Biomedical subjects

John Damilakis

Publications and source records attributed to John Damilakis.

At least 37 records · Page 2Linked to original sources

PubMed2005

Anticipation of radiation dose to the conceptus from occupational exposure of pregnant staff during fluoroscopically guided electrophysiological procedures.

UNLABELLED: Conceptus dose from occupational exposure. INTRODUCTION: A female employee working in the electrophysiology suite has the right to know potential radiation hazards to the unborn child before she is pregnant or before she decides to formally declare her pregnancy. Moreover, the employer of a declared pregnant worker must evaluate the work situation and ensure that the conceptus dose is kept below the maximum permissible level during the remaining gestation period. The aim of this study was to develop a method for conceptus dose anticipation and determination of maximum workload allowed for the pregnant employee who participates in fluoroscopically guided electrophysiological procedures. METHODS AND RESULTS: A C-arm fluoroscopy system, an anthropomorphic phantom, and a radiation meter were used to obtain scattered air kerma dose rates separately for each of the three fluoroscopic projections typically used in the electrophysiology suite. Air kerma to conceptus dose conversion factors for all trimesters of gestation were calculated using Monte Carlo simulation. A formula is presented for the anticipation of the conceptus dose from occupational exposure of pregnant staff during fluoroscopically guided electrophysiological procedures. Normalized data are provided for conceptus dose estimation from occupational exposure of pregnant staff working in any electrophysiology laboratory. A methodology for estimation of maximum workload allowed for each month of the remaining gestation period of a worker who declared her pregnancy is proposed, which ensures that the regulatory dose limits are not exceeded. CONCLUSION: Data presented may be used for the implementation of a radiation protection program designed for pregnant staff working in an electrophysiological suite.

Electrophysiologic Techniques, Cardiac↗

PubMed2005

Reduction of eye lens radiation dose by orbital bismuth shielding in pediatric patients undergoing CT of the head: a Monte Carlo study.

Our aim in the study was to assess the eye lens dose reduction resulting from the use of radioprotective bismuth garments to shield the eyes of pediatric patients undergoing head CT. The Monte Carlo N-particle transport code and mathematical humanoid phantoms representing the average individual at different ages were used to determine eye lens dose reduction accomplished with bismuth shielding of the eye in the following simulated CT scans: (a) scanning of the orbits, (b) scanning of the whole head, and (c) 20 degrees angled scanning of the brain excluding the orbits. The effect of bismuth shielding on the eye lens dose was also investigated using an anthropomorphic phantom and thermoluminescence dosimetry (TLD). Eye lens dose reduction achieved by bismuth shielding was measured in 16 patients undergoing multiphase CT scanning of the head. The patient's scans were divided in the following: CT examinations where the eye globes were entirely included (n=5), partly included (n=6) and excluded (n=5) from the scanned region. The eye lens dose reduction depended mainly on the scan boundaries set by an operator. The average eye lens dose reduction determined by Monte Carlo simulation was 38.2%, 33.0% and <1% for CT scans of the orbits, whole head, and brain with an angled gantry, respectively. The difference between the Monte Carlo derived eye lens dose reduction factor values and corresponding values determined directly by using the anthropomorphic phantom head was found less than 5%. The mean eye lens dose reduction achieved by bismuth shielding in pediatric patients were 34%, 20% and <2% when eye globes were entirely included, partly included and excluded from the scanned region, respectively. A significant reduction in eye lens dose may be achieved by using superficial orbital bismuth shielding during pediatric head CT scans. However, bismuth garments should not be used in children when the eyes are excluded from the primarily exposed region.

Adolescent↗

PubMed2004

Occupational gonadal and embryo/fetal doses from fluoroscopically assisted surgical treatments of spinal disorders.

