Diagnostic X-Ray Imaging Quality Assurance

Diagnostic X-Ray Imaging Quality Assurance (QA) and Quality Control (QC)

Diagnostic X-Ray Imaging Quality Assurance (QA): It is a program used by the caregiver management to retain the best possible diagnostic image quality with the least risk and suffering to patients. Included under the program are quality control tests at regular intervals, measures for preventive maintenance, administrative procedures and training. Besides, it also includes continuous evaluation of the competence of the imaging service and the way to start remedial action. The main objective of a radiology quality assurance program is to guarantee the continual provision of quick and precise diagnosis of patient. This objective will be effectively fulfilled by having in place a QA program having three secondary goals as follows: (i) diagnostic imaging quality maintenance (ii) minimize the radiation exposure to patient and staff; and (iii) cost effectiveness. (Health Canada, 2006)

Diagnostic X-Ray Imaging Quality Control (QC): Under this program, sequences of standardised tests are conducted to find out modifications or alterations in X-ray equipment functionality from its original level of performance. The purpose of such tests when carried out on a routine basis permits immediate remedial action to retain the quality of X-ray image. However, it is essential to bear in mind that the doctor in charge of the X-ray facility bears the final responsibility for quality control and not with the regulatory body. (Health Canada, 2006) total diagnostic X-ray Imaging QA consists of six different constituents. These comprise of radiation exposure monitoring, radiographic unit monitoring, sensitometry and darkroom monitoring, the application of technique charts, the evaluation of repeat rates and continuing education. Radiation Exposure Monitoring: For safety measures all radiology departments must apply a system for monitoring the cumulative occupational exposure to employees working with ionizing radiation. Every employee must be provided with thermoluminescent dosimeters or film badges must be given to all employees and monthly dosages posted on a bulletin board. This apart, a lot of departments also scrutinize patient exposure to radiation by simple methods as a patient advisement device as well as a legal precaution. For instance, the total fluoroscopy exposure time collected at the time of a fluoroscopic procedure can be obtained from the fluoro times and recorded on patient database. The number of overhead exposures obtained for each method can even be recorded on the patient database. (Carrol, n. d.)

Radiographic Unit Monitoring: Majority of the quality control and basic measurement checks for radiographic apparatus can be done by the radiographer. The value of this type of evaluation is demonstrated by the reality that the radiation output per milliampere has been observed to differ by 50% from one unit to the subsequent within a radiology department and to the extent of 100% between units in different radiology departments. Besides, it is suggested that each of the equipment inside a department is meticulously inspected by a radiation physicist once every six months at the minimum. (Carrol, n. d.)

Sensitometery and darkroom Monitoring: Majority of these functions are possible and must be carried out by the professional radiographer with intermittent backup from processor experts. In situations when no quality control program is present, processing mistakes and conditions are responsible for more than 35% of every repeats. Hence every quality control programs much start with the processor. (Carrol, n. d.)

Use of technique charts: Repeat rates of radiology departments are reduced by as much as 25% when a systematic approach to the development of techniques is applied. It is seen that 73% of all the repeats are caused due to radiographs emerging as either very light of very dark. Some of this problem is because of darkroom and processing variables; and the remaining is due to inappropriate choice of methods. At the time when technique charts are applied on concert with processing sensitometry, repeats can be reduced to 50%. (Carrol, n. d.)

Analysis of repeat rates: Implementing any other feature of a quality control program in the absence of repeat analysis bear scanty meaning. The maximum value of repeat analysis remains in the finding out of continuing education requirements in case of the imaging personnel. While dealing with those requirements by delivering in-service education, repeat rates are able to be lowered as also patient exposure. Hence education remains an integral constituent in any quality control endeavour, however the exclusive educational requirements of the personnel must be found out in case it has to be effective. (Carrol, n. d.)

Continuing Education: At the time when the technological variables are evaluated and controlled, the highest aspect finding out radiographic consistency and the quality happens to be the expertise of the radiographer. The sphere of radiography is progressing in such a rapid manner with latest image receptor systems, computerization, and various new sub-specialities in imaging methods for which sustained learning must be an issue of survival as also professionalism. (Carrol, n. d.)

