Organ Doses and Radiation Risk of Computed Tomographic Coronary Angiography in a Clinical Patient Population: How Do Low-Dose Acquisition Modes Compare?

OBJECTIVE: To compare the organ doses and lifetime-attributable risk of cancer for electrocardiogram-triggered sequential and high-pitch helical scanning in a clinical patient population. METHODS: Phantom thermoluminiscence dosimeter measurements were used as a model for the organ dose assessment of 314 individual patients who underwent coronary computed tomographic angiography. Patient-specific lifetime-attributable cancer risks were calculated. RESULTS: Phantom measurements showed that heart rate had a significant influence on the delivered radiation exposure in sequential mode, and calcium scoring and contrast bolus tracking scans make a nonnegligible contribution to patients' dose. Therefore, they should be taken into account for patients' organ dose estimations. Median cancer induction risks are low, with 0.008% (0.0016%) and 0.022% (0.056%) for high-pitch and sequential scanning for men (women), respectively. CONCLUSIONS: The use of high-pitch helical scanning leads to 65% and 72% lower lifetime-attributable risk values for men and women, respectively, compared with sequential scanning.

Investigation of radiation protection of medical staff performing medical diagnostic examinations by using PET/CT technique.

Positron emission tomography (PET) is now one of the most important methods in the diagnosis of cancer diseases. Due to the rapid growth of PET/CT centres in Poland in less than a decade, radiation protection and, consequently, the assessment of worker exposure to ionising radiation, emitted mainly by the isotope (18)F, have become essential issues. The main aim of the study was to analyse the doses received by workers employed in the Medical Diagnostic Centre. The analysis comprises a physicist, three nurses, three physicians, three technicians, as well as two administrative staff employees. High-sensitivity thermoluminescent detectors (TLDs) were used to measure the doses for medical staff. The personnel was classified into categories, among them employees having direct contact with the 'source of radiation'-(18)FDG. The TLDs were placed on the fingertips of both hands and they were also attached at the level of eye lenses, thyroid and gonads depending on the assigned category. The highest dose of radiation was observed during the administration of the (18)FDG to the patients. In the case of the physicist, the highest dose was recorded during preparation of the radiopharmaceutical-(18)FDG. The body parts most exposed to ionizing radiation are the fingertips of the thumb, index and middle finger.

Cone-beam computed tomography imaging: therapeutic staff dose during chemoembolisation procedure.

Cone-beam computed tomography (CBCT) imaging is an important requirement to perform real-time therapeutic image-guided procedures on patients. The purpose of this study is to estimate the personal-doseequivalent and annual-personal-dose from CBCT imaging during transarterial chemoembolisation (TACE). Therapeutic staff doses (therapeutic and assistant physician) were collected during 200 patient (65 ± 15 years, range: 40­86) CBCT examinations over six months. Absorbed doses were assessed using thermo-luminescent dosimeters during patient hepatic TACE therapy. We estimated personal-dose-equivalent (PDE) and annual-personal-dose (APD) from absorbed dose based oninternational atomic energy agency protocol. APD for therapeutic procedure was calculated (therapeutic physician: 5.6 mSv; assistant physician: 5.08 mSv) based on institutional work load. Regarding PDE, the hands of the staff members received a greater dose compared to other anatomical locations (therapeutic physician: 56 mSv, 72 mSv; assistant physician: 12 mSv, 14 mSv). Annual radiation doses to the eyes and hands of the staff members were lower compared to the prescribed limits by the International Commission on Radiological Protection (ICRP). PDE and APD of both therapeutic staff members were within the recommended ICRP-103 annual limit. Dose to the assistant physician waslower than the dose to the therapeutic physician during imaging. Annual radiation doses to eye-lenses and hands of both staff members were lower than prescribed limits.

[Measurement of personal dose equivalent of X and gamma radiation by ring dosimeter: results of intercomparison measurements]. / Pomiar indywidualnego równowaznika dawki promieniowania X i gamma za pomoca dozymetru pierscionkowego--wyniki porównan miedzylaboratoryjnych.

