Nuclear Medicine Technology

Read the article from the Journal of Nuclear Medicine Technology and answer the following question:

The Need for Increased Awareness About Potential Quality Control Problems in Aging y-Cameras Sarah Frye, Ross Frye2, Barbara Sterkel2, Razi Muzaffar’, and Medhat M. Osman’ ‘Clinical Health Sciences, St. Louis University, St. Louis, Missouri; 2John Cochran Division, VA St. Louis Healthcare System, St. Louis, Missouri; and Division of Nuclear Medicine, St. Louis University Hospital, St. Louis, Missouri A published IAC study showed that dated equipment Quality control in a nuclear medicine department plays an predicts poor laboratory quality and delay in echocardiol- important role in providing quality care for patients. Closely ogy and nuclear accreditation. "During the study period monitoring the uniformity values on extrinsic quality control can [2012 to 2014].. .there was a statistically significant trend give insight into problems outside typical equipment issues. This facility noticed increasing uniformity values along with a photo- towards an increasing lack of quality metrics with increase penic image artifact. The detector required photocoupling gel ing quartiles of equipment age" (2). This study showed that replacement and a full rebuild by service engineers. This process the interaction between equipment age and the number of required time for the rebuild and time for the gel to set. Another missing quality metrics was a significant predictor of lack adjustment of the voltage to the photomultiplier tubes (PMTs) was of accreditation (2). The IAC is dedicated to ensuring qual- required due to photocathode excitation in every cathode in every ity patient care and "Improving health care through accred- PMT in that detector. After the detector was rebuilt, the voltage itation" (3). Since its creation, the IAC nuclear/PET was retuned with the field service engineers’ knowledge that the PMTs would need to be retuned due to this excitation. Commu- accreditation program has offered a pathway for those using nication and understanding of equipment problems in aging y- nuclear/PET to document their quality and comply with cameras can lead to proper equipment use and better quality in insurers’ payment policies that mandate accreditation (1). nuclear medicine departments. Achieving accreditation assures patients that a department Key Words: quality assurance; cathode; excitation; gamma provides high quality and safety; it also helps a facility camera; photomultiplier tube; quality meet governmental and third-party payer criteria (4). J Nuci Med Technol 2019; 47:223-226 As imaging equipment ages, many institutions may choose DOI: 10.2967/jnmt. 118.222489 to make repairs rather than buy new equipment. The repair process can increase the likelihood that parts will need re- placement. Closely monitoring the integral uniformity values and daily extrinsic images on QC is vital to patient care. During routine daily QC on y-cameras, technologists Imaging professionals strive for the best quality of care. may habitually look for issues that arise from the crystal, One way to provide quality care is to produce excellent photomultiplier tube (PMT), electronics, and collimator. images. Image quality can be verified through quality con- However, it is not always routine to test for issues out- trol (QC) and quality assurance. Quality assurance usually side these commonplace ones. Some service engineers and includes departmental requirements that technologists be physicists work on only routine issues and may not know certified and participate in continuing education to maintain the steps to prevent further scanner downtime when these that certification. In addition, equipment must work prop- less common problems occur. "Photopenic Circular Artifact erly and must function within the guidelines provided by That Resulted in a Gamma Camera Head Rebuild: A Tech- the Nuclear Regulatory Commission. Many imaging de- nologist Case Study" (5) was presented at the Society of partments choose to have either Intersocietal Accreditation Nuclear Medicine and Molecular Imaging annual meeting Commission (IAC) or American College of Radiology ap- in 2016 and has sparked follow-up discussion. We want proval. In numerous states, reimbursement directives that technologists to be aware of this issue and the experiences require accreditation of the facility have been instituted by encountered. Medicare carriers and by private, third-party insurers (1). This article describes how close monitoring of the QC helped uncover a major problem in a detector and brings Received Oct. 25, 2018; revision accepted Feb. 20, 2019. attention to a lesser known equipment problem. For correspondence or reprints contact: Sarah Frye, Department of Clinical Health Sciences, Doisy College of Health Sciences, Saint Louis University, 3437 Caroline St., St. Louis, MO 63104. MATERIALS AND METHODS E-mail: [email protected] Published online Apr. 24, 2019. During daily extrinsic QC, it was discovered that detector 2 of COPYRIGHT @ 2019 by the Society of Nuclear Medicine and Molecular Imaging. a Philips Forte Anger-style y-camera had an integral uniformity PROBLEMS WITH AGING Y-CAMERAS . Frye et al. 223

