Therefore, it is critical to closely monitor images that appear degraded, as this could indicate faulty QC results. In addition, it is crucial to keep track of all QC results and look for any significant shifts in trends. Most faulty QC results can be corrected by repeating the QC steps; however, reviewing results with trained service engineers or physicists can be beneficial. Once a year, a QA committee meeting should be held to manage the issue and audit the QC results.
Quality is not an individual responsibility and is a collective effort. A QA committee should include radiologists, NMT, pharmacists, medical physicists, radiology managers, and nurses.
Any minor QC flaw in imaging instruments can impact the overall outcome of the image and the diagnostic decision-making process. Every NM department must have a robust QA plan to avoid any minor imaging instrument flaws and maintain the highest standards of image production for a more extended period.
The NM department QA plan should be reviewed and updated every two years. A bi-annual review of the department's quality control protocols is highly recommended, and local regulatory bodies should evaluate the results. All employees should be encouraged to participate in any ongoing training opportunities to learn more about QA procedures.
NM QA is not limited to instruments and includes other factors that can reduce the overall diagnostic quality of acquired images. These factors include:. QC is not an individual responsibility but rather a team effort involving everyone in a department. It becomes even more critical in the setting of an NM department, where there is a risk of radiation exposure.
Any minor QC flaw can negatively impact the overall diagnostic quality of images, resulting in a higher radiation burden for patients. Therefore, every team member should actively participate in the QA plan, including a radiologist, NMT, radiology manager, nurses, service engineers, medical physicists, and administrative staff.
Regular meetings and an evidence-based approach can help reduce the likelihood of QC failure and help to upkeep standard services. This book is distributed under the terms of the Creative Commons Attribution 4. Turn recording back on. National Center for Biotechnology Information , U. StatPearls [Internet]. Search term. Affiliations 1 Mumbai University, India. Continuing Education Activity Quality control is an essential part of the nuclear medicine department as it ensures that radiation exposure is minimal during imaging procedures.
Introduction Nuclear medicine NM relies heavily on imaging and non-imaging instruments to accurately count and detect radiation.
Function Nuclear Medicine equipment both imaging and non-imaging QC must be performed in various frequencies daily, monthly, semi-annually, annually, and bi-annually. Table1 Routine quality control procedures for Nuclear Medicine equipment imaging and non-imaging equipment Table Instruments Type of instruments. Background reading to make sure that the dose calibrator is contamination-free.
Elute Mo generator and try to get at least mCi MBq or more equal to or higher than the maximum activity capacity of the calibrator. Record in an excel sheet and trace a curve. Issues of Concern Any NM department's routine QC procedure is essential as this practice helps maintain high-quality images consistently while also reducing the risk of radiation exposure to patients and staff. Proprietary graphical display GE Healthcare , detector block—by—detector block, of relative values of PET scanner operational parameters derived from blank scan, including coincidence counting rate, singles counting rate, detector dead time, coincidence timing window, and energy setting.
Such display allows operator to quickly and easily discern out-of-tolerance results, displayed with grossly different i. A Display for acceptable blank scan; that is, blank scan for which all detector parameters are within tolerance. B Display for blank scan in which coincidence counting rate, singles counting rate, and dead-time results for 1 block detector are out of tolerance, indicated by black areas arrows in respective displays.
In practice, the use of a long-lived 68 Ge cylinder is preferred because constant refilling of a cylinder with short-lived 18 F is avoided. Tomographic uniformity should be evaluated daily or at least weekly. In addition to the pronounced differences in sensitivities between direct and cross planes and artifacts between adjoining detector rings Fig. Among the 10,—20, detector elements in a modern ring scanner, slight variations among the detector elements in thickness, light emission properties, electronics performance, and so on result in slightly different line-of-response LOR counting rates for the same activity.
Reconstructed coronal images of 68 Ge uniform-cylinder phantom without A and with B normalization applied. A Unnormalized i. B Appropriate normalization virtually eliminates these and other artifacts related to nonuniformity of scanner response. The normalization scan can be performed using a positron-emitting rod source e. Alternatively, a uniform cylinder of a positron-emitting radionuclide can be scanned and the data thus acquired analytically corrected for attenuation; for a well-defined geometry such as a uniform cylindric source, this correction is straightforward.
However, for 3-dimensional PET, the contribution of and correction for scatter with such a large-volume source are nontrivial. In practice, either approach is somewhat problematic because of limited count statistics and, in the case of 3-dimensional PET, because of scatter.
The PET scanner normalization should be created or updated at installation, after major service, whenever deteriorating image quality suggests a new normalization is required, or otherwise at least annually. Once PET emission data have been corrected for dead time, randoms, system response by normalization , scatter, and attenuation, the signal per voxel in the reconstructed tomographic images is proportional to the local activity concentration.
If not, Equation 10 must be appropriately adjusted:. In principle, differences between the geometries of the calibrated source and a patient may introduce some inaccuracy in the determination of activity concentration in situ Eq. The PET scanner well-counter calibration should be created or updated at installation, after major service, or otherwise at least annually.
CT scanners have been in widespread clinical use long before their incorporation into multimodality devices i. Daily testing of a CT scanner begins with the manufacturer-prescribed x-ray tube warm-up procedure and automatic monitoring, perhaps at various tube voltage kVp or current mA settings, of the tube output and detector response. Assuming the operator has received the appropriate system-ready message, the daily QC procedures are then performed These include, at a minimum, evaluation of tomographic uniformity, the accuracy of the CT number of water, and image noise i.