STUDY DESIGN: Simulation of lumbar spine fluoroscopy used during surgical treatments of spinal disorders on a humanoid phantom and monitoring of the scattered radiation levels. OBJECTIVES: To assess the potential of adverse effects to progeny due to the preconceptual and embryo/fetal exposure to ionizing radiation resulting from the parental occupational exposure to scattered radiation from lumbar fluoroscopy. SUMMARY OF BACKGROUND DATA: There are no available data on embryo/fetal doses resulting from maternal occupational exposure in the orthopedic theater. Besides, studies on staff gonadal doses from fluoroscopically assisted spine surgery are scarce and their results are not generally applicable. METHODS: Lumbar spine anterior-posterior and lateral fluoroscopy were performed on an anthropomorphic phantom. Scattered radiation within the orthopedic theater was recorded at the staff genitals and waist level. Gonadal, abdominal surface, and embryo/fetal doses normalized to the dose-area-product specific to each projection were calculated. RESULTS: If the annual dose limits of occupational exposure are continuously exhausted for 10 years, the resulting radiogenic risk of congenital malformation in infants born to the orthopedic theater staff will be at least two orders of magnitude lower than the corresponding spontaneous probability. The occupational exposure of the pregnant mother bears a negligible contribution to the risk of hereditary effect on the newborn's progeny compared with the natural incidence rate. CONCLUSIONS: Radiogenic genetic and embryo/fetal risks resulting from occupational exposure due to fluoroscopically assisted surgical treatments of spinal disorders are well within tolerance levels provided that rigorous confinement to all pertinent occupational dose constraints is established.

Dose-Response Relationship, Radiation↗

PubMed2004

Patient exposure and associated radiation risks from fluoroscopically guided vertebroplasty or kyphoplasty.

PURPOSE: To derive normalized data for the estimation of effective, gonadal, and peak skin doses to patients undergoing vertebroplasty or kyphoplasty and to investigate the potential for cancer induction, genetic effects, and radiation-induced skin injury after such procedures. MATERIALS AND METHODS: Dose values normalized over dose-area product were determined for all radiosensitive organs and tissues by using a humanoid phantom and thermoluminescence dosimetry separately for anteroposterior and lateral projections. Measurements were obtained for treatments of the fifth, eighth, and 11th thoracic vertebrae and the first, third, and fifth lumbar vertebrae. Total fluoroscopy time and resultant dose-area product from each fluoroscopic exposure were monitored in 11 consecutive patients (seven women and four men) undergoing kyphoplasty. The age range of these patients was 41-78 years, and the mean age was 58 years. RESULTS: Mean total fluoroscopy time for kyphoplasty was 10.1 minutes +/- 2.2 (standard deviation). Mean effective dose to patients from kyphoplasty was 8.5-12.7 mSv, and mean gonadal dose was 0.04-16.4 mGy, depending on the level of the treated vertebra. Skin injuries after kyphoplasty are improbable if source-to-skin distance is 35 cm or more; however, such injuries may occur if the total fluoroscopy time per projection is extended and/or the source-to-skin distance is less than 35 cm during the procedure. CONCLUSION: Patient radiation exposure and associated risks from vertebroplasty or kyphoplasty may be considerable. Data obtained in the current study may be used to establish patient effective dose, gonadal dose, and entrance skin exposure, as well as associated risks, from these fluoroscopically guided surgical treatments of spinal disorders.

Adult↗

PubMed2004

Estimation of patient dose and associated radiogenic risks from fluoroscopically guided pedicle screw insertion.

STUDY DESIGN: An experimental model for the assessment of patient dose and associated radiogenic risks associated with pedicle screw internal fixation surgical procedures. OBJECTIVES: To provide data for the accurate determination of patient effective dose, gonadal dose, and entrance skin dose from fluoroscopically assisted pedicle screw insertion procedures and to investigate the potential of both stochastic and deterministic radiogenic effects to occur following such procedures. SUMMARY OF BACKGROUND DATA: There is increased concern on radiation exposure of patients undergoing fluoroscopically guided interventional procedures. METHODS: The cumulative screening time and dose area product, for each fluoroscopic projection used, were monitored in 20 patients undergoing pedicle screw internal fixation. The dose absorbed by each radiosensitive organ/tissue was determined from direct measurements obtained using an anthropomorphic phantom appropriately loaded with thermoluminescence dosimeters. RESULTS: An average pedicle screw insertion procedure requires 1.2 minutes and 2.1 minutes of fluoroscopic exposure along anteroposterior and lateral projections, respectively, resulting in a dose area product of 232 cGy cm and 568 cGy cm, correspondingly. Gender-specific normalized data for the determination of effective, gonadal, and entrance skin dose to patients undergoing fluoroscopically guided pedicle screw internal fixation procedures were derived. The effective dose from an average procedure was 1.52 and 1.40 mSv and the gonadal dose 0.67 and 0.12 mGy for female and male patients, respectively. The average radiogenic risks for fatal cancer and genetic defects were 115 and 4 per million of patients treated, respectively. Induction of skin injuries might be induced when fluoroscopy along the lateral projection is highly extended and the source to skin distance is kept low. CONCLUSIONS: Patient dose and radiogenic risks associated with an average pedicle screw internal fixation procedure are tolerable. However, for young patients with complex spinal disorders requiring extended fluoroscopy, radiogenic risks may be considerable. Present data may beused for estimation of effective dose, gonadal dose, and entrance skin exposure and associated radiogenic risks to patients undergoing fluoroscopically guided pedicle screw insertion in any institution.

