Estimation of radiation doses to patients and surgeons from various fluoroscopically guided orthopaedic surgeries

In this study, a mathematical method was used to estimate the entrance surface dose (ESD) to the patient and the scattered dose (Ds) to the operating surgeon during various fluoroscopically guided surgical orthopaedic procedures. For 204 patients, the procedure type, the fluoroscopy time and the highest tube potential and current values observed during fluoroscopy were recorded. For the most often performed procedures (intramedullary nailing of peritrochanteric fractures, open reduction and internal fixation of malleolar fractures and intramedullary nailing of diaphyseal fractures of the femur), the respective mean fluoroscopy times were 3.2, 1.5 and 6.3 min while the estimated mean ESDs were 183, 21 and 331 mGy, respectively. The estimated Ds rates for the hands, chest, thyroid, eyes, gonads and legs of the operating surgeon were on average to 0.103, 0.023, 0.013, 0.012, 0.066 and 0.045 mGy min(-1), respectively, and compare well with the literature. The mathematical estimation of doses cannot replace actual measurements; however, it can be used for a preliminary assessment of the radiation dose levels during various surgical procedures, so that the operator, the surgeon and the rest of the medical staff involved could be aware of the associated radiation risk and the radiation protection measures required.     

Estimation of doses received by patients undergoing radiological examinations in Greece

This study deals with the estimation of doses received by patients undergoing radiological examinations in order to establish diagnostic reference levels (DRLs) within the process of optimisation of patients' exposure in Greece. Six large hospitals in Athens were selected and 385 patients made up the sample. The entrance surface doses (ESDs) to patients undertaking five common X ray examinations (chest, cervical spine, lumbar spine AP and LAT, pelvis) were estimated using both thermoluminescence dosemeters (TLDs) attached to the patient's skin and an ionisation chamber for air kerma measurements. Exposure settings and patient's data were recorded. Results concerning the kilovoltage and focus-to-film-distance (FFD) settings and the ESD values were analysed and compared to those recommended by the EU. Discrepancies in the patient doses and techniques used for the examinations studied were found among the different hospitals denoting the importance of establishing a national quality assurance programme and examination protocols to ensure patient doses are kept as low as possible. All the examinations studied fulfilled the EU recommendations except that for the chest where the doses were considerably higher due to the use of low kVP settings.     

Distribution of equivalent doses to skin of the hands of nuclear medicine personnel

During direct contact with radiation sources, for example in nuclear medicine departments, the skin of the hands of workers is the area most exposed to radiation. Measurements with finger dosemeters containing thermoluminescent detectors showed that doses received may reach values as high as 100 mSv y(-1). The specific nature of work performed with isotopes contributes to the considerable differences in the value of an equivalent dose received by the metacarpus, wrist and fingertips. The annual equivalent doses to which fingertips are exposed may exceed the annual dose limit of 500 mSv.     

Scattered doses to different parts of cancer patients during radiotherapy treatment in Nigeria

The doses over various parts of the body of 7 patients with cancers of the pharynx, breast and cervix during radiotherapy treatment with a megavoltage 60Co therapy machine were measured using LiF TL dosemeters. The doses on the surface of the patients outside the primary beam were found to vary with a maximum of 366 mGy at the abdomen of a cervix cancer patient to a minimum value of 1.1 mGy at the left arm and left leg of a pharynx cancer patient. The observed variations in the doses were attributed to the difference in patients' tumour location, exposure and anatomy. In the treatment of pregnant women and women of childbearing age, the results presented will be a good starting point for estimation of fetus doses and doses to organs outside the planning region.     

Radiation doses to patients from enteroclysis

The purpose of this study was to determine the patient doses during enteroclysis and compare them with the available bibliographical data. For 14 enteroclysis examinations, the dose-area product (DAP) meter readings, fluoroscopy time, number of radiographs and exposure data were recorded. From these data, the fluoroscopy and radiography contributions to DAP, the entrance surface dose (ESD) and the effective dose (E) for each examination were estimated. The mean DAP was 81 Gy cm(2) and the mean fluoroscopy time was 19.5 min. The fluoroscopy contribution to DAP was 77% and 8.7 films were acquired in each examination on average. The mean ESD and E were estimated to be 428 mGy and 21 mSv, respectively. The mean DAP and fluoroscopy time calculated in this study are quite high when compared with those reported in the literature, suggesting that the examination technique should be reviewed and the ways to reduce patient exposure without compromising the diagnostic quality should be acquired.     

