Study of the relationships between brachytherapy plan parameters in an attempt to verify total dwell time in vaginal cylinder applications.

PURPOSE: Source strength (Sk ), sizes of vaginal cylinder applicators (VCA), number of dwell positions (DPs), and the prescribed dose (D) are basic parameters in brachytherapy (BT) treatment planning contributing to total dwell time (TDT). This study was aimed at assessing the relationships between the specified variables in an attempt to verify the TDT in high-dose-rate (HDR) vaginal cylinder applications. METHODS: One hundred and twenty-one patients treated with Gynesource-Co60 (Bebig, Germany) using VCAs of diameters 20, 25, and 30 mm at University College Hospital, Nigeria, were enrolled in this study. Brachytherapy doses ranging from 3 to 7 Gy were always prescribed to points 5 mm away from the cylinder's surface. Treatment planning was undertaken on HDR-Basic treatment planning system (TPS) which utilizes source step size of 5 mm. Data on the stated parameters related to the first BT fractions of the patients were acquired. With the aid of EViews statistical software, two forms of mathematical models were thereafter developed. The resulting TDTs from the models were compared with the TPS values using Minitab statistical software. RESULTS: The relationships obtained for the increasing sizes of the VCA were TDT1(min)=2.22+3.17DSk;TDT1(min)=3.52+3.74DSk;TDT1(min)=-1.96+6.91DSkandTDT2(min)=0.50-0.03Sk+0.02D+0.55DPs;TDT2(min)=7.08-0.06Sk+0.02D+0.67DPs;TDT2(min)=7.02-0.11Sk+0.03D+1.25DPs The model-based TDTs correlate with the TPS-calculated values with r1 = 0.80 (P = 0.412) and r2 = 0.97 (P = 0.468). CONCLUSIONS: The findings of this study could suggest likely variations in the treatment time when certain changes occur in the related parameters. The increasing size of the vaginal cylinder has a positive influence on the brachytherapy treatment time. The latter model has been a useful tool in the verification of the dose delivery time at the first HDR brachytherapy center in Nigeria and West Africa.

Survey of dose area product received by patients undergoing common radiological examinations in four centers in Nigeria.

Patient dosimetry studies in diagnostic radiology in Nigeria have been on measurement of entrance skin dose and effective dose. Another important and easy to measure radiation dose descriptor that could be used to assess patient dose in radiological procedures is dose area product (DAP). Knowledge of DAP with location and projection of X-ray beam allows direct calculation of organ dose and effective dose. In this study, DAP for commonly performed radiological examinations (abdomen, chest, lumbo sacral joint, pelvis, paranasal sinus, and skull) in four diagnostic centers in Nigeria were determined. These centers comprise of three classes of health care center namely tertiary, private, and specialist hospitals. Mathematical method was used to determine DAP received by 336 patients undergoing radiological examinations at the selected diagnostic centers. The DAP received by patient from each radiological examination varies from center to center. The range factor (RF) of DAP for individual patients ranged from 1.55-4.56, while RF of DAP among the selected centers was 2.27-55.84. The highest RF of DAP (55.84) was obtained from X-ray examination of the chest. This variation was due to the application of anti-scatter grid, and high kVp and high mAs values for chest examination by only one of the centers. The very wide variation in DAP found among diagnostic centers in this survey showed that there is need to harmonize radiological techniques of common X-ray examination among different diagnostic centers. This would ensure optimal protection of patient against excessive radiation dose.

Gamma camera intrinsic uniformity in an unstable power supply environment.

The main objective of this work was to show that a gamma camera in a developing country could perform efficiently despite electricity outages using intrinsic flood uniformity tests as an index of performance. A total of 143 intrinsic uniformity test results for a new gamma camera in use in an environment with unstable power supply are presented. The integral uniformity for the central field of view (CFOV) was found to be between 3.43% and 1.49% (3.29% for acceptance test) while the integral uniformity for the useful field of view (UFOV) was between 4.51% and 1.9% (5.21% for acceptance test). The differential uniformity for the CFOV was between 1.99% and 1.04% (2.25% for acceptance test) while that of the UFOV was between 2.84% and 1.23% (2.63% for acceptance test). In conclusion, these results show that the uniformity of the gamma camera under this condition is within an acceptable range for both planar and SPET imaging.

Awareness and Training in Medical Physics: An Avenue to Enhance Cancer Care Delivery in a Low-Resource Setting.

