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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.

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 30(0), and this trend reduced with larger angles.

Background: The role of Computed Tomography (CT) in the medical diagnosis of diseases has greatly expanded, despite the potential risk of cancer following exposures to ionising radiation (XRay) from this modality. This risk is particularly of great concern in children, who are more radiosensitive and have many years to manifest radiation effect than adults. Aims: To estimate risk of cancer induction from Pediatric cranial CT. Materials and Methods: A total of 203 patients, who were referred from various pediatric clinics and wards for cranial CT in a teaching hospital in the South Western Nigeria between the year 2011 and 2013 were considered. All patients were grouped into four age (year) groups: less than 1, 1-5, 5-10 and 10-15. A mathematical method was used to estimate the risk of cancer from the Original Research Article Atalabi et al.; BJMMR, 9(10): 1-7, 2015; Article no.BJMMR.18079 2 effective dose(ED) calculated from volume computed tomography dose index (CTDIvol), dose length product (DLP) and standard conversion factor. Results: The range of CTDIvol (mGy) received by all patients was 10–250 mGy while majority of the patients received 50–100. The range of DLP (mGy.cm) received by all patients and majority of patients was 500–5000 and 2001–2500 respectively. The range of ED (mSv) received by all patients and majority of the patients was 1–25 and 5–10 respectively. The risk estimated with respect to patients’ age showed that patient in the age group 1–5 years have the highest risk of cancer induction while the risk based on gender showed no significant difference. Conclusion: Over 60% of pediatric patients received more than the recommended values of CTDIvol, DLP and ED from cranial CT. Urgent steps must be taken to ensure compliant with international recommended precautions for dose reduction in pediatric medical imaging.

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.