Showing papers in "British Journal of Radiology in 1998"

Radiation exposure to medical staff in interventional and cardiac radiology.

Abstract: The aim of this work has been to determine typical occupational dose levels in interventional radiology and cardiology installations and to relate doses to patient and occupational dosimetry through the dose-area product. An experimental correlation between environmental dosimetric records and dose-area products in the centres studied was established. The study covered a sample of 83 procedures performed by 10 specialists in six laboratories. The radiologists and cardiologists monitored wore nine thermoluminescent chips next to eyes, forehead, neck, hands, left shoulder, left forearm and left arm during each single procedure. In addition, direct reading electronic devices for environmental dosimetry were placed in the C-arm of the X-ray system, to estimate roughly the occupational radiation risk level. Typical shoulder doses derived from electronic dosimetry range between 300 and 500 muSv per procedure, assuming no lead protective screens were used. Using these values and patient dose-area data from two laboratories, averaged ratios of 84 and 120 muSv per 1000 cGy cm2 are obtained for cardiology procedures. Finally, occupational dose reductions of approximately 20% when using highly filtered X-ray beams with automatic tube potential (kV) reduction (available in some facilities), and by a factor of about three when using ceiling mounted screens, have been found.

Lens injuries induced by occupational exposure in non-optimized interventional radiology laboratories.

Abstract: Several cases of ophthalmologically confirmed lens injuries, caused by occupational radiation exposure, have occurred in two X-ray rooms devoted to vascular and visceral interventional radiology procedures. Both laboratories were equipped with overcouch X-ray systems not designed for interventional radiology and without specific tools for radiation protection of the eyes. Typical workloads ranged from between two and five procedures per day. For the two radiologists affected, estimates for the dose to eye lens ranged from 450 to 900 mSv per year, over several years. Once the incidents had been detected, the X-ray systems in both rooms were removed and new equipment specifically designed for interventional radiology was installed, including suspended shielding screens. Since these lens injuries were only detected accidentally, measures to avoid similar occurrences in the future are discussed.

CT measurement of main pulmonary artery diameter.

Abstract: The aim of this study was to determine the upper limit of the normal main pulmonary artery diameter using a modern CT system. This was measured at the level of the pulmonary artery bifurcation in 100 normal subjects using unenhanced contiguous 10 mm CT slices viewed at fixed mediastinal window settings (400/20). These normal subjects were then compared with similar unenhanced 10 mm images from 12 patients with proven pulmonary arterial hypertension (mean pulmonary artery pressure > 20 mmHg). The main pulmonary artery diameter in normal subjects was 2.72 cm (SD = 0.3). Main pulmonary artery diameter in patients with pulmonary arterial hypertension was significantly greater (p < 0.01) at 3.47 cm (SD = 0.33). A pulmonary artery diameter of 3.32 cm (main pulmonary artery diameter + 2 SD) had a 58% sensitivity and 95% specificity for the presence of pulmonary arterial hypertension. It is concluded that, using unenhanced axial 10 mm CT sections, the upper limit of normal main pulmonary artery diameter is 3.32 cm. Pulmonary arterial hypertension should be considered in patients with values above this level.

Dosimetric and radiation protection considerations based on some cases of patient skin injuries in interventional cardiology.

Abstract: Recently, several cases of skin injuries have been detected in patients undergoing cardiac radiofrequency catheter ablation. These procedures were performed on a biplane X-ray system used in a large Spanish hospital for interventional cardiology procedures. Interventional procedures performed and radiation lesions produced on patients are described. The radiation lesions were mainly erythematous lesions and chronic radiodermatitis. Results of the dosimetric evaluations and an analysis of the operational aspects of radiological protection are discussed. Poor image quality could have influenced the length of the procedures. Dose rate at the image intensifier entrance was within usual reported values in literature. However, the focus-to-skin distance for the horizontal X-ray beam was too short, resulting in a high skin dose rate. Additionally, X-ray beams are of fixed orientation, and accumulated skin dose in the patient's right side has been estimated as 11-15 Gy per procedure. In conclusion, practical radiation protection considerations to avoid further incidents of this sort are proposed, concerning the use of X-ray systems specially designed for interventional radiology, the improvement of cardiologists' training in radiation protection and routine patient dose measurements for complex interventional procedures.

