Evaluation of the voluntary deep inspiration breath-hold reproducibility in left-sided breast radiotherapy.

PURPOSE: Voluntary deep inspiration breath hold (v-DIBH) reduces cardiac dose during left-sided breast irradiation. The purpose of this study is to evaluate the reproducibility and variability of breath-hold level (BHL) using breath-hold curves and lateral kV setup images together. MATERIAL/METHOD: A retrospective analysis of 30 left breast cancer patients treated using the v-DIBH technique in our department is performed. The BHL difference is measured from breath hold curves and lateral (LAT) kilo-Voltage (kV) setup images. The planning CT image and the selected treatment fraction data are collected. If the changes in BHL relate to the displacement of various bones in the kV setup, images are assessed. Furthermore, the maximum heart distance inside the treatment field is compared from LAT MV portal images. RESULTS: The median and mean values of the BHL are nearly identical in different fractions (good reproducibility). However, the mean BHL values between planning and all measured fractions are statistically different; 16.3 vs. 20.8 mm for the planning and measured fractions (p < 0.001), which indicates that the variability of BHL is significantly different. CONCLUSION: While reproducibility testing shows good agreement for inter-fractional breath-hold level, the variability between planning and fractions is relatively poor.

Design and manufacturing of a dynamically deformable liver phantom for radiotherapy.

Phantoms representing anatomical deformations are necessary to investigate and improve dynamic treatments. In this study, we aimed to produce a deformable liver phantom by simulating respiratory motion. The dynamically DEformable Liver Phantom (DELP) is designed to create a human-specific respiratory model and to produce synchronised, repeatable motion with this model. For the deformation effect of this movement, an artificial liver was created using silicone material and mold. A stepper motor was used to compress the liver in the inferior direction according to an adjustable respiratory motion. Reference markers (fiducial) placed on the DELP helped to verify the movement and calculate the deformation. In dynamic deformation tests, the greatest amount of deformation was found in the edge region of the silicone liver. The average deformation was 3.45 ± 0.93 mm when 5 mm amplitude movement was applied and 5.98 ± 0.01 mm when 10 mm amplitude movement was applied. DELP is a deformable liver phantom with motion reproducibility. Its performance in radiotherapy application was evaluated using dosimetric equipment.

Dosimetric Performance Evaluation of MLC-based and Cone-based 3D Spatially Fractionated LATTICE Radiotherapy.

This study aims to dosimetrically compare multi-leaf collimator (MLC)-based and cone-based 3D LATTICE radiotherapy (LRT) plans. Valley-peak ratios were evaluated using seven different 3D LATTICE designs. Target volumes of 8 cm and 12 cm were defined on the RANDO phantom. Valley-peak dose patterns were obtained by creating high-dose vertices in the target volumes. By changing the vertex diameter, vertices separation, and volume ratio, seven different LATTICE designs were generated. Treatment plans were implemented using CyberKnife and Varian RapidArc. Thermoluminescent dosimeter (TLD), EBT3 films, and electronic portal-imaging device (EPID) were employed for dosimetric treatment verification, and measured doses were compared to calculated doses. By changing the vertex diameter and vertices separation, the valley-peak ratio was exhibited little difference between the two systems. By changing the vertex diameter and volume ratio, the valley-peak ratio was observed nearly the same for the two systems. The film, TLD, and EPID dosimetry showed good agreement between the calculated and measured doses. Based on the results, we concluded that although smaller valley-peak ratios were obtained with cone-based plans, the dose-volume histograms were comparable in both systems. Also, when we evaluated the treatment duration, the MLC-based plans were more appropriate to apply the treatment in a single fraction.

The effect of lower urinary tract substructure doses on side effects of cervical cancer image-guided adaptive brachytherapy.

OBJECTIVE: Image-Guided Adaptive Brachytherapy (IGABT) provides a survival advantage in locally advanced cervical cancer (LACC). Although side effects are seen less with this technique, dose parameters that cause urinary side effects are still questionable. We aim to investigate whether the radiotherapy doses of the lower urinary tract substructures (LUSS) affect the urinary system side effects (USSE) of cervical cancer external beam radiotherapy (EBRT) and the IGABT. METHODS: LUSS (bladder, trigone, bladder neck, and urethra) doses were calculated in 40 patients diagnosed with LACC and receiving primary EBRT, IGABT, and concomitant chemotherapy. D0.1cc, D2cc, and D50% values were examined by contouring the bladder, trigone, bladder neck, and urethra from the intracavitary BT planning computed tomography (CT) images taken every 4 BT fractions, retrospectively. Besides, late USSE (urgency, dysuria (recurrent), frequency, obstruction, incontinence, hematuria, fistula, cystitis) were queried and categorized according to Common Toxicity Criteria for Adverse Events version 5.0. STATISTICAL ANALYSIS USED: The Chi-square and Fisher's exact tests, Mann-Whitney U-test. RESULTS: For the whole study population, for both incontinence and dysuria, trigone (D50%), urethra (D50%, D0.1cc,), and bladder neck (D50%, D0.1cc, D2cc) volume and hot spot doses remained significant. For cystitis, urethra (D50%, D0.1cc,) and bladder neck doses (D0.1cc, D50%, D2cc) are worth investigating. CONCLUSIONS: Although USSE is less common in the intensity-modulated radiation therapy and IGABT era, it may be meaningful to take the doses of LUSS into account when planning IGABT. In addition, delineation of LUSS using only CT seems feasible. More proof is needed to determine delineation technique and dose constraints for LUSS for IGABT.