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Year : 2001  |  Volume : 11  |  Issue : 4  |  Page : 181-184
Radiation doses to patients from X-ray examinations involving fluoroscopy


Directorate of Radiation Safety Medical College, Kozhikode-673008, India

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   Abstract 

Objectives : X-rays used in medical diagnosis contribute a major share to population doses from man-made sources of radiation. This paper attempts to measure the patient and organ doses in patients undergoing some special procedures involving fluoroscopy.Materials and Methods : Radiation doses received by 93 patients undergoing five special procedures (Barium Swallow, Barium Meal, Barium Enema, IVP and myelograms) were measured with CaSO4-Dy thermo luminescent dosimeters following standard TLD Procedures. Doses to critical organs like ovary, testes and thyroid were estimated by applying suitable correction factors. Result : The study revealed a maximum surface dose 75.92 mSv for barium meal study. The ovary doses were significant for Barium meal enema, and myelograms. Conclusion : The dose levels as measured by this study were significant but not alarming. Attempts could be made to lower the doses received during these procedures.

Keywords: Radiography, fluoroscopy, Image intensifier

How to cite this article:
Ramakrishnan G, Padmanabhan V. Radiation doses to patients from X-ray examinations involving fluoroscopy. Indian J Radiol Imaging 2001;11:181-4

How to cite this URL:
Ramakrishnan G, Padmanabhan V. Radiation doses to patients from X-ray examinations involving fluoroscopy. Indian J Radiol Imaging [serial online] 2001 [cited 2014 Sep 17];11:181-4. Available from: http://www.ijri.org/text.asp?2001/11/4/181/28398

   Introduction Top


The collective effective dose to a population, among man made sources of radiation, is due to a large number of medical x-ray examinations performed [1] . It is also evident that 25% of the effective collective doses is from barium studies despite its low frequency [1] . These investigations are different from simple diagnostic investigations as they involve a shift in technique and procedures. Wide difference exists between radiographic and fluoroscopic parameters among radiologists performing these procedures [2] . Many attempts have been made in the past to measure the patient doses during special procedures using dose area product and Monte Carlo techniques [3],[4],[5],[6],[7] . The impact of digital imaging on patient dose was studied [8],[9] . A specific dose calculation related to particular investigations has also been attempted. These include reduction of doses in Micturating Cysto Urethrography (MCU) in pediatric radiography [10] , and reduction of patient doses through equipment set up [11], [12], [13], [14] . Thermoluminescent Dosimetry methods were used for patients dose evaluation in fluoroscopy procedure [15],[16] .

The equipment used for special procedures in our country is mainly conventional fluoroscopy or image intensifiers which display and record data analogously. These have strict exposure requirements and because of narrow latitudes offer very little possibility of image processing. More over no clear dosage patterns are available from our country as very little attempts have been made in measuring dose values in these procedures.

In this study, an attempt has been made to measure dose values and dose levels in five special procedures (IVP, Myelogram, Barium Swallow, Meal and Enema).


   Materials and Methods Top


The radiation doses received by patients undergoing Barium Swallow, meal, enema, IVP and myelograms (Lumbo sacral) were included. Ninety-three patients who attended these investigations in three X-ray rooms were randomly selected from all age groups and both sexes. Critically ill patients were excluded. Of the three rooms one had an image intensifier (Fisher 1000 mA) and other two had conventional fluoroscopy attachment. Both were Wipro GE of 500mA and 700 mA capacity.


   Measurement Procedure Top


The three machines were subjected to Quality Control tests by the kit supplied by BARC. The tabletop exposures measured were within limits. All the requirements for quality control were satisfied in these units.


   Thermo Luminescents Dosimetry Calibration Top


Among the TLD dosimeters CaSO4- Dy have found to exhibit very high sensitivity in the diagnostic range and their response have been found to be with in 8-11% as against 8-10% reports in literature [17] .

These dosimeters were annealed at 300° C for two hours prior to dose measurements and cooled to room temperature. They were batch selected by exposing to 10 mSv and grouped into different batches of + 5%, numbered and put into polythene covers. A Calibrated pocket dosimeter and ion chamber was used for calibration measurements also.

During the radiographic procedure the numbered TLD disc were kept in the required position and secured in place with cello tapes. When the radiographic procedure was over they were retrieved and measurement of TL Response was done after 24 hours.

Two number of disc were kept for calibration and calibration factor was obtained by exposing it to know quantity of X-radiation measured with pocket dosimeter.



The exposure was then converted into mSv using a factor 0.922 and radiation-weighting factor of I. Necessary correction for background and due to light irradiation was done with set of measurements.

Patient Dosimetry

Dose measurements were anatomically oriented to suit a particular investigation. Both anterior and posterior points were selected. Different calibration factors were assigned for posterior points [18],[19] . The mid line of the patient at the level of umbilicus was used as reference points for ovary dose measurements. The sinus process in the third vertebra was selected as a representative points for measurements of entrance exposure [20] . The thyroid and testes doses were assessed by directly keeping TLDs in the organ sites. The radiographic factors such as KVp, mAs, screening time, screening mA and screening KVp were noted in each patient. Thirty TLD's were used per investigation.