Radiation doses to patients undergoing enteroclysis

Enteroclysis is a minimally invasive radiographic examination of the small intestine. During the procedure, considerable radiation dose is delivered to the patients. This study intends to: (a) evaluate the radiation dose to the patient using thermoluminescent dosemeters (TLDs, according to the protocol used at Radiology Department, University Hospital of Larissa, Greece; (b) estimate the thyroid surface dose (TSD) and doses to some radiosensitive organs located in the irradiation field. A total of 46 patients was examined. Patients were divided into two groups according to the digital X-ray machine used. The mean entrance surface dose (ESD) was 601.2 ± 96.2 mGy and the mean fluoroscopy time was 8.5 ± 3 min, while the mean TSD was 0.34 ± 0.6 mGy. The ESD for group A was lower by 20 % than group B due to fluoroscopic mode used. The dose values were higher than those in the literature. A local diagnostic reference level was introduced for further patient dose optimisation.     

Patient and personnel dosimetry in endovascular radiotherapy with 90Sr/90Y sources

Endovascular brachytherapy (EVBT) is an established treatment to reduce the probability of restenosis after a percutaneous coronary intervention. The purpose of this study was to assess (1) the manufacturer's stated dosimetric data for (90)Sr/(90)Y source trains to be used in EVBT and (2) the procedure-related radiation burden. The radiation fields in water around six (90)Sr/(90)Y source trains were studied using phantoms made of 'solid water' and MD55-2 radiochromic films. The water equivalence of the phantom material was tested by applying quantitative computed tomography. Thermoluminescence dosemeters were used to assess personal radiation burden and crosscheck the dose distribution along the source trains. Technical failure was observed in one source train and this train was excluded from analysis. The measured dose rate in water at 2 mm radial distance was on average 8% higher than the manufacture's stated value (range of measured to stated values 1.05--1.15). The dose rate decreased exponentially with radial distance between 2 and 6 mm. The dose rate in contact with the source viewing window of the delivery devices ranged between 0.5 and 7.5 mGy h(-1). Low-energy photons were the main contributors to personal dose.     

Radiation doses to patients from digital subtraction angiography

This investigation determined patient doses during digital subtraction angiography (DSA). Fluoroscopy time, dose-area product (DAP) and entrance surface air kerma (ESAK) were analysed from 263 DSA examinations, classified into seven categories: (1) abdominal aorta, iliac, femoral, popliteal and leg arteries; (2) abdominal aorta and superselective DSA of renal arteries; (3) combination of (1) and (2); (4) superselective DSA of common carotid and vertebral arteries, intracranial branches in face and profile projections; (5) superselective DSA of hepatic, splenic, superior and inferior mesenteric arteries; (6) combination of (1) and (4); and (7) celiac trunk and branches. Median DAP values were 67.7, 92.9, 76.6, 53.6, 105.7, 76.1 and 2.6 Gy cm2, respectively. With the exception of one examination, ESAK values were below 2 Gy: the limit for erythema. Compared with published data, DAP values were within the range reported for (1) and (4), slightly larger for (2) and (5), whereas no references were identified for the remaining three categories.     

Radiation doses to neonates during X ray computed tomography examinations

As the survival rate of newborns has increased, the number of X ray computed tomography (CT) examinations performed on neonates has been increasing. The exposure doses from CT examinations are known to be higher than those from conventional radiography. Although radiation sensitivity of neonates is higher than that of adults, there are few reports on dose estimates of neonates in CT examinations. Four cylindrical phantoms and one neonatal phantom have been developed to estimate doses to neonates during CT examinations. Using these phantoms and glass dosemeters, absorbed doses were measured. Estimated exposure doses to neonates were higher than those to adults, and our results suggest a need to optimise carefully CT examinations in newborns.     

Radiation doses to paediatric patients and comforters undergoing chest X rays

Pneumonia is an important cause of hospital admission among children in the developed world and it is estimated to be responsible for 3-18 % of all paediatric admissions. Chest X ray is an important examination for pneumonia diagnosis and for evaluation of complications. This study aims to determine the entrance surface dose (ESD), organ, effective doses and propose a local diagnostic reference level. The study was carried out at the university hospital of Larissa, Greece. Patients were divided into three groups: organ and effective doses were estimated using National Radiological Protection Board software. The ESD was determined by thermoluminescent dosemeters for 132 children and 76 comforters. The average ESD value was 55 ± 8 μGy. The effective dose for patients was 11.2 ± 5 μSv. The mean radiation dose for comforter is 22 ± 3 μGy. The radiation dose to the patients is well within dose constraint, in the light of the current practice.     

