Radiology Quality Research Articles

Relationship Between Medical Requirements and Technical Parameters of Good Imaging Performance and Acceptable Dose

An important aspect of the workshop on optimisation of image quality and patient exposure in diagnostic radiology in Oxford 1989 was the need to elaborate on objective criteria for the image radiograph and its parameters in accordance with defined physical quantities and units. Procedures to assess the radiographic image in a way appropriate for the clinical problem are based on understanding the information generated by X rays and the properties of the visual system that perceives this information. The physical parameters for the evaluation of clinical radiographs are mainly: mean optical density, useful density range, detail size and detail contrast, object contours and transitions, noise, mottle and texture, amount of scattered radiation, image distortion, artefacts, and dose. The fundamental relationships between these parameters will be discussed together with their variation and accepted tolerances. The methods for measuring these parameters, i.e. densitomery, microdensitometry, histogram methods and luminance are briefly described. The final image, produced as a function of imaging conditions, also including viewing is converted to the quantitative information derived from test objects, although these objects bear no resemblance to radiographs of the human body. In evaluating diagnostic X ray systems, the use of anthropomorphic phantoms may therefore solve the problem and bridge the gap between physical parameters and the diagnostic need to perform optimal and harmonic radiographs.

Gel-Based Phantoms for Diagnostic Radiology

Tissue-equivalent phantoms are desirable for evaluation of image quality and dose in diagnostic radiology. A simple and inexpensive method for fabricating tissue-equivalent phantoms simulating soft tissues for use in radiologic imaging is presented. The tissue-equivalent materials are based on the combination of three basic constituents whose quantity, within limits, can be independently adjusted. Protein is supplied by the use of gelatin (collagen) mixed with water to form a gel, and lipid can be supplied using one of a variety of animal or vegetable fats. CT phantoms have been constructed with simulated tumours in a liver background. Contrast down to 0.1% can be reliably produced. Mammographic phantoms have been produced simulating compressed breasts. A gel step wedge is used to measure image contrast. Simulated tumours with a spiculated border are cast into individual steps to assess tumour visability over a range of optical densities.

Gel-Based Phantoms for Diagnostic Radiology

Tissue-equivalent phantoms are desirable for evaluation of image quality and dose in diagnostic radiology. A simple and inexpensive method for fabricating tissue-equivalent phantoms simulating soft tissues for use in radiologic imaging is presented. The tissue-equivalent materials are based on the combination of three basic constituents whose quantity, within limits, can be independently adjusted. Protein is supplied by the use of gelatin (collagen) mixed with water to form a gel, and lipid can be supplied using one of a variety of animal or vegetable fats. CT phantoms have been constructed with simulated tumours in a liver background. Contrast down to 0.1% can be reliably produced. Mammographic phantoms have been produced simulating compressed breasts. A gel step wedge is used to measure image contrast. Simulated tumours with a spiculated border are cast into individual steps to assess tumour visability over a range of optical densities.

National Health Service breast screening programme results for 1991-2.

To report the results of the NHS breast screening programme for the year March 1991 to April 1992. A report of statistics was derived from Körner (K62) returns and from the radiology quality assurance programme. Detection rates for breast cancer and small (< or = 10 mm diameter) invasive cancer, benign biopsy rates, and recall and acceptance rates. The acceptance rate for screening across the United Kingdom was 71.3%. The referral rate for further investigation was 6.2% (regional 4.3-9.0%). The breast cancer detection rate was 6.2 cancers per 1000 women screened (5.1-9.0) and the detection rate of invasive cancers < or = 10 mm was 1.4/1000 (1.0-2.3). 72% of screening programmes reached the target 70% acceptance rate, and 95% of programmes achieved a recall rate of less than 10%. 75% of programmes had a cancer detection rate of more than 5/1000, but only 32% had a detection rate for invasive cancers < or = 10 mm of more than 1.5/1000. Overall, the results of the screening programme for the year 1991-2 can be regarded as extremely satisfactory, given the size and complexity of the operation.

How to Implement a Radiology Quality Improvement Program

To get started and to help overcome some of the problems with implementation mentioned above, five essential things need attention: 1. Top level commitment; 2. Physician participation; 3. On-going education; 4. Performance measurement (both of the department and individual); 5. Up-front investment of time and resources. The fundamental changes in technology, financing, and accountability present formidable challenges to departments of radiology today. Fortunately, quality management techniques offer a way to meet the challenges and simultaneously improve efficiency of care and quality. Learning and practicing these techniques is not an easy task, but overcoming the obstacles to implementation and getting on with the job will prove very rewarding.

