Cervix Brachytherapy Research Articles

Evaluation of rectal dose discrepancies between planned and in vivo dosimetry using MOSkin detector and PTW 9112 semiconductor probe during 60Co HDR CT-based intracavitary cervix brachytherapy

PurposeDose to the rectum during brachytherapy treatment may differ from an approved treatment plan which can be quantified with in vivo dosimetry (IVD). This study compares the planned with in vivo doses measured with MOSkin and PTW 9112 rectal probe in patients undergoing CT based HDR cervical brachytherapy with Co-60 source. MethodsDose measurement of a standard pear-shaped plan carried out in phantom to verify the MOSkin dose measurement accuracy. With MOSkin attached to the third diode, RP3 of the PTW 9112, both detectors were inserted into patients’ rectum. The RP3 and MOSkin measured doses in 18 sessions as well as the maximum measured doses from PTW 9112, RPmax in 48 sessions were compared to the planned doses. ResultsPercentage dose differences ΔD (%) in phantom study for two MOSkin found to be 2.22 ± 0.07% and 2.5 ± 0.07%. IVD of 18 sessions resulted in ΔD(%) of −16.3% to 14.9% with MOSkin and ΔD(%) of −35.7% to −2.1% with RP3. In 48 sessions, RPmax recorded ΔD(%) of −37.1% to 11.0%. MOSkin_measured doses were higher in 44.4% (8/18) sessions, while RP3_measured were lower than planned doses in all sessions. RPmax_measured were lower in 87.5% of applications (42/47). ConclusionsThe delivered doses proven to deviate from planned doses due to unavoidable shift between imaging and treatment as measured with MOSkin and PTW 9112 detectors. The integration of MOSkin on commercial PTW 9112 surface found to be feasible for rectal dose IVD during cervical HDR ICBT.

Automated applicator digitization for high-dose-rate cervix brachytherapy using image thresholding and density-based clustering

PurposeThe purpose of the study was to develop and evaluate an automated digitization algorithm for high-dose-rate cervix brachytherapy, with the goal of reducing the duration of treatment planning, staff resources, variability, and potential for human error. MethodsAn automated digitization algorithm was developed and retrospectively evaluated using treatment planning data from 10 patients with cervix cancer who were treated with a titanium tandem and ovoids applicator set. Applicators were segmented, without human interaction, by thresholding CT images to isolate high-density voxels and assigning the voxels to applicator and nonapplicator structures using HDBSCAN, a density-based linkage clustering algorithm. The applicator contours were determined from the centroid of the clustered voxels on each image slice and written to a treatment plan file. Automated contours were evaluated against manual digitization using distance and dosimetric metrics. ResultsA close agreement between automatic and manual digitization was observed. The mean magnitude of contour disagreement for 10 patients equaled 0.3 mm. Hausdorff distances were ≤1.0 mm. The applicator tip coordinates had submillimeter agreement. The median and mean dose volume histogram parameter differences were less than or equal to 1% for high-risk clinical target volume D90, high-risk clinical target volume D95, bladder D2cc, rectum D2cc, large bowel D2cc, and small bowel D2cc. The average execution time for the automated algorithm was less than 30 s. ConclusionThe digitization of titanium tandem and ovoids applicators for high-dose-rate brachytherapy treatment planning can be automated using straightforward thresholding and clustering algorithms. The adoption of automated digitization is expected to improve the consistency of treatment plans and reduce the duration of treatment planning.

Differences Between MRI- and CT-Based Delineation of Target Volume and Organs at Risk in High-Dose-Rate Brachytherapy of Cervix