PURPOSE: Awareness and training in medical physics (MP) is crucial to enhance productivity and safety in cancer management. We evaluated the impact of the pioneer teaching hospital in Nigeria on awareness and training in MP in an attempt to appraise and enhance cancer care delivery. METHODS: We reviewed physics students' training records in the MP unit of University College Hospital (UCH), Ibadan, Nigeria, from June 2009 to June 2019. These included demographic data, institutions, levels of study, time and training duration, and contact details. Trainees were contacted for updated information on their professional status. Awareness of the profession had been created at UCH and institutions within and outside Ibadan. Data were analyzed using Microsoft Excel 2016. RESULTS: One hundred thirteen trainees (mean age, 24.1 ± 2.3 years) composed of 65.5% male and 34.5% female students attended UCH within the 10-year period. They were categorized as undergraduates, (n = 83; 73.5%), Master's students (n = 25; 22.1%), Doctoral students (n = 2; 1.8%), and workers within nuclear field (n = 3; 2.7%). Of the 83 undergraduates, 5 (6.0%) were on training as of mid-September 2019, 25 (30.1%) were still in universities or serving in the mandatory national youth service, 11 (13.3%) were in the MP profession, and 42 (50.6%) were in other career pathways. Candidates' institutions spread across 5 of the 6 geopolitical zones in the country. Furthermore, 207 physics students took part in awareness seminars at 2 universities in commemoration of International Day of Medical Physics. CONCLUSION: Candidates from almost all parts of Nigeria benefitted from workplace experience at UCH, which continues to promote the profession. A greater feat will be attained when the University of Ibadan commences MP postgraduate programs.

Assessment of cartesian co-ordinates-based bladder and rectal dose and variability with tandem-ring angles first Nigerian experience in high-dose-rate brachytherapy.

OBJECTIVE:: This study assessed bladder and rectal dose based on Cartesian-coordinates in intracavitary brachytherapy and examined the variations resulting from use of tandem-ring (T-R) of different angles. METHODS:: Cartesian-co-ordinates of bladder and rectum points were derived on orthogonal-radiographs of 90 patients who had high-dose-rate brachytherapy for cervical cancer at the Department of Radiation Oncology, University College Hospital, Ibadan, Nigeria. The patients were classified in three groups of 30, based on T-R angles 30°, 45° and 60° used, bearing same lengths and diameters across sets. The measured co-ordinates and the related percentage doses to points of interest in the two organs were analysed using EViews and SPSS statistical softwares. RESULTS:: The mean rectal point dose (RPD) obtained was 68.97 ± 13.57 % of the prescribed doses as against 56.57 ± 11.83% for bladder point dose. While the maximums of the mean RPD were 95.7, 90.5 and 82.5% for T-R angles 30°, 45° and 60° respectively; corresponding values for the bladder point were 72.8, 87.8 and 62.3%. CONCLUSION:: The baseline data obtained in this study served as guidelines for subsequently achieving acceptable values of bladder point dose and RPD at University College Hospital, Nigeria. Special attention should be paid to the application of 2 cm-tandems in relation to the RPD. ADVANCES IN KNOWLEDGE:: This is one of the few studies assessing the influence of T-R angles on organs-at-risk. The increase in RPD with the use of intrauterine tandem-2 cm is found to be most pronounced with T-R 300, and this trend reduced with larger angles.

Comparison of doses to the rectum derived from treatment planning system with in-vivo dose values in vaginal vault brachytherapy using cylinder applicators.