BACKGROUND: The aim of the study was to present the results of the interlaboratory comparisons for ring dosimeters and to confirm that the applied method is suitable for measuring the personal dose equivalent H(p)(0.07). In addition, calibration procedures used in dosimetric measurements in persons occupationally exposed to ionizing photon radiation X and gamma were presented. MATERIALS AND METHODS: Ring dosimeters made of flexible plastics with the diameter of approximately 20 mm, equipped with two thermoluminescence (TL) detectors type MTS-N, were the subject of interlaboratory comparisons. Irradiated detectors were red out using a new manual TLD's reader (FIMEL, France). All TLD exposures were done for validation of TLD readers and were performed using the reference X-ray and gamma beams with the ISO rod phantom. The methodology of performed exposures corresponded with the methods applied by the European Radiation Dosimetry Group (EURADOS), the European organizer ofinterlaboratory comparisons. RESULTS: The energy, dose and angular characteristics of the ring dosimeter allowed to elaborate the formula for estimating and verifying the personal dose equivalent H(p)(0.07). The test was performed to check and confirm the correctness of the estimated characteristics. The test results were satisfactory, and thus the readiness to implement TLD reader in the used method and to participate in interlaboratory comparisons was confirmed. CONCLUSIONS: According to the requirements of the Polish Centre for Accreditation, the laboratory was participating in the interlaboratory comparison organized by EURADOS in terms of the personal dose equivalent H(p)(0.07). The result of the comparison was satisfactory, therefore the correctness of the testing procedure was confirmed.

Step back from the patient: reduction of radiation dose to the operator by the systematic use of an automatic power injector for contrast media in an interventional angiography suite.

BACKGROUND: During arterial interventional procedures, power injectors allow the operator to step back from the patient or exit the angiography suite during digital subtraction angiography (DSA) acquisitions. Increasing the distance to the radiation source reduces exposure to the operator and staff. PURPOSE: To systematically investigate the effect of increasing the distance between the radiation source and the operator during DSA acquisitions in a daily clinical setting, regarding radiation exposure to the operator and patient, as well as the duration of the procedure using a power injector to deliver contrast media. MATERIAL AND METHODS: Patients scheduled for arterial interventional procedures in the pelvis or lower extremities were consecutively included. In phase one (duration 6 weeks, 44 patients) contrast media were injected manually. In phase two (duration until the total dose area product [DAP] was equal to phase 1, 41 patients) the operator used a power injector and exited the suite whenever possible. Patient, procedure, and examination data were recorded. Collective dose to the operator's collar, lead apron, and hands was recorded using thermo luminescent dosimetry (TLD). RESULTS: Our results showed a dose reduction of 50% to the operator's hands, lead apron, and thyroid collar when using a power injector during DSA, with no significant increase in DAP or procedure time when performing pelvic procedures. For lower extremity procedures there was a small but significant increase in procedure time and DAP. Pelvic procedures yielded substantially higher DAP than lower extremity procedures during both phases. CONCLUSION: Utilization of a power injector, thus allowing the operator to step back from the patient, facilitates a radiation dose reduction to the operator of approximately 50% with no significant increase in patient dose or procedure time during pelvic procedures.

Peak skin and eye lens radiation dose from brain perfusion CT: CTDIvol and Monte Carlo based estimations.

PURPOSE: To quantify the eye lens, peak skin and brain doses associated with head CT perfusion exam by means of thermoluminescent dosimeters (TLDs) measurements in a cadaver and compare them to Monte Carlo (MC) dose estimations as well as to the CTDIvol. METHOD: 18 TLDs were inserted in the brain, skin, and eye lenses of a female cadaver head, who underwent a CT brain perfusion scan using a Siemens Definition Flash. The table-toggling protocol used 80 kVp, 200 mAs, 32 × 1.2 mm collimation and 30 sequences. From the CT images, a voxel model was created. Doses were calculated with a MC framework (EGSnrc) and compared to TLD measurements. TLD measurements were also compared to the displayed CTDIvol. RESULTS: The average measured doses were: 185 mGy for the eyes lenses, 107 mGy for the skin, 172 mGy for the brain and 273 mGy for the peak skin. The reported CTDIvol of 259 mGy overestimated the averaged organ doses but not the peak skin dose. MC estimated organ doses were 147 mGy for the eyes (average), 104 mGy for the skin and 178 mGy for the brain (-20 %, -3% and 4% difference respect to the TLDs measurements, respectively). CONCLUSIONS: CTDIvol remains a conservative metric for average brain, skin and eyes lenses doses. For accurate eye lens and skin dose estimates MC simulations can be used. CTDIvol should be used with caution as it was of the same order of magnitude as the peak skin dose for this protocol and this particular CT scanner.