With superior soft tissue imaging characteristics, MRI is better than CT in determining the local disease extent during intracavitary brachytherapy of carcinoma cervix. The aim of the study is to evaluate the differences in dimensions and volumes of the target and organs at risk and the subsequent changes in dosimetry between MRI- and CT-based plans. MRI and CT datasets of 34 locally advanced cervical cancer patients taken up for intracavitary brachytherapy between January and September 2017 were analyzed. The target volumes and organs at risk, namely bladder, rectum and sigmoid, were contoured by the same radiation oncologist on both the MRI and CT images as per the GEC ESTRO guidelines. The dimensions of HRCTV, the dose volume parameters of the target and OAR were recorded for the CT and MRI plans. CT image significantly overestimated the width (p = 0.000) and thickness (p = 0.009) of HRCTV. The volumes of HRCTV (p = 0.000) and IRCTV (p = 0.041) were larger with CT image compared to MRI. There was no statistically significant difference between rectal (p = 0.107) and sigmoid (p = 0.365) volumes on CT and MRI. There was statistically significant difference (all p 0.05) in the dose received by rectum and sigmoid on CT and MR plans. MRI-based brachytherapy planning has shown considerable improvements in tumor control and reductions in normal tissue toxicity. However, the high cost of MRI and non-availability of MRI preclude its use in many centers. CT, on the other hand, is widely available, but it can lead to overestimation of the target, at the time of brachytherapy. Hence, it is important to identify the subset of patients who will benefit from MRI-based planning at the time of brachytherapy.

Evaluation of variation of interfraction doses to organs at risk during brachytherapy of cervical cancer

BackgroundTwo-dimensional treatment planning using radiographs or simulator films was the standard in planning brachytherapy for patients with cervical cancer. Three-dimensional (3D) treatment planning has improved treatment efficacy. This retrospective study compares conventional and 3D treatment planning of brachytherapy in patients with cervical cancer and interfraction dose variation to bladder and rectum (D2cc). MethodsThe mean doses to bladder and rectum (D2cc) were computed by computed tomography (CT)–based planning during 100 sessions of intracavitary brachytherapy for carcinoma cervix with the same source configuration as generated for conventional planning, and these estimates were compared with the doses at International Commission on Radiation Units and measurements (ICRU) rectal, bladder points and point A. Interfraction variation of doses to bladder and rectum during various sessions was also analysed. ResultThe mean ICRU bladder dose and D2cc of the bladder for all patients was 3.7 Gy and 7.4 Gy, respectively (p < 0.001). The mean ICRU rectal dose from conventional plan was 4.3Gy and with CT planning, 4.45 Gy (p = 0.04). Interfraction dose variations for D2cc of the bladder were min −5.3 Gy and max 4.8 Gy and those of the rectum were min −1.8 Gy and max 1.72Gy. ConclusionDosimetric evaluation of conventional and 3D CT-based treatment planning for the same brachytherapy sessions demonstrated underestimation of ICRU bladder dose points (p < 0.001) and the rectal ICRU point dose and D2cc (p=0.04). The doses to organs at risk did not show a statistically significant variation between the fractions. However, large variation was noted between the interfractional maximum and minimum doses to bladder and rectum.

Rectal Toxicity in Intracavitary Brachytherapy for Carcinoma Cervix with Fixed Retroverted Uterus: A Retrospective Analysis from a Prospectively Maintained Database

Intracavitary Brachytherapy in cases of cancer cervix with retroverted uterus has been both a procedural and dosimetric dilemma for a long time.This study was designed to associate applicator type , Geometry and uterine anatomy with rectal dosimetry and incidence of clinical toxicity

Impact of different dose prescription schedules on EQD2 in high-dose-rate intracavitary brachytherapy of carcinoma cervix.

