[P244] Accuracy of ct numbers obtained by dira and monoenergetic plus algorithms in quantitative dual-energy computed tomography (original) (raw)
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Journal of Contemporary Brachytherapy
Purpose: Interstitial brachytherapy (ISBT) is often used as post-external beam radiotherapy (EBRT) to treat locally advanced gynecological malignancies. Female urethra is in close proximity to the target during ISBT. However, it has not been evaluated as an organ-at-risk (OAR). Overlapping symptoms caused by radiation-induced bladder toxicity vs. urethral toxicity make it difficult to identify and report urethral toxicities separately. This was a retrospective study to estimate dose-volume parameters of female urethra during high-dose-rate ISBT. Material and methods: Data of 24 patients with gynecological malignancies treated by ISBT were selected. Urethra and periurethral regions were retrospectively contoured. Mean volume, D max , D mean , D 2cc , D 1cc , D 0.5cc , D 0.2cc , and D 0.1cc were documented. Unpaired t-test was used for comparison of means. Results: 20/24 Ca. cervix, 1/24 Ca. vagina, and 3/24 Ca. vaginal vault received 6-6.5 Gy in 4 ISBT fractions. Mean urethral length was 3.54 ±0.55 cm. Mean doses received by urethra per BT fraction were D max = 4.23 ±1.32 Gy, D mean = 2.71 ±1.01 Gy, D 0.2cc = 3.31 ±1.07, and D 0.1cc = 3.54 ±1.09 Gy. Comparison of total BT 2 Gy equivalent dose (EQD 2) with 4 fractions for urethra between patients with (9/24) and without anterior vaginal wall (15/24) involvement included D mean
International Journal of Radiation Oncology*Biology*Physics, 2008
Purpose: To investigate the effect of bladder filling on dosimetry and to determine the best bladder dosimetric parameter for vaginal cuff brachytherapy. Methods and Materials: In this prospective clinical trial, a total of 20 women underwent vaginal cylinder highdose-rate brachytherapy. The bladder was full for Fraction 2 and empty for Fraction 3. Dose-volume histogram and dose-surface histogram values were generated for the bladder, rectum, and urethra. The midline maximal bladder point (MBP) and the midline maximal rectal point were recorded. Paired t tests, Pearson correlations, and regression analyses were performed. Results: The volume and surface area of the irradiated bladder were significantly smaller when the bladder was empty than when full. Of the several dose-volume histogram and dose-surface histogram parameters evaluated, the bladder maximal dose received by 2 cm 3 of tissue, volume of bladder receiving 5050% of the dose, volume of bladder receiving 5070% of the dose, and surface area of bladder receiving 5050% of the dose significantly predicted for the difference between the empty vs. full filling state. The volume of bladder receiving 5070% of the dose and the maximal dose received by 2 cm 3 of tissue correlated significantly with the MBP. Bladder filling did not alter the volume or surface area of the rectum irradiated. However, an empty bladder did result in the nearest point of bowel being significantly closer to the vaginal cylinder than when the bladder was full. Conclusions: Patients undergoing vaginal cuff brachytherapy treated with an empty bladder have a lower bladder dose than those treated with a full bladder. The MBP correlated well with the volumetric assessments of bladder dose and provided a noninvasive method for reporting the MBP dose using three-dimensional imaging. The MBP can therefore be used as a surrogate for complex dosimetry in the clinic. Ó 2008 Elsevier Inc.
The British Journal of Radiology, 2009
The purpose of this study was to assess the impact of bladder volume on bladder base doses during gynaecological intracavitary high dose rate (HDR) brachytherapy. 42 different intracavitary HDR brachytherapy applications (tandem and ovoid, 25; ovoid, 17) were performed in 41 patients treated for cervical (n529) and endometrial (n512) cancer. The International Commission on Radiation Units and Measurements (ICRU) bladder reference point (BRP) dose and doses of 17 points selected on the bladder base were calculated using planning orthogonal radiographs taken after applicator placement with 100 ml and 270 ml bladder volumes. The effect of bladder volume on ICRU BRP and bladder base maximum point (BBMP) doses were analysed for both types of applications. Median ICRU BRP doses (in percentage of prescription dose) were 36.2% (18.2-69.8%) and 40.0% (21.0-61.8%) for ovoid applications (p50.13) and 34.9% (15.7-81.0%) and 33.8% (16.5-88.1%) for tandem and ovoid applications (p50.48) in 100 ml and 270 ml bladder volumes, respectively. Median BBMP doses were 75.1% (33.8-141.0%) and 104.0% (62.8-223.0%) for ovoid applications (p,0.001) and 116% (51.2-242.0%) and 124.0% (62.0-326%) for tandem and ovoid applications (p50.018) in 100 ml and 270 ml bladder volumes, respectively. Although the BBMP dose significantly increases, the ICRU BRP dose does not change with increasing bladder volume in gynaecological intracavitary HDR brachytherapy. Increasing bladder volume increases bladder base maximum dose in intracavitary gynaecological brachytherapy.