Radiation doses to patients undergoing barium meal and barium enema examinations

The radiation doses received by patients during 41 barium meal (BM) and 42 barium enema (BE) examinations in two Greek hospitals are presented. Radiation dose was measured in terms of the dose area product (DAP). The effective dose and doses to certain organs were estimated using the ODS-60 software. Mean total DAP values were found to be 25 +/- 11 Gy cm2 for BM and 60 +/- 35 Gy cm2 for BE examinations, whereas the estimated mean values of effective dose were 8.6 +/- 4.0 and 24 +/- 16 mSv respectively. DAP to effective dose conversion coefficients were estimated to be 0.34 mSv per Gy cm2 for BM and 0.41 mSv per Gy cm2 for BE.     

Dose measurement for patients and physicians using a glass dosemeter during endovascular treatment for brain disease

It has been reported that exposure of patients and physicians to radiation from interventional radiological procedures cannot be disregarded. Direct measurement of patient exposure used to be difficult due to possible interference by the detector with the observation of X ray images. Recently, a dosemeter system consisting of small-sized glass chips and a reader which adopts pulsed UV laser stimulation has been developed. Owing to its small size, radiolucency and physical characteristics, direct monitoring of surface dose has become feasible. Dose measurement for patients and physicians during neurointervention was done using the photoluminescence glass dosemeter system. The dose-response of the dosemeter was almost linear over a broad dose range, but its energy dependency was rather high without a filter, the use of which is recommended by the manufacturer to compensate for energy dependency. Variation of sensitivity of about 20% was observed for effective energies of 45-60 keV which are used in neurointervention. In spite of this shortcoming, the photoluminescence glass dosemeter system was judged to be a convenient means for monitoring dose during neurointervention.     

Evaluation of organ doses in brachytherapy treatment of uterus cancer using mathematical reference Indian adult phantom

Quantifying organ dose to healthy organs during radiotherapy is essential to estimate the radiation risk. Dose factors are generated by simulating radiation transport through an anthropomorphic mathematical phantom representing a reference Indian adult using the Monte Carlo method. The mean organ dose factors (in mGy min(-1) GBq(-1)) are obtained considering the microselectron (192)Ir source and BEBIG (60)Co sources in the uterus of a reference Indian adult female phantom. The present study provides the factors for mean absorbed dose to organs applicable to the Indian female patient population undergoing brachytherapy treatment of uterus cancer. This study also includes a comparison of the dimension of organs in the phantom model with measured values of organs in the various investigated patients.     

Radiation doses to Norwegian heart-transplanted patients undergoing annual coronary angiography

Heart-transplanted patients in Norway undergo annual coronary angiography (CA). The aims of this study were to establish a conversion factor between dose-area product and effective dose for these examinations and to use this to evaluate the accumulated radiation dose and risks associated with annual CA. An experienced cardiac interventionist performed a simulated examination on an Alderson phantom loaded with thermoluminescence dosemeters. The simulated CA examination yielded a dose-area product of 17 Gy cm(2) and an effective dose of 3.4 mSv: the conversion factor between dose-area product and effective dose was 0.20 mSv Gy cm(-2). Dose-area product values from 200 heart-transplanted patients that had undergone 906 CA examinations between 2001 and 2008 were retrieved from the institutional database. Mean dose-area product from annual CA was 25 Gy cm(2), ranging from 2 to 140 Gy cm(2). Mean number of CA procedure was 8 (range, 1-23). Mean accumulated effective dose for Norwegian heart-transplanted patients between 2001 and 2008 was 34 mSv (range, 5-113 mSv). Doses and radiation risks for heart-transplanted patients are generally low, because most heart transplantations are performed on middle-aged patients with limited life expectancy. Special concern should however be taken to reduce doses for young heart-transplanted patients who are committed to lifelong follow-up of their transplanted heart.     

Patient and endoscopist radiation doses during ERCP procedures

The aim of the study was to calculate radiation doses for patients and staff during interventional Endoscopic retrograde cholangiopancreatography (ERCP) procedures. Patient age (A), kerma-area product (KAP), fluoroscopy time (T) and total number of films (F) were collected for 157 interventional ERCP procedures. One endoscopist (>10 y of experience) monitored using a thermoluminescent dosemeter worn over the lead apron performed the ERCPs. Median (range) KAP was 3.1 Gy cm(-2) (0.1-106.7 Gy cm(-2)). Median (range) A, T and F were 72 y, 2.6 (0.2-26.0) min and 2 (1-4) images, respectively. No correlation was observed between KAP and A, T or F. Monthly endoscopist dose was negligible due to the use of lead apron, collar and two lead-articulated ceiling mounted shields. The endoscopist dose is minimal when using appropriate protective measures. Patient doses showed large variation that has to be further investigated.     

