Entrance Dose Measurements on Patients and Their Relation to Organ Doses

Purpose Exposure to ionizing radiation is a concern for children during intraoperative imaging. We aimed to assess the radiation exposure to the paediatric patient with 2D and 3D imaging. Methods To evaluate the radiation exposure, patient absorbed doses to the organs were measured in an anthropomorphic phantom representing a five-year-old child, using thermoluminescent dosimeters. For comparative purposes, organ doses were measured using a C-arm for one minute of fluoroscopy and one acquisition with an O-arm. The cone-beam was centred on the pelvis. Direct and scattered irradiations were measured and compared (Student’s t-test). Skin entrance dose rates were also evaluated. Results All radiation doses were expressed in µGy. Direct radiation doses of pelvic organs were between 631.22 and 1691.87 for the O-arm and between 214.08 and 737.51 for the C-arm, and were not significant (p = 0.07). Close scattered radiation on abdominal organs were between 25.11 and 114.85 for the O-arm and between 8.03 and 55.34 for the C-arm, and were not significant (p = 0.07). Far scattered radiation doses on thorax, neck and head varied from 0.86 to 6.42 for the O-arm and from 0.04 to 3.08 for the C-arm, and were significant (p = 0.02). The dose rate at the skin entrance was 328.58 µGy.s−1 for the O-arm and 1.90 with the C-arm. Conclusion During imaging of the pelvis, absorbed doses for a 3D O-arm acquisition were higher than with one minute fluoroscopy with the C-arm. Further clinical studies comparing effective doses are needed to assess ionizing risks of the intraoperative imaging systems in children.

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Systematic in vivo dosimetry for quality assurance using diodes 2: Assessing radiotherapy techniques and developing an appropriate action protocol

Journal of Radiotherapy in Practice ◽

10.1017/s1460396905000208 ◽

2004 ◽

Vol 4 (4) ◽

pp. 143-154 ◽

Cited By ~ 5

Author(s):

R. Appleyard ◽

K. Ball ◽

F. E. Hughes ◽

W. Kilby ◽

R. Nicholls ◽

...

Keyword(s):

Head And Neck ◽

In Vivo Dosimetry ◽

Entrance Dose ◽

Treatment Category ◽

P Type ◽

Dose Measurements ◽

Action Levels

Purpose: Having previously reviewed the implementation of systematic in vivo dosimetry at the Norfolk and Norwich Hospital this paper examines the results of entrance dose measurements for specific sites/techniques and determines whether different action/alert protocols are required for these different categories.Methods and materials: Entrance dose measurements using p-type diodes were analysed for the following treatment categories: Breast, head and neck in beam direction shell, abdomino-pelvic and intrathoracic. A 4% tolerance was applied.Results: Mean deviations from expected dose and proportion of measurements exceeding tolerance were: Breast: +1.15%±3.04% (1SD), 238/1073≥4%; Head and neck: +0.35%±2.20% (1SD), 21/326≥4%; Abdomino-pelvic: +0.52%±2.75% (1SD), 93/712≥4%; Intrathoracic: −0.01%±2.75% (1SD), 22/119≥4%. Significant improvements in results for breast patients were noted following the introduction of a commercial breast board. The results for abdomino-pelvic patients confirmed a substantial variation in diode response under short FSD, wedged fields at 16MV (that had not been corrected for). The statistical uncertainty in dose measurement for each treatment category was calculated in order to assist determination of appropriate tolerance levels.Conclusions: A blanket tolerance of 4% was generally too low given the extent of measurement uncertainty. The relatively high number of readings outside tolerance where identification of errors was difficult/impossible resulted in inconsistent application of the action protocol. Some widening of tolerances is likely to improve quality of procedure and treatment. Appropriate action levels are recommended for each treatment category.