Repeat Analysis: It has been observed that one out of every ten radiographs have to be retaken. A lot of radiology departments have been fruitful in lowering their repeat rates down to 5-7% through total quality control program. A lot of variations are possible for repeat analysis program. In cases where there are no QC program, majority of the repeats are due to substandard technical quality of the radiograph, however in cases where a QC program is applied, 41% of all repeats are caused by positioning defects. Hence in these situations, the burden of the errors cannot be placed on electrical line surges, unpredictable processors and the technician of the darkroom. The two largely efficient methods of categorising repeat rates happen to be (i) by type of cause like positioning defects vs. technical defects and (ii) by the type of procedure, like head procedures vs. spine procedures. In case of radiographic quality control, the total number of repeats after deducting the number of green and blank films must be divided by the sum of the repeats and the good films made use for the period. (Carrol, n. d.)

Timer Quality Control in Radiographic Equipment: Modern day exposure timers are able to gauge a single pulse of electricity as short as 1/120 second in duration. Wrong exposure times can be can result in erratic methodology and a loss of control over the density of image. For accuracy, it is recommended that a workable range of accuracy for regular timers will be positive or minus 5%. (Carrol, n. d.)

Collimator Quality Control: In cases where the real size of the X-ray field is higher compared to that stated on the collimator control knobs, needless exposure of patients and more scatter fogging of the radiograph happens. At the time when the real field size is less compared to that stated, the anatomy of interest might be deducted from the field of view, needing repeat exposures. It is important for the radiographer, thus that the size of the field control knobs on the collimator as well as the projected visual light field correctly show the size and location of the real x-ray beam. (Carrol, n. d.)

Vertical Beam Alignment Quality Control: Sometimes, a light field that seems to be off-centered to the x-ray table transversely actually is off-centered however mis-angled. There is a possibility of this happening when the transverse tube angle lock has been used by a radiographer who failed to accord special care to put it to a precise vertical position following use. (Carrol, n. d.)

Two disciplines of activity have been designed to guarantee that the best possible diagnosis at an acceptable radiation dose and with the least cost. These disciplines are Quality Assurance -- QA and Quality Control -- QC. While it is important to note that QA deals with people, QC deals with devices and equipment. A QA program evaluates appropriate patient scheduling, reception and preparation. Besides, QA even entails interpretation of image as regards outcome analysis. On the other hand, QC is more tangible and apparent compared to the QA. A program of QC is devised to guarantee that the radiologist is provided with an optimal image that outcomes from a good equipment performance. QC starts with the X-ray device made use of to produce the image and persists with the regular evaluation of the image-processing facilities. QC ends up with a committed analysis of every image to locate the deficiencies and artifacts and to make the least use of reexamination. The type of QC program is determined largely by the features of the image produced. Normally, the QC program concentrates on the potency of the image to guarantee that those strengths are sustained. Maybe the most vital patient safeguard characteristic in case of a radiographic unit happens to be filtration of its X-ray beam. State laws need that general purpose radiographic units have a minimum total filtration of 2.5mm A1. (Bushong, n. d.)

Collimation: The X-ray field should coincide with the light field of the variable-aperture light-localizing collimator. In case these fields are not aligned in the proper manner, the proposed anatomy will be missed and the unplanned anatomy removed. Sufficient collimation can be found out with the help of any number of test tools devised for the purpose. It is observed that majority of the beams have in them positive beam limiting collimators -- PBL. The distinguishing features of these devices are that these are automatic collimators which gauge the proportion of the image receptor and make adjustment of the collimating shutters to that size. (Bushong, n. d.)

Focal-spot size: The spatial resolution of radiographic system is basically found out by calculating the focal-spot size of the x-ray tube. At the time when new equipment or a replacement x-ray tube is deployed, the focal-spot size should compulsorily be measured. The three most important tools which are used for calibration of focal-spot size are the pinhole camera, the star pattern and the slit camera. While the pinhole camera poses difficulty in use and needs a great exposure time, the star pattern is simple to use but has a great deal of limitations for focal-spot sizes less than 0.3 mm. The preciseness of the exposure timer must be evaluated every year or in fewer intervals in case a component of the operating console or the high-voltage generator has been put under major repairs. A preciseness of 20% both on the positive or negative side is acceptable for exposure time of 10 ms or lower. Subsequently Automatic Exposure Control -- AEC needs also to be evaluated. These instruments have been designed to give a fixed optical density irrespective of the thickness of the tissue, make-up, or the lack of success of the reciprocity law. (Bushong, n. d.)