Adult↗

PubMed2004

Radiation dose and cancer risk to children undergoing skull radiography.

BACKGROUND: Limited data exist in the literature concerning the patient-effective dose from paediatric skull radiography. No information has been provided regarding organ doses, patient dose during PA skull projection, risk of cancer induction and dose to comforters, i.e. individuals supporting children during exposure. OBJECTIVE: To estimate patient-effective dose, organ doses, lifetime cancer mortality risk to children and radiation dose to comforters associated with skull radiography. MATERIALS AND METHODS: Data were collected from 136 paediatric examinations, including AP, PA and lateral skull radiographs. Entrance-surface dose (ESD) and dose to comforters were measured using thermoluminescent dosimeters. Patients were divided into the following age groups: 0.5-2, 3-7, 8-12 and 13-18 years. The patient-effective dose and corresponding organ doses were calculated using data from the NRPB and Monte Carlo techniques. The risk for fatal cancer induction was assessed using appropriate risk coefficients. RESULTS: For AP, PA and lateral skull radiography, effective dose ranges were 8.8-25.4, 8.2-27.3 and 8.4-22.7 microSv respectively, depending upon the age of the child. For each skull projection, the organs receiving doses above 10 microGy are presented. The number of fatal cancers was found to be less than or equal to 2 per 1 million children undergoing a skull radiograph. The mean radiation dose absorbed by the hands of comforters was 13.4 microGy. CONCLUSIONS: The current study provides detailed tabular and graphical data on ESD, effective dose, organ doses and lifetime cancer mortality risk to children associated with AP, PA and lateral skull projections at all patient ages.

Adolescent↗

PubMed2004

Stereological estimation of total intracranial volume on CT images.

This study aims to investigate the possibility of generating stereological estimations of total intracranial volume (TIV) on CT scans. The study group included 16 consecutive patients referred for a cranial CT examination. The TIV was estimated using the stereological point counting technique. Volume measurements were optimized by systematically sampling CT sections and by defining an optimum spacing between test points of the grid. The intraobserver and interobserver variability of the optimized volumetric technique was determined. Stereological TIV estimations were compared with the respective planimetric measurements. The application of a test grid with a point spacing of 2.4 cm on 6-8 systematically sampled CT sections provided TIV estimations with a coefficient of error of less than 5%. The intraobserver and interobserver coefficient of variation values were found to be 2.4 and 4.0%, respectively. The 95% limits of agreement between stereological and planimetric TIV measurements were equal to -91.4 and 103.4 cm3. The mean time (+/- SD) needed to obtain stereological TIV estimations was 2.9 +/- 0.6 min. The application of the optimized stereological technique on CT scans enables the efficient estimation of TIV.

Aged↗

PubMed2004

Assessment of the skeletal status by MR relaxometry techniques of the lumbar spine: comparison with dual X-ray absorptiometry.

