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Biomedical subjects

E J van der Merwe

Publications and source records attributed to E J van der Merwe.

15 recordsLinked to original sources
PubMed1992

Exposure of surgeons-in-training to radiation during intramedullary fixation of femoral shaft fractures.

Owing to the continuous turnover of registrars and radiographers, most of the trauma-related orthopaedic surgery in this academic hospital is done by inexperienced surgeons-in-training and the fluoroscopy by junior radiographers. This could result in excessive radiation doses. Calibrated lithium fluoride thermoluminescent chips were secured to various parts of the primary surgeon's body to quantify the radiation dose received during the insertion of an intramedullary nail. Closed intramedullary fixation of 15 fractures of the femur was done with interlocking as necessary. The total average exposure time was 14 minutes 45 seconds per procedure. Distal locking took up 31% of this time. The mean radiation dose to the surgeon's eyes and thyroid was 0.13 mGy and to the dominant hand 2.10 mGy. This would allow the performance of about 350 such procedures per year before the maximum permissible dose level was reached. Recommendations to decrease irradiation dosage are made.

Femoral Fractures↗
PubMed1991

The leaded apron revisited: does it reduce gonadal radiation dose in dental radiology?

A tissue-equivalent anthropomorphic human phantom was used with a lithium fluoride thermoluminescent dosimetry system to evaluate the radiation absorbed dose to the ovarian and testicular region during dental radiologic procedures. Measurements were made with and without personal lead shielding devices consisting of thyroid collar and apron of 0.25 mm lead thickness equivalence. The radiation absorbed dose with or without lead shielding did not differ significantly from control dosimeters in vertex occlusal and periapical views (p greater than 0.05). Personal lead shielding devices did reduce gonadal dose in the case of accidental exposure (p less than 0.05). A leaded apron of 0.25 mm lead thickness equivalent was permeable to radiation in direct exposure testing.

Gonads↗
PubMed1987

The relative biological effectiveness of 100 kV X-rays determined by the V-79 cell colony assay.

The relative biological effectiveness (RBE) of 100 kV X-rays compared with cobalt-60-gamma-irradiation was determined using a cell colony assay based on the survival of Chinese hamster V-79 lung fibroblasts. The 37% dose (Do) was found to range from 1.12 to 1.47 and from 1.33 to 1.63 Gy for X-rays and 60Co-gamma-irradiation respectively. The mean RBE value calculated from the Do values was found to be 1.13 +/- 0.04. This figure compares favourably with RBE values calculated from Do values using other endpoints.

Animals↗
PubMed1980

[A comparative study of 2 capacitor discharge X-ray units].

Two capacitor discharge X-ray units of different make were compared. The same radiological examinations were carried out with both units and the radiation exposure for every examination was measured on a Rando phantom with calibrated LiF-TLD Teflon discs. A large difference in radiation exposure for the same image quality was found between the two units. Factors such as the use of rare earth intensifying screens with capacitor discharge X-ray units, independent tube current settings and automatic charge replenishment are stressed.

Radiation Dosage↗
PubMed1980

[The frequency of repeat radiograpy].

A study of the rates of repeat radiography in two hospitals in the Cape Peninsula was undertaken. The relationship between these rates and the type of examination as well as the contributing factors was established. The total frequencies for the two hospitals varied from 10,1% to 14%. The predominant reasons for 78% of repeat radiographs were over-exposure, under-exposure and positioning.

Hospitals↗
PubMed1977

[Effective energy values of 90 degree scattered photons during urological and bronchial fluoroscopy].

During fluoroscopic bladder and bronchial examinations the radiation workers concerned are exposed to 90 degrees--scattered photons. The effective energy expressed in mm AI was measured for these photons exited at tube potentials in the 60--100 kV RANGE. An increase also depends on whether the measurements are made in the direction of the long axis or the short axis of the phantom. These findings are contrary to the recommendations stipulated in the code of practice SABS 07-1972.

Bronchography↗