A comparison of patient dose for examinations of the upper gastrointestinal tract at 11 conventional and digital X-ray units in The Netherlands

The objective of this study was to derive the effective dose to patients from examinations of the upper gastrointestinal (GI) tract at 11 X-ray units in 10 Dutch hospitals. Entrance dose and entrance dose rate were measured at the surface of a homogeneous PMMA phantom and at the entrance surface of the image intensifier. Dose-area products (DAPs) were assessed during examinations of patients. The patients (334 females and 256 males) ages were 18-95 years (average 52 years). Effective dose was assessed from DAP using Monte Carlo computer calculations for male and female mathematical anthropomorphic phantoms. The DAPs measured during the survey showed substantial variations, i.e. an overall average value of 21 Gy cm2 and a range of average DAP per X-ray unit varying from 7 to 56 Gy cm2. Variations in the number of images (8-28) and the fluoroscopy time (1.7 min-7.0 min) were also large. A DAP to effective dose conversion factor of 0.32 mSv Gy cm-2 was derived for upper GI studies. The dose survey yielded an overall average effective dose of 6.7 mSv. At one location an examination involving as many as 28 projections was performed, whilst maintaining a DAP well below 15 Gy cm2 and an effective dose below 6 mSv. This was achieved using modern equipment (i.e. high frequency generator, digital spot films) with 0.2 mm additional copper filtration and a relatively high tube voltage. For examinations of the upper GI tract, the application of a reference value of 30 Gy cm2 for the DAP will ensure that, in general, the effective dose to individual patients will not exceed 15 mSv.     

Influence of dose reduction recommendations on changes in chest radiography techniques

A previous dosimetric study on chest radiography identified ways to reduce patient entrance surface dose (ESD). This present study was designed to monitor changes that had occurred in the use of applied potential and film-screen sensitivity, after a series of recommendations were issued. The study falls into two parts: (1) an assessment of the impact of the recommendations and (2) what factors were responsible for change. Where changes had occurred, exposure factors were collected for 30 patients per tube and the mean ESD was calculated for each tube. Intercomparison (r = 0.93, p < 0.001) was made between calculated and measured (TLDs) values of mean ESD for 10 X-ray units, to ensure that the calculated values provided accurate estimates of the new mean ESDs. 89% of units previously monitored for patient ESD now use average applied potentials greater than 90 kVp and 51% are using film-screen sensitivities of 400. The mean ESD has been reduced on average by 47%, from 0.15 mGy to 0.08 mGy. It has been estimated that the annual collective dose from diagnostic radiology procedures in 30 hospitals in the West Midlands has been reduced by a value in excess of 40 man Sv. Reasons for change could be attributed to some of the following factors: (a) a knowledge of dose levels in comparison with other centres; (b) personal contact with departments; (c) feedback in terms of results and dose savings and (d) positive encouragement to make changes.     

Nationwide survey of fluoroscopy: radiation dose and image quality

PURPOSE: To determine the average abdominal entrance air kerma, low-contrast sensitivity, and spatial resolution in upper gastrointestinal tract fluoroscopy in the United States. MATERIALS AND METHODS: A random sample of fluoroscopic facilities was selected to be surveyed for the Nationwide Evaluation of X-ray Trends program. Measurements were performed by using a newly developed fluoroscopic phantom. The surveys were conducted by state radiation control personnel. RESULTS: Average air kerma rates 1 cm above the tabletop, free in air, were 43 mGy/min (n = 340). The rate increased to 64 mGy/min when a 1.6-mm-thick copper filter, which simulated the use of barium contrast medium, was added to increase attenuation. The average entrance air kerma, free in air, for radiographs was 3.4 mGy, and an average of 12 radiographs were obtained per examination. Of 352 facilities surveyed, 306 (87%) were able to resolve wire mesh with 20 or more lines per inch. Of 339 facilities for which percentage contrast could be calculated, 192 (57%) had minimum percentage contrast values of 4% or more. CONCLUSION: Spatial resolution for fluoroscopy is adequate for most of the facilities surveyed, but a substantial proportion of facilities could not visualize low-contrast test objects, which strongly suggests image quality problems.     