PURPOSE: To measure lumbar spine T2*, T2, T2' and T1 MR relaxometry parameters and compare them with lumbar spine bone mineral density (BMD) in a group of postmenopausal women. MATERIALS AND METHODS: Lumbar spine T2*, T2, T2' and T1 MR relaxometry parameters and BMD values were assessed in 101 postmenopausal women (mean age: 61.8 +/- 7.1 (1 S.D.) years); of them 63 referred to as control subjects (group A, BMD T-scores > or = -2.5 S.D.) and 38 as osteoporotic (group B, BMD T-scores < -2.5 S.D.). All magnetic resonance imaging (MRI) examinations were performed on an 1.5 T imaging system using: (a) a 2D single slice multi echo (32 echoes) gradient echo (MEGRE) sequence (TR/TE1/TE32/FA: 160/2.7/74.93 ms/25 degrees for the T2* measurement, (b) a respiratory gated 2D single slice Multi Echo (16 echoes) Spin Echo (MESE) sequence (TR/TE1/TE16/FA: 2000-2500/22.5/360 ms/90 degrees) for the T2 measurement and (c) a 2D single slice multi TI (18 repeats) turbo Fast Low Angle Shot (turbo FLASH) sequence (TR/TE/TI1/TI16/FA: 11/4.2/10/5000 ms/10 degrees) for the T1 measurement. T2' was calculated from its definition equation: (1/T2' = 1/T2* - 1/T2). Lumbar spine BMD was assessed using DXA. RESULTS: All measured parameters showed statistically significant differences between groups A and B (from P < 0.05 to <0.001). All parameters showed significant associations with subject's age ranging from r = 0.245 (P < 0.05) for the T2 up to r = 0.377 (P < 0.001) for the T2*. All parameters showed significant associations with subject's BMD measurements ranging from r = -0.184 (P < 0.05) for the R1 = (1/T1) up to r = -0.345 (P < 0.0005) for the T2. CONCLUSION: Among the MR relaxometry parameters studied, T2* and T2 showed better discrimination of patients with osteoporosis from control subjects.

Absorptiometry, Photon↗

PubMed2004

Discrimination of hip fractures by quantitative ultrasound of the phalanges and the calcaneus and dual X-ray absorptiometry.

The aim of the current study was to evaluate the ability of different techniques used for the assessment of bone status to discriminate between postmenopausal women with and without hip fracture. Fifty-one postmenopausal women (mean age 64.5 +/- 6.5) who had sustained a low energy hip fracture and 51 age-matched controls (mean age 64.6 +/- 6.0) were studied. Quantitative ultrasound (QUS) assessment was carried out using the Ubis 3000 device capable of measuring broadband ultrasound attenuation (BUA) and speed of sound at the calcaneus (SOSC) and the Sunlight Omnisense device capable of estimating speed of sound at the phalanges (SOSP). Femoral neck bone mineral density (BMD) was assessed using dual X-ray absorptiometry. Correlations between QUS variables ranged from r = 0.35 to 0.72 and between QUS variables and BMD from r = 0.30 to 0.36. BMD was the best discriminator of hip fractures (odds ratio = 3.61, area under curve = 0.824). All QUS variables were significant discriminators of hip fractures with odds ratios ranging from 1.88 to 2.63 and areas under the ROC curves ranging from 0.663 to 0.740. Among the QUS variables, the SOSP showed the best odds ratio and area under curve. Comparison between the areas under the ROC curve did not show any significant difference between SOSP, BUA and BMD. On the contrary, the difference between SOSC and BMD was significant (P < 0.05). In conclusion, BMD and QUS variables investigated in the current study were significant discriminators of hip fractures. The differentiation of the hip fractures by BMD was significantly better than that of BUA measured at the calcaneus. Moreover, BMD discriminated fractured patients better than BUA and SOS(P), although the difference did not reach statistical significance.

Absorptiometry, Photon↗

PubMed2004

Stereology versus planimetry to estimate the volume of malignant liver lesions on MR imaging.

Liver tumor volume measurements are clinically useful in patients undergoing cancer treatment. The techniques of planimetry and stereology were applied for this purpose on magnetic resonance (MR) imaging. Fifty-eight malignant liver lesions were depicted on MR images in 20 consecutive patients. The volume of all lesions was estimated using stereology technique, based on point counting. Stereological tumor volume estimations were compared with those determined by manual planimetry. The repeatability of both techniques was assessed. Tumor volumes estimated by the two techniques were highly correlated (r = 0.98, p < 0.0001). The 95% limits of agreement showed that the stereological volume estimations may differ from the planimetric assessments by less than 23%. Both techniques presented comparable intra- and interobserver variability. The planimetry was 1.5 times faster than the stereology. Both volumetric techniques may provide reliable and reproducible liver tumor volume estimations. The planimetry may be the method of choice because of its superior speed.

Adult↗

PubMed2004

Patient effective dose and radiogenic risks from fluoroscopically assisted surgical reconstruction of femoral fractures.