An NTCP Analysis of Urethral Complications from Low Doserate Mono- and Bi-Radionuclide Brachytherapy
Prostate cancer, 2011
Urethral NTCP has been determined for three prostates implanted with seeds based on (125)I (145 Gy), (103)Pd (125 Gy), (131)Cs (115 Gy), (103)Pd-(125)I (145 Gy), or (103)Pd-(131)Cs (115 Gy or 130 Gy). First, DU(20), meaning that 20% of the urhral volume receive a dose of at least DU(20), is converted into an I-125 LDR equivalent DU(20) in order to use the urethral NTCP model. Second, the propagation of uncertainties through the steps in the NTCP calculation was assessed in order to identify the parameters responsible for large data uncertainties. Two sets of radiobiological parameters were studied. The NTCP results all fall in the 19%-23% range and are associated with large uncertainties, making the comparison difficult. Depending on the dataset chosen, the ranking of NTCP values among the six seed implants studied changes. Moreover, the large uncertainties on the fitting parameters of the urethral NTCP model result in large uncertainty on the NTCP value. In conclusion, the use of N...
Journal of applied clinical medical physics / American College of Medical Physics, 2016
The purpose of this study was to investigate the concurrent effects of tandem length and bladder volume on dose to pelvic organs at risk (OARs) in HDR intracavitary brachytherapy treatment of cervical cancer. Twenty patients with locally advanced cervical cancer were selected for brachytherapy using Rotterdam applicators. The patients were CT scanned twice with empty and full bladder. Two treatment plans were prepared on each of the image sets. Patients were categorized into two groups; those treated with a tandem length of 4 cm or smaller (T ≤ 4 cm) and those with tandem length larger than 4 cm (T > 4 cm). Only one tandem tip angle of 30° was studied. Dose-volume histograms (DVHs) of OARs were calculated and compared. Bladder dose was significantly affected by both bladder volume and tandem physical length for T ≤ 4 cm. This was reflected on the values obtained for D2cm³, D1cm³, and D0.1cm³ for both empty and full bladder cases. When T > 4 cm, no correlation could be establis...
Asian Pacific Journal of Cancer Prevention, 2014
Background: CT based brachytherapy allows 3-dimensional (3D) assessment of organs at risk (OAR) doses with dose volume histograms (DVHs). The purpose of this study was to compare computed tomography (CT) based volumetric calculations and International Commission on Radiation Units and Measurements (ICRU) reference-point estimates of radiation doses to the bladder and rectum in patients with carcinoma of the cervix treated with high-dose-rate (HDR) intracavitary brachytherapy (ICBT). Materials and Methods: Between March 2011 and May 2012, 20 patients were treated with 55 fractions of brachytherapy using tandem and ovoids and underwent post-implant CT scans. The external beam radiotherapy (EBRT) dose was 48.6Gy in 27 fractions. HDR brachytherapy was delivered to a dose of 21 Gy in three fractions. The ICRU bladder and rectum point doses along with 4 additional rectal points were recorded. The maximum dose (D Max) to rectum was the highest recorded dose at one of these five points. Using the HDRplus 2.6 brachyhtherapy treatment planning system, the bladder and rectum were retrospectively contoured on the 55 CT datasets. The DVHs for rectum and bladder were calculated and the minimum doses to the highest irradiated 2cc area of rectum and bladder were recorded (D 2cc) for all individual fractions. The mean D 2cc of rectum was compared to the means of ICRU rectal point and rectal D Max using the Student's t-test. The mean D 2cc of bladder was compared with the mean ICRU bladder point using the same statistical test .The total dose, combining EBRT and HDR brachytherapy, were biologically normalized to the conventional 2 Gy/fraction using the linear-quadratic model. (α/β value of 10 Gy for target, 3 Gy for organs at risk). Results: The total prescribed dose was 77.5 Gyα/β10. The mean dose to the rectum was 4.58±1.22 Gy for D 2cc , 3.76±0.65 Gy at D ICRU and 4.75±1.01 Gy at D Max. The mean rectal D 2cc dose differed significantly from the mean dose calculated at the ICRU reference point (p<0.005); the mean difference was 0.82 Gy (0.48-1.19Gy). The mean EQD2 was 68.52±7.24 Gy α/β3 for D 2cc , 61.71±2.77 Gy α/β3 at D ICRU and 69.24±6.02 Gy α/β3 at D Max. The mean ratio of D 2cc rectum to D ICRU rectum was 1.25 and the mean ratio of D 2cc rectum to D Max rectum was 0.98 for all individual fractions. The mean dose to the bladder was 6.00±1.90 Gy for D 2cc and 5.10±2.03 Gy at D ICRU. However, the mean D 2cc dose did not differ significantly from the mean dose calculated at the ICRU reference point (p=0.307); the mean difference was 0.90 Gy (0.49-1.25Gy). The mean EQD2 was 81.85±13.03 Gy α/β3 for D 2cc and 74.11±19.39 Gy α/β3 at D ICRU. The mean ratio of D 2cc bladder to D ICRU bladder was 1.24. In the majority of applications, the maximum dose point was not the ICRU point. On average, the rectum received 77% and bladder received 92% of the prescribed dose. Conclusions: OARs doses assessed by DVH criteria were higher than ICRU point doses. Our data suggest that the estimated dose to the ICRU bladder point may be a reasonable surrogate for the D 2cc and rectal D Max for D 2cc. However, the dose to the ICRU rectal point does not appear to be a reasonable surrogate for the D 2cc .