Some methodological questions concerning receiver operating characteristic (ROC) analysis as a method for assessing image quality in radiology

This paper raises five methodological questions concerning receiver operating characteristic (ROC) analysis: (1) can the ROC "confidence criterion" be applied in a valid, reliable way?; (2) can ROC deal with ambiguous findings?; (3) can ROC deal effectively with false-negative findings?; (4) are ROC curves susceptible to valid statistical testing?; and (5) are ROC results useful in choosing among alternative imaging modalities? A review of the evidence leads to six conclusions. First, using ROC, all radiological findings must be unambiguously scored as true-positive, true-negative, false-positive, or false-negative, often forcing arbitrary, procrustean choices on readers and evaluators. Second, ROC requires radiologists to report findings by confidence level on a consistent, reliable basis throughout a ROC experiment; something that seems unrealistic, given what is known about human performance in almost all perceptual tasks of comparable complexity. Third, as gathered during the typical experiment, ROC data are probably nominal, but treated as if ordinal (or even interval) data, leading to distorted results. Fourth, ROC does not deal effectively with false-negatives, despite their importance. Fifth, there is no satisfactory method for statistically testing the significance of observed differences between two ROC curves if they are based on nominal data. Finally, the artificial tasks required of radiologists in a ROC evaluation limit the usefulness of ROC results in choosing among the imaging modalities.

Optimization of Image Quality and Patient Exposure in Diagnostic Radiology

Optimization of Image Quality and Patient Exposure in Diagnostic Radiology

Quality assurance of viewing boxes: proposal for establishing minimum requirements and results from a Spanish quality control programme

The Medical Physics Group at the Complutense University of Madrid has undertaken a project, during the last 3 years, under a CEC contract on “Optimization of Radiation Protection in Diagnostic Radiology” (Vañó, 1989) in which a pilot programme of Quality Control (QC) was included (Gonzalez, 1989). Exhaustive patient and occupational dose measurements showed differences between the test results from similar equipment. This fact moved us to set up a Quality Control Programme (Guibelalde &amp; Llorca, 1989), and then several Quality Assurance (QA) programmes. The necessity to establish minimum performance requirements for image quality, and the convenience of denning objective parameters to make possible further advances in the reduction of patient doses and optimization of image quality, has been pointed out at several Workshops of the Commission of European Communities (CEC) on Image Quality in Diagnostic Radiology. A Working Document of the CEC (1989) has recently been issued emphasizing the need to develop appropriate quality criteria. The aim of these activities is to produce standards and quality criteria that will provide a framework, throughout the European Community, for producing images with minimum patient dose and maximum quality. Efforts to ensure the best quality and consistency of viewing boxes must aid these objectives. The brightness and uniformity of viewing boxes are two factors that can be measured in absolute units. These factors are not influenced by other elements of image quality control and, therefore, can be used for comparisons between different centres.

The effect of rare earth filtration on patient exposure, dose reduction, and image quality in oral panoramic radiology.

Rare earth intensifying screen material (Gd2O2S:Tb) was added to the standard Al filtration of an oral panoramic x-ray unit, resulting in a beam capable of achieving reductions in patient dose without a loss of image quality. The added rare earth filtration technique resulted in patient dose reductions of 21-56%, depending on anatomic sites, when compared to the conventional Al filtration technique. Films generated from both techniques were measured densitometrically and evaluated by a panel of practicing clinicians. Diagnostically significant differences were minimal. The results indicate that use of rare earth filters in oral panoramic radiography is an effective means of reducing exposures of dental patients to ionizing radiation.

Diagnostic quality control: The missing link in dental radiology quality assurance

A diagnostic quality-control program that includes assessment of film quality, critique, and remediation as an ongoing process is described.

A technique for routine calibration of thermoluminescent dosimeters in the diagnostic energy range.

