PubMed Health⌕ Search

Biomedical subjects

K Cranley

Publications and source records attributed to K Cranley.

15 recordsLinked to original sources
PubMed2001

Provision of MRI can significantly reduce CT collective dose.

The purpose of this study was to investigate the proportion of patients currently being investigated by CT that could be investigated by MRI with a potential reduction in exposure to ionizing radiation. The health detriment arising from the radiation dose associated with CT has been quantified in terms of the number of likely cases of serious health effects. The results show that a significant saving in the collective radiation dose is possible, with an associated detriment of between 0.23 and 0.33 cases of cancer or severe hereditary effects averted in one imaging department every year. In selecting the balance of provision of MRI and CT facilities, the health detriment associated with the radiation dose from CT should be considered.

Adolescent↗
PubMed2000

Application of draft European Commission reference levels to a regional CT dose survey.

A survey of CT doses in Northern Ireland in the period between October 1995 and March 1997 was carried out. The survey included all but one of the 10 scanners in use at the time, and, additionally, two others that were replacement machines. The method used was to study standard protocols and calculate doses to the NRPB mathematical phantom, so that a direct comparison could be made with other surveys carried out in a similar fashion elsewhere. The survey addressed the patient radiation dose but not image quality or clinical outcomes. It is estimated that in Northern Ireland the contribution to collective dose to the population from CT is about 40% of that from all medical X-rays. The proposed European Commission reference quantities, weighted CT dose index and dose-length product were computed and their potential use evaluated. A full study of mean values of effective dose per examination revealed the average dose per examination was not significantly different from that found in the 1989 UK survey, although several procedures gave rise to doses that were high enough to be investigated with a view to justification or reduction. One of the scanners was found to give consistently high doses. It is likely that a revision of the mAs values used on this scanner will produce a significant reduction in patient doses without compromising image quality. When compared with the draft EC reference levels, fewer procedures were found to have excessively high dose values. The proposed EC reference levels would therefore be useful for continual monitoring of CT dose status, but do not appear to provide as comprehensive an assessment of patient exposure as that given by consideration of effective doses.

Clinical Protocols↗
PubMed1998

Digital imaging: a valuable technique for the postoperative assessment of cochlear implantation.

Cochlear implantation with a multi-channel electrode array which provides stimulation via the auditory nerve has become a standard treatment for profound deafness. Postoperative radiography demonstrates electrode position and enables confirmation of satisfactory intra-cochlear electrode placement. The number of active electrodes which have been inserted can be determined and possible complications such as electrode kinking or slippage can be assessed. We evaluated digital radiography with confirmation of electrode position by intermittent fluoroscopy and assessed the relative radiation dose of the digital technique, conventional radiography and CT scanning. Radiation dose for this method usually ranges between 40 microGy and 440 microGy compared with a single exposure on the skull stand which produces a dose to the region of the cochlea of 470 microGy and a CT exposure of 950 microGy. The digital technique is comfortable for the patient, easily reproducible and provides images of high diagnostic quality enabling each electrode to be identified, which is especially valuable in association with postoperative electrode mapping. It also involves a lower radiation dose than conventional radiography. We now use digital radiography for all postoperative cochlear implant assessment.

Adolescent↗
PubMed1996

The potential for dose reduction in diagnostic radiology using low attenuation materials in table tops.

It is important to be able to assign priorities to the purchase of radiological equipment. The ability to incorporate potential dose savings into a ranking procedure involving costs is therefore of interest. In this paper we have considered the question of the dose saving made available by the selection of low attenuation table tops and have described how to generate a factor which can be used in a ranking procedure such as cost effectiveness analysis. We describe how data on the expected dose saving can be obtained from measurements of the aluminium equivalent thickness in air used in conjunction with theoretical spectral data. The magnitude of the overestimate when in air measurements alone are used is presented, as is a ready reckoner for determining the true dose saving when changes in table top are considered. Unless the table to be replaced is of some age, the expected dose saving will vary between 6% and 1%.

Cost-Benefit Analysis↗
PubMed1995

Technical note: perspex blocks for estimation of dose to a standard breast--effect of variation in block thickness.

