Excellent treatment setup accuracy with highly conformal radiation technique will improve oral mucosal sparing by
limiting uninvolved mucosal structures from receiving high dose radiation. Therefore, a study was conducted to identify
the ideal immobilization device for interfraction treatment setup accuracy improvement. A total of twelve oral cancer
patients underwent volumetric modulated arc therapy (VMAT) was categorized into three different group depending on
immobilization device they used for treatment. HFW: headFIX® mouthpiece molded with wax, SYR: 10 cc/ml syringe and
TDW: wooden tongue depressor molded by wax. Each patient underwent image-guided radiotherapy with a total of 292
cone beam computed tomography (CBCT) data sets for position treatment setup errors measurement. The variations in
translational (lateral, longitudinal, vertical) and rotational (pitch, yaw, roll) in each CBCT image were calculated. Patient
positioning errors were analyzed for time trends over the course of radiotherapy. CTV-PTV margins were calculated from
the systematic (Σ) and random (σ) errors. Mean ± SD for absolute treatment setup error was statistically significant
(p < 0.001) lower for all translational errors and yaw direction in HFW. The interfraction 3D vector errors were 1.93 ±
0.66, 3.84 ± 1.34 and 2.79 ± 1.17 mm for the HFW, SYR and TDW respectively. There are positive increments between 3D
vector errors over the treatment fraction for all devices. The calculated CTV-PTV margins were 3.08, 2.22 and 0.81 mm,
3.76, 6.24 and 5.06 mm and 3.06, 3.45 and 4.84 mm in R-L, S-I and A-P directions, respectively. HFW shows smaller errors
in almost all comparison indicating higher accuracy and reproducibility of the immobilization device in maintaining
patient’s position. All margins calculated did not exceed hospital protocol (5 mm) except S-I and A-P directions using
SYR. However, in some special situations, such as re-irradiation or the close proximity of organs at risk and high-dose
regions or lower (i.e., 3 mm) margins could benefit from daily image guidance.
Body sizes of patients undergoing x-ray examination vary in body mass index (BMI) and waist circumference (WC). This study aimed to evaluate the relationship between BMI and WC on the image quality of abdominal computed radiography (CR). Anteroposterior supine abdomen projection was conducted on 69 patients from Hospital Raja Perempuan Bainun, Ipoh using a Siemens Multixtop general x-ray unit, and the images were processed with CR Carestream Direct view Max. Samples were categorised into normal BMI (n = 23), overweight (n = 23) and obese (n = 23). Image quality was measured quantitatively in signal-to-noise ratio (SNR) and qualitatively by visual grading analysis (VGA) based on the Commission of the European Communities (CEC) image criteria. Data were analysed by analysis of variance (ANOVA) and Pearson’s correlation for comparison and determining the relationship among BMI, WC and image quality. Results showed a significant difference (p < 0.01) in image quality of VGAmean (normal = 4.40 ± 0.15, overweight = 4.35 ± 0.13, obese = 4.03 ± 0.34) and SNRmean (normal = 60.79 ± 2.19, overweight = 59.66 ± 1.68, obese = 55.78 ± 4.31). A moderate to high negative correlation existed between SNR (r = −0.73), VGA (r = −0.7) with BMI (p < 0.01) and between SNR (r = −0.83), VGA (r = −0.79) with WC (p < 0.01). This study suggests that WC has a higher negative linear relationship than BMI and can be used as an effective image quality predictor for abdominal CR examination.
The aims of this study were to compare the entrance surface dose (ESD) between anteroposterior (AP) supine with
posteroanterior (PA) prone projection of computed radiography (CR) abdominal examination and to determine the
relationship between body mass index (BMI) and ESD of a patient. AP supine and PA prone projections on the same
patients for CR abdominal examination of intravenous urography (IVU) were acquired on 50 patients at Hospital Raja
Permaisuri Bainun, Ipoh. All the radiographic examinations were carried out on a Siemens Multixtop general x-ray unit
and the images were processed with CR Carestream Direct view Max. Entrance surface dose (ESD) in miligray (mGy)
was measured using optical stimulated luminescence dosimeters (OSLD) calibrated by the Malaysian Nuclear Agency.
Data were analyzed using dependent t-test comparing the AP and PA projections on the same subject and Pearson
correlation was used to determine the relationship between BMI and percentage of reduction of ESD. Results showed a
significant different (p < 0.01) between AP supine (mean ESD = 6.42 ± 7.13 mGy) and PA prone (mean ESD = 3.92 ± 3.56
mGy) projection at all BMI. The BMI has a positive correlation with percentage of reduction of ESD (r = 0. 61) and was
statistically significant (p < 0.01). In conclusion, PA abdomen prone projection significantly reduces the radiation dose
and there is a positive correlation between BMI and percentage of reduction of ESD. The use of PA prone projection for
CR abdominal examination should be considered as the routine projection at all BMIs level. Awareness that as the BMI
increases the ESD also increases at a moderate positive linear relationship.