These parameters should be evaluated using a clinically routine set of scan parameters i. Acceptable image uniformity may be confirmed by visual inspection i.
In the latter approach Fig. The HU scale is based on a linear transformation of the linear attenuation coefficient as measured by CT, in which the radiodensity of water is assigned a value of 0 HU and that of air at standard temperature and pressure a value of 1, HU. Cross-sectional diagrams of GE quality assurance phantom 24 illustrating respective sections inserts for evaluation of laser-light alignment, image slice thickness, spatial resolution, linearity, and high-contrast contrast resolution A ; low-contrast uniformity B ; and image uniformity and noise C.
Various short black lines in acrylic insert in section shown in A are cavities that fill with water when phantom is filled, providing high contrast between cavities and acrylic; portion of this section outside this insert, although not shown in black, is also water-filled.
Diagonally arranged sets of line cavities ranges are 1. Section shown in B includes polystyrene membrane with series of holes 10, 7.
D Side-view diagram not to scale of section of phantom in A, showing only 1 of slice-thickness measurement components of insert; these line cavities are air-, not water-, filled. They are staggered offset 1 mm apart in longitudinal direction. Also shown in D, as well as in A, is laser-alignment groove around circumference of phantom and 2 corresponding laser-alignment cavities.
Boxes indicate pertinent ROIs for different analyses. See text for details. In addition to the these daily checks of CT performance, monthly or at least quarterly evaluations of laser alignment, image slice thickness, spatial resolution, linearity i.
At the same time, image uniformity and noise, as discussed earlier, should also be evaluated for different tube voltages i. Evaluation of these parameters requires appropriate phantoms. The Quality Assurance Phantom GE Healthcare 24 , for example, is a water-fillable polymethylmethacrylate acrylic cylinder with multiple sections i.
Laser alignment. The laser lights should lie precisely on the circumferential surface groove of the phantom. If the lasers are properly aligned, the 2 laser alignment cavities in the reconstructed transverse image will be horizontal and at precisely the same y -position coordinate Figs. Slice thickness. Because the line cavities in each of the 2 slice-thickness measurement components of the insert are staggered offset 1 mm apart in the longitudinal direction Figs.
However, if 1 of the lines appears as gray rather than black, the slice thickness in millimeters equals the number of black lines plus one half, with 0. Spatial resolution. Linearity i. High-contrast contrast resolution. Low-contrast contrast resolution. Low-contrast contrast resolution is evaluated using the insert and the ROIs boxes, Fig. According to information published by GE Healthcare 24 , this difference should agree within 0.
Optionally, low-contrast resolution can also be evaluated as a function of object size by calculating the foregoing parameter for each of the circular holes in the polystyrene membrane Fig. Daily and monthly or quarterly image uniformity and noise can be evaluated using the uniform plain section of the GE quality assurance phantom. Finally, on at least an annual basis, radiation dose should be evaluated by a health physicist or a medical physicist by measuring the CT dose index CTDI for various scan parameters i.
The CTDI w thus reflects the mean absorbed dose over the transverse x and y dimensions of such a phantom and is an approximation of the average radiation dose to the cross-section of a patient. Measurements of the CTDI p and CTDI c are typically performed using ionization chambers or thermoluminescent dosimeters positioned in a commercially available soft-tissue—equivalent acrylic phantom, cylindric in shape and either 16 or 32 cm in diameter, approximating an adult head or torso body , respectively Fig.
Ionization chambers actually measure exposure, which is then converted to absorbed dose using the f factor discussed earlier. Thermoluminescent dosimeters, however, yield absorbed dose directly. Setup for measurement of CT radiation exposures using ionization chamber and cm-diameter acrylic torso body phantom. Multimodality i. The advantage of phantoms having point or line markers Fig. Although visual assessment may generally suffice, the misregistration may be quantitated as the mean or maximum Euclidean distance in mm , among all the markers, between the positions of each marker in the 2 modalities.
However, point and line markers suffer from the disadvantage that their dimensions are typically well below the spatial resolution of either SPECT or PET scanners and therefore their activities cannot be reliably measured because of partial-volume averaging As a result, the accuracy of the CT-based attenuation corrections cannot be meaningfully assessed.
Such tests of multimodality image registration should be performed at least monthly. Phantoms adaptable to evaluation of accuracy of multimodality image registration. A Uniform phantom with 2 channels for line sources. These procedures and their respective frequencies are presented only as general guidelines. Certainly, there are numerous variations of these procedures that may comprise a sound and compliant QC program. We thank Dr. Sadek Nehmeh, Keith Pentlow, Dr. Osama Mawlawi of the M. Anderson Cancer Center for their contributions.
No potential conflict of interest relevant to this article was reported. Combine industry-leading therapy response tools for PET with advanced Nuclear Medicine display and processing. MIM SurePlan MRT provides timesaving tools for organ and tumor segmentation, deformable registration, and voxel-based dosimetry for molecular radiotherapy. With our quantitative analysis software at work, we make it easy for you to review your exams and gather your results. Experience multi-tracer support and quick quantitative analysis all at your fingertips.
Learn more about the features and see how you can visualize the difference with MIMneuro. Stress less and rest more with MIMcardiac at your fingertips. A central idea has been the exchange of data in the form of software phantoms between different groups. Thus, for example, a series of validated cardiac studies would be collected and then redistributed to various participants with known expected results, to validate the software on that participants sytems. For this reason a common interchange file format was required.
Working group 1 is responsible for maintaining this format, which has been published [1]. Translators have already been written between Interfile and most of the commercially available systems, and data has been distributed in this form in a number of clinical areas.
0コメント