PurposeTo observe the effect of different high-dose-rate (HDR) intracavitary brachytherapy dose schedules on equieffective dose in 2 Gy per fraction (EQD2).Material and methodsIt is a retrospective study involving 50 cervical cancer patients, who received external radiotherapy of 45 Gy in 25 fractions and underwent intracavitary brachytherapy (ICBT). Computed tomography (CT) simulation was done after insertion of the applicators. High-risk clinical target volume (CTVHR) and organs at risk (OARs) such as bladder, rectum, and sigmoid were contoured. Four different plans were generated for each patient, with dose prescriptions of 5.5 Gy × 5 fractions (plan A), 6.5 Gy × 4 fractions (plan B), 7 Gy × 4 fractions (plan C), and 9 Gy × 2 fractions (plan D), delivered to CTVHR. The total EQD2 for 0.1 cm3 and 2 cm3 of bladder, rectum, and sigmoid as well as dose received by 90% of the CTVHR (D90) and point A were calculated. The values were analyzed and compared with available literature.ResultsThe mean CTVHR volume was 47.12 ±13.8 cm3. All plans delivered similar EQD2 for 0.1 cm3 and 2 cm3 of sigmoid. Plan D delivered lesser EQD2 compared to other plans for bladder, rectum, D90 CTVHR, and point A (p = 0.0001). Plan C delivered higher EQD2 to OARs compared to other plans (p = 0.001). Plan A, B, and plan C delivered similar EQD2 for D90 CTVHR and point A.ConclusionsEQD2 of bladder, rectum, sigmoid, D90 CTVHR, and point A were similar with 5.5 Gy × 5 fractions, 6.5 Gy × 4 fractions, and 7 Gy × 4 fractions, whereas EQD2 of 9 Gy × 2 fractions was significantly unfavorable compared to other schedules. Further clinical studies are recommended to observe clinical outcomes.

A Dosimetric Analysis of the Rectal Doses in Intracavitary Brachytherapy of Carcinoma Cervix: A Prospective Study from a Single Institute.

Introduction:Carcinoma cervix is a common gynecologic malignancy in India and is treated with radical chemoradiation where intracavitary brachytherapy (ICR) is an integral part. In ICR of cervix, the two-dimensional (2D) point-based dosimetry cervix is the most common method used in high-volume centers with rectal dose calculation at modified ICRU rectal point with rectal wire placement. The rectal dose measurement using this method underestimates the dose to the rectum, and rectal dose also varies with the type of applicator used. The aim of our study is to compare the rectal dose calculated by ICRU 38 method versus rectal dose calculated by the rectal wire method using Henschke applicator.Materials and Methods:This is a single-institute, dosimetric comparison study done prospectively. Fifty patients were planned for ICR after 2D orthogonal radiograph-based, computer planning by iridium 192 high-dose rate remote afterloading technique after placing the appropriate Henschke applicator. The vaginal packing was done using sterile gauze with contrast material for defining the ICRU 38 rectal point, and a rectal wire was placed for the modified ICRU rectal point. Rectal doses were calculated by both the methods and compared.Results:The modified ICRU rectal point recorded a lower rectal dose (mean of 25%) compared to ICRU 38 rectal point in the study patients. There were ten patients (20%) with either too much or too little contrast material which made the visualization of the rectal point and radiation planning difficult. P value by paired t-test method was 0.0001, which was statistically significant.Conclusion:The modified ICRU rectal point is easier to visualize than ICRU 38 method (100% vs. 80%) for dosimetry, but it underestimates the rectal doses when compared to ICRU 38 rectal point. There needs to be a correction factor applied (25% in our study for Henschke applicator) when evaluating the rectal doses calculated by rectal wire method, to reduce the rectal toxicity.

Interfraction physical dose variations in high-dose-rate brachytherapy for carcinoma cervix based on computed tomography image dataset to find the compatibility of the first fraction plan to treat successive fractions.

Due to limited resources and/or affordability by majority of the patients, many centers in low- and middle-income countries are still not able to adapt three-dimensional image-based brachytherapy planning in their routine practice. The aim of the study was to see the feasibility of using computed tomography (CT)-based plan of the first fraction to treat successive fractions of intracavitary brachytherapy based on the estimation of the physical dosimetric differences between successive applications. CT image-based brachytherapy plans of 38 patients who received three insertions of intracavitary application with high-dose-rate brachytherapy have been analyzed. Revised plans for the second and third insertions were generated by adapting dwell time and dwell position of the first insertion plan. The dose to point "A" and maximum doses to 2, 1, and 0.1 cc volumes of the rectum and bladder have been used for dosimetric comparison. The statistical differences of mean point "A" doses were observed insignificant except between original and revised plans for the second insertions. The dosimetric differences between consecutive original and revised plans for the bladder and rectum have not shown any significance except minimum dose to 0.1 cc volume of the rectum for the third insertions. Dosimetric deviation for tumor and organs at risk is within acceptable limit while using CT image-based brachytherapy plan of the first fraction for treating successive fractions.