Contrast media-induced nephrotoxicity—questions and answers

Abstract: The intravascular administration of contrast media (CM) can produce acute haemodynamic changes in the kidney characterized by an increase in renal vascular resistance and a decrease in the glomerular filtration rate (GFR). These changes may lead to clinically significant reduction in renal function in patients with pre-existing risk factors such as diabetic nephropathy, congestive heart failure and dehydration. The pathophysiology of the renal haemodynamic effects of CM involves activation of the tubuloglomerular feedback (TGF) mechanism and the modulation of the intrarenal production of vasoactive mediators such as prostaglandins, nitric oxide, endothelin and adenosine. The TGF response is osmolality-dependent and accounts for about 50% of the acute functional effects of high osmolar CM on the kidney. Reduction in the synthesis of the endogenous vasodilators nitric oxide and prostaglandins increases the nephrotoxicity of CM. Endothelin and adenosine play a crucial role in mediating the acute functional effects of CM. Antagonists of these mediators attenuate the reduction in renal function induced by contrast agents. Vacuolization of the cells of the proximal tubules and necrosis of those of the medullary ascending limbs of loops of Henle are the main structural effects of CM in the kidney. The reduction in renal function induced by CM could be minimized by the use of low osmolar CM and adequate hydration. The prophylactic administration of calcium channel blockers and adenosine antagonists such as theophylline may also offer some protective effect.

Patient radiation doses during cardiac catheterization procedures.

Abstract: 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.

A study of patient radiation doses in interventional radiological procedures.

Abstract: 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 estim...

Entrance skin dose estimates derived from dose-area product measurements in interventional radiological procedures.

Abstract: Patient skin doses resulting from interventional radiological procedures have the potential to exceed threshold doses for deterministic effects such as erythema and epilation. If the irradiation geometry is known, the entrance skin dose can be estimated from the measured dose-area product. For each of 10 non-coronary interventional procedures, a nominal geometry was identified. From a previous survey of patient dose-area products, the entrance skin doses were estimated under the assumption that all procedures were performed with the nominal geometry specific to it. An analysis of the uncertainties in these doses caused by realistic deviations from the nominal geometry was also performed and it was shown that the estimated entrance skin dose values are at least to within 40%, and generally to within about 30%, of those actually received. For example, the median estimated entrance skin doses for the posteroanterior and lateral projections of cerebral angiography were 100 and 110 mGy. respectively, and for hepatic angiography 425 mGy. The largest entrance skin dose estimate for a single projection was for the angiography component of a CT arterial portography procedure at 670 mGy. Comparisons between entrance skin dose estimates obtained from this study are made with data from other interventional radiology patient dose surveys.

The clinical radiobiology of brachytherapy.

Abstract: The unique geometrical features of brachytherapy, together with the wide variety of temporal patterns of dose delivery, result in important interactions between physics and radiobiology. These interactions exert a major influence on the way in which brachytherapy treatments should be evaluated, both in absolute and comparative terms. This article reviews the main physical and radiobiological aspects of brachytherapy and considers examples of their influence on specific types of treatment. The issues relating to the optimization of high dose rate brachytherapy are presented, together with the implications of multiphasic repair kinetics for low dose-rate and pulsed high dose rate brachytherapy. The opportunities for application of radiobiological principles to improve various brachytherapy techniques, together with the integration of brachytherapy with teletherapy, are also outlined. Equations for the numerical evaluation of brachytherapy treatments are presented in the Appendices.

Failure to detect intrauterine growth restriction following in utero exposure to MRI.

