Biomedical subjects

John Damilakis

Publications and source records attributed to John Damilakis.

12 recordsLinked to original sources

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↗

PubMed2002

Broadband ultrasound attenuation imaging: algorithm development and clinical assessment of a region growing technique.

This paper presents a computerized method for the selection of an irregular region of interest (ROI) in broadband ultrasound attenuation (BUA) images. A region growing algorithm searches an initial region in the posterior part of the calcaneus until the pixel with the lowest attenuation value is found; this is the starting seed. Then, the algorithm evaluates the values of the eight pixels neighbouring the starting seed. Pixels that have the closest value to the starting seed are accepted. This procedure is the first processing level. The procedure is repeated for the group of pixels neighbouring those accepted from the previous processing level. The algorithm ceases when the number of accepted pixels reaches a user-specified number. The clinical part of this study compares measurements of BUA at an automatic ROI implemented on a quantitative ultrasound imaging device, defined as the circular region of lowest attenuation in the posterior part of the calcaneus, and at irregular ROIs of various sizes generated by the algorithm developed in this study. The algorithm was applied to BUA images obtained from 24 post-menopausal women with hip fractures and 26 age-matched healthy female subjects. The use of the irregular ROI with a size of 2400 pixels is proposed because that region yielded better clinical results compared to irregular ROIs with different size and the circular automatic ROI.

Algorithms↗

PubMed2002

Comparison of two volumetric techniques for estimating liver volume using magnetic resonance imaging.

PURPOSE: To compare the conventional technique of manual planimetry with the point counting technique for estimating liver volume from magnetic resonance imaging (MRI) data. MATERIALS AND METHODS: This study comprised abdominal MR examinations of 38 consecutive patients. Evaluation of the images showed that liver size appeared normal in 27 patients and increased in 11. Liver volume was estimated using the techniques of planimetry and point counting. Both techniques were used in combination with the Cavalieri method of modern design stereology. A systematic slice sampling procedure was performed to estimate liver volumes using both volumetric techniques. The point counting technique was optimized by altering the point spacing of the grid. The agreement between the two techniques was found. Measurement repeatability of both volumetric techniques was also evaluated. RESULTS: Both techniques allowed the same degree of optimization through the procedure of systematic section sampling. The application of a point spacing of 2.5 cm reduced the time measurement by a factor of 3.5 in relation with the time needed with planimetry. An excellent agreement was observed between the two volumetric techniques with mean differences (+/-SD) of 2.4 +/- 41.6 cm(3) and 8.5 +/- 49.8 cm(3) for the patients presenting normal and increased liver sizes, respectively. Both techniques were highly reproducible. CONCLUSION: The point counting technique could be considered a more efficient approach than planimetry for estimating liver volume from MRI, due to its speed and simplicity.

Adult↗

PubMed2002

Patient effective radiation dose and associated risk from transmission scans using 153Gd line sources in cardiac spect studies.

The aim of the present study was to determine the contribution of transmission measurements acquisition to total patient effective dose from cardiac SPECT studies. A dual-head L-shaped gamma camera equipped with a transmission scan acquisition system based on two 153Gd line sources was used to simulate transmission measurements acquisition exposure on an anthropomorphic phantom. Thermoluminescence dosimeters were used to directly monitor the dose to 550 measuring points in the phantom. The effective dose and associated risk from transmission scans acquisition were estimated and compared to those associated to the radiopharmaceutical injected. The maximum effective dose from a typical transmission measurements acquisition was 1.3 microSv and 1.9 microSv for male and female patients, respectively. The contribution of the typical transmission scans acquisition to total patient radiation risk from a cardiac SPECT study is less than 10(-3). Thus, radiation exposure may not be considered as a limiting factor for the clinical application of attenuation correction methods based on transmission measurements in cardiac SPECT.

Gadolinium↗

PubMed2002

Assessment of patient effective radiation dose and associated radiogenic risk from extracorporeal shock-wave lithotripsy.