Study of the effects of dwell time deviation constraints on inverse planning simulated annealing optimized plans of intracavitary brachytherapy of cancer cervix.

High Dose Rate (HDR) remote afterloading brachytherapy machine and advanced treatment planning system have made it possible to make variations in individual dwell times across a catheter according to tumour density and for sparing normal structures. New inverse planning technique such as Inverse Planning Simulated Annealing (IPSA) has also been introduced. But very few institutions are venturing towards volume based IPSA optimised intracavitary brachytherapy. This study focuses on dwell time deviation constraint (DTDC) feature of IPSA based optimization which restricts the large variation of dwell time across the catheter. For this retrospective study we have generated IPSA optimised intracavitary brachytherapy plans for 20 cancer cervix applications. The initial DTDC value of each IPSA plan was kept 0.0. Later on gradual increment was made in DTDC values in step of 0.2. Plan modulation index (M) defined by Ryan L. Smith et al was used for characterising the variation of dwell time modulation with respect to gradual increase in DTDC parameter. Plan modulation index gradually decreases with increasing value of DTDC from 0.0 to 1.0. There was the 83% decrease in M value from IPSA of DTDC 0.0 to fully constrained IPSA of DTDC1.0. There is reduction of 8.26% and 6.95% for D2cc values of rectum and bladder respectively for DTDC 1.0 compared to DTDC 0.0. One of the benefits of applying DTDC constrained in IPSA plan is that, it removes local hot spots. It's another advantage is the reduction in rectum and bladder dose.

Dose to pelvic lymph nodes in image based high dose rate brachytherapy of carcinoma cervix.

The aim of this study is to analyse the dosimetry to the pelvic lymph nodes and its correlation to point B using CT based high dose rate brachytherapy of carcinoma cervix. Conventionally, dose to pelvic lymph nodes from intracavitary brachytherapy was reported by point B and by the reference points of the lymphatic trapezoid. 30 consecutive CT based high dose rate applications were reviewed between February and March 2016. The high risk clinical target volume and the organs at risk and the pelvic nodal groups were contoured. DVH parameters for the right and left obturator nodal group, right and left external iliac nodal group and right and left internal iliac nodal group were recorded. Right and left point B doses were also recorded. On analysis of the combined dose, it was found that all the DVH parameters were significantly different from point B, except the D100 obturator and D2cc internal iliac lymph node. There was a significant correlation between all DVH parameters and point B, except D2cc, D1cc and D0.1cc of external iliac. The obturator group received the highest dose contribution from brachytherapy. The mean D90 dose received per fraction for the obturator, external iliac and internal iliac nodes was 2.7Gy, 1.17Gy and 1.41Gy, respectively. There is a significant dose contribution to the pelvic lymph nodal groups during intracavitary brachytherapy. There is a low degree of correlation between point B dose and dosimetric parameters of the individual nodal groups. Hence, it is important to analyse the dose delivered to individual nodal groups during intracavitary brachytherapy, at least in patients with enlarged lymph nodes to calculate the cumulative dose delivered.

Preliminary Results of Intracavitary/Interstitial MRI/CT-Based Cervix Brachytherapy using Non Intracavitary/Interstitial (IC/IS) Dedicated Applicator

Preliminary Results of Intracavitary/Interstitial MRI/CT-Based Cervix Brachytherapy using Non Intracavitary/Interstitial (IC/IS) Dedicated Applicator

OC-0073: Isodose surface volume in cervix brachytherapy: dependence on image guided adaptation and applicator

OC-0073: Isodose surface volume in cervix brachytherapy: dependence on image guided adaptation and applicator

SP-0235: Facial growth and developmental outcomes following pediatric head and neck brachytherapy

SP-0235: Facial growth and developmental outcomes following pediatric head and neck brachytherapy

Outcomes of Computed Tomography-Guided Image-Based Interstitial Brachytherapy for Cancer of the Cervix Using GEC-ESTRO Guidelines.

