Phase contrast X-ray imaging of mice and rabbit lungs: a comparative study.

The significant degree of X-ray phase contrast created by air-tissue interfaces, coupled with the poor radiographic contrast of conventional chest radiographs, makes the inflated lung an ideal candidate for investigating the potential diagnostic improvement afforded by phase contrast X-ray imaging. In small animals these methods highlight the lung airways and lobe boundaries and reveal the lung tissue as a speckled intensity pattern not seen in other soft tissues. We have compared analyser-based and propagation-based phase contrast imaging modalities, together with conventional radiographic imaging, to ascertain which technique shows the greatest image enhancement for various lung sizes. The conventional radiographic image of a mouse was obtained on a Siemens Nova 3000 mammography system, whilst phase contrast images of mice and rabbit chests were acquired at the medical imaging beamline (20B2) at the SPring-8 synchrotron radiation research facility in Japan. For mice aged 1 day, 1 week and 1 month old it was determined that analyser-based imaging showed the greatest overall image contrast, however, for an adult rabbit both techniques yielded excellent contrast. The success of these methods in creating high quality images for rabbit lungs raises the possibility of improving human lung imaging using phase contrast techniques.

Optimization of scanning parameters for multi-slice CT colonography: experiments with synthetic and animal phantoms.

AIM: To determine the optimal collimation, pitch, tube current and reconstruction interval for multi-slice computed tomography (CT) colonography with regard to attaining satisfactory image quality while minimizing patient radiation dose. MATERIALS AND METHODS: Multi-slice CT was performed on plastic, excised pig colon and whole pig phantoms to determine optimal settings. Performance was judged by detection of simulated polyps and statistical measures of the image parameters. Fat and muscle conspicuity was measured from images of dual tube-current prone/supine patient data to derive a measure of tube current effects on tissue contrast. RESULTS: A collimation of 4 x 2.5 mm was sufficient for detection of polyps 4 mm and larger, provided that a reconstruction interval of 1.25 mm was used. A pitch of 1.5 allowed faster scanning and reduced radiation dose without resulting in a loss of important information, i.e. detection of small polyps, when compared with a pitch of 0.75. Tube current and proportional radiation dose could be lowered substantially without deleterious effects on the detection of the air-mucosal interface, however, increased image noise substantially reduced conspicuity of different tissues. CONCLUSION: An optimal image acquisition set-up of 4 x 2.5 mm collimation, reconstruction interval of 1.25 mm, pitch of 1.5 and dual prone/supine scan of 40/100 mA tube current is proposed for our institution for scanning symptomatic patients. Indications are that where CT colonography is used for colonic polyp screening in non-symptomatic patients, a 40 mA tube current could prove satisfactory for both scans.

X-ray refraction effects: application to the imaging of biological tissues.

The purpose of this study was to explore the potential of refraction contrast X-ray imaging of biological tissues. Images of dissected mouse lungs, heart, liver and legs were produced using the medical beamline at the Elettra Synchrotron at Trieste, Italy. The technique used was diffraction enhanced imaging. This utilizes a silicon crystal positioned between the tissue sample and the detector to separate refracted X-rays from transmitted and scattered radiation by Bragg diffraction. The contrast in the images produced is related to changes in the X-ray refractive index of the tissues, resulting in remarkable clarity compared with conventional X-ray images based on absorption effects. These changes were greatest at the boundaries between different tissues, giving a marked edge enhancement effect and three-dimensional appearance to the images. The technique provides a way of imaging a property of biological tissues not yet exploited, and further studies are planned to identify specific applications in medical imaging.

A comparison of bolus chasing and static digital subtraction arteriography in peripheral vascular disease.

The purpose of this study was to compare the techniques of bolus chasing angiography (BCA) and digital subtraction angiography (DSA). 75 patients with symptomatic atherosclerotic peripheral vascular disease were randomly assigned to have their lower limbs examined by BCA or DSA. Dose-area product (DAP), time of examination and dose of contrast medium were measured. Staff doses were measured with personal electronic dosemeters. Image quality was assessed from the laser printed images. DSA produced better images of vessels below the inguinal ligament, particularly the crural vessels (1/76 vs 17/74 non-diagnostic examinations, p < 0.00001) but at a higher DAP (median 53.8 Gy cm2 vs 18.9 Gy cm2, p < 0.01). Contrast medium dose was higher with BCA (29.8 gI2 vs 25.3 gI2, p < 0.01). Staff doses per unit patient dose were 2.3-3.3 times higher with BCA than DSA. Because of the poor long-term prognosis of patients with peripheral vascular disease, the improved image quality obtained by DSA justifies the increased radiation dose.

Radiation risk estimation in varicocele embolization.

Varicocele embolization is performed in healthy young men with normal life expectancy. Therefore, it is essential that the radiation risks associated with the procedure are minimized. The radiation risks associated with varicocele embolization have been estimated retrospectively from dose-area product records in a series of 41 cases and compared with a prospective series of 10 cases. Lithium fluoride dosemeters were used to measure gonad dose in the prospective series. Estimated lifetime fatal cancer risk was of the order of 0.1% in the retrospective series. A seven-fold reduction in median radiation dose was observed in the prospective series. The results indicate that with meticulous attention to technique, substantial reductions in radiation exposure can be achieved.

Breast cancer diagnosis using scattered X-rays.

