Direction-modulated brachytherapy for high-dose-rate treatment of cervical cancer. I: theoretical design.

Direction-modulated brachytherapy for high-dose-rate treatment of cervical cancer. I: theoretical design.

International journal of radiation oncology, biology, physics (2014-04-23)

Dae Yup Han, Matthew J Webster, Daniel J Scanderbeg, Catheryn Yashar, Dongju Choi, Bongyong Song, Slobodan Devic, Ananth Ravi, William Y Song

PMID24751413

ABSTRACT

To demonstrate that utilization of the direction-modulated brachytherapy (DMBT) concept can significantly improve treatment plan quality in the setting of high-dose-rate (HDR) brachytherapy for cervical cancer. The new, MRI-compatible, tandem design has 6 peripheral holes of 1.3-mm diameter, grooved along a nonmagnetic tungsten-alloy rod (ρ = 18.0 g/cm(3)), enclosed in Delrin tubing (polyoxymethylene, ρ = 1.41 g/cm(3)), with a total thickness of 6.4 mm. The Monte Carlo N-Particle code was used to calculate the anisotropic (192)Ir dose distributions. An in-house-developed inverse planning platform, geared with simulated annealing and constrained-gradient optimization algorithms, was used to replan 15 patient cases (total 75 plans) treated with a conventional tandem and ovoids (T&O) applicator. Prescription dose was 6 Gy. For replanning, we replaced the conventional tandem with that of the new DMBT tandem for optimization but left the ovoids in place and kept the dwell positions as originally planned. All DMBT plans were normalized to match the high-risk clinical target volume V100 coverage of the T&O plans. In general there were marked improvements in plan quality for the DMBT plans. On average, D2cc for the bladder, rectum, and sigmoid were reduced by 0.59 ± 0.87 Gy (8.5% ± 28.7%), 0.48 ± 0.55 Gy (21.1% ± 27.2%), and 0.10 ± 0.38 Gy (40.6% ± 214.9%) among the 75 plans, with best single-plan reductions of 3.20 Gy (40.8%), 2.38 Gy (40.07%), and 1.26 Gy (27.5%), respectively. The high-risk clinical target volume D90 was similar, with 6.55 ± 0.96 Gy and 6.59 ± 1.06 Gy for T&O and DMBT, respectively. Application of the DMBT concept to cervical cancer allowed for improved organ at risk sparing while achieving similar target coverage on a sizeable patient population, as intended, by maximally utilizing the anatomic information contained in 3-dimensional imaging. A series of mechanical and clinical validations are to be followed.

MATERIALS

Product Number

Brand

Product Description

GF35221081

Tungsten, wire reel, 5m, diameter 0.75mm, clean, 99.95%

GF27924655

Tungsten, wire, straight, 100mm, diameter 0.25mm, 99.9+%

GF05990621

Tungsten, foil, 0.1m coil, thickness 0.076mm, coil width 2mm, as rolled, 99.95%

GF31722263

Tungsten, foil, 0.2m coil, thickness 0.05mm, coil width .51mm, as rolled, 99.95%

GF07832729

Tungsten, foil, 0.2m coil, thickness 0.6mm, coil width 1mm, as rolled, 99.95%

GF37265429

Tungsten, foil, 150x150mm, thickness 0.15mm, as rolled, 99.95%

GF51630375

Tungsten, foil, 50x50mm, thickness 0.125mm, as rolled, 99.95%

GF52573079

Tungsten, foil, 100x100mm, thickness 0.2mm, as rolled, 99.95%

GF20592604

Tungsten, foil, 50x50mm, thickness 0.1mm, as rolled, 99.95%

GF06473033

Tungsten, foil, 0.2m coil, thickness 0.05mm, coil width 1.5mm, as rolled, 99.95%

GF75550866

Tungsten, foil, 0.2m coil, thickness 0.025mm, coil width 1mm, as rolled, 99.95%

GF59431451

Tungsten, foil, 150x150mm, thickness 0.1mm, as rolled, 99.95%

GF87565135

Tungsten, foil, 10mm disks, thickness 1.0mm, as rolled, 99.95%

GF13618155

Tungsten, foil, 2m coil, thickness 0.035mm, coil width 1.5mm, as rolled, 99.95%

GF67192544

Tungsten, foil, 0.2m coil, thickness 0.02mm, coil width .1mm, as rolled, 99.95%

GF42014078

Tungsten, foil, 2m coil, thickness 0.6mm, coil width 1mm, as rolled, 99.95%

GF09054053

Tungsten, foil, 1m coil, thickness 0.6mm, coil width 1mm, as rolled, 99.95%

GF74651698

Tungsten, foil, 100x100mm, thickness 0.5mm, as rolled, 99.95%

GF66018999

Tungsten, foil, 2m coil, thickness 0.04mm, coil width 0.7mm, as rolled, 99.95%

GF85971268

Tungsten, foil, 50x50mm, thickness 0.2mm, as rolled, 99.95%

GF54518733

Tungsten, foil, 25mm disks, thickness 1.0mm, as rolled, 99.95%

GF54025040

Tungsten, foil, 2m coil, thickness 0.05mm, coil width .51mm, as rolled, 99.95%

GF86574831

Tungsten, foil, 2m coil, thickness 0.016mm, coil width .36mm, as rolled, 99.95%

GF49335015

Tungsten, foil, 1m coil, thickness 0.025mm, coil width 1mm, as rolled, 99.95%

GF19334156

Tungsten, foil, 2m coil, thickness 0.05mm, coil width 1.5mm, as rolled, 99.95%

GF08123295

Tungsten, foil, 0.5m coil, thickness 0.08mm, coil width .9mm, as rolled, 99.95%

GF53840099

Tungsten, foil, 0.2m coil, thickness 0.10mm, coil width .9mm, as rolled, 99.95%

GF68135025

Tungsten, foil, 0.5m coil, thickness 0.6mm, coil width 1mm, as rolled, 99.95%

GF31462163

Tungsten, foil, 150x150mm, thickness 0.5mm, as rolled, 99.95%

GF37965943

Tungsten, foil, 50x50mm, thickness 0.3mm, as rolled, 99.95%