The estimation of organ doses during special procedure involving screening is complex. The variation of beam size and areas vary from patients to patient. Additional TLDs were used in situations when it is needed. Organ doses were estimated from the patient skin doses with correction factors for X-ray spectral variations and inverse square variations [5] . In the case of IVP and myelograms only anterior dose values were required. The distance of ovary was assumed to be 10cm away from anterior side and mid way between points. In the cases of thyroid and testes, a depth of 2cms was assumed.


   Results Top


[Table - 1] give the detail of patients included in the study. The average radiographic and screening parameters are also given in the same table. Out of 93 patients in the study, 39 were men and 54 women. Most of the patients were in the age group 15-50 years. The radiographic factors varied considerably between investigations and between patients. The variations were in the range of 70-100 for radiographic KVp, 30-60 for mAs, 70-100 for screening KVp and 1-3 for mA. The screening time ranged between 10 and 50 seconds. There were variations in the number of films taken three to eight. All these investigations were performed by specialist radiologists who had sufficient experience in this field.

Patients doses measured in mSv are presented in [Table - 2]. The data is presented for both conventional and image intensified fluoroscopy. In each of the above, mean doses, median doses, range and standard deviations were recorded. The dose values show a maximum mean dose of 75.92 mSv for barium meal when conventional fluoroscopy was used. For the same investigation when Image intensifier was used the dose measured was only 12.41 mSv. Similar variations do occur in the case of other barium studies. This yielded a dose reduction of 12% for barium swallow, 16% for barium meal and 28% in the case of barium enema. In case of myelograms, the dose values are 73.79 and this study was done only with the convention techniques. The mean doses in the case of IVP were 30.07 mSv and this dose does not involve fluoroscopy.

The measured organ doses are given in [Table - 3]. Ovary doses were estimated for barium meal, barium enema, myelogram and IVP. The thyroid doses were estimated during barium swallow. The ovary dose was lowest for IVP (926.73mSv) and maximum for barium meal (64.82 mSv). The testes doses was maximum for barium enema (25.28 mSv) and minimum for IVP (2.40 mSv0. The thyroid doses during Barium swallow measured 6.13 mSv.


   Discussion Top


The measurement of organ doses or computing the same with sufficient accuracy is a difficult job. The uncertainties in the dose-meters and variations in the exposure factors contribute very much. The largest organ dose is measured when the organ is in the field of view i.e. in the primary beam. In these conditions, the organ dose computed will be accurate. When the organ is outside the primary, the question of accuracy will be doubtful. This is because of uncertainties in the low dose measurements. Because of the sensitivity of CaSO4 dosimeters for low doses the results are more reliable. The difficulties when the organ doses are computed for special procedure lies in the orientation of the beam.

The measured values of skin doses were significant in these investigations. The dose values should be viewed in the light of exposure factors used by experienced radiologists. The ovary dose values obtained by our study was significant in the case of barium meal and enema but not significant for myelograms and IVP. The thyroid doses were not significant and comparable with C spine or lateral chest investigations.

Comparison of doses received during our study and other studies of similar nature are given in [Table 4]. The doses were compared with those done by Podvani R and Langemead WA [15],[16] . The dose comparisons were difficult as the skin doses and organ doses vary much depending on the techniques practiced by different radiologists. The individual screening mA, screening time and number of spot films vary from patient to patient. The correlation becomes difficult. The surface doses were less when compared with other studies but the ovary doses and testes doses were higher than other studies.

As in the case of routine investigations shielding of gonads were not practiced in the investigations. The testes doses could be brought down significantly if shielding of the gonads were used. The modern high frequency multi pulse high frequency units also give a lower dose to patients [21] . In this study, no attempts were made to standardize the techniques and doses were measured as they are practiced.


   Conclusions Top


The study on patient and organ dose measurements with reference to five selected common investigations revealed the following. Fluoroscopy was not used in IVP studies, and limited fluoroscopy was used in myelograms. In the case of intra venous pyelography IVP a mean dose of 30.07 mSv was measured. The ovary dose was 26.73 mSv and testes dose 2.40 mSv. In the case of myelograms, the dose values were 73.79 mSv for skin surface, 58.03 mSv fokr ovary and 4.43 mSv for testes.

In the case of barium swallow the maximum dose to skin was 61.60 mSv when conventional fluoroscopy was used. A reduction of 12% was achieved when image intensifier was used. Similar reduction was obtained in the case of other barium studies also - 75.92 to 12.41 (61%) in the case of barium meal and 63.62 to 18.13 mSv (28%) in the case of barium enema. The ovary doses for barium meal were 64.82mSv and barium enema 49.58 mSv. The testes dose values for the same investigations were 22.59 mSv and 25.28 mSv. For barium swallow the thyroid doses recorded were only 6.31 mSv.