Abstract: Echo planar imaging is a form of MRI with short image acquisition times, which permits in utero fetal imaging without motion artefacts. Echo planar imaging has been used to measure accurately fetal organ volume and to assess placental function. Two small animal studies have suggested the possibility of intrauterine growth restriction consequent upon MRI. We thus performed a prospective study of pregnancies in which fetuses were exposed to echo planar imaging, compared with a control group in which there was no in utero echo planar imaging exposure. There were no significant differences between the groups when maternal age, parity, proportion of smokers and proportion of Caucasian women were compared. Although the gestational age of delivery was lower in the echo planar imaging group, the proportion of women delivering prematurely was not significantly different. Although infant birthweights were significantly lower in the MRI group, the corrected birthweight for gestational age centiles (individualized birthweight ratio) was not significantly different between the two groups. In utero exposure to echo planar imaging thus did not have a marked effect on intrauterine fetal growth. A 10 year follow-up study of all infants imaged in utero is being performed.

Improved diagnostic accuracy in dynamic contrast enhanced MRI of the breast by combined quantitative and qualitative analysis

Abstract: To develop an optimized interpretation strategy of dynamic contrast enhanced breast MRI based on a combination of quantitative and qualitative criteria, the features of 120 histopathologically verified lesions were retrospectively analysed on contrast enhanced dynamically acquired (before and 1, 2, 4 and 7 min following injection of 0.2 mmol kg-1 gadolinium-DOTA) three-dimensional gradient echo images. Quantitative criteria, based on relative signal intensity measurements and qualitative morphological features, including lesion shape, margins and enhancement patterns were analysed in regard to differentiating malignant (n = 70) from benign (n = 50) lesions. Quantitative assessment of enhancement profiles was most accurate when analysis was based on early 1 min measurements. Using a 90% threshold, sensitivity and specificity in detecting breast cancer were 83% and 66%, respectively. When based on qualitative morphological analysis alone, sensitivity and specificity were 83% and 54%. Combined quantitative a...

Dual phase spiral CT in the detection of small insulinomas of the pancreas.

Abstract: Dual phase contrast enhanced spiral computed tomography (DPSCT) has the potential to improve detection of small insulin secreting islet cell tumours of the pancreas. Seven patients with biochemically proven insulinoma, who had previously undergone a range of negative radiological procedures, were referred for DPSCT. Images of the pancreas were obtained using 3 mm collimation in the arterial and arteriovenous perfusion phase following the rapid injection of contrast medium. Six tumours were localized in seven patients. The six insulinomas identified on DPSCT ranged in size from 6 mm to 18 mm and were located in the uncinate process (2), head (1), neck (2) and body (1). All six tumours were detected in the arterial phase and four in the arteriovenous phase. The four insulinomas detected on both perfusion phases were more conspicuous in the arterial phase in three patients and more conspicuous in the arteriovenous phase in one patient. In conclusion, high resolution arterial phase acquisition of the pancreas is very valuable in the detection of small insulinomas.

Signal-to-noise ratio in MRI.

Abstract: in RF receiving coil design. However, modern is proportional to 0 , so that their population imaging techniques often demand very high speed difference is larger at high values of 0 . Since the and spatial resolution, so that the highest possible ratio of the energy difference to thermal energy is SNR is still required to avoid poor image quality. very small, the population difference increases in In this commentary, the physics underlying the direct proportion to 0 , as does the size of the variation of SNR with static field strength will be nuclear magnetic dipole moment. Secondly, the briefly reviewed, practical methods of optimizing Larmor frequency at which the dipole moment SNR will be outlined, including a discussion of the precesses is proportional to 0 so that the rate of principles of quadrature and phased-array RF change of flux linked to the RF coil also increases coils, and methods of measuring SNR for acceptin proportion to 0 . Therefore, by Faraday’s law ance testing and quality assurance will be of electromagnetic induction, the signal produced discussed. by a dipole magnetic moment of constant magni-

Metastases to the pancreas.