Radiation exposure of medical staff from interventional x-ray procedures: a multicentre study.

The purpose of this study was to analyse the radiation exposure of medical staff from interventional x-ray procedures. Partial-body dose measurements were performed with thermoluminescent dosimeters (TLD) in 39 physicians and nine assistants conducting 73 interventional procedures of nine different types in 14 hospitals in Germany. Fluoroscopy time and the dose-area product (DAP) were recorded too. The median (maximum) equivalent body dose per procedure was 16 (2,500) microSv for an unshielded person; the partial-body dose per procedure was 2.8 (240) microSv to the eye lens, 4.1 (730) microSv to the thyroid, 44 (1,800) microSv to one of the feet and 75 (13,000) microSv to one of the hands. A weak correlation between fluoroscopy time or DAP and the mean TLD dose was observed. Generally, the doses were within an acceptable range from a radiation hygiene point of view. However, relatively high exposures were measured to the hand in some cases and could cause a partial-body dose above the annual dose limit of 500 mSv. Thus, the use of finger dosimeters is strongly recommended.

Assessment of effective dose and dose to the lens of the eye for the interventional cardiologist.

This study investigates the relationship between personal dosemeter (PD) reading, effective dose and dose to the lens of the eye for interventional cardiologists in Norway. Doses were recorded with thermoluminescence dosemeters (TLD-100) for 14 cardiologists, and the effective doses were estimated using the Niklason algorithm. The procedures performed were coronary angiography and percutaneous coronary intervention, and all the hospitals (eight) in Norway, which are performing these procedures, were included in the study. Effective dose per unit dose-area product varied by a factor of 5, and effective dose relative to PD reading varied between 4 and 39%. Eye lens doses ranged from 39 to 138% of the dosemeter reading. On the basis of an estimated annual workload of 900 procedures, the annual effective doses ranged from 1 to 11 mSv. The estimated annual doses to the unprotected eye ranged from 9 to 210 mSv. According to the ICRP dose limits, the results indicate that the eye could be the limiting organ.

Dosimetric properties of KMgF3:Tb + PTFE.

This work presents the results obtained from the dosimetric properties of the new radiation detectors of KMgF3:Tb + PTFE. The thermoluminescent material was obtained by microwave technique. The polycrystalline powder obtained was mixed with polytetrafluoroethylene resin powder in the ratio 2:3 to make dosimeters in pellet form. The thermoluminescent response of these new detectors presented a linear behavior, in the dose range between 1 and 1000 Gy 60Co gamma radiation, the repeatability test in the measurements, during ten cycles of heat treatment, irradiation and readouts, showed ±â€¯3.7% DS, the stability test of thermoluminescent signal, during two months showed that the fading is practically null. For the results obtained, this new detector could be very useful for radiation dosimetry, in clinical applications.

Tailor-made Ge-doped silica-glass for clinical diagnostic X-ray dosimetry.

In the modern clinical practice of diagnostic radiology there is a growing demand for radiation dosimetry, it also being recognized that with increasing use of X-ray examinations additional population dose will result, accompanied by an additional albeit low potential for genetic consequences. At the doses typical of diagnostic radiology there is also a low statistical risk for cancer induction; in adhering to best practice, to be also implied is a low but non-negligible potential for deterministic sensitive organ responses, including in regard to the skin and eyes. Risk reduction is important, in line with the principle of ALARP, both in regard to staff and patients alike; for the latter modern practice is usually guided by Dose Reference Levels (DRL) while for the former and members of the public, legislated controls (supported by safe working practices) pertain. As such, effective, reliable and accurate means of dosimetry are required in support of these actions. Recent studies have shown that Ge-doped-silica glass fibres offer several advantages over the well-established phosphor-based TL dosimeters (TLD), including excellent sensitivity at diagnostic doses as demonstrated herein, low fading, good reproducibility and re-usability, as well as representing a water impervious, robust dosimetric system. In addition, these silica-based fibres show good linearity over a wide dynamic range of dose and dose-rate and are directionally independent. In the present study, we investigate tailor made doped-silica glass thermoluminescence (TL) for applications in medical diagnostic imaging dosimetry. The aim is to develop a dosimeter of sensitivity greater than that of the commonly used LiF (Mg,Ti) phosphor. We examine the ability of such doped glass media to detect the typically low levels of radiation in diagnostic applications (from fractions of a mGy through to several mGy or more), including, mammography and dental radiology, use being made of x-ray tubes located at the Royal Surrey County Hospital. We further examine dose-linearity, energy response and fading.