Preliminary reference levels in interventional cardiology

This article describes the European DIMOND approach to defining reference levels (RLs) for radiation doses delivered to patients during two types of invasive cardiology procedures, namely coronary angiography (CA) and percutaneous transluminal coronary angioplasty (PTCA). Representative centres of six European countries recorded patients' doses in terms of dose-area product (DAP), fluoroscopy time and number of radiographic exposures, using X-ray equipment that has been subject to constancy testing. In addition, a DAP trigger level for cardiac procedures which should alert the operator to possible skin injury, was set to 300 Gyxcm2. The estimation of maximum skin dose was recommended in the event that a DAP trigger level was likely to be exceeded. The proposed RLs for CA and PTCA were for DAP 45 Gyxcm2 and 75 Gyxcm2, for fluoroscopy time 7.5 min and 17 min and for number of frames 1250 and 1300, respectively. The proposed RLs should be considered as a first approach to help in the optimisation of these procedures. More studies are required to establish certain "tolerances" from the proposed levels taking into account the complexity of the procedure and the patient's size.     

Must radiation dose for CT of the maxilla and mandible be higher than that for conventional panoramic radiography?

We evaluated the feasibility of performing preoperative spiral CT of the maxilla and mandible with a radiation dose similar to that used for conventional panoramic radiography. The skin entrance doses of radiation used for spiral CT (collimation, 1 mm; pitch, 2; tube voltage, 80 kV; tube current, 40 mA) and for panoramic radiography (75 kV, 8 mA, 15 seconds) were measured in one patient by using thermoluminescent dosimeter chips. Results were 0.56 +/- 0.06 mGy for CT and 0.59 +/- 0.04 mGy for radiography. Image quality was adequate for preoperative implant planning. Spiral CT of the mandible and maxilla may therefore be feasible with a radiation dose of similar magnitude as that used for conventional panoramic radiography.     

A comparison of doses and techniques between specialist and non-specialist centres in the diagnostic X-ray imaging of children

A dosimetric survey of 14 routine X-ray examinations in children was carried out between 1993 and 1995. Two children's hospitals and four general hospitals took part in the survey which involved the calculation and measurement of nearly 3000 doses. Entrance surface doses (ESD) were calculated from exposure factors for radiographic procedures, and dose-area products (DAP) were recorded for both radiographic and fluoroscopic procedures. Doses were in good agreement with earlier studies, but for some procedures were significantly lower than those reported from other European countries. The main dose influencing factors for radiographic procedures were found to be the speed of the film-screen system and the use of an antiscatter grid. For the main head/trunk examinations, specialist centres often delivered higher doses to the younger children as a result of widespread use of a grid. In fluoroscopy, where the main dose influencing factors were the use of a grid and the dose rate dependence of the image intensifier, the children's hospitals consistently delivered significantly lower doses. Both ESDs and DAPs were found to increase with patient age for the main head/trunk examinations, although in some cases (AP/PA chest) this relationship was weak. The dependence of dose on age necessitates the subdivision of the paediatric sample into a number of age categories. It is suggested that all authors use the same age groupings.     