Abstract: Disparity in prognosis and management between primary and secondary pancreatic tumours makes recognition of metastases to the pancreas on CT and MRI an important goal. Three different patterns of secondary pancreatic tumours may be seen: localized, multifocal, or diffuse enlargement. CT findings include hypodense lesions, which show rim enhancement following intravenous contrast medium. On MR examination, the lesions are usually hypointense on T1 weighted and hyperintense on T2 weighted images.

The management of peripheral arterial aneurysms using percutaneous injection of fibrin adhesive.

Abstract: Most peripheral arterial aneurysms are pseudoaneurysms and are iatrogenic or related to trauma. They can be treated by several techniques that can be performed by the radiologist, negating the need for surgery. Ultrasound guided compression repair is usually the treatment of choice, but is not always successful. The number of available treatment options reflects the varying site and nature of pseudoaneurysms and perhaps the lack of a consistently reliable method. We have successfully treated 13 patients with peripheral aneurysms (11 femoral, 1 popliteal and 1 posterior tibial aneurysm) using a commercial fibrin tissue adhesive. The method involves percutaneous injection of the adhesive components using ultrasound and screening control, following successful occlusion of the aneurysm neck by angioplasty balloon.

In vivo assessment of neovascularization of liver metastases using perfusion CT.

Abstract: Neovascularization of tumours produces a high microvessel density. Although diagnostic imaging is unable to visualize microvessels directly, it is possible to demonstrate associated changes in tissue perfusion. The aim of this study was to use the quantitative functional information and high spatial resolution of perfusion computed tomography to study neovascularization of hepatic metastases. Perfusion CT was performed in 13 patients with hepatic metastases from various primary tumours. Arterial perfusion was measured in the metastasis; both arterial and portal perfusion were measured in a small rim of liver tissue immediately adjacent to the metastasis. Perfusion measurements were correlated against survival of the patient in nine cases. Arterial perfusion was increased above normal values, both in the metastasis (median: 0.62 ml min-1 ml-1; range: 0.26-3.05 ml min-1 ml-1) and in the adjacent liver (median: 0.51 ml min-1 ml-1; range: 0.14-1.60 ml min-1 ml-1). Portal perfusion of adjacent liver was highly...

A comparative study of radioprotection by Ocimum flavonoids and synthetic aminothiol protectors in the mouse.

Abstract: The radioprotective effects of two flavonoids, orientin (Ot) and vicenin (Vc), obtained from the leaves of Ocimum sanctum, and the synthetic compounds WR-2721 and MPG (2-mercaptopropionyl glycine) have been compared by examining chromosome aberration in cells of bone marrow in irradiated mice. Healthy adult Swiss mice were injected intraperitoneally (i.p.) with 50 micrograms kg-1 body weight of Ot or Vc; 20 mg kg-1 of MPG; 150 mg kg-1 of WR-2721 or double distilled water (DDW). They were exposed to whole body irradiation of 2.0 Gy gamma radiation 30 min later. After 24 h, chromosomal aberrations were studied in the bone marrow of the femur by routine metaphase preparation after colchicine treatment. Radiation (2 Gy) increased the number of aberrant cells from less than 1% in controls to almost 20%. Pre-treatment with all the protective compounds resulted in a significant reduction in the percentage of aberrant metaphases as well as in the different types of aberration scored. Vc produced the maximum reduc...

Carotid artery stenosis in patients who have undergone radiation therapy for head and neck malignancy.

Abstract: Although it is established that small and medium sized arteries undergo extensive radiation damage, the effect on large vessels such as the carotid arteries is less well understood. We sought to determine if an increased severity of carotid artery stenosis is present in patients who have undergone radiotherapy for head and neck tumours. 45 patients aged 43-90 years (average 67) with head and neck malignancies treated with radiotherapy underwent colour Doppler ultrasonographic scanning of the carotid arteries. These patients were compared with a population of asymptomatic historical controls. 60% of patients demonstrated stenosis ranging from 21 to 86%. 38% of patients demonstrated a stenosis greater than or equal to 50%. Carotid artery stenosis appears to be increased in patients who have previously undergone treatment with radiotherapy to the head and neck regions compared with controls (p < 0.001). These findings suggest that radiation has an adverse effect on large vessels. Colour Doppler follow-up may be indicated for patients receiving head and neck radiation therapy.