The objectives were to assess patient effective radiation dose from fluoroscopically guided surgical reconstruction of femoral fractures and provide normalized data for the estimation of patient effective dose and risks associated with such procedures performed in any laboratory. The fluoroscopic control required during surgical reconstruction of femoral fractures was classified into two types identified by beam orientation, i.e., posterior-anterior (PA) and lateral crosstable (LC) exposures. The duration and the dose area product (DAP) of each exposure were monitored in 24 patients with femoral fractures. Patient dose per DAP unit and per minute of fluoroscopy were measured at 14 radiosensitive organs/tissues using an anthropomorphic phantom and thermoluminescence dosimetry. The typical effective dose to patients with femoral fracture treated surgically in our institution was 11.6-21.7 microSv. This effective dose is estimated to cause an excess of 1.4 fatal cancers per million patients treated, and an excess of 0.4 hereditary disorders per million of births. Induction of deterministic skin injuries to treated patients is highly improbable at the dose levels found in this study. Patient effective dose and associated risks from a typical fluoroscopically guided surgical fixation of femoral fracture are low. However, they may be significantly elevated if treated patients are young individuals and/or the fluoroscopic exposure is prolonged. The present data may be used to determine effective dose to patients undergoing surgical reconstruction of femoral fracture in any institution.

Adult↗

PubMed2004

Discriminatory ability of magnetic resonance T2* measurements in a sample of postmenopausal women with low-energy fractures: a comparison with phalangeal speed of sound and dual x-ray absorptiometry.

RATIONALE AND OBJECTIVES: We sought to assess the ability of magnetic resonance T2* measurements to discriminate between patients with and without osteoporotic fracture and compare the results with the discriminatory ability of speed of sound (SOS) measured at the phalanx and axial bone mineral density (BMD). MATERIALS AND METHODS: T2* measurements of lumbar spine were obtained at 1.5 T in 26 postmenopausal women with osteoporotic fractures and 28 age-matched healthy control subjects. A multiecho gradient echo (MEGRE) pulse train sequence was used with echo times of 2.70-74.93 milliseconds using 2.33-millisecond interecho intervals. BMD measurements were made in the axial skeleton. SOS also was measured at the finger phalanges. RESULTS: The in vivo short-term reproducibility for T2* was 1.85%. T2*, spinal BMD, total hip BMD, and SOS measurements were found to give comparable discrimination between normal and osteoporotic women with odds ratios of 2.6, 2.6, 3.2, and 2.2, respectively. CONCLUSIONS: T2* measurements of lumbar spine are reproducible and capable of differentiating between postmenopausal women with and those without osteoporotic fractures.

Absorptiometry, Photon↗

PubMed2003

Radiogenic risks from hysterosalpingography.

The aim of this study was to determine ovarian dose, effective dose and associated radiogenic risks from hysterosalpingography (HSG), and to provide data for the estimation of radiogenic risks related to HSG studies performed in any laboratory. The fluoroscopy time, number of radiographs taken and entrance surface dose were measured in a series of 78 consecutive patients undergoing HSG as part of their infertility work-up. Organ-dose values per radiograph and per minute of fluoroscopy were separately determined using an anthropomorphic phantom and thermoluminescence dosimetry. The radiogenic risk for deleterious effects on a possible future embryo and the radiogenic risk for cancer induction on the patient undergoing HSG were estimated. The average HSG procedure in our laboratory involves a mean fluoroscopic time of 0.3 min and a mean number of radiographs of 3.2. The dose to female gonads from an average HSG procedure was 2.7 mGy and the patient effective dose was 1.2 mSv. The risk for radiogenic anomalies in a future embryo of the woman undergoing an average HSG procedure and the risk for radiogenic fatal cancer induction in the exposed woman were estimated to be less than 10(-3) of the correspondent nominal risks. Radiation risks from a typical HSG are low, but they may be elevated if fluoroscopic and/or radiographic exposures are prolonged for any reason. Present data allow the estimation of radiogenic risks associated with HSG procedures performed in other laboratories with use of different equipment, screening time and number of radiographs taken.

Abnormalities, Radiation-Induced↗

PubMed2003

Radiation dose to conceptus resulting from tangential breast irradiation.