Locally advanced cancer of the cervix is treated by concurrent chemoradiation followed by brachytherapy. Interstitial brachytherapy is used to treat large tumors with involvement of parametrium, post-hysterectomy, and narrow, conical vagina. The GYN GEC-ESTRO working group described target volume delineation and also 3D image-based planning using MRI and 3D dose-volume parameters for brachytherapy of carcinoma cervix. CT-based as compared to MR-based image-guided brachytherapy (IGBT) is much more feasible and practical because MR access is still difficult for most departments. This is a retrospective study done to assess the local control in cancer of the cervix, treated based on these guidelines and dose received by 2cm3 of the rectum as defined by the GEC-ESTRO guidelines and its correlation with long-term toxicity. Sixty-three patients of cancer of the cervix received 45Gy/25 fractions of external beam radiotherapy with concurrent weekly cisplatin followed by interstitial brachytherapy. A central tandem was inserted into the uterine cavity. The needles were inserted based on the concept of gross tumor volume (GTV), high-risk clinical target volume (HRCTV), and intermediate-risk CTV (IR CTV) as defined by the GYN GEC-ESTRO guidelines. All patients underwent CT-based planning. A dose of 6.5Gy × 4 fractions was delivered in two sessions such that the HRCTV received a total dose of 26Gy. Dose optimization was done to prevent 2cm3 of rectum from receiving > 400cGy (60% of prescribed dose) per fraction and 2cm3 of bladder from receiving 500cGy per fraction. At a median follow-up of 41.5months (range 6-106months), 74.6% (47/63) of the patients were alive, with no local, loco-regional, or distant metastasis. Loco-regional control rate was 88% (56/63). Eight percent (5/63) of the patients developed grade I proctitis which was managed conservatively. There was no grades II, III, or IV proctitis. There was no bladder or sigmoid toxicity. GEC-ESTRO guidelines can be modified for CT-based planning also with very minimal late toxicity without compromising local control.

Brachytherapy in Head and Neck Cancers: "Are We Doing It or Are We Done with It".

We performed an e-Survey and reviewed the literature on the prevalence of use of brachytherapy in head and neck cancers in order to understand the patterns of care and probable application of this modality. A five-point questionnaire was prepared and sent to 300 oncologists through a web-based survey engine. This was done in preparation for my lecture on "Ongoing Research and Potential Research Avenues" in IBSCON held in Chennai in August 2016. SPSS software was used for the statistical analysis. Of a total of 300 emails that were sent out for the survey, 120 replies were received, which is 40%. Among the results of various questions, (i) 65% of the oncologists felt that there were > 300 ongoing studies in brachytherapy and out of them only 10-20 were on head and neck brachytherapy; (ii) 58% of the responders felt that external beam radiotherapy (EBRT) advances followed by lack of training and experience are the reasons for declining role of brachytherapy; (iii) among the responders, numbers of head and neck brachytherapy performed stand third after gynecological and breast brachytherapy. This survey shows that brachytherapy in head and neck cancers is an essential tool, but seldom practiced. If no path-breaking event happens, we may be dealing with it as a dying art.

Comparison of dosimetric parameters derived from whole organ and wall contours for bladder and rectum in cervical cancer patients treated with intracavitary and interstitial brachytherapy

For volumes up to 2 cm3 of the bladder and possibly up to 5 cm3 of the rectum, doses computed from the whole organ were good estimates of the doses in the wall in cervix brachytherapy, and there were no significant differences between patients treated with or without interstitial needles.

Interfraction Variations in Organ Filling and Their Impact on Dosimetry in CT Image Based HDR Intracavitary Brachytherapy.