PURPOSE: In-vivo measurements to determine doses to organs-at-risk can be an essential part of brachytherapy quality assurance (QA). This study compares calculated doses to the rectum with measured dose values as a means of QA in vaginal vault brachytherapy using cylinder applicators. MATERIAL AND METHODS: At the Department of Radiotherapy, University College Hospital (UCH), Ibadan, Nigeria, intracavitary brachytherapy (ICBT) was delivered by a GyneSource high-dose-rate (HDR) unit with (60)Co. Standard 2D treatment plans were created with HDR basic 2.6 software for prescription doses 5-7 Gy at points 5 mm away from the posterior surface of vaginal cylinder applicators (20, 25, and 30 mm diameters). The LiF:Mg, Ti thermoluminescent dosimeter rods (1 x 6 mm) were irradiated to a dose of 7 Gy on Theratron (60)Co machine for calibration purpose prior to clinical use. Measurements in each of 34 insertions involving fourteen patients were performed with 5 TLD-100 rods placed along a re-usable rectal marker positioned in the rectum. The dosimeters were read in Harshaw 3500 TLD reader and compared with doses derived from the treatment planning system (TPS) at 1 cm away from the dose prescription points. RESULTS: The mean calculated and measured doses ranged from 2.1-3.8 Gy and 1.2-5.6 Gy with averages of 3.0 ± 0.5 Gy and 3.1 ± 1.1 Gy, respectively, for treatment lengths 2-8 cm along the cylinder-applicators. The mean values correspond to 48.9% and 50.8% of the prescribed doses, respectively. The deviations of the mean in-vivo doses from the TPS values ranged from -1.9 to 2.1 Gy with a p-value of 0.427. CONCLUSIONS: This study was part of efforts to verify rectal dose obtained from the TPS during vaginal vault brachytherapy. There was no significant difference in the dose to the rectum from the two methods of measurements.

Tandem-ring dwell time ratio in Nigeria: dose comparisons of two loading patterns in standard high-dose-rate brachytherapy planning for cervical cancer.

PURPOSE: In high-dose-rate (HDR) brachytherapy (BT), the source dwell times and dwell positions are essential treatment planning parameters. An optimal choice of these factors is fundamental to obtain the desired target coverage with the lowest achievable dose to the organs at risk (OARs). This study evaluates relevant dose parameters in cervix brachytherapy in order to assess existing tandem-ring dwell time ratio used at the first HDR BT center in Nigeria, and compare it with an alternative source loading pattern. MATERIAL AND METHODS: At the Radiotherapy Department, University College Hospital (UCH), Ibadan, Nigeria, a total of 370 standard treatment plans in two alternative sets were generated with HDR basic 2.6 software for one hundred and eighty five cervical cancer patients. The initial 185 individual plans were created for clinical treatment using the tandem-ring dwell time ratio of 1 : 1. Modifying the initial applicator loading ratio, the second set of plans with related dose data were also obtained for study purposes only. Total reference air kerma (TRAK), total time index (TTI), ICRU volume, treatment time, point B dose, ICRU bladder dose, and rectal points dose were evaluated for both sets of plans. RESULTS: The means of all evaluated dose parameters decreased when the existing tandem-ring dwell time ratio (1 : 1) was modified to other dwell weightings (1 : 1 - 3 : 1). These reductions were 13.43% (ICRU volume), 9.83% (rectal dose), 6.68% (point B dose), 6.08% (treatment time), 5.90% (TRAK), 5.88% (TTI), and 1.08% (bladder dose). Correspondingly, coefficients of variation changed by -7.98%, -5.02%, -5.23%, -4.20%, -3.93%, 8.65%, and 3.96% from the existing pattern to the alternative one. CONCLUSION: Tandem-ring dwell time ratio has significant influence on dosimetric parameters. This study has indicated the need to modify the existing planning approach at UCH.

High Dose Rate Brachytherapy in the Treatment of cervical cancer: preliminary experience with cobalt 60 Radionuclide source-A Prospective Study.

UNLABELLED: Iridium-192 is widely used for high-dose rate brachytherapy. Co-60 source with similar geometric and dosimetric properties are now available. It has a longer half life but higher energy than Iridium-192. If Co-60 source can produce similar results, it will be more economical for low resource settings. OBJECTIVE: To evaluate the acute gastrointestinal and genitourinary toxicity associated with Co-60 source in the brachytherapy of cervical cancer. METHODS: Seventy patients with cervical cancer received 45 Gy in 22 fractions of pelvic external beam radiotherapy and 19.5 Gy in 3 fractions of HDR with Co-60 source using tandem and ring applicators with 6 courses of cisplatin 50 mg/m(2) and 5 fluorouracil 1000 mg/m(2) every 3 weeks Toxicity was scored using NCI-CTC version 4.0. RESULTS: The median total BED (Gy(10)) for tumor was 86.2 (84.4-88.8) while that for rectum (BED Gy(3)) was 124.4 (120-133). Two patients (3%) had grade 3 gastrointestinal toxicity while all others had ≤grade 2 toxicity and this is comparable with previous results. CONCLUSION: Co-60 as HDR brachytherapy source is tolerable and is economical for low resource settings.