PURPOSE: To estimate the radiation dose to the conceptus resulting from tangential breast irradiation. METHODS AND MATERIALS: Conceptus radiation doses were measured in anthropomorphic phantoms simulating the geometry of a pregnant woman at the first, second, and third trimesters of gestation. Medial and lateral field irradiations were generated using a 6-MV X-ray beam. Dose measurements were performed with thermoluminescent dosimeters. RESULTS: For a treatment course delivering 50 Gy to the tumor, conceptus dose at the first trimester of gestation was found to be 2.1-7.6 cGy, depending on the field size used and the distance between conceptus and primary irradiation field. The corresponding dose ranges to the conceptus during the second and third trimesters of gestation were 2.2-24.6 cGy and 2.2-58.6 cGy, respectively. Dose data and formulas are presented to estimate conceptus dose for individual patients undergoing breast radiotherapy during the entire pregnancy. CONCLUSIONS: This study may be of value in the management of pregnant women needing tangential breast irradiation, because it provides the required information to estimate conceptus dose.

Adult↗

PubMed2003

Radiotherapy of Hodgkin's disease in early pregnancy: embryo dose measurements.

BACKGROUND AND PURPOSE: Limited information exists on the possibility of pregnant women undergoing radiotherapy for Hodgkin's disease in early pregnancy. The purpose of this study was to measure embryo dose resulting from treatment of supra-diaphragmatic Hodgkin's disease at the first trimester of gestation. MATERIALS AND METHODS: A humanoid phantom was used to simulate pregnancy at the first trimester of gestation. Embryo dose, was measured using three different field sizes that may be applied for local field irradiation in each of the regions of neck, axilla, neck-mediastinum and for mantle treatment. A shielding device consisting of 5 cm of lead was used to reduce the embryo dose. Dose measurements were carried out using thermoluminescent dosimeters. Phantom exposures were made with a 6 MV photon beam. RESULTS: Local field irradiation in the regions of neck or axilla always resulted in embryo doses below 10 cGy. For local field irradiation in the region of neck-mediastinum and for mantle treatment, the radiation dose to a shielded embryo was 2.8-18.6 and 4.2-24.5 cGy depending upon the distance from the field isocenter and the field size used, respectively. The corresponding dose for an unshielded embryo exceeded 10 cGy. All the above embryo doses were obtained for a tumor dose of 40 Gy. CONCLUSIONS: Local field irradiation in the regions of neck or axilla may be safely performed even without uterus shielding. For local field irradiation in the region of neck-mediastinum and for mantle radiotherapy, the extent of the irradiated area, the distance separating the embryo from the field isocenter and the tumor dose are the factors, determining whether the radiation dose to a shielded embryo may possibly be reduced below 10 cGy.

Female↗

PubMed2003

Ultrasound velocity through the cortex of phalanges, radius, and tibia in normal and osteoporotic postmenopausal women using a new multisite quantitative ultrasound device.

RATIONALE AND OBJECTIVES: To assess a new multisite quantitative ultrasound (QUS) device (Sunlight Omnisense 7000 S) suitable for the measurement of speed of sound (SOS) in the phalanges, radius, and tibia. METHODS: The study group consisted of 270 healthy Caucasian postmenopausal patients (mean age: 60.0 +/- 7.6 years) and 53 Caucasian postmenopausal patients (mean age: 67.2 +/- 7.4 years) with osteoporotic fractures. Measurements of SOS and bone mineral density (BMD) were carried out in all subjects. RESULTS: Intraobserver in vivo short-term precision was on average 0.76% for the radius, 0.47% for the tibia, and 1.54% for the phalanges. The interobserver precision ranged from 0.77% to 2.39%. Measurements of SOS at the 3 skeletal sites were significantly correlated (r = 0.28-0.44; P < 0.001). Significant correlations were found between SOS at all sites and BMD (r = 0.21-0.41; P < 0.001). The odds ratio for fracture prediction for SOS was 1.47 for tibia, 1.69 for radius, and 2.69 for phalanx. The corresponding odds ratios for BMD at the lumbar spine, femoral neck, and total hip ranged from 2.08 to 3.26. The area under the receiver operating characteristic curve ranged from 0.611 to 0.741 for SOS measurements and from 0.745 to 0.797 for BMD measurements. CONCLUSIONS: The Omnisense multisite QUS device exhibits reproducible performance. Among the QUS variables, the phalangeal SOS provides the best discrimination of fracture patients.