Radiological assessment of a new bone densitometer--the Lunar EXPERT

Dual energy X-ray absorptiometry (DXA) is one of the most widely used techniques in the management of osteoporosis and other skeletal diseases. Although patient doses from DXA are generally low, it is still necessary to measure them to assess the risk of radiation injury. We report on a study to estimate the effective dose (ED) to patients and staff from a new DXA scanner--the Lunar EXPERT, and make a comparison with a similar study carried out on a Lunar DPX-L. The entrance surface doses were measured to be 895 microGy and 10.25 microGy for the EXPERT and DPX-L, respectively. The EXPERT maximum EDs were calculated to be 74.7 microSv and 44.9 microSv for the anteroposterior (AP) lumbar spine and the proximal femur, respectively. More than 50% reduction in ED could be achieved by using a smaller scanning width. The maximum EDs for the DPX-L were calculated to be 0.21 microSv and 0.15 microSv for the AP lumbar spine and the proximal femur, respectively. The scattered dose rates (ambient dose equivalent) were measured to be less than 2 and less than 1 microSv h-1 at 50 cm and 100 cm, respectively, for the DPX-L, and the equivalent values for the EXPERT were 240 and 64 microSv h-1. Although both the patient dose and scattered dose rates are quite low relative to other radiological examinations, good practice aimed at dose reduction should still be implemented. Whilst protection for the operator is not needed for the DPX-L system, it may be (depending on the size of the room) for the EXPERT system.     

Real-time measurement of skin radiation during cardiac catheterization

A novel skin dose monitor was used to measure radiation incident on maximal X-ray exposed skin during 135 diagnostic and 65 interventional coronary procedures. For the diagnostic studies (n = 135), mean skin dose was 180 +/- 64 mGy; for PTCA (n = 35), it was 1021 +/- 674 mGy, single stents (n = 25) 1529 +/- 601 mGy, and multiple stents with rotational atherectomy (n = 5) 2496 +/- 1028 mGy. The dose independently increased with more cine runs, more fluoroscopy, and greater patient weight. Physicians should consider the potential for adverse radiation exposure when planning coronary interventional cases and deciding on the X-ray mode and angles used.     

A study of patient radiation doses in interventional radiological procedures

Patient radiation doses received during interventional radiological procedures can be significant. To aid in the establishment of reference dose levels, a patient dose survey has been conducted of such procedures. A total of 288 non-coronary procedures (177 classified as diagnostic and 111 as therapeutic) were accrued into the study. For each procedure, the fluoroscopy screening time and the fluoroscopic and digital radiographic dose-area products were recorded in a computer database. For example, median dose-area product values (due to fluoroscopy and digital radiography combined) of 24.2, 27.9, 69.6 and 74.7 Gy cm2 were obtained for nephrostomy, biliary stent removal/insertion, cerebral angiography and percutaneous transhepatic cholangiography procedures. While the effective dose is not an accurate measure of patient risk, it is convenient for comparing the radiological risks associated with various procedures. Effective doses were estimated from the total dose-area products. The respective median estimated effective dose values for the four procedures noted above were 3.9, 4.5, 7.0 and 12.0 mSv. While an infrequently performed procedure at this institution (n = 4 during this survey), the transjugular intrahepatic portosystemic shunt (TIPS) procedure had the greatest median dose-area product and effective dose values: 347 Gy cm2 and 55.5 mSv, respectively. Excluding the extreme case of TIPS, it was found that among commonly-performed procedures, those that are categorized as therapeutic do not necessarily present a statistically significant greater radiation risk than those which are diagnostic. Comparisons between dose-area product values obtained from this study are made with data from other interventional radiology patient dose surveys and reasons for some differences noted are discussed.     

The relationship of effective dose to personnel and monitor reading for simulated fluoroscopic irradiation conditions

The exposure of staff during fluoroscopic procedures was simulated for overcouch x-ray tube/undercouch image intensifier and undercouch x-ray tube/overcouch image intensifier geometries. A Rando phantom with film badge dosimeters attached to the skin surface at seven commonly used monitoring sites and loaded with lithium fluoride thermoluminescent dosimeters was irradiated for an extended period in the vicinity of a patient couch. Scattered radiation generated from the irradiation of an anthropomorphic phantom using primary radiation in the range of 70 kVp-110 kVp was used. The radiation dose to organs which were shielded by a lead apron was estimated from the unattenuated organ dose readings by applying an experimentally determined scattered radiation transmission factor. The ratio of effective dose to film badge reading was obtained for a range of irradiation conditions and lead apron thicknesses. For most irradiation conditions studied, a dosimeter worn above the lead apron will significantly overestimate effective dose by a factor of between 2 and 60, depending on the irradiation conditions. A dosimeter worn under the apron at either waist or chest level, will generally yield a closer (although usually an underestimate of) effective dose, typically within a factor of 7 for the most common lead apron thicknesses and irradiation conditions. No single dosimeter can accurately monitor effective dose for all irradiation conditions in fluoroscopy.     