The use of nuclear medicine in infections.

Abstract: The spectrum of infectious diseases has changed over the last few years, hence the requirements for radionuclide imaging for the detection of infection are becoming more demanding so that, although gallium-67 and labelled leucocytes remain useful agents, there is currently great interest in the development of new agents especially able to target chronic, non-pyogenic inflammation. Agents can be classified according to the site at which the radiolabel is targeted: pre-endothelial (for example, labelled leucocytes), endothelial (for example, labelled anti-endothelial monoclonal antibodies) or post-endothelial (for example, fluorine-18-fluorodeoxyglucose (FDG)). 67Ga and labelled polyclonal human immunoglobulin (HIG) localize at inflammation initially as a result of increased endothelial permeability, followed by retention of the label through binding to local extravascular receptors. Labelled leucocytes are avidly taken up by acute pyogenic inflammatory foci but perform less well in chronic inflammation. Ot...

Radiotherapy treatment planning of brain tumours using MRI alone.

Abstract: MRI of the brain can provide images of very high quality revealing detailed information especially concerning the extent of abnormalities. As such MRI has great potential in the radiotherapy (RT) planning of brain tumours. However MRI has rarely been used alone as the basis for treatment planning primarily due to concern over potential geometric distortions. Treatment planning using MRI has therefore usually been carried out in conjunction with CT images. This work demonstrates that geometric distortions can be minimized by using a relatively small field-of-view, an increased receiver bandwidth, and a fast spin echo acquisition sequence, and that it is thus possible to perform RT planning using MRI.

Differential diagnosis of lymph node lesions: a semiquantitative approach with colour Doppler ultrasound.

Abstract: The aim of this study was to evaluate reactively enlarged cervical lymph nodes and nodal metastases in patients with squamous cell carcinoma, as well as nodes involved by malignant lymphoma, by means of colour Doppler ultrasound (CDUS) and to describe perfusion sites for each nodal group in order to determine if typical flow patterns exist for nodes with different pathology. In a prospective study, 63 untreated patients with palpable cervical lymph node enlargement (n = 208) underwent examination with CDUS. The sites of perfusion were subdivided into three groups: central, peripheral and hilar perfusion. The intensity of perfusion was subjectively quantified in a semiquantitative scale from 0 (no perfusion) to III (high perfusion). Finally, the overall perfused area of the lymph nodes was measured and the percentage of perfused nodal area was calculated. CDUS showed perfusion in 178 of 208 lymph nodes. Histological examination showed 49 reactively enlarged lymph nodes, 82 containing metastases and 47 with lymphoma. Reactively enlarged lymph nodes showed characteristically intense hilar perfusion (91.8%), whereas nodal metastases had mainly peripherally located flow (84.1%) of intensity grades I-III. Lymph nodes invaded by malignant lymphoma were highly perfused, showing colour signals in the centre as well as in the nodal periphery (78.7%). In conclusion, perfusional patterns may provide useful additional information in the differential diagnosis of cervical lymphadenopathy.

Diagnosis and staging of pancreatic cancer by endoscopic ultrasound.

Abstract: The aim of this study was to evaluate the usefulness of and problems associated with endoscopic ultrasonography (EUS) in the diagnosis and pre-operative staging of pancreatic cancer. 96 patients suspected of having pancreatic cancer were pre-operatively examined with EUS. 37 of these 96 patients had pancreatic cancer. Results of the EUS imaging were compared with findings of histology and/or surgery, and the patient's clinical course. The sensitivity and specificity of EUS for diagnosing pancreatic cancer were 89% and 97%, respectively. EUS had excellent sensitivity regardless of tumour size or location. EUS was accurate (90%) in determining tumour size in pancreatic cancers less than 3 cm in maximum diameter, but not for tumours greater than 3 cm (30%). The accuracy of tumour (T) and nodal (N) staging were 64% and 50%, respectively. EUS is a promising method for the early diagnosis and pre-operative staging of pancreatic cancers, but requires further refinement.