Radiation doses to patients undergoing coronary angiography and percutaneous transluminal coronary angioplasty

A detailed study of radiation doses received by 168 patients who underwent coronary angiography (CAG) and 102 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) in two Greek hospitals is presented. Radiation dose was measured in terms of dose-area product (DAP). The contribution of fluoroscopy and cineradiography to the total DAP was examined separately for each radiological projection used in both procedures. Effective dose and doses to various organs were estimated with the help of the ODS-60 software. Total DAP was found to correlate linearly to fluoroscopy time and cine film length. Mean DAP values were found to be 80.8 +/- 28.0 Gy cm2 for CAG and 86.2 +/- 65.6 Gy cm2 for PTCAs, whereas the estimated mean values of effective dose were 20.9 +/- 7.5 and 23.2 +/- 18.1 mSv respectively. DAP to effective dose conversion coefficients were estimated to be 0.26 mSv/Gy cm2 for CAG and 0.27 mSv/Gy cm2 for PTCAs.     

Electrochemical and microstructural studies of tantalum and its oxide films for biomedical applications in endovascular surgery

The most popular coronary stents are made of 316L stainless steel and self-expandable Nitinol. Nevertheless, Ta has already been used to make stents for endovascular surgery and may constitute a good alternative to the other materials because of its higher corrosion resistance and radio-opacity property, which may facilitate the follow-up of stent catheterization. The characterization of Ta and its natural passive oxide films has been performed in a 0.15 M NaCl solution (simulated body fluid – SBF) using anodic polarizations, electrochemical impedance spectroscopy and photoelectrochemical techniques. Changes in microstructure have been observed by atomic force microscopy (AFM). Polarization curves show the existence of a current density increase between 1.40 and 1.80 V. Bode complex plots show that some perturbation of the film occurred in this potential interval which may be associated with a decrease in polarization resistance, Rp, indicating that the film may be less resistant to corrosive attack. Mott–Schottky capacity measurements show that the density of donors, Nd, varies with polarization. The optical band gap, E _g , which is equal to 4.1 eV did not show variations in our experiments. The localized formation on the electrode surface, in the above potential interval of a Ta compound (possibly an oxide-hydroxide) was observed by AFM, and this may explain the appearance of the current density peak and capacity behavior at those potentials.     

Skin doses to patients undergoing coronary angiography in a Greek hospital

In this study, the skin dose (SD) to patients undergoing coronary angiography (CA) were measured with thermoluminescence dosemeters (TLD) attached to various anatomical locations on the patient's skin during 93 CA procedures in a Greek hospital. The dose-area product (DAP) for every radiological projection was also measured for each procedure. The SD values were measured to be in the range 2.4-427.5 mGy, lower than the 2 Gy dose threshold for transient erythema. No general correlation was observed between the SD and the total DAP.     

Estimation of minimum doses for optimized quantum dot contrast-enhanced vascular imaging in vivo

Quantum dot (QD) contrast-enhanced molecular imaging has potential for early cancer detection and image guided treatment, but there is a lack of quantitative image contrast data to determine optimum QD administered doses, affecting the feasibility, risk and cost of such procedures, especially in vivo. Vascular fluorescence contrast-enhanced imaging is performed on nude mice bearing dorsal skinfold window chambers, injected with 4 different QD solutions emitting in the visible and near infrared. Linear relationships are observed among the vascular contrast, injected contrast agent volume, and QD concentration in blood. Due primarily to differential light absorption by blood, the vasculature is optimally visualized when exciting in the 435-480 nm region in 81% of the cases (89 out of 110 regions of interest in 22 window chambers). The threshold dose, defined here as the quantity of injected nanoparticles required to yield a vascular target-to-autofluorescence ratio of 2, varies from 10.6 to 0.15 pmol g(-1) depending on the QD emission wavelength. The wavelength optimization maximum and broadband gain, defined as the ratio of threshold doses estimated for optimal and suboptimal (worst wavelength or broadband) spectral illumination, has average values of 4.5 and 1.9, respectively. This study demonstrates, for the first time, optimized QD imaging in vivo. It also proposes and validates a theoretical framework for QD dose estimation and quantifies the effects of blood absorption, QD emission wavelength, and vessel diameter relative to the threshold dose.     

Estimation of transducer errors during operation

A procedure is proposed for sequential testing of statistical hypotheses on the detection of an unserviceable transducer in systems monitoring interdependent parameters.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 21–22, November, 1993.