Aim:Since anatomical and geometric variations occur with every fraction, planning, and dose optimization is necessary for every fraction of high-dose rate intracavitary brachytherapy of carcinoma cervix. In this study, we have tried to quantify the differences in doses to organs at risk (OAR) for each fraction of brachytherapy.Methods and Materials:One hundred and seventy computed tomography datasets of cervical cancer patients receiving intracavitary brachytherapy at our institution between January and April 2015 were analyzed. The volumes of the high-risk clinical target volume and OAR contoured were recorded for every insertion. Dose-volume histograms were generated and D90 and D100CTV and D0.1, D1, and D2cc were recorded for bladder, rectum, and sigmoid for each insertion.Results:Sixty-one percent had a decrease in bladder volume in the second fraction, 35% had an increase in bladder volume and 4% had no change in bladder volume. There was a strong positive correlation between increase in volume and dose (D2cc), which was statistically significant, rs = 0.441, P = 0.013. Nearly 49.4% of patients had an increase in rectal volume during the second fraction. 45.9% had decrease in rectal volume during the second fraction. There was a positive correlation between the increase in volume and dose (D2cc), which was statistically significant, rs = 0.393, P = 0.010. About 63.5% of the patients had a decrease in sigmoid volume during the second fraction, whereas 30.6% had an increase in volume and 5.9% had no change in volume.Conclusion:First, this study emphasizes the importance of imaging and planning for every fraction of brachytherapy to quantify the exact doses to the target and OAR s. Second, it is important to follow a uniform bladder protocol for every fraction, and adequate bowel preparation is needed for every fraction to minimize the interfraction variations. Finally, it also opens the realm of an adaptive planning strategy in cervical cancers which are known for rapid tumor regression during radiotherapy.

Intracavitary/Interstitial MR-Based Cervix Brachytherapy: First Look at Implant Quality

Image-guided adaptive brachytherapy (BT) holds promise for improved cervical cancer outcomes, with lesser normal tissue toxicity. Key to this are better tumor visualization (via MRI), defined dose-volume targets (via international recommendations), and plan conformity (via interstitial (IS) sources added to traditional intracavitary (IC) applicators). Hybrid IC/IS implant quality is not well characterized, nor its impact on overall BT plan quality. Our institutional experience with IC/IS MRI-based cervix BT (no volumetric preplanning; post-implant planning on MRI assisted by CTsim) was reviewed. Tandem-ring (T&R) and tandem-ovoid (T&O) based IC/IS implant quality was evaluated for variability in the IS component, with attention to intent at implant vs post-implant geometry. Descriptive statistics were performed. From 07/2013 – 12/2016, IC/IS technique was used in n=43 single-fraction pulsed dose rate BT boost cases, during curative (chemo)radiotherapy for locally advanced cervix cancer. Median HR-CTV D90 (EQD2) was 90.7 Gy [76.4 – 96.6], median D2cc 75.8 Gy [43.2 – 90.4] for bladder, 64.3 Gy [52.3 – 74.2] rectum, 62.2 Gy [46.6 – 73.6] sigmoid, and ICRU rectovaginal point dose, 64.2 Gy [52.0 – 82.1]. Of a median of 3 [1 – 6] IS catheters implanted per case (79% T&R), 2 [1 – 5] were loaded, for an overall load rate of 82%, with no appreciable difference by applicator type. More IS catheters (N=10, in 6 unique implants) remained unused among our first 15 cases, compared to the latest 15 (N=7, in 6 implants) in our evolving experience. Radial IS positions, selected based on pre-BT clinical/radiological tumor residuum and patient anatomy, were loaded most frequently lateral for T&O, and lateral more than anterior for T&R. Least loaded were posterior (T&R) and medial (T&O) positions. There was no change in IS catheter depth on CTsim vs MRI, suggesting no significant movement. Median IS depth beyond ring/ovoid surface was 26.0 mm [7.5 – 47.1], closely matching intended insertion depths, with mean difference of 1.4 ± 3.0 mm. IS catheter deflection was observed (median 1.7 deg [0 – 35.6] anterior-posterior; 1.0 deg [0 – 34.4] medial-lateral), reaching > 5 deg for median insertion depths of 25.6 mm [11.5 – 43.0]. IS weighting ranged from 0.5% to 70.2%, although the median was 7.7% relative to the IC component, with outliers reflecting individual anatomic and tumor topographies. The technical quality of IC/IS cervix BT implants improves with experience, but small variabilities persist in measured IS catheter positions. To what extent post-implant BT planning processes can safely mitigate for suboptimal IS tracks (assuming IC applicator selection appropriate to the target) remains unknown.

