Optimization and deconvolution of lithium fluoride TLD-100 in diagnostic radiology

Extremity Exposure with 99mTc - Labelled Radiopharmaceuticals in Diagnostic Nuclear Medicine

BACKGROUND

Extremity exposures may raise the risk of cancer induction among radiographers involved in the preparation and administration of technetium-99m labelled radiopharmaceuticals.

OBJECTIVE

To estimate finger doses on radiographers at a South African tertiary hospital.

METHODS

Adhesive tape was used to securely fix a calibrated thermoluminescent dosimeter (TLD) on fingertips and bases of ring and index fingers of both hands of five radiographers who prepared and administered technetium-99m labelled radiopharmaceuticals. Rubber gloves were worn to avoid TLD contamination. TLDs doses were read with a Harsaw TLD Reader (Model 3500) after a week.

RESULTS

Five radiographers prepared and administered technitium-99m labelled radiopharmaceuticals (activity range; 78.20 GBq - 132.78 GBq during a one-week measurement period). A radiographer handling 132.78 GBq received 4.74±0.52 mSv on both hands; 5.52, 4.55, 5.11 and 4.60 mSv on the fingertip of the index finger of the dominant hand (FIDH), fingertip of the ring finger of the dominant hand (FRDH), fingertip of the index finger of the non-dominant hand (FINDH) and fingertip of the ring finger of the non-dominant hand (FRNDH), respectively. The respective doses received on the finger bases were 4.50 mSv, 4.60, 4.21 and 3.48 mSv. The radiographer handling 78.20 GBq received 0.85±0.18 mSv on both hands, 1.04, 1.17, 0.77 and 1 mSv for the FIDH, FRDH, FINDH and FRNDH, respectively, while respective doses for the bases were 0.8, 0.9, 0.6 and 0.8 mSv.

CONCLUSION

The extremity exposures were below the annual limit (500 mSv). However, the use of syringe shields could still reduce the finger doses further.

Highlights and pitfalls of 20 years of application of computerised glow curve analysis to thermoluminescence research and dosimetry

The technical and dosimetric aspects of computerised glow curve analysis are described in detail including a review of the current 'state-of-the-achieved' in applications to environmental and personal dosimetry, clinical dosimetry, quality control, characterisation of new materials, continuing characterisation of 'old' materials, heavy charged particle dosimetry, mixed field n-gamma dosimetry, X-ray dosimetry and other aspects of thermoluminescence dosimetry. Fearless emphasis is placed on 'pitfalls' as well as successes.

Radiation doses from some common paediatric X-ray examinations in Sudan

Radiation doses to patients from some common paediatric X-ray examinations were studied in three hospitals in Khartoum state, Sudan. Entrance surface dose (ESD) was determined from exposure settings using DosCal software. Totally, 459 patients were included in this study. Mean ESDs obtained from anteroposterior projection for chest, skull, abdomen and pelvis for neonates falls in the range of 52-100, 115-169, 145-183, 204-242 microGy, respectively. For a 1-y-old infant, mean ESD range was 80-114, 153-202, 204-209, 181-264 microGy, respectively. Some doses for neonates and infants were exceeding the reference doses by >20%. The results highlighted that a good technique has to adhere to guidelines necessarily. As demonstrated elsewhere, patients' doses were high in departments using single-phase generators compared with those using constant potential. The results presented will serve as a baseline data needed for deriving reference doses for paediatric X-ray examinations in Sudan.

Radiation doses to patients undergoing standard radiographic examinations: a comparison between two methods

The objective of the study was to derive a mathematical method for calculating the entrance surface dose (ESD) from exposure factors for all tube potentials used in clinical practice and to compare the calculated ESDs (ESD(C)) with those measured (ESD(TLD)) using thermoluminescent dosemeters (TLDs). The exposure parameters of 43 patients who underwent (a) posteroanterior (PA) and lateral (LAT) chest examination (13 patients), (b) supine abdomen (10 patients), (c) erectus abdomen (10 patients), or (d) urinary tract examination (10 patients) were recorded. Patient ESD was directly measured by TLDs and calculated from exposure factors. The differences between ESD(C) and ESD(TLD) were quite small and could be explained by the uncertainties involved in both methods, in all but the PA chest examination where the ESD(C) was about 50% larger than ESD(TLD). However, in PA chest the ESD(TLD) was close to the minimum detectable dose of TLDs, questioning the accuracy of ESD(TLD). Further investigation showed that using the high tube potential technique (130 kV) in the PA chest examination resulted in very short exposure times, in the region of 4 ms. In such short exposure times, the X-ray generator operation presented stability problems that led to loss of output linearity and consequently to false calculation of ESD. The calculation method offers a reliable and cheap alternative to the measurement of ESD by TLD, provided that the exposure times are not as short as in the PA chest examinations recorded in this study, so that the output linearity with tube current-time product (mAs) is maintained.

Dose reduction in a paediatric X-ray department following optimization of radiographic technique

A survey of radiation doses to children from diagnostic radiography has been carried out in a dedicated paediatric X-ray room. Entrance surface dose (ESD) and dose-area product (DAP) per radiograph were simultaneously measured with thermoluminescent dosemeters (TLDs) and a DAP meter to provide mean dose values for separate age ranges. Results of ESD and DAP were lower than the mean values from other UK studies for all ages and radiographs, except for the infant pelvis AP radiograph. Comparison of ESD and radiographic technique with CEC quality criteria highlighted a need for reduction of dose to infants and implied an increase in tube filtration might overcome the limitations of the room's three-phase, 12-pulse generator, allowing higher tube potentials to be used on infants. Additional tube filtration of 3 mmA1 was installed following assessment of dose reduction and image quality with test objects and phantoms, and confirmation from the paediatric radiologist that clinical image quality was not-significantly altered. The tube potential was increased from 50 to 56 kVp for the infant pelvis AP radiograph. The resulting ESD and effective dose fell by 51% and 38%, respectively. The CEC quality criteria have proved useful as a benchmark against which technique in X-ray departments can be compared, and as such are a useful tool for optimizing radiographic technique and reducing patient dose.