Four different techniques for calibrating lithium fluoride thermoluminescent dosimeters were compared at two beam qualities in the diagnostic energy range. The techniques included in-air, saturation backscatter, and Bureau of Radiological Health (BRH) test stand geometry with and without an ionization chamber. The results indicate that there are no statistical differences between any of the calibration techniques evaluated. Hence, the technique using the BRH test stand with an ionization chamber is a simple and reproducible calibration procedure which may be used in a routine diagnostic radiology quality assurance program.

Backscatter factors for diagnostic radiology (1-4 mm Al HVL)

Backscatter factors (BSF) in the diagnostic radiology quality range (1-4 mm Al) have been determined by ionisation chamber and TLD techniques. Ionisation chamber measurements are subject to systematic errors due to displacement of the scattering medium, although high precision allows the demonstration of the kVp dependence of BSF for a given first HVL. TLD techniques lead to a reduction of these systematic errors although the read-out procedures lead to lower precision than ionisation chamber measurements. Comparison of the TLD-based measurements with the data of Br. J. Radiol. Supplement 11 (1972) indicates good agreement (<2%) for HVLS greater than 2 mm Al and field sizes greater than 10 cm*10 cm. Comparison with the work of other authors not covered by Supplement 11 indicates, in general, good agreement only where kVp-filter combinations are similar. The importance is stressed of taking into account the kVp-filter combination when defining the quality of an X-ray beam.

Development of a radiographic chest phantom with disease simulation.

An anthropomorphic chest phantom with realistic disease simulation is described with a review of previously available chest phantoms. The need for subjective image analysis is discussed and compared with the existing physics parameters as a means of evaluating image quality in chest radiology. An introduction to the use of such a radiographically realistic chest phantom with lung parenchymal detail and disease simulation is illustrated.

Scanning multiple slit assembly: a practical and efficient device to reduce scatter

A scanning multiple slit assembly consisting of an array of long narrow beam-defining slits coupled with scatter-eliminating slots beneath the patient is a feasible, practical, and efficient method of reducing scatter and increasing contrast and image quality in diagnostic radiology. Measurements of the ratio of scattered-to-primary radiation transmitted by a scanning multiple slit assembly and a conventional high ratio grid under similar conditions showed the relative intensity of scatter transmitted by the slit assembly to be only one-third that of the grid. A noticeable improvement in contrast was obtained using the slit assembly, without increase in patient exposure. The design, construction, and clinical implications of such a scatter-eliminating technique are discussed.

Reynold F. Brown, A.B., M.D. President, Radiological Society of North America.

The Radiological Society of North America has elected and installed as its new President a statesman of radiology, a man of many talents who epitomizes the broad aspects of radiology and the many facets of which it is composed. A fearless fighter for improved quality of radiology, for radiation protection of patient and radiologist, an organizer and leader in setting radiology on a scientific basis, the new President brings distinction to the University of California, to the West Coast, and to the Radiological Society of North America. Reynold F. Brown was born in Homestead, Penna., Dec. 26, 1916. All of his advanced education was obtained at the University of California. He was graduated from the Berkeley campus with Honors in 1944. He attended the medical school of that University in San Francisco, graduating high in his class in 1947, after achieving membership in the Alpha Omega Alpha Society. Following his internship at the same institution, Dr. Brown decided to go into radiology. From then on his na...

Economy and Quality in Radiology

One of the outstanding features of the modern X-ray equipment shown at the Paris Congress last summer was the increasing tendency towards complete protection. Certain milestones on the road to safety have, I am pleased to recall, already been described to the Institute. After the penetration into medical practice of the ordinary self-protected tube, the shockproof tube and apparatus quickly came into prominence. At the Paris exhibition, apparatus which was not shockproof was somewhat overshadowed and certainly in the minority. All apparatus described in the course of this paper are of the fully self-protected type. The question of protection, however, can, I think, be dismissed as a topic which is well understood. I will therefore confine myself to the subject of economy, which is perhaps of equal importance. Economy of energy, economy of tension, economy of space. We should perhaps discuss first the economy of energy. In the past, we have seen the appearance of gigantic apparatus and tubes which were intended to stand tremendous loads, all for the purpose of the abbreviation of exposure times. It is problematical whether the values of such powerful installations is not sometimes overestimated. It is clear that the use of very powerful tubes with focal surfaces of corresponding area is only justified for instantaneous radiography, for with slowly moving or stationary objects a small focus tube will certainly give a better image than a powerful one with large focus.