mendez et al [19] and Shin et al [20] reported that MC applicators may be used instead of interstitial BRT in small lesions up to 1 cm in depth.…”

“…Even with these MC applicators, vaginal lesions thicker or deeper than 1 cm cannot be covered effectively without an additional unwanted dose to the surrounding normal tissues such as bladder, rectum or sigmoid colon. Therefore standard MC applicators lose their advantage in these cases and interstitial BRT is frequently required [12,13,14,15], which needs expertise in the field, general anesthesia and hospitalization.…”

Clinical implementation of MR‐guided vaginal cylinder brachytherapy

“…Applicator reconstruction is an important part of this process. There have been several proposed methods for applicator reconstruction using MR images including the use of an MR compatible marker (32,33) and an applicator library (13,34) . Each of these methods have known limitations, such as the limited availability of commercial MR compatible markers, difficulties fabricating leak‐tight MR markers, and limits to the available applicators for which vendors have provided applicator models.…”

Pseudo Central-Catheter Method for Asymmetrical Vaginal Prescription with Multi-Channel Cylindrical Applicators in Image-Guided High Dose-Rate Brachytherapy

“…In most situations, the HDR source will not dwell inside the central channel because there is no catheter; the source will only dwell in the surrounding catheters, though the time at each dwelling positions are often optimized. The advantages of the multi-channel design for cylindrical applicator was recognized in the later time [2] [3], and until recent a step-by-step treatment methodology with multi-channel (Miami) applicators was reported following the guideline of American Brachytherapy Society [4]. Nevertheless, the original purpose for multi-channel applicator was for treatments of cervical cancer rather than vaginal cancers [1].…”