Dose reduction in a paediatric X-ray department following optimization of radiographic technique

A survey of radiation doses to children from diagnostic radiography has been carried out in a dedicated paediatric X-ray room. Entrance surface dose (ESD) and dose-area product (DAP) per radiograph were simultaneously measured with thermoluminescent dosemeters (TLDs) and a DAP meter to provide mean dose values for separate age ranges. Results of ESD and DAP were lower than the mean values from other UK studies for all ages and radiographs, except for the infant pelvis AP radiograph. Comparison of ESD and radiographic technique with CEC quality criteria highlighted a need for reduction of dose to infants and implied an increase in tube filtration might overcome the limitations of the room's three-phase, 12-pulse generator, allowing higher tube potentials to be used on infants. Additional tube filtration of 3 mmA1 was installed following assessment of dose reduction and image quality with test objects and phantoms, and confirmation from the paediatric radiologist that clinical image quality was not-significantly altered. The tube potential was increased from 50 to 56 kVp for the infant pelvis AP radiograph. The resulting ESD and effective dose fell by 51% and 38%, respectively. The CEC quality criteria have proved useful as a benchmark against which technique in X-ray departments can be compared, and as such are a useful tool for optimizing radiographic technique and reducing patient dose.     

Evaluation of patient exposure to radiation during x-ray diagnostic examinations (in selected health service centers in the city of Wroc?aw and in the province of Wroc?aw)

In 35 x-ray laboratories, randomly selected, in the city of Wroc?aw an in the voivodship, the following measurements were performed: -exposure doses (mGy) for different kinds of x-ray examinations, -exposure doses (mGy) for examinations employing conventional intensifying cassettes and cassettes equipped with intensifying screens of rare earths, -basic exposure parameters, ie high voltage (kV), anodic current intensity (mA), and exposure duration. An average number of exposure per one examination was also defined. The values of standard deviation (SD) for doses measured and for exposure parameters were identified. The doses were compared with the values recommended in "Basic Safety Standards for Protection Against Ionizing Radiation" (IAEA, Safety Series No 115). Two differences were discussed between the values measured and those recommended, particularly in exposures when conventional cassettes were used. The assessment of exposure parameters for the same x-ray examinations performed in different laboratories pointed to a lack of any analogy between the results. It bears witness to the fact that x-ray equipment is very much diversified, and that subjective factors play a significant role.     

Isolation of coccidian enteroepithelial stages of Toxoplasma gondii from the intestinal mucosa of cats by Percoll density-gradient centrifugation

The number of nuclear medicine studies is increasing and they are becoming more complex and time-consuming. In particular, this is true of myocardial perfusion investigations. We use a one-day protocol for these studies, utilizing 99Tc(m)-MIBI or 99Tc(m)-tetrofosmin with tomographic rest images (250 MBq) acquired in the morning and exercise images (750 MBq) approximately 4 h later after pharmacological stress. Imaging technologists are concerned about continual exposure to 1000 MBq 99Tc(m) per study. Radiation doses were measured during rest (1.0 microSv, n = 18), exercise (2.5 microSv, n = 18) and stress administration (2.0 microSv, n = 16), giving a total dose of 5.5 microSv per combined cardiac study. We have previously shown that the average dose per radionuclide study (excluding myocardial perfusion studies) is 1.5 microSv. Although 5.5 microSv is higher, a technologist is highly unlikely to exceed current dose limits. New EC legislation, however, is expected to reduce these limits, which may lead to more classified workers. Pregnant technologists should avoid, if possible, combined cardiac studies, especially if performing other nuclear medicine duties.     