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HOW MANY DOSEMETERS ARE NEEDED FOR CORRECT MEAN ORGAN DOSE ASSESSMENT WHEN PERFOMING PHANTOM DOSIMETRY? A PHANTOM STUDY EVALUATING LIVER ORGAN DOSE AND INVESTIGATING TLD NUMBERS AND WAYS OF DOSEMETER PLACEMENT

Radiation Protection Dosimetry ◽

10.1093/rpd/ncaa062 ◽

2020 ◽

Vol 189 (4) ◽

pp. 475-488

Author(s):

Peter H Pedersen ◽

Asger G Petersen ◽

Svend E Ostgaard ◽

Torben Tvedebrink ◽

Søren P Eiskjær

Keyword(s):

Statistical Difference ◽

Handling Time ◽

Statistical Modelling ◽

Organ Dose ◽

Dose Assessment ◽

Organ Doses ◽

X Ray ◽

Linear Effect ◽

Organ Specific ◽

Dose Measurements

Abstract This study evaluated repeated mean organ dose measurements of the liver by phantom dosimetry and statistical modelling in order to find a way to reduce the number of dosemeters needed for precise organ dose measurements. Thermoluminescent dosemeters were used in an adult female phantom exposed to a biplanar x-ray source at three different axial phantom rotations. Generalised mixed linear effect modelling was used for statistical analysis. A subgroup of five to six organ-specific locations out of 28 yielded mean liver organ doses within 95% confidence intervals of measurements based on all 28 liver-specific dosemeter locations. No statistical difference of mean liver dose was observed with rotation of the phantom either 10° clockwise or counter-clockwise as opposed to the coronal plane. Phantom dosimetry handling time during organ dose measurements can be markedly reduced, in this case the liver, by 79% (22/28), while still providing precise mean organ dose measurements.

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Correction factors in in-vivo dosimetry. With reference to entrance dose measurements

Radiotherapy and Oncology ◽

10.1016/0167-8140(96)80505-6 ◽

1995 ◽

Vol 37 ◽

pp. S19 ◽

Cited By ~ 2

Author(s):

Rikner Göran ◽

Grusell Erik

Keyword(s):

In Vivo Dosimetry ◽

Correction Factors ◽

Entrance Dose ◽

Dose Measurements

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327 poster Reduction of the influence of electron contamination on correction factors for entrance dose measurements with diodes in pelvic treatments

Radiotherapy and Oncology ◽

10.1016/s0167-8140(01)80970-1 ◽

2001 ◽

Vol 61 ◽

pp. S104

Keyword(s):

Correction Factors ◽

Entrance Dose ◽

Dose Measurements

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Amber Chest Radiography and Patient Dose Measurements

Acta Radiologica ◽

10.1177/028418519503600466 ◽

1995 ◽

Vol 36 (4-6) ◽

pp. 641-643

Author(s):

J. Persliden ◽

S.-G. Fransson

Keyword(s):

Radiation Dose ◽

Chest Radiography ◽

Patient Dose ◽

Chest Imaging ◽

Entrance Dose ◽

Thermoluminescence Dosimetry ◽

Lower Lung ◽

The Mean ◽

Dose Measurements ◽

Patient Radiation Dose

Purpose: Improved chest imaging has been reported with the usage of AMBER (advanced multiple-beam equalization radiography) equipment but with a higher patient radiation dose compared with conventional chest radiography. Most studies, however, describe dose measurements from phantoms. This study presents a comparison of radiation dose measurements in 57 patients for p.a. projections from an AMBER unit with and without an extra Cu filtration and from a formerly used conventional Siemens chest stand. Material and Methods: Dose measurements were performed with thermoluminescence dosimetry. Entrance surface doses were recorded from 5 dosimeters, placed on the patient's back. Four were placed over the upper and lower lung fields, respectively, and 1 over the mediastinal area. The dose values were then compared with the values obtained from the conventional chest stand and from the measurements with the extra filtration on the AMBER system. Results: The mean entrance dose for the mediastinal area was 0.25 mSv (range 0.15–0.49). With the extra Cu filtration it was 0.16 mSv (0.07–0.29). For the lung fields the values were 0.19 mSv (0.07–0.44) and 0.10 mSv (0.02–0.31), respectively. For the conventional chest stand the entrance dose to the patient was 0.23 mSv. Conclusion: AMBER entrance surface doses for the p.a. projection without extra Cu filtration were comparable to the doses obtained with the formerly conventional Siemens chest stand and were well within European recommendations. With extra Cu filtration the AMBER entrance surface doses were reduced by a factor of almost 2.

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