Radioluminescence sensing of radiology exposures using P-doped silica optical fibres.

In previous work we investigated the real-time radioluminescence (RL) yield of Ge-doped silica fibres and Al2O3 nanodot media, sensing electron- and x-ray energies and intensities at values familiarly obtained in external beam radiotherapy. The observation of an appreciable low-dose sensitivity has given rise to the realisation that there is strong potential for use of RL dosimetry in diagnostic radiology. Herein use has been made of P-doped silica optical fibre, 2 mm diameter, also including a 271 µm cylindrical doped core. With developing needs for versatile x-ray imaging dosimetry, preliminary investigations have been made covering the range of diagnostic x-ray tube potentials 30 kVp to 120 kVp, demonstrating linearity of RL with kVp as well as in terms of the current-time (mAs) product. RL yields also accord with the inverse-square law. Given typical radiographic-examination exposure durations from tens- to a few hundred milliseconds, particular value is found in the ability to record the influence of x-ray generator performance on the growth and decay of beam intensity, from initiation to termination.

Type testing of a locally made LiF:Mg,Ti + PTFE TLD for its use as a personal dosimeter.

Our research group has developed a thermoluminescence dosimeter (TLD) based on pellets of LiF:Mg,Ti mixed with polytetrafluoroethylene (LiF:Mg,Ti +PTFE). This TLD can be used as a personal dosimeter. Extensive type testing, carried out with reference to the International Electrotechnical Commission (IEC) Standard, were performed for the purpose of accepting the LiF:Mg,Ti+PTFE as a personal TL dosimeter. Tests performed include repeatability, batch homogeneity, linearity, detection threshold, and light sensitivity. Results showed that locally made LiF:Mg,Ti+PTFE TLDs met all the standard requirements.

QA measurement of gamma-ray dose and neutron activation using TLD-400 for BNCT beam.

TLD-400 (CaF2:Mn) chips were applied for the gamma-ray dose measurement in a PMMA phantom exposed to a BNCT beam because of their very low neutron sensitivity. Since TLD-400 chips possess an adequate amount of Mn activator they have been employed in this work simultaneously for neuron activation measurement. The self-irradiation TL signals owing to the decay of the neutron induced 56Mn activity have been applied for a calibration of the TLD-400 chip in situ, where the activities were measured by an HPGe detector system and the energy deposition per disintegration of 56Mn was calculated by applying a Monte Carlo code. It was accidentally found that the irradiated TLD-400 chips were capable of emitting prominent scintillation lights owing to the induced 56Mn activity, which can easily be recorded by the TLD reader without heating and after a calibration can be used to determine the 56Mn activity.

Measurements of air kerma index in computed tomography: A comparison among methodologies.

As CT exams impart high doses to patients in comparison to other radiologist techniques, reliable dosimetry is required. In this work, dosimetry in CT beams was carried out in terms of air kerma index in air or in a phantom measured by a pencil ionization chamber, thermoluminescent (TL) detectors and radiochromic film. Calibration results showed the low energy dependence of all three dosimetric systems for the 100-120kV range, the very high uncertainty of the TL dosimeters in comparison to the other systems and high nonlinearity response in terms of air kerma of the radiochromic film. Measurements with the three systems in a 120kV CT protocol showed an acceptable agreement among the weighted air kerma index values, but TL dosimeters presented the highest uncertainties in the values.

Preparation and investigation of thermoluminescence properties of CaSO4:Tm,Cu.