Radiation exposure during thoracic radiography at the intensive care unit. Dose accumulation and risk of radiation-induced cancer in long-term therapy

PURPOSE: Assessment of the additional morbidity risk due to repeated bedside chest radiography according to ICRP 60 during intensive care. MATERIAL AND METHODS: Ventral surface doses were recorded by thermoluminescence dosimetry in 2 man and 7 women, mean age 36 +/- 12 years, mean height 169 +/- 5 cm, mean weight 74 +/- 8 kg, receiving long-term ventilation therapy due to Adult Respiratory Distress Syndrome (ARDS). RESULTS: From 18 to 126 days duration of therapy 9 patients received a total of 348 bedside chest radiographs, mean 39 +/- 22 radiographs per patient. 217 chest radiographs yielded 217 surface doses and 217 gonadal doses. Patient's mean surface dose varies between at least 0.31 +/- 0.12 mGy and at most 0.56 +/- 0.09 mGy. The surface dose representing gonadal exposure is less than 0.03 mGy per exposure. The mean effective dose is about 0.15 mSv per exposure. The cumulative effective dose Heff ranges between 2.49 mSv and 14.09 mSv, thus estimating the additional individual cancer risk ranges between 0.01% and 0.07%. CONCLUSION: In comparison with the decreased prognosis of severely ill long-term ventilated patients the additional morbidity risk due to chest radiographs is a negligible quantity.     

How great is radiation exposure in the area surrounding patients after administration ov 99mTc-sestamibi?

AIM: The aim of the present study was to estimate the additional radiation exposure to personnel, other patients and members of the family caused by patients who had been injected with 99mTc-Sestamibi (Cardiolite DuPONT PHARMA) for preoperative localization of parathyroid adenoma. METHODS: Dose rates were measured from 16 patients who had received an intravenous injection of 600 +/- 50 MBq 99mTc-Sestamibi. All measurements were performed with a portable dosimeter (Berthold LB 133) at 3 different distances (0.5, 1 and 2 m) at 10 min, 180-200 min and 24 h after administration of the tracer. RESULTS: The dose rates amounted to 20.5 microSv/h at 0.5 m, 5.25 microSv/h at 1 m and 1.55 microSv/h at 2 m distance from patients respectively. The biological half-life was 54 h. The calculated maximal dose to other persons in the waiting area was 31.2 microSv, to family members 27.6 microSv and to nurses in a ward 31.2 microSv. CONCLUSION: Our results indicate that the calculated maximal radiation exposure for personnel, family members and other patients even under very unfavourable conditions was below the maximal allowed dose for non-professionally exposed persons.     

New TIPS placement in pregnancy in recurrent esophageal varices hemorrhage--assessment of fetal radiation exposure

Recurrent variceal bleeding due to liver cirrhosis led to treatment with a transjugular intrahepatic portosystemic shunt (TIPS) in a pregnant woman at 20 weeks' gestation. Fetal radiation exposure was estimated to be less than 10 mSv. The use of a graduated catheter allowed measurement of field size and reliable determination of the patient's entrance dose. Radiation exposure of an approximated fetal dosage of 5.2 mSv did not justify abortion for medical reasons. Therefore, TIPS procedure is not generally contraindicated during pregnancy itself. TIPS placement may be a therapeutic option related to the severity of the underlying maternal disease, after radiation exposure of the fetus has been estimated.     