Target volume definition for three-dimensional conformal radiation therapy of lung cancer.

Abstract: Three-dimensional conformal radiation therapy (3DCRT) is a mode of high precision radiotherapy which has the potential to improve the therapeutic ratio of radiation therapy for locally advanced non-small cell lung cancer. The preliminary clinical experience with 3DCRT has been promising and justifies further endeavour to refine its clinical application and ultimately test its role in randomized trials. There are several steps to be taken before 3DCRT evolves into an effective single modality for the treatment of lung cancer and before it is effectively integrated with chemotherapy. This article addresses core issues in the process of target volume definition for the application of 3DCRT technology to lung cancer. The International Commission on Radiation Units and Measurements Report no. 50 definitions of target volumes are used to identify the factors influencing target volumes in lung cancer. The rationale for applying 3DCRT to lung cancer is based on the frequency of failure to eradicate gross tumour with conventional approaches. It may therefore be appropriate to ignore subclinical or microscopic extensions when designing a clinical target volume, thereby restricting target volume size and allowing dose escalation. When the clinical target volume is expanded to a planning target volume, an optimized margin would result in homogeneous irradiation to the highest dose feasible within normal tissue constraints. To arrive at such optimized margins, multiple factors, including data acquisition, data transfer, patient movement, treatment reproducibility, and internal organ and target volume motion, must be considered. These factors may vary significantly depending on technology and techniques, and published quantitative analyses are no substitute for meticulous attention to detail and audit of performance.

Prevalence of deep vein thrombosis in suspected and proven pulmonary embolism: a meta-analysis.

Abstract: The purpose of this study was to determine the prevalence of lower extremity deep venous thrombosis (DVT) in patients with suspected and proven pulmonary embolism (PE). A meta-analysis was performed, based on literature from January 1983 to June 1997. Papers obtained from a computer-aided literature search were divided into studies with pulmonary angiography or ventilation-perfusion (V/Q) scintigraphy as the reference study. Our own observational data of the prevalence of DVT in 149 patients suspected of PE were also reported. The estimated prevalence of DVT in patients with proven and suspected PE was calculated. In the 149 patients studied, the prevalence of DVT was 12% with suspected PE and 32% (95% confidence interval 20-46%) in patients with proven PE. The individual studies showed a considerable heterogeneity, the prevalence of DVT in proven PE ranged from 10 to 93%. The pooled estimate of the prevalence of DVT in patients suspected of PE, over all studies, was 18% (95% confidence interval 15-20%). The DVT prevalence in proven PE was 36% (95% confidence interval 22-52%) in the angiography-based studies, and 45% (95% confidence interval 33-58%) in the V/Q scintigraphy-based studies. In conclusion, the current meta-analysis shows that the prevalence of DVT in suspected PE is approximately 18%, and in proven PE 36-45%.

A simple method for investigating the effects of non-uniformity of radiofrequency transmission and radiofrequency reception in MRI

Abstract: Inhomogeneity of the transmitted or received B1 field leads to intensity variations in MR images and spatial dependence in apparent concentration in MR spectra. We describe a simple method for investigating such variations. The transmitted B1 field can be measured both in vivo and in vitro which allows investigation of sample dependent effects that can not be measured on phantoms. For homogeneous regions the method also allows the received B1 field to be measured both in vivo and in vitro. Our method uses only a standard spin echo pulse sequence and simple region of interest analysis and should be implementable on any commercial scanner. The method is demonstrated using a variety of transmission and reception radiofrequency coils both in vivo and in vitro.