Fluoroscopy Quality Control: Fluoroscopic tests can outcome in high patient dose. The entrance skin exposure -- ESE in case of an adult shows an average of 3 to 5 R/min or 30 to 50 mGy/min at the time when the fluoroscopy is being conducted and it can outcome in a skin dose of 10 rad or 100 mGy in case of a lot of fluoroscopic examinations. Fairly accurate doses are to be administered to patients which can be guaranteed through the performance of suitable QC measurements. Some of the measurements might be needed more on a regular basis following changes in the operating console, high voltage generator or the x-ray tubing. (Bushong, n. d.)

Automatic Exposure Systems: Every fluoroscope is built-in with some type of automatic brightness control -- ABC or Automatic Exposure Control -- AEC. Every system works similar to the photo-timer of a radiographic imager generating regular image brightness on the video monitor irrespective of the thickness or constitution of the anatomy. Since these systems are prone to damage or failure with use; fluoroscopic ABC must be examined every year. (Bushong, n. d.)

Tomography Quality Control: Apart from the evaluations conducted in the tenure of a QC of a radiographic system, a lot of additional measurements are needed in case of those systems which are also able to perform normal tomography. However, accurate performance standards are not present in case of conventional tomography. QC measurements are devised to guarantee that the features examined stay constant. It is important that the patient exposure must be measured for the most usual type of tomographic examinations. Exhibit -I shows a sample of the results derived from a three phase system and six representative tomographic examinations. (Bushong, n. d.)

Standard Quality Control -- QC tests that are undertaken with care during prescribed period of time are devised to spot gradually evolving functional X-ray and problems in the ancillary apparatus and to allow remedial action prior to major decline of image quality happens. The important cause for a QA program is undertaken in order to optimize the process of diagnosis and thus the benefits are obtained. A QA program merits the expenses that include (i) personnel costs - QA duties consists of not just the performance of QC tests but also initial education as also training (ii) Test equipment: QC test equipment cost is comparatively small as compared to total capital outlay of a radiology department (iii) reduction in patient flow from testing: It is imperative that QC tests are conducted outside the normal working hours, to the extent possible. (Parelli, n. d.)

The main cost savings in case of QA program happens to be the result of a lowering in repeat studies i.e. avoidance of unwarranted radiation dose to the patient. The savings in cost also comprise (i) Reduction in film wastage (ii) reduction in the wastage of chemicals (iii) reduced wear and tear of the equipment (iv) Reduced downtime of equipment (v) less time consumption of the personnel (vi) patient flow improvement (vii) lowered cost of equipment service. It is important that each X-Ray units has a QA Manual containing the list of names and qualifications of personnel responsible for supervision of QA, performance of QC tests and troubleshooting or servicing X-Ray and its allied apparatus. Besides, QA and QC records are also needed to be maintained for X-ray equipments and allied apparatus which must include (i) performance evaluation of the X-ray machine, covering acceptance testing and surveys of radiation safety. (ii) Confirmation that the X-ray apparatus is functioning in a secured operating manner and conducting of later QC tests outcomes are done. The most important QC lies with ensuring Photographic QC. Under this are included quality of the image, contrast, density, base plus fog and also the exposure of patients. The Optical density range must be within the ideal range of 0.5 to 2.5 OD values. (Parelli, n. d.)

Ensuring QC in conventional radiographic systems:- Under the conventional radiographic systems there are a lot of constituents whereby each one is subjected to variability with the passage of time. Within this system, the elements which are important are (i) kilovoltage (kVp) (ii) Milliamperage (mA) (iii) Exposure time (iv) X-ray beam filtration (v) Collimation i.e. X-ray beam restriction (vi) focal spot size (vii) Grid under which the parameters to be checked are type, uniformity and alignment. (viii) Intensifying screens (ix) Cassettes (x) Radiographic or X-ray films (xi) Darkroom conditions and (xii) photographic processors and chemicals. Any of the above components within the system holds the potential to sway or damage in such a manner so that the image quality might be degraded. Hence, to undertake all the activities in a feasible way, it is imperative to calibrate and control all of the suitable variables in the radiographic imaging chain. The correct QC tests shall be done, following the repair and replacement of any constituent of the X-ray system, before making use of the equipment in humans and whether such repair and/or replacement might impact (i) quality of image (ii) phototimer reproducibility (iii) accuracy of the exposure timer (iv) Linearity of Milliampere-seconds (v) kilovolt peak (kVp) accuracy (vii) skin entrance radiation dose (viii) Focal spot size. (Parelli, n. d.)