Radiation dose and diagnosticity of barium enema examinations by radiographers and radiologists: a comparative study

With the current emphasis on the extension of the role of the radiographer, radiographers in some hospitals now undertake some of the procedures traditionally performed by radiologists. In the present study, dose-area product (DAP) measurements for over 1000 barium enema examinations performed by radiologists and radiographers were analysed and compared to ascertain whether there were significant differences in the radiation dose to the patient, depending on the category of staff performing the examination. All examinations were reported by a radiologist. The radiologist's reports were analysed against the known outcomes to compare the diagnosticity of the examination when carried out by the two categories of staff. The study shows that although radiographers are able to produce consistent diagnostic results, there is an increase in patient dose due to extra films taken for reporting, which may be difficult to justify. Measures for reducing the dose from this component of the examination were explored.     

Hawthorne effect: shortening of fluoroscopy times during radiation measurement studies

Screening times were recorded before (n = 92, 13 radiologists) and after (n = 75, 6 radiologists) commencing a protocol with dose-area product (DAP) measurements and filling of structured questionnaires. Fluoroscopy times were significantly (p = 0.0001) longer before starting these measurements (median 4.3, mean 5.2 min) than during them (median 3.2, mean 3.6 min), which indicates a Hawthorne effect. Fluoroscopy times did not increase during the DAP measurement period up to 21 barium enemas and a study period of up to 45 days per radiologist. Previous fluoroscopic radiation measurements based on action during an analysis period may be biased towards too short fluoroscopy times and too low doses. Radiation measurement, even if not scientifically indicated, seems a practical way of reducing doses.     

Patient radiation doses during cardiac catheterization procedures

The objective of the present project was the determination of the dose received by patients during cardiac procedures, such as coronary angiography, percutaneous transluminal coronary angioplasty (PTCA) and stent implantation. Thermoluminescent dosemeters (TLDs), suitably calibrated, were used for the measurement of the dose received at four anatomical locations on the patient's skin. A dose-area product (DAP) meter was also used. The contribution of cinefluorography to the total DAP was higher than that of fluoroscopy. A DAP to effective dose conversion factor equal to 0.183 mSv Gy-1 cm-2 was estimated with the help of a Rando phantom. Thus, the effective dose received by the patients could be assessed. Mean values of effective dose equal to 5.6 mSv, 6.9 mSv, 9.3 mSv, 9.0 mSv and 13.0 mSv were estimated for coronary angiography, PTCA, coronary angiography and ad hoc PTCA, PTCA followed by stent implantation and coronary angiography and ad hoc PTCA followed by stent implantation, respectively.     

Radiation dose in critical organs due to non-coplanar irradiation of the hypophysis

BACKGROUND: In order to estimate the somatic and genetic risk associated with a non-coplanar linac-based radiation technique of the pituitary gland, systematic secondary-dose measurements in a phantom and sample measurements of the dose near critical organs of patients were performed. PATIENTS AND METHODS: For measurements of the dose outside the primary radiation field an acrylic-PVC phantom was used which was irradiated with a single field (4 x 4 cm2). Eight patients with pituitary tumors were treated isocentrically with a combination of sagittal and transverse rotational arcs. To measure the dose in critical organs. LiF thermoluminescence dosimeters (TLD) in chip form were placed onto 1 eyelid, the skin over the thyroid, and the patient's clothes covering the region of breasts and ovaries of female patients and the testicles of male patients. Measurements were performed for all patients during 1 sagittal irradiation and for the majority of patients during 1 transverse irradiation. RESULTS: The phantom measurements demonstrated that the secondary dose measured on the patients surface can be considered as a good approximation for the dose in adjacent organs. The median dose in critical organs for sagittal irradiation was in the range of 25.8 mGy (eyes) to 1.9 mGy (testicles), and for transverse irradiation in the range of 23.3 mGy (eyes) to 1.3 mGy (testicles). The ratio of median organ doses for sagittal and transverse irradiation was 2.1 for the thyroid gland, 1.1 for the eyes, and 1.5 for the other organs. CONCLUSIONS: The dose in critical organs due to non-coplanar irradiation of the pituitary gland is only a small fraction of the dose delivered to the reference point of the planning target volume. The risk of a radiation-induced tumor and a genetic consequence associated with these small doses is generally less than 1% and 0.1%, respectively.