This is an experimental study conducted at University of Sharjah, Medical Imaging Laboratory between January-February 2018. For the objective of this investigation institutional ethics committee approval was not required. The experiment was performed using Philips X-ray unit with total filtration 2.5 mm Aluminum equivalent. X-ray unit was calibrated, and quality assurance measures were performed on regular basis as well as before the experiment according to IPEM 91 report, and the results fell within an acceptable range [11]. The images obtained using digital radiography system by Agfa HealthCare Instant DR solution, which includes the NX image acquisition software with MUSICA processing and detector.

The experiment included radiographic examinations of three body parts (hand, wrist and elbow). An adult phantom was used to simulate the patient position and orientation during hand, wrist and elbow radiographic procedure. The radiographic technique, positioning, centring point, collimation, exposure parameter, SID, set according to Merrill’s Atlas of Radiographic Positioning and Procedures [12]. Exposure parameters were peak tube potential 60 kVp, mAs were set at 2, 2.5 and 3.2 for hand, wrist and elbow accordingly, 100 cm SID, no tube angulation, no grid and fine focal spot. FOV was adjusted in order to include the desired region of interest.

Thermo Luminescence Dosimetry (TLD) is an essential tool in clinical, personal and environmental monitoring of Ionising radiation. The TLD-100 card was of Harshaw™ design, (LiF: Mg, Ti) used to obtain radiation dose to the eye and gonads. The Lithium Fluoride (LiF) is near tissue equivalent, provide excellent energy response and not sensitive to light, it is suitable for research and clinical with linear range 10 mGy-1Gy. The TLD dosimeter processed using Harshaw TLD card reader Model 6600 plus, it is able to measure photon energy >5 keV, Neutrons from thermal to fast, Beta, energy >70 keV [13].

Two patient orientations were simulated: (i) standard sitting position; where the gonad and eye were positioned away from the radiation beam direction and the leg beside the table [Table/Fig-1a]; and (ii) modified sitting position whereas patient facing the radiation beam and leg positioned under the table [Table/Fig-1b]. TLD’s were placed at the eye level and gonad area. Twenty radiographic examinations were performed for each body part including standard and modified positions. Following the exposure, the ESD, effective dose was calculated from TLD’s readings and average ESD and average effective dose were used for LAR estimation.

[Table/Fig-1]:

a) Standard patient orientation; b) Modified patient orientation.

BEIRVII report was used to estimate the LAR of cancer due to radiation dose [14,15]. The report is based on a 100 mSv equivalent dose for different age, sex, and organ. For the phantom used in the study, linear interpolation was performed from the nearest two ages (30 and 40). The LAR calculation based on the dose received by the patient and measured by the TLD. For example, using BEIR VII model the LAR to calculate prostatic cancer for a male 35-year-old who received 100 mSv is 35 cases per 100,000. Therefore, the LAR from 6.5 mSv received during modified upper limbs patient orientation is (6.5/100)×(35/100,000)=0.0023%. The whole body LAR was estimated by summing organ-specific LARs. The using of BEIR VII methods employed in this study were used before in a similar study [16].

Statistical packages for the Social Sciences software (SPSS, version 23.0, by the SPSS, USA) used for data analysis. A t-test was used to compare different data obtained for each pair orientations. The differences were statically significant, if p-value was <0.05.

Radiographic exposure was performed for the phantom simulating the two patient orientation. A total of 20 exposures for each projection performed followed by the collection of ESK, ED and LAR calculation. Kolmogorov-Smirnov Test of normality was conducted to examine if the data to be tested had a normal distribution. The test of normality between patient position and radiation dose resulted in a normal distribution (p>0.05). The main difference between the two positions (standard-position and modified position) ED, ESD for the eye and testes is tested using two-way ANOVA, mean and Standard Deviation (SD). Results indicate that there were difference between the radiation dose received by the eyes and gonads in different patient orientation. [Table/Fig-2] showed the comparisons of effective doses (mSv), ESD of the eye and tests for each patient orientation. The ESK reduced by 12% and 50% and the ED dose reduce by 50% for the eyes and gonads respectively. Results showed significant ESD, effective dose, and LAR reduction when the patient was sitting beside the table and not facing the radiation beam [Table/Fig-3].

The results of this study highlighted the importance of applying the proper patient positions during radiographic examination examinations of upper limbs to reduce the stochastic harm of Ionising radiation. Diagnostic imaging modalities will keep on giving considerable advantages to modern healthcare. In spite of the fact that the benefit the patient receives from an adequately conducted radiological exam outweighs the risks, quantification of such risks is vital. Consideration should be made to reduce the entrance surface dose to the sensitive organs during upper limbs projection. Patient doses can be reduced significantly by the use of common ALARA principle, which includes most proper distance from the source of radiation and application of protective lead shielding as well as applying the appropriate patient positioning, exposure factor, and SID. In this study, the ESD, effective dose, LAR for cancer risk was estimated for an adult 32 years who underwent upper limbs radiography. The main reason for conducting this study is to ensure appropriate positions are adopted during medical imaging procedures. It is noticed that in some practices, the patient orientation facing the radiation beam and legs positioned under the table during exposure, such methods increase the radiation harm to the patients from Ionising radiation. The ESD at the level of the eyes and testes were measured in both orientations for comparison of the radiation effects in different projections. Many studies were conducted on other radiographic projection such as the lumbar spine, abdomen, pelvis, and clavicle had been done to compare between the effect of different patient orientation and projection on the amount of radiation dose the patient receives [17,18].

The [Table/Fig-2] shows a reduction of the effective dose 49% (P<0.001) when the patient does not face the radiation beam as well as reduction of the ESD to the eye and testes by 12% and 49% respectively. This reduction associated with the decrease in the LAR risk by 50.7%. Measuring the dose received by the testes can be used to estimate the genetic risk arising from radiation for men and women in reproductive age and this fact has also been confirmed in the recent report of ICRP (ICRP 121). The LAR for the prostate cancer in this study reduced by 48%. The current study demonstrated consistent significant dose-reductions to the thyroid and gonads when patients are seated either on the right or left side of the table rather than placing the lower limb under the table.

Although the modified projection is used during radiography practice, it is not possible to apply the same experiments on real patients. The experimental context of the study provide a simulated situation that uses an average patient but it may not fully represent the real-life circumstances as other factors such as patient size, weight and height might affect the patient radiation dose.

Although the recommended projection is based on patient’s co-operation, conditions, and anatomical part, it is critical to ensure image quality and radiation dose. In some other body parts and projections, there were no significant differences in image quality, i.e., the image quality dose not degraded or improved in the chosen projection. The orientation and projection of the radiation beam do not affect the patient comfort because the patient responses will not change whether the patient is facing or sitting beside the table. This study confirmed the relation between dose reduction and patient orientation and it aligns with the ALARA principle to apply all efforts to minimise unnecessary radiation exposure.