Since, the discovery of X-rays by Conrad Roentgen in 1895, it has been that the largest contribution to the total risk of population due to man-made sources of radiation is from medical use of X-Rays (Bennet, 1992). On average per cap put contribution of diagnostic radiology to annual effect dose is around 0.4 mSv. The percentage contribution may vary from country to country (Beentyes, 1991). Among the man made radiation sources in India. Diagnostic X-ray is the main contributor to population exposures around 0.02mSv. Hence the radiation doses received by the patients and reduction of the doses without significant loss of image quality have become an important issue in the recent years. This is an important means to maximize the benefits of radiation and at the same time reduce the risks associated with it.

As early 1980 variations in radiation doses were notices in patients undergoing diagnostic examinations involving X-rays (Shirmpton and Wall, 1986, Calazdo, 1991). Several workers have evaluated patient doses from diagnostic exposures (ICRP 60, NRPB R – 289, Papageorgiou, 2001). In India, during the past several years patient dose measurement has been carried out using TLD( Supe 1992, Sasane 1997, Arun Chougule 1992, Rama Krishnan 2000).
The statistics from different countries indicate that the abdominal radiograph examinations are carried out commonly and frequently among the public (UNSCAR – 1993). Frequency of different types of X-ray examination in India abdominal radiography involves around 20% (Iyer-1995). During the radiological examination of the abdominal region (abdomen, KUB, LS) radiosensitive organs may be exposed to radiations. An abdominal examination constitutes a fairly large percentage of radiographs advised by physician. Even though are benefited by clinical procedure, knowledge of radiation doses received by the patients during the radiological examination is necessary. Dose to individual patients is influenced by several factors such as body size, constitution, performance of equipment used, training of personnel and method of examination. During this study, an attempt was made to measure the entrance skin dose during abdominal radiology examination using the indigenously developed, tissue equivalent, high sensitive TL material.

Material & Method
Indigenously prepared, high sensitive, almost energy independent, tissue equivalent LIF: Mg, Cu, P (Lithium Fluoride: Magnesium Copper Phosphor) was used to estimate the entrance skin dose (ESD). About 50 mg TLD phosphor was sealed in 1x1 cm2 polyethylene pouch. This pouch was attached to the patient’s body in the center of the field during their abdominal region X-ray examinations. As the pouches are very thin, they do not cast any shadow on the radiograph. Exposed TLDs were read in the indigenously developed TLD reader with EHT-1000 volts, and heating rate of 100 c having EMI 9524B Photo multiplier tube, which has its maximum response at 400 nm. An infrared (IR) filter was used to reduce the IR contribution. Calibration of TLD powder was done against UNFORS(Unfors Instruments AB Sweden) dose-measuring system
Patients Selection:
Patient who under went radiological examination of abdominal radiography randomly selected with age group of patients varying from 23 years to 53 years for males and 16 years to 46 years for females. Patient thickness ranged between 13cm to 23 cm in both male and female patients. Focus to film distance for all projection was at 90 cm. Exposure parameters for abdominal region radiography during AP view kV ranges from 55 to 63 and mAs ranges from 80 to100. For lateral view ; kV ranges from 66 to 77 and mAs ranges from to125-200.
Machine used in this study.
The study was performed using 3 phase multiples, polymate 50 I Siemenes unit with 640mA.The machine has an over couch tube with total filtration of 2.5mm aluminum. The size of the focal spot was 0.8mm for fine focus and 1mm for broad focus .In small focus and large focus unit works up to 40 to 125 kV. The machine has an image intensifier set up. The consistency and linearity in the tube out put were checked and verified for various exposure settings. The cassettes with calcium tungsstate screen with 200 ultra speed (kiran X-Ray, Mumbai, India) were used for capturing images.

RESULTS & DISCUSSION
Entrance skin dose were estimated for total 30 patients during abdominal radiography. (Abdomen, Lumbar spine AP, and lateral, pelvis).The measured entrance skin dose during the abdominal radiography ranged from 2.76 mSv to 22.74 mSv. The Results are shown in table1. The studies of entrance skin dose reveled that maximum doses were measured from lumber spine lateral view radiography examination.


CONCLUSIONS:
The entrance skin dose during the abdominal region radiography ranges from 2.76 mSv to 22.74 mSv. LIF: Mg, Cu, P TL phosphor is one of the suitable TL material for entrance skin dose measurements. This studies shows that maximum entrance skin dose is during Lumbar spine radiography. This data can be used for estimation organ dos e as risk associated due abdominal region radiography.

REFERENCE:

1. Arun chougule, Rahul, K., Gupta, Gopi Ram Agarwal. Evolution of radiation doses to patient organs during radiography of the abdomen. Ind. J.Radiol 2, 139-142(1992)
2. Arun chougule, Rahul K., Gupta, Gopi Ram Agarwal. Measurement of patient skin exposure by thermoluminescences dosimetry during some radiological examinations. Ind.J.Radiol.Imag 2, 193-195, (1992)
3. Beentyes, L.B.,Timmermanc, C.W.M. Patient dose in Netherland, Rad. Prot. Dosim. 36, 265-268(1991)
4. Bennett, B. G. Exposure from medical radiation worldwide, Rad. Prot. Dosim. 43, 25-29(1992)
5. Calzado, A., et al, Estimation of dose to patients from complex conventional x-ray examinations, Brit.j.Radiol.64, 539-546 (1991)
6. ICRP, Recommendations of International commission of Radiological protection; publication 60, Ann.ICRP 21(1-30) (Pergamon, Oxford;) (1991)
7. Iyer, P.S., Sasane, J.B., Pradhan, A.S., Medical radiation exposure from Diagnostic X-ray procedures in India. Ind. J. Radiol. Imag 5:4 219-223 (1995)
8. NRPB Doses to patients from Medical x-ray examination in the UK -1995 Review; NRPB-R-289 (London Hmso) ( 1996)