The study revealed that testes and ovary doses were higher than the other studies and skin doses were lower. The doses measured by this study were not alarming but significant.

 
   References Top

1.Hughes JS, O'riordan MC, Radiation doses to UK population. Review (National Radiation Project Board Report No R 263) London:HMSO, 1993.   Back to cited text no. 1    
2.Rowley KA, Hill SF, Watkins RA, Moores RM, An investigation into levels of exposure in diagnostic investigations involving fluoroscopy, Br J Radiol . 1987; 60:167-173.   Back to cited text no. 2    
3.Drxler G, Williams G, Zankl M, The meaning and principle of deterministic effective dose equivalent protection. Rad. Pro. Dosim. 1985; 12:95-100.   Back to cited text no. 3    
4.Jones DG, Wall BF, Organ doses from Medical X-ray examinations using Monte carlo techniques. NPRB Report. NPRB D-186-1985.   Back to cited text no. 4    
5.Rosentien M. Hand book of selected tissue dose projection common in diagnostic radiology, HHS Publication (FDA) US Department of Health, 1998.   Back to cited text no. 5    
6.Shrimpton PC, Wall BF, Jones DG, Fisher ES, The measurement of X-ray energies imparted to patients during diagnostic X-ray examination using diameter exposure area product meter. Phy. Med. Bio 1984; 29:1999-1208   Back to cited text no. 6    
7.Calzado A, Vano E, Morgan P, Castle Ruiz S et al, Estimation of doses to patient from complex conventional X-ray examinations. Br J Radiol 1991;64: 539-546.  Back to cited text no. 7    
8.Broadhead A, Chaple, CL, Faulkner K, The impact of digital imaging in patients does during barium studies. Br J Radiol 1995; 68:992-996.   Back to cited text no. 8    
9.Waren Forward HM, Haddway MJ, Temperton DH, Mc Call. Dose area product for fluoroscopy and plain film examinations including an analysis of source of variations for barium enema examinations, Br J Radiol 1998; 71:961-967   Back to cited text no. 9    
10.Gonzale L Vano E, Ruitz MJ, Radiation doses to paediatric patients undergoing Micturating Cystourethography examinations and potential reduction protection optimisation Br J Radiol 1995; 68:291-295.   Back to cited text no. 10    
11.Martin CJ, Hunter S, Reduction of patient doses from barium meal and barium enema through changes in equipment factors Br J Radiol 1994; 67:1196-1205.   Back to cited text no. 11    
12.Rudin S, Breadnarek DR, Minimising Radiation dose to patient and staff doing fluoroscopic nasoenterial tube insertions Br J Radiol 1992; 65:162-166.  Back to cited text no. 12    
13.Seymour R, Patient dose reduction by audit of grid usage in barium enema Br J Radiol 1997; 70:489-491.   Back to cited text no. 13    
14.Simddy PF, Quinn AD, Freyne BJ, Marsh D, Murphy M. Dose reduction in double contrast Barium enema by the usage of low fluoroscopy currents Br J Radiol 1996; 69:852-854   Back to cited text no. 14    
15.Podvani R, Contento G. Patient doses and risks from diagnostic radiology in North East Italy. Br J Radiol 1987; 60:155-165.  Back to cited text no. 15    
16.Langemead KA, Wall BF. An assessment of lithium borate thermoluminescent dosemeters for patient dose measurements in diagnostic radiology Br J Radiol 1977; 49:956-962.  Back to cited text no. 16    
17.Pradhan AS, Suani JB, Gopalkirishnan AK, Shirva PK, Iyer PS. TLD method for evaluation of radiation quality and measurement of entrance skin dose from diagnostic radiology Rad. Pro. Dosim 1992; 40:49-52.   Back to cited text no. 17    
18.Pradhan AS, Shirva PK, Dash Sharma PK, Jayalekshmi V, Iyer PS, Response of CaSO4-Dy TLD discs to diagnostic X-rays for entrance and exit beams in phantom Dosimetry. Bull. Rad. Pro. 1993; 16:67-69   Back to cited text no. 18    
19.Pradhan AS, Shirva PK, Dash Sharma PK, Jayalekshmi V, Iyer PS. Response of CaSO4-Dy TLD discs to diagnostic X-rays for entrance and exit beam dosimetry Rad. Pro. Dosim. 1993; 48:359-362.  Back to cited text no. 19    
20.Faulkner K, Brenett G, Radiation doses received by patients from barium meal examinations Br J Radiol. 1985; 58:31-34.  Back to cited text no. 20    
21.Morison GD, Underwood AC, Entrance doses during lateral lumbar spine and antero posterior abdomen examinations generator waver from dependence Br J Radiol 1995; 68:491-494.  Back to cited text no. 21    

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Correspondence Address:
G Ramakrishnan
Division of Radiation Physics, Ragional Cancer Centre, Medical College, Thrivantapuram
India
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    Tables

[Table - 1], [Table - 2], [Table - 3]

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