Mean glandular dose in mammography may be deduced from measurements made using Perspex blocks. This method is almost universally used in the National Health Service Breast Screening Programme. The effect on the estimated mean glandular dose of variations in the measured thickness of Perspex from a nominal thickness of 40 mm was investigated. Results are presented from three UK Regions. Variations in measured Perspex thicknesses ranged from almost 8% below to about 2% above the 40 mm nominal, causing errors in dose estimation, if uncorrected, of about +20% to -6.5%. A means of correcting dose estimates for measured differences in block thickness is presented. An alternative method of ensuring consistent dosimetry would be to use accurately machined Perspex blocks.

Breast↗
PubMed1988

The measurement of total filtration of diagnostic X-ray tubes.

New data based on calculated X-ray spectra for X-ray tubes of different target angles and various magnitudes of kilovoltage ripple are presented. Currently available published data relating the total filtration of diagnostic X-ray tubes to the measured half-value thickness (HVT) are of limited use to those carrying out such measurements. Electronic penetrameters are now widely available, which allow improved accuracy in the measurement of tube kilovoltage, and the monitoring of waveforms. This has highlighted the necessity to refer to data which apply to the correct waveform ripple value, and to the correct tube target angle. A wide range of data referring to 10 degrees and 16 degrees target angles has been calculated. An experimental example is presented where measured values of HVT on nine X-ray tubes are converted to values of total filtration, using the calculated data.

Filtration↗
PubMed1987

Radionuclide monitoring in Northern Ireland of the Chernobyl nuclear reactor accident.

Northern Ireland received higher radiation doses due to the radionuclide contamination from the Chernobyl nuclear reactor accident than did the south of England. Levels of radioactive iodine ((131)I) and caesium ((137)Cs) in cows' milk in Northern Ireland increased to 166 and 120 Bq/l respectively in May 1986, but had decreased by factors of one million, and of twenty-five, respectively, by 1 September 1986. The resultant radiation doses represent less than one per cent of those received by a Northern Ireland individual over a period of 40 years from natural background radiation sources. The added risk to any individual from the Chernobyl accident will therefore be very small and may best be judged in the context of the enormously greater risk of death due to potentially preventable diseases, such as smoking-related lung cancer, and coronary heart disease.

Adult↗
PubMed1982

A preliminary investigation of radiation dose reduction on an EMI CT5005 whole body scanner using a copper wedge.

The effects of the existing filtration system upon a narrow, parallel beam of X rays were considered. The profile of a Cu filter to be placed on the tube-side A1 wedge was calculated on the basis that the total energy incident on the detector box would remain unchanged when the other A1 wedge was removed. A Cu wedge was machined according to this profile. The effects of this modification on surface radiation dose delivered to a 25 cm EMI water phantom were both predicted and measured for horizontal traverses, and were in broad agreement. The reduction in integral radiation dose to the 25 cm water phantom was predicted as 39%. Dose reductions measured at several points on the surface and within an Alderson Rando anthropomorphic phantom head averaged 53% and 20% respectively. The modified system was evaluated in terms of imaging ability, and although some degradation was seen, images of the EMI composite phantom remained "diagnostic" in quality, despite non-ideal responses of some photomultiplier tubes at intermediate and extreme positions of the traverse periphery.

Copper↗
PubMed1981

An evaluation of count rate losses due to dead time in static and mobile gamma camera data analysis systems.

The count rate responses of a gamma camera and data analysis system have been shown to behave as two separate components. Five systems made up of combinations of two static gamma cameras, two data analysis systems, and a mobile gamma camera system were investigated. Camera and data analysis system dead times are quoted and percentage corrections are plotted against radioactivity of 99 Tcm in a patient phantom within the field of view. It is recommended that such a detailed study should be performed for any gamma camera system as part of a quality assurance programme.

Gamma Rays↗
PubMed1980

Correction for deadtime losses in a gamma camera/data analysis system.

In quantitative analyses of dynamic radionuclide studies, using large activities of 99mTc flowing through organs it is necessary to determine accurately count-rate losses and to provide appropriate corrections. A method is described for estimating deadtimes and applying corrections to the observed counting rates using a two component model where the gamma camera is considered to have a purely paralyzable deadtime and the data analysis system a purely non-paralyzable deadtime.

Radionuclide Imaging↗