Dosimetric analysis of the effect of bladder volume on brachytherapy dose to organs at risk (OARs) in volume based intracavitary brachytherapy of carcinoma cervix: An institutional study.

e17006 Background: External beam radiotherapy combined with intracavitary brachytherapy is the standard of care in Carcinoma cervix. Due to its characteristics of rapid dose fall off, brachytherapy limits the toxicity to organs at risk while escalating radiation dose to target. Still, the organs near the radioactive source are at risk of considerable exposure, toxicity and post treatment morbidity. Alteration of bladder volume, alters the relative anatomy of uterus, rectum, sigmoid colon causing changes in the radiation dose to these organs. Methods: Aim:To correlate between the bladder volume and its effects on the dose received by bladder, rectum and sigmoid colon in volume based HDR brachytherapy in carcinoma cervix.30 patients (78 Intracavitary Brachytherapy applications) of Carcinoma Cervix (FIGO stage II-III) treated with EBRT followed by volume based HDR brachytherapy at our institute between July 2014 to Jan 2016 were studied. Bladder volume data was tabulated into five groups according to increasing volume of bladder. It was correlated with D2cc dose received by bladder, rectum and sigmoid colon. Results: Statistical Analysis Linear regression and correlation analysisof the HRCTV with dose to the bladder was 0.2 (.i.e HRCTV does not influence the bladder dose.) Pearson correlation of bladder volume and D2cc bladder and D2cc rectum was positive for all groups and for sigmoid D2cc was positive for group B and negative for all other groups. P value = 0.064 Conclusions: Keeping the bladder volume low (&lt;130 cc) during brachytherapy would reduce the dose to bladder and rectum and the probability of late bladder and rectal toxicity reduces. [Table: see text]

Design and Construction of Cervix Phantom for Brachytherapy Dose Assessment Procedure for Clinical Application

An important point to consider in a brachytherapy dosimetry study is the design of an appropriate phantom size in calculations or experimental measurements. Perspex sheets of various size and thickness are used to design the cervix phantom. The aim of the study is to design and construct cervix phantom to mimic the pelvic segment of a standard adult human patients undergoing Brachytherapy. This is to allow assessment of dose to cervix and the surrounding tissues during cervix Brachytherapy. The methodology include; first phantom design where physical dimensions of the phantom were determined from a sampling of 30 patients’ cases to simulate an average patient size. Secondly, construction of phantom with fabricated cylindrical shape, composed of 6 mm Perspex sheets, and the assembly enclosed with the 4 mm Perspex sheet. The result of the constructed phantom had lateral separation of 34 cm, an anterior and posterior separation of 27 cm; with length of 33 cm. The Perspex pieces were glued to each other with Trichloromethane (chloroform) at room temperature. Chloroform dissolves the Perspex (PMMA), and when applied to the surfaces of the Perspex sheets, the surfaces stick together after the chloroform dries up. In forming the surface of the phantom, the 4 mm Perspex sheet was oven heated to a temperature of 140?C to make the sheet malleable. One end of the phantom was made thicker than the other end by gluing another 6 mm Perspex sheet such that the thickness of that particular end of the phantom was 12 mm. A hole of diameter 6.5 cm, which was a little bit posterior to the phantom, was created central to the 12 mm end of the phantom. The opening created was covered by 11 x 11 cm2 and 12 mm Perspex slab which was formed by gluing two 6 mm sheets together. A hole of diameter 5 cm was also made central to the cover created, such that the centre of this hole matches that of the hole on the end of the phantom. A 2.4 cm thick ring with internal diameter of 5 cm and external diameter of 6 cm was fabricated from 2.4 cm Perspex slab, which was formed from gluing four pieces of 6 mm Perspex sheets together. The fabricated ring was mounted on the 11 x 11 cm2 cover created such that the internal walls of the ring and that of the hole in the cover matches. The ring was then glued to the cover using the chloroform. The built phantom simulate actual patient anatomy and produce an excellent result to be use for clinical application.