Radiation Safety/QA Program: It is important that every facility establishes a committee of individuals to be responsible for the radiation safety/QA program including those departments that employ X-rays for diagnostic purposes. The Committee must be constituted of at least a Radiologist, the Chief technologist, the QC Technologist and also a Medical Physicist and a member of the internal X-ray service or engineering group in case of availability. The Committee shall allocate QC responsibilities in writing. Particular assignments must be recorded in the manual. The persons charged with the responsibilities shall have to be properly directed. Proof of continuing education shall be available in case of the individuals actively involved in the QC testing and evaluation process. As regards Equipment Monitoring, every facility shall prepare various tests at the duration stated, and keep records of the data. The type of experiments as also the frequency of the experiments might also be changed at the orders of the Department in case the facility is able to display recorded proof that other tests or programs will guarantee efficient diagnostic image quality. (Department of Health: New York State, 2007)

Test Frequency: Every day at the time of the X-Ray generator start up and prior to conducting the x-ray, it is important the operator verifies for defects of indicator dial as also the mechanical and electric safety of the X-ray system. Defects and other risky conditions have to be remedied at the earliest. Besides, the solution temperatures and rates of exhaustion must also be verified at the time when correcting speed and contrast defects. The Half Value Layer -- HVL has also to be checked. In case of certified equipment the minimum HHVL must not fall below the figures as stated in Exhibit -II. Fluoroscopic Timers: The certified equipment shall show with a signal which is audible to the operator, the ending of a pre-determined time gap, not higher than 5 minutes. At the time of the engagement, the signal must go on until the reset button is pressed. In case of equipments that are not certified, the passage of a preset time, not higher than 5-minute should be recorded by a signal that is audible to the operator or an interruption of the fluoroscopic beam. The most important is the exposure rate measurements of the fluoroscopic apparatus which is manufactured prior to the year 1995. (Department of Health: New York State, 2007)

The readings are: automatic mode: 10 R. per minute, Manual mode 5R per minute. High Level control -- HLC Mode: 5R per minute at the time of non-operation in HLC and HLC Mode: 20 R. per minute at the time of operating in HLC and not keeping the records of the image. It is important that the fluoroscopic exposure rate in automatic and/or manual mode must never be higher than 5R/min at the time of measurement with a patient equivalent phantom comprising of 1 inches of Type 1100 aluminum and 0.5 mm of copper or a similar device. The film screen contact must be state the regions of substandard contact in the center of the image receptor. It is important that the screens that have been in use for more than four years are evaluated every year for film/screen contact. For better QC, it is important that each X-ray unit is equipped with a technique chart placed in a prominent position for reference by the operators. Since the minimum of the chart shall consist of patient size, versus the technique factors, SID, grid data, film/screen combination, gonad or breast protection as suitable and patient exposure. These charts must be kept up-to-date at the time when different film / screen combinations are procured and also during new X-ray tubes or measurements alter the baseline data from which the charts have been developed. (Department of Health: New York State, 2007)

Different Types of Tests and duration: The various QC tests are (i) Acceptance Test (ii) Monitoring Test (iii) Annual Test (iv) Post repair or replacement of tube. Acceptance test is conducted on equipment that has been installed newly to check purchase specifications and also to set up performance baseline. On the other hand monitoring test is required to be conducted for important parameter on a regular basis the frequency of which is every 2 to 3 months. As the name suggests, the annual tests is conducted for vital parameters, the frequency of which is annually. The various types of machines are (i) Radiograpy (ii) Fluoroscopy - fixed and C-Arm (iii) Angiography (iv) Mammography (v) CT Scan and (vi)Processors. The various parameters that need to be checked are (i) alignment of the beam and accuracy of the collimator (ii) Constancy of radiation output and linearity of mR/MAs vs. kV consisting of small and large focus. (iii) Evaluation of the Total Beam Filtration (HVL) (iv) evaluation of the focal spot size which is Line Pain Ph. (v) the preciseness and constancy of the timer exposure (vi) calculation of the dispersed radiation through the use of water phantom and (vii) leakage radiation from the X-Ray tube. The checking of beam alignment and collimator accuracy is stated in Exhibit -III. Beam Alignment and Collimator accuracy is central to radiography. This is due to the fact that erroneous central ray alignment will disfigure a radiographic image and when it is used with the Collimator Test Tool, this equipment gives an easy method of finding out whether the X-Ray beam is perpendicular to the image receptor and centered as against the light field. An image of Beam Alignment and Collimator Accuracy is stated in Exhibit -IV. (Mukhtar, n. d.)