A new sort of thermoluminescent phosphor has been developed with the purpose of enlarging the range of linear dose-response. The thermoluminescence properties of CaSO(4):Tm,Cu, prepared according to our method, were studied in the dose range of 0.5 Gy-125.0 kGy. The results of the present work show that the CaSO(4):Tm,Cu is an excellent new dosimetric material due to its relatively simple glow curve, as a consequence of its simple trap system. Several applications are possible in dosimetry due to its wide range of linearity (2 x 10(-6) to 2 x 10(3) Gy), from environmental and space dosimetry to accidental and high-dose irradiation, e.g. gamma irradiation facilities, electron accelerators, nuclear power plants, radiotherapy, medical physics, and so on.

International intercomparison of retrospective luminescence dosimetry method: sampling and distribution of the brick samples from Dolon' village, Kazakhstan.

There are still many differences in dose estimates depending on the applied methods of retrospective dosimetry in the areas, which were affected by nuclear tests at the Semipalatinsk nuclear test site (SNTS). In order to provide more correct estimation of radiation doses to population in proximity to the SNTS an International Intercomparison of Retrospective Luminescence Dosimetry (RLD) method had been proposed. It was suggested there be a comparison of the dose estimates for the brick samples from the buildings in the settlement, suffered following nuclear tests at the SNTS. With this purpose, during the September-October 2002 field mission, the team of specialists from Kazakhstan and Japan had collected four whole bricks for RLD International Intercomparison. Three buildings were selected as sampling locations in Dolon' village (Kazakhstan). The slices from these bricks were distributed between six laboratories in Finland, Germany, Japan, Russia, UK and USA for independent estimations by the RLD method of the accumulated dose of external irradiation. The descriptions of sampling, locations, data on geographical coordinates, dates of building construction, mode of cutting of samples for distribution, labeling, condition of transportation, order of the distribution of samples and information concerning 137Cs and 239+240Pu soil contamination density in the village and near sampling locations are presented in the paper.

Intercomparison of luminescence measurements of bricks from Dolon' village: experimental methodology and results from Japanese laboratory.

We have applied the thermoluminescence dosimetry technique to measure the total external dose from all the nuclear explosions in a few locations near the Semipalatinsk nuclear test site in Kazakhstan. The technique was optimized at our laboratory by fundamental study of the method of thermoluminescence dosimetry. The measured values of each sample at 10 mm depth were 248+/-102 mGy (KSD-1), 30+/-76 mGy (2(1-3)), 222+/-63 mGy (2(3-2)), 217+/-55 mGy (2(4-1)). The results are part of an international intercomparison exercise using bricks collected from the areas surrounding the Semipalatinsk nuclear test site.

Intercomparison of luminescence measurements of bricks from Dolon' village: experimental methodology and results of European Study Group.

Thermoluminescence (TL) and optically stimulated luminescence (OSL) techniques were applied to quartz grains extracted from various depths in bricks taken from buildings in the village of Dolon', Kazakhstan, to determine the cumulative absorbed dose, DT. The measurements were performed in four laboratories (EU supported Measurement Group). The results obtained using TL and OSL are compared and discussed with reference to known sources of experimental uncertainty and relevant luminescence characteristics that may affect the evaluation of the absorbed dose. The external nature of the irradiation due to gamma rays from artificial radionuclides is verified by the measurement of depth-dose profiles, and these are compared with those obtained in previous studies for bricks from the same region. To produce these profiles, the cumulative dose due to natural background radiation, DBG, was assessed, particularly based on the concentrations of radionuclides of lithogenic origin within the bricks and the surrounding environment. The consistency of these estimates of DBG was assessed using depth-dose data and absorbed dose determinations for bricks collected from shielded locations. The values of cumulative absorbed dose since the onset of fallout, DX, were calculated as the difference between the values of total cumulative dose in bricks since its manufacture, DT, and values of DBG. Furthermore, estimations of the cumulative absorbed doses in air in the reference location near the sampled buildings, RLDX, were obtained using corresponding conversion factors, CRL, estimated on the basis of previous work. In addition to results for samples distributed for the International Intercomparison, reference is made to relevant results from samples that were collected in 1999 from Dolon' village and studied as part of EU-supported research.