Small-angle X-ray diffraction data has been collected from 99 ;core-cut' breast tissue specimens representing a number of different pathologies. Data in the range 75-1390 A have been compared with controls from patients with no breast disease. Bessel functions and Bragg maxima resulting from the fibrillar structure of collagen have been identified. The Bragg maxima indexed onto a 649 A lattice. Systematic differences in the intensities and D-spacings between the collagen of malignant, benign and normal tissue groups have been clearly demonstrated and quantified. These differences appear to be due to a significantly lower structural order within the malignant tissues. Possible explanations for this are discussed and the potential for utilizing this observation in cancer diagnosis is considered.

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

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.

Use of a remotely controlled mechanical pump for coronary arteriography: a study of radiation exposure and quality implications.

BACKGROUND: Exposure to radiation is a hazard of invasive cardiology. To minimise the risk it is essential to keep the doses received as low as possible. AIM: To assess the effect on cardiologist radiation exposure and the quality of coronary artery opacification of the use of a remotely controlled mechanical pump for coronary arteriography. A secondary aim was to assess any disadvantages and safety. METHODS: 319 patients were randomised to have coronary arteriography carried out with contrast injected either by hand or by a remotely controlled mechanical pump. Six cardiologists participated: two catheter laboratories were used and both brachial and femoral approaches were included. The exposure of the cardiologists to radiation was assessed by film badge dosimetry. The badges were worn on the hat. The total time for the procedure, screening time, the dose-area product meter reading, and any complications were recorded for each examination. The quality of arterial opacification was reported on a scale of 0-5. RESULTS: The mean radiation dose per procedure was 0.011 mSv for hand injection of contrast and 0.005 mSv for mechanical injection (p < 0.01). There were no differences in procedure times or screening times. There were no complications attributable to mechanical injection. Arterial opacification was not significantly different in the two groups (4.01 v 4.03 for the left coronary artery, 4.68 v 4.78 for the right coronary artery). The right coronary artery was consistently better opacified than the left by both techniques (4.59 v 3.89, p < 0.001). CONCLUSIONS: Use of a remotely controlled mechanical pump for coronary arteriography reduced cardiologist radiation exposure by half. It was not associated with any inconvenience, expense, or complications and produced arterial opacification at least as good as injection by hand.

The use of effervescent agents in the small bowel meal examination.

Some perceived disadvantages of the small bowel meal examination are failure of adequate distension, lack of a double contrast effect and the duration of the procedure. A new use for effervescent granules during the small bowel meal is described which reduces the examination time by 70% and reduces the radiation dose to the patient.

Lead thickness in shielding in the protection of radiodiagnostic staff.

We indicate the principles which can be used to apply cost-benefit analysis to radiation protection of staff in an X-ray department. The cost of saving radiation exposure to staff by varying the lead equivalence of lead gowns and lead protective screens is calculated. The cost is compared with the financial values of the detriment as assessed by the National Radiological Protection Board. The expenditure required to avoid a man-Sv for staff protection in diagnostic departments is suggested. In the examples we take, it is found that the larger staff dose reductions, and often the cheaper reductions, can be obtained by reducing the radiation dose to the patient. There are, of course, major additional advantages to the patient in reducing this dose.

The use of carbon fibre material in table tops, cassette fronts and grid covers: magnitude of possible dose reduction.

The X-ray transmission of a number of radiographic components, some of conventional construction and some incorporating carbon fibre material, has been measured under clinically realistic conditions. At 80 kVp the use of carbon fibre materials enables the patient dose to be reduced by 30-50% depending on the existing equipment, type of examination and technique used. Typically the dose can be reduced by 3-15% by changing the table top, 6-12% by changing the front of the film cassette and 20-30% by using a grid with carbon fibre covers and fibre interspace. The higher cost of carbon fibre components can normally be justified by such dose savings. An indication of the absorption of all such components should be provided by manufacturers.

Argon laser therapy for cutaneous lesions.

This paper presents a review of the results of treatment of a series of cutaneous vascular lesions with the argon laser. The lesions were evaluated before treatment, both clinically and histologically. Argon laser therapy appears to be most effective for purple port wine stains on the faces of adults and telangiectatic lesions involving the nose and forehead. Complications seem to be particularly associated with its use in children and about the upper lip and chin.

Radiation dose to the fetus in obstetric radiography.

The mean dose to the fetus and fetal head, together with the doses to the fetal gonads and maternal gonads, have been estimated to be 107, 56, 131 and 136 mrad respectively for an obstetric prone oblique examination of the abdomen, using a rare-earth screen-film combination. The doses were derived by measuring skin doses on a series of women in late pregnancy undergoing the above examination and by using measured depth-dose information. The position of the fetus relative to the maternal skin surface was determined by ultrasonic scanning.

A quantitative evaluation of film and film/screen combinations for mammographic examination.

A test phantom containing simulated micro-calcifications was constructed. This was imaged by seven systems suitable for use in mammography, firstly in scatter-free conditions and secondly with the addition of tissue-equivalent scattering material. The ability of the systems to resolve micro-particles of known size was assessed using the techniques of signal detection theory. The resultant receiver operating characteristic curves separated the systems into three major groups. Firstly, high resolution systems requiring high radiation dose techniques; secondly at the other extreme, a mediocre imaging system producing its results at low radiation levels; and thirdly a larger middle group producing intermediate resolution of fine particles at similar, acceptable dose levels. The ability to image small particles does not increase linearly with the radiation dose. Scatter did not affect all of the systems to the same extent.