Comparison of ultrasound and dual energy X-ray absorptiometry measurements in the calcaneus

Abstract: Ultrasound measurements have been proposed as a means of providing structural information on bone but have also been shown to correlate with density. High correlation coefficients have been obtained in vitro, but are lower for in vivo work. The aim of this study was to investigate the relationship of broadband ultrasound attenuation (BUA), speed of sound (SOS) and stiffness, to bone mineral density (BMD) measured in the calcaneus at a closely matched region of interest (ROI). Measurements were made in 55 post-menopausal and 20 young, normal women. Calcaneus BMD measurements were made using an ROI (fixed by reference to external axes) to represent the area and location of the ultrasound transducers and an ROI based on anatomical markers, positioned in the posterior part of the calcaneus. BUA was significantly correlated with calcaneus BMD in the fixed ROI (r = 0.77, p < 0.0001) and the anatomical ROI (r = 0.78, p < 0.0001). Correlation of BUA with axial BMD was lower at r = 0.63, p < 0.0001 for the spine (L2-L4) and r = 0.59, p < 0.0001 for the femoral neck. Results for SOS and stiffness were very similar. From the calcaneus dual energy X-ray absorptiometry (DXA) scan images the region representing the ultrasound measurement area was found to contain cortical bone edges in 60% of cases. In 16% of scans a small part (4.5 +/- 4.0%) of the ROI measurement area fell partially outside the heel. However, there was no obvious discrepancy in the ultrasound results in the individual cases where this occurred. The correlation between calcaneus BMD and BUA was improved from r = 0.72 to r = 0.86 when scans with a cortical edge in the measurement ROI were excluded. The values for SOS were similar. In summary, BMD of the calcaneus, when closely matched to the site of ultrasound measurement shows significant correlation with ultrasound measurements. By excluding scans in which the ultrasound measurement appeared to include bone edges, correlations of approximately r = 0.86 were obtained. However, the BMD result still does not explain all of the variance in the ultrasound results.

CT dimensions of the normal pericardium.

Abstract: Previous studies have suggested that the upper limit of the thinnest portion of the pericardium is 3-4 mm using 10 mm CT slices. However, these studies suffered from small sample sizes, long data acquisition times and unconventional viewing parameters. We have measured the width of the thinnest portion of the normal pericardium using 10 mm (100 patients) and 1 mm (100 patients) high resolution CT (HRCT) slices with modern CT equipment and fixed mediastinal window settings (400/20). The pericardium was identified in all patients and was best seen anterior to the heart. The pericardium is exceptionally well seen using 1 mm HRCT slices and this may be the optimal technique for visualization of the pericardium. The upper limit of the thinnest portion of the normal pericardium (mean value + 2 SD) was 1.2 mm (10 mm CT slices) and 0.7 mm (1 mm HRCT slices). These values are substantially lower than those previously reported and in line with anatomical findings.

Digital radiography in paediatrics: radiation dose considerations and magnitude of possible dose reduction.

Abstract: The purpose of this study was to evaluate the radiation doses received by paediatric patients examined using a digital radiography unit, and to compare these doses with those received from conventional screen-film systems. In this way, guidelines could be drawn up concerning the magnitude of possible dose reductions achievable using digital radiography. The study was undertaken on approximately 900 patients undergoing abdomen, chest, pelvis and skull examinations. Patients were categorized into the following age groups: 0-1 month, 1-12 months, 1-5 years, 5-10 years and 10-15 years. Approximately half were X-rayed using a Fuji computed radiography system and half using a conventional screen-film system. Entrance surface dose was calculated from the recorded exposure parameters and measured X-ray tube outputs. Dose-area product was recorded directly. Image quality was assessed clinically using criteria recommended by a working group of the Commission of the European Communities. Apart from chest examinations, it was found possible to reduce doses by about 40% on average, by using a computed radiography system instead of a 600 speed screen-film combination. There was no significant difference in the dose for chest examinations. Satisfactory image quality can therefore be achieved by using computed radiography as a 1000 speed system for abdomen, pelvis and skull examinations, and as a 600 speed system for chests. Since very few departments appear to use screen-film systems of speeds greater than 400, then, for most departments, the use of computed radiography would result in dose reductions of at least 60%, or 33% for chests.