Aged↗

PubMed2003

Occupational exposure from common fluoroscopic projections used in orthopaedic surgery.

BACKGROUND: Personnel assisting in or performing fluoroscopically guided procedures may be exposed to high doses of radiation. Accurate occupational dosimetric data for the orthopaedic theater staff are of paramount importance for practicing radiation safety. METHODS: Fluoroscopic screening was performed on an anthropomorphic phantom with use of four projections common in image-guided orthopaedic surgery. The simulated projections were categorized, according to the imaged anatomic area and the beam orientation, as (1) hip joint posterior-anterior, (2) hip joint lateral cross-table 45 degrees, (3) lumbar spine anterior-posterior, and (4) lumbar spine lateral 90 degrees. The scattered air kerma rate was measured on a grid surrounding the operating table. For each grid point, the effective dose, eye lens dose, and face skin dose values, normalized over the tube dose area product, were derived. For the effective dose calculations, three radiation protection conditions were considered: (1) with the exposed personnel using no protection measures, (2) with the exposed personnel wearing a 0.5-mm lead-equivalent protective apron, and (3) with the exposed personnel wearing both an apron and a thyroid collar. Maximum permissible workloads for typical hip, spine, and kyphoplasty procedures were derived on the basis of compliance with effective dose, eye lens dose, and skin dose limits. RESULTS: We found that the effective dose, eye lens dose, and face skin dose to an orthopaedic surgeon wearing a 0.5-mm lead-equivalent apron will not exceed the corresponding limits if the dose area product of the fluoroscopically guided procedure is <0.38 Gy m (2). When protective eye goggles are also worn, the maximum permissible dose area product increases to 0.70 Gy m (2), while the additional use of a thyroid shield allows a workload of 1.20 Gy m (2). The effective dose to the orthopaedic surgeon working tableside during a typical hip, spine, kyphoplasty procedure was 5.1, 21, and 250 micro Sv, respectively, when a 0.5-mm lead-equivalent apron alone was used. The additional use of a thyroid shield reduced the effective dose to 2.4, 8.4, and 96 micro Sv per typical hip, spine, and kyphoplasty procedure, respectively. CONCLUSIONS: The levels of occupational exposure vary considerably with the type of fluoroscopically assisted procedure, staff positioning, and the radiation protection measures used. The data presented in the current study will allow for accurate estimation of the occupational dose to orthopaedic theater personnel.

Fluoroscopy↗

PubMed2002

Conceptus radiation dose and risk from chest screen-film radiography.

The objectives of the present study were to (a) estimate the conceptus radiation dose and risks for pregnant women undergoing posteroanterior and anteroposterior (AP) chest radiographs, (b) study the conceptus dose as a function of chest thickness of the patient undergoing chest radiograph, and (c) investigate the possibility of a conceptus to receive a dose of more than 10 mGy, the level above which specific measurements of conceptus doses may be necessary. Thermoluminescent dosimeters were used for dose measurements in anthropomorphic phantoms simulating pregnancy at the three trimesters of gestation. The effect of chest thickness on conceptus dose and risk was studied by adding slabs of lucite on the anterior and posterior surface of the phantom chest. The conceptus risk for radiation-induced childhood fatal cancer and hereditary effects was calculated based on appropriate risk factors. The average AP chest dimension (d(a)) was estimated for 51 women of childbearing age from chest CT examinations. The value of d(a) was estimated to be 22.3 cm (17.4-27.2 cm). The calculated maximum conceptus dose was 107 x 10(-3) mGy for AP chest radiographs performed during the third trimester of pregnancy with maternal chest thickness of 27.2 cm. This calculation was based on dose data obtained from measurements in the phantoms and d(a) estimated from the patient group. The corresponding average excess of childhood cancer was 10.7 per million patients. The risk for hereditary effects was 1.1 per million births. Radiation dose for a conceptus increases exponentially as chest thickness increases. The conceptus dose at the third trimester is higher than that of the second and first trimesters. The results of the current study suggest that chest radiographs carried out in women at any time during gestation will result in a negligible increase in risk of radiation-induced harmful effects to the unborn child. After a properly performed maternal chest X-ray, there is no need for individual conceptus dose estimations.

Abnormalities, Radiation-Induced↗