Dataset Information

Dosimetric Evaluation of a Flexible Dual Balloon-Constructed Applicator in Treating Anorectal Cancer.

ABSTRACT:

Background and purpose

To assess the dosimetric flexibility of a dual balloon brachytherapy applicator developed for the treatment of anorectal lesions.

Materials and methods

Different amounts of water were infused into the inner and outer balloon separately to study the asymmetrical distribution of the catheter, the radial distance of the active source channel to the inner surface of the global target volume , the space between the active source channels, and their dosimetric impact to target tissues and uninvolved rectum.

Results

Increasing inner balloon volume directly increased both the space between the active source channels and the radial distance of the active source channel to the inner surface of the global target volume. The space between the active source channels and the percentage of global target volume received 150% or more of the prescribed dose to target had a strong inverse correlation (-0.881/P = .007, -0.976/P = .001, respectively) with the radial distance of the active source channel to the inner surface of the global target volume. Conformity index, dose to 2 cm³ of rectum, and total reference air kerma were strongly correlated with the radial distance of the active source channel to the inner surface of the global target volume, with values of 0.952 (P = .001), 0.833 (P = .015), and 0.922 (P = .002), respectively. Percentage of global target volume received 150% or more of the prescribed dose was significantly correlated with the space between the active source channels (0.81/P = .022), and conformity index was strongly inversely correlated with the space between the active source channels (-0.833/P = .015).

Conclusion

The dual balloon-constructed Anorectal Applicator offers a flexible way to adjust the distances of the active source positions to the target in relation to uninvolved rectal wall. This flexibility simplifies planning which results in a highly conformal dose distribution to the target lesion while minimizing dose to normal rectal tissue.

SUBMITTER: Kuo HC

PROVIDER: S-EPMC5762043 | biostudies-literature | 2017 Dec

REPOSITORIES: biostudies-literature

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Publications

Dosimetric Evaluation of a Flexible Dual Balloon-Constructed Applicator in Treating Anorectal Cancer.

Kuo Hsiang-Chi HC Mehta Keyur J KJ Yaparpalvi Ravindra R Lee Alan A Mynampati Dinesh D Bodner William W Garg Madhur M Huang David D Tomé Wolfgang A WA Kalnicki Shalom S

Technology in cancer research & treatment 20170508 6

<h4>Background and purpose</h4>To assess the dosimetric flexibility of a dual balloon brachytherapy applicator developed for the treatment of anorectal lesions.<h4>Materials and methods</h4>Different amounts of water were infused into the inner and outer balloon separately to study the asymmetrical distribution of the catheter, the radial distance of the active source channel to the inner surface of the global target volume , the space between the active source channels, and their dosimetric imp ...[more]

PMID: 28481175

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Project description:PurposeTo quantify daily residual deviations from the planned geometry after image-guided prostate radiotherapy with endorectal balloon and to evaluate their effect on the delivered dose distribution.MethodsDaily kV-CBCT imaging was used for online setup-correction in six degrees of freedom (6-dof) for 24 patients receiving definitive (12 RTdef patients) or postoperative (12 RTpostop patients) radiotherapy with endorectal balloon (overall 739 CBCTs). Residual deviations were evaluated using several spatial and dosimetric variables, including: (a) posterior Hausdorff distance HDpost (=maximum distance between planned and daily CTV contour), (b) point Pworst with largest HDpost over all fractions, (c) equivalent uniform dose using a cell survival model (EUDSF ) and the generalized EUD concept (gEUDa with parameter a = -7 and a = -20). EUD values were determined for planned ( EUDSFplan ), daily ( EUDSFind ), and delivered dose distributions ( EUDSFaccum ) for plans with 6 mm (=clinical plans) and 2 mm CTV-to-PTV margin. Time series analyses of interfractional spatial and dosimetric deviations were conducted.ResultsLarge HDpost values ≥ 12.5 mm (≥15 mm) were observed in 20/739 (5/739) fractions distributed across 7 (3) patients. Points Pworst were predominantly located at the posterior CTV boundary in the seminal vesicle region (16/24 patients, 6/7 patients with HDpost ≥ 12.5 mm). Time series analyses revealed a stationary white noise characteristic of HDpost and relative dose at Pworst . The EUDSF difference between planned and accumulated dose distributions was < 5.4% for all 6-mm plans. Evaluating 2-mm plans, EUDSF deteriorated by < 10% (<5%) in 75% (58.5%) of the patients. EUDSFaccum was well described by the median value of the EUDSFind distribution. PTV margin calculation at Pworst yielded 8.8 mm.ConclusionsAccumulated dose distributions in prostate radiotherapy with endorectal balloon are forgiving of considerable residual distortions after 6-dof patient setup if they are observed in a minority of fractions and the median value of EUDSFind determined per fraction stays within 95% of prescribed dose. Common PTV margin calculations are overly conservative because after online correction of translational and rotational errors only residual deformations need to be included. These results provide guidelines regarding online navigation, margin optimization, and treatment adaptation strategies.

Project description:The patients with anorectal malformations (ARM) have been identified with specific and non-specific pathological changes. The present study was conducted with the aim to study histomorphological changes and various immunohistochemical (IHC) markers (calretinin, S-100, CD117) in intestinal wall specimens to assess neuronal dysfunction in ARM patients.Thirty children having ARM were included in our study. In all the cases, a representative biopsy was received. The tissue sections were processed and wax blocks were prepared. Various histopathological changes were examined on routine H&E. Representative sections were further subjected to IHC staining for ganglion cells (calretinin), interstitial cells of Cajal (CD117) and nerve bundles (S-100 protein). Descriptive variables were analyzed to assess neuronal dysfunction in cases of ARM. Chi-square was used to compare the categorical values. P-value <0.05 was accepted as statistically significant.Biopsies were studied for histological changes using H&E stain. The most frequently observed histological finding in mucosa was inflammation and congestion in 87% and 67% of cases respectively. Disrupted muscularis mucosa was observed in 60%, eroded mucosa in 57%, and hemorrhage in 40% of cases. Submucosal inflammation and congestion were most common finding observed in submucosa in 87% and 80% cases respectively. CD117 was used to demonstrate altered density and distribution of interstitial cells of Cajal (ICC) in cases of ARM. Majority of them belong to grade 2+ category (n=17, 57%) followed by grade 1+ (n=8, 17%) for ICC cells. Altered density and distribution of ICC was observed in ARM which was statistically significant (p=0.02).The malformed segments in ARM show various specific and non-specific histomorphological changes. Examination of H&E sections along with IHC stains evaluation can minimize need for repeated biopsies and unnecessary radical treatment. CD117 immunohistochemistry is reliable adjunctive test in evaluation of ICC in motility disorders of bowel. Calretinin is good marker for identification of ganglion cells. In ARM, density and distribution of ICCs is significantly altered which can explain postoperative dysmotility.

Dataset Information

Dosimetric Evaluation of a Flexible Dual Balloon-Constructed Applicator in Treating Anorectal Cancer.

Background and purpose

Materials and methods

Results

Conclusion

Publications

Dosimetric Evaluation of a Flexible Dual Balloon-Constructed Applicator in Treating Anorectal Cancer.

Similar Datasets

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