Dosimetric analysis of radiation therapy oncology group 0321: The importance of urethral dose
Practical Radiation Oncology, 2014
Purpose: Radiation Therapy Oncology Group 0321 is the first multi-institutional cooperative group high-dose-rate (HDR) prostate brachytherapy trial with complete digital brachytherapy dosimetry data. This is a descriptive report of the data and an analysis of toxicity. Methods and Materials: Patients are treated with external beam radiation therapy at 45 Gy and 1 HDR implant with 19 Gy in 2 fractions. Implants are done with transrectal ultrasound guidance, and computed tomography (CT)-compatible nonmetallic catheters. HDR planning is done on ≤ 3mm-thick CT slices. The "mean DVH" (dose-volume histogram) of the planning target volume (PTV), implanted volume (IP), and organs at risk are calculated. This includes the mean and standard deviation (SD) of the volume at 10-percentage-point intervals from 10% to 200% of the prescribed dose. The conformal index (COIN), homogeneity index (HI), catheters per implant, and patients per institution are calculated. Multivariate analysis and hazard ratios calculation of all the variables against reported grade ≥ 2 (G2 +) genitourinary (GU) adverse events (Common Terminology Criteria for Adverse Events, version 3) are performed. Results: Dosimetry data are based on 122 eligible patients from 14 institutions. The mean of PTV, IP, catheters per implant, and patients per institution are 54 cc, 63 cc, 19 and 9, respectively. The mean of %V100 PTV , V80 Bladder , V80 Rectum , and V120 Urethra were 94%, 0.40 cc, 0.15 cc, and 0.25 cc, respectively. There are too few G2 + gastrointestinal adverse event (GI AE) for correlative analysis; thus, the analysis has been performed on the more common G2 + GU AE. There are positive correlations noted between both acute and late G2 + GU AE and urethral dose at multiple levels. Positive correlations with late AE are seen with PTV and IP at high-dose levels. A negative Note-Earn CME credit by taking a brief online assessment at https://www.astro.org/JournalCME. Practical Radiation Oncology (2014) 4, 27-34 correlation is seen between HI and acute AE. A higher patient accrual rate is associated with a lower rate of G2 + acute and late AE. Conclusions: Higher urethral dose, larger high-dose volumes, and lower dose homogeneity are associated with greater toxicities. A mean dose-volume histogram comparison at all dose levels should be used for quality control and future research comparison.
Radiology and Oncology, 2014
Background. The aim of the study was to examine on the CT basis the inter-application displacement of the positions D0.1cc, D1ccand D2ccof the brachytherapy dose applied to the bladder and rectum of the patients with inoperable cervical cancer.Patients and methods. This prospective study included 30 patients with cervical cancer who were treated by concomitant chemo-radiotherapy. HDR intracavitary brachytherapy was made by the applicators type Fletcher tandem and ovoids. For each brachytherapy application the position D0.1ccwas determined of the bladder and rectum that receive a brachytherapty dose. Then, based on the X, Y, and Z axis displacement, inter-application mean X, Y, and Z axis displacements were calculated as well as their displacement vectors (R). It has been analyzed whether there is statistically significant difference in inter-application displacement of the position of the brachytherapy dose D0.1cc, D1ccand D2ccof the bladder and rectum. The ANOVA test and post-hoc a...
Brazilian Journal of Radiation Sciences, 2018
The gynecological treatment with High Dose Rate (HDR) Brachytherapy implies delivering dose to the tumor and spare the dose in organs at risk. In this work, we apply the recommendations for prescribing dose given by the International Commission of Radiation Units (ICRU) reports 38, 89 and the American Brachytherapy Society (ABS). With both schemes of optimization, recommendation of ICRU 38 or ABS with vaginal point from ICRU 89. Doses received by the organs at risk were analyzws, in this case rectum and bladder and also the irradiated volume for patients that receive HDR brachytherapy treatment. An afterloading technique is applied with an Eckert & Ziegler MultiSource ® equipment using a 60 Co source, 30 patients with 4 applications with cervical cancer are planning with HDR brachytherapy. This work analyzes 120 single applications with orthogonal images using the treatment planning system (TPS) HDRplus version 3.0.4 through "Auto dwell time determination" optimization method, using the recommendation for optimization dose from the ABS and vaginal point from ICRU 89. The volume of the isodose curve of prescription is 15% less using ABS recommendation than ICRU 38. The bladder dose is 11% and rectum dose is 21% less using ABS recommendation than ICRU 38. The analysis of dose prescription using ICRU 38 and ABS recommendations in the patients analyzed shows less irradiated volume at the dose prescribed and also less mean dose in rectum and bladder of applications using ABS in contrast with ICRU 38 recommendations.