The aim of the present study was to calculate patient effective dose and associated radiogenic risk from fluoroscopy guided extracorporeal shock-wave lithotripsy procedures. Fluoroscopy required during extracorporeal shock-wave lithotripsy was classified in two types identified by beam orientation: antero-posterior and 30 degrees anterior-oblique projected exposures. Duration of each exposure was monitored in 124 patients undergoing extracorporeal shock-wave lithotripsy treatment for ureteral stones. The dose from a kidney-ureter-bladder radiograph and the dose per min of fluoroscopy along antero-posterior and anterior-oblique projections were measured at 13 organs/tissues using an anthropomorphic phantom and thermoluminescence dosimetry. A radio-opaque object was placed in the phantom to simulate an ureteral stone at the proximal and distal ureter. The total effective dose in male and female patients with proximal ureteral stones was 1.71 mSv and 1.82 mSv, respectively. The corresponding values for male and female patients with distal ureteral stones was 0.76 mSv and 1.62 mSv, respectively. In the United States, the theoretical sex-averaged radiogenic excess of fatal cancers was estimated to be 140 per million and 85 per million of patients treated for proximal and distal ureteral stone, respectively. The average radiogenic risk for genetic defect associated to treatments of proximal and distal ureteral stones was found to be 2.5 and 24.4 per million of births, respectively. The radiation risk from a typical fluoroscopy guided extracorporeal shock-wave lithotripsy treatment of ureteral stones is low. Presented data may be used to determine patient effective dose from extracorporeal shock-wave lithotripsy procedures performed in any laboratory.

Dose-Response Relationship, Radiation↗

PubMed2002

Comparison of four methods for assessing patient effective dose from radiological examinations.

Three methods of indirect effective dose estimation were reviewed and compared to a direct effective dose determination method. An anthropomorphic phantom and thermoluminescence dosimetry were used to obtain dosimetric data associated with anterior-posterior (AP) abdominal radiography, posterior-anterior (PA) chest radiography, PA head radiography, and AP heart fluoroscopy. Effective dose was determined using: (i) organ specific dose values directly determined by thermoluminescence dosimeters, (ii) data published by National Radiological Protection Board (NRPB) and entrance surface dose (ESD), (iii) NRPB data and dose area product (DAP), (iv) energy imparted derived from DAP. The effective dose values estimated from the Rando phantom measurements were 161, 32.3, and 8.4 microSv/projection for the abdomen, chest, and head radiographs, respectively. Cardiac fluoroscopy yielded an effective dose value of 111 microSv/min. The effective dose values obtained indirectly using NRPB data and DAP were in good agreement with directly assessed values in all simulated exposures (difference <8%). The effective doses using NRPB data and ESD values differed from directly assessed values by less than 15% for the radiographic exposures and 60% for heart fluoroscopy. The energy imparted method yielded 136, 31, and 6.6 microSv/projection for the abdomen, chest, and head radiographs, respectively, and 111 microSv/min for heart fluoroscopy. Indirect patient effective dose determination using the NRPB dosimetric data and the measured value of incident radiation allows for reliable patient effective dose estimates. The use of DAP rather than ESD is recommended because it yields accurate results even for complex radiologic exposures involving fluoroscopy. The value of energy imparted may be used for the accurate determination of patient effective dose, especially when specific organ dose values are not of interest. The calculation of energy imparted with the use of EAP provides a reliable starting point for estimation of effective dose from radiologic examinations for which dosimetric data are not provided by NRPB.

Abdomen↗

PubMed2002

Normalized conceptus doses for abdominal radiographic examinations calculated using a Monte Carlo technique.

The aim of the present study was to develop a reliable method for estimating conceptus radiation doses resulting from abdominal radiographic examinations for all trimesters of pregnancy. The method is based on normalized conceptus doses estimated using Monte Carlo modeling. The Monte Carlo N-Particle (MCNP) radiation transport code was employed in the current study. The validity of the MCNP computational approach was verified by comparison with dose data obtained in anthropomorphic phantoms simulating pregnancy at the three trimesters of gestation using thermoluminescence dosimetry (TLD). The results consist of radiation doses normalized to air kerma so that conceptus dose from any technique and x-ray unit used for abdominal radiography can be easily calculated. Normalized conceptus doses are presented for the first, second, and third trimesters of gestation for various kVp and total beam filtration values. Data apply to radiographic systems equipped with high frequency or 3 phase 12 pulse generators. A very good agreement was observed between the normalized conceptus doses estimated by TLD measurements and the MCNP simulation for all periods of gestation (maximum difference 8.1%). The results of MCNP procedures were compared to published data obtained by TLD measurements. Normalized conceptus dose values agree well, with most differences being lower than 10%. The normalized doses obtained in the current study are dependent on field size. However, for small changes in the size of the x-ray field, the change in normalized doses is not considerable. Accurate estimation of conceptus doses due to abdominal conventional x-ray examinations can be made using the dose data provided in the current study.

Adult↗