this article include the total counts for each on that day). By that time, the values had image. Once the 5% deviation range was Detector 2 UFOV normalized, and the image artifact was reached, the scanner was taken out of service. not seen. Because the daily uniformity values had been increasing over the previous several days, DISCUSSION the technologists kept watch on the QC and The importance of thoroughly mon- patient images to ensure no problems were itoring QC cannot be overstated. After present. The Forte (Fig. 1E) had undergone 218 1 2010 8/9/2016 214 212010 1581 18 / 2016 $12016 B/15/2010 2712016 8/21/2016 B130/2010 the integral uniformity values were noted Detector 2 UFOV E routine maintenance since its installation in 2003. On in-depth QC image review, there to exceed the manufacturer’s maximum was a photopenic circular image artifact no- FIGURE 3. (A) Extrinsic QC uniformity image from detector 2 on August 18, 2016 (15 recommendation, servicing was requested. ticed on the day the scanner was taken out million counts, thermal intensity at 91% [printed in gray scale]), after detector rebuild. The service engineers who found the of service (Figs. 1A and 1B), which resulted (B) Line graph showing QC problems again; arrow points to August 24, 2016, which problem worked quickly and efficiently. in a call to the field service engineers. was after first rebuild. (C) Extrinsic QC uniformity image from detector 2 on August 24, 3/12/2016 The field service engineers performed 2016 (15 million counts, thermal intensity at 91% [printed in gray scale]). Extensive On further investigation, the engineers noted that the factory assembles the 813/2016 8/6/2016 8/9/2016 8/15/2016 8/18/2016 121/2016 8127/2016 8/24/2010 modeling (arrows) across field of view is due to PMT excitation; tuning was done to intrinsic QC uniformity with the mask re- remove modeling (5). UFOV = useful field of view. detectors in dar moved (Fig. 1C) and found that detector 2 e the time taken to stabilize. An FIGURE 1. (A) Extrinsic QC uniformity image from detector 2 on August 15, 2016 (15 would require a rebuild. A rebuild involves excerpt from the PMT manual (Fig. million counts, gray scale). (B) Extrinsic QC uniformity image from detector 2 on disassembly of the detector, cleaning of all coupling gel. Detector 2 was functional again 2 d later (5). The 2D) noted that light should be avoided when one is working August 15, 2016 (15 million counts, thermal intensity increased to 91% [printed in coupling gel from each PMT and from the extrinsic QC imaging (Fig. 3A) was satisfactory again, but a with the cathode substrate (photocoupling gel) (7). Avoiding gray scale]). (C) Intrinsic QC uniformity image from detector 2 on August 17, 2016, crystal/light-pipe assembly, and then applica- with mask removed (11.706 million counts, thermal intensity at 12% [printed in gray tion of new coupling gel to the tubes followed new artifact was introduced 4 d later (Fig. 3C). The cause light in an imaging room can be difficult if the room has scale]). (D) Line graph of daily integral uniformity measurements of useful field of view by their reinstallation. A rebuild is necessary of this artifact was cathode excitation, which required a windows (Figs. 2A-2C). The excitation issue may have (UFOV). (E) Image of Forte y-camera at VA Saint Louis Healthcare System, John Cochran when the gel gets old or too hot and air tuning session (5). Because the new artifact looked like caused the loss of tuning after the initial detector rebuild, Division, St. Louis, MO (5). bubbles form between the tube and light the first artifact, a person with an untrained eye might have which caused the second artifact and the required retuning pipe or when the tubes fail (Mark Schmidt, performed another time-consuming rebuild with new gel, Because this was an older y-camera, a tuning session of 4 h field-of-view value that was slowly increasing (Fig. ID) (5). Most written communication, February 22, 2018) (5). As part of the when only tuning of the detector was required. The unifor- was required to adjust the voltage signal on the PMTs. Older of the rising values were not significant enough to raise alarm during rebuild, the service engineers tuned the PMTs. Because of the mity values were increasing again (Fig. 3B), and the scanner equipment has older hardware. Hardware degrades over QC, as the results were within the manufacturer recommendation cathode excitation, the service engineers predicted that a second or was operating outside the acceptable range. Servicing was time, and some of the electronic parts in this y-camera of less than a 5% deviation. The manufacturer recommends that third tuning might be necessary. Cathode excitation can occur when once again requested to assess the problem, resulting in an- had been replaced. It was difficult for us to determine the both intrinsic and extrinsic uniformity floods be 15 million counts the tube is exposed to light, and the tube may need to remain in other 1.5 d of service work (5). After this additional work of exact cause of the slowdown of this y-camera, which had at 20,000-50,000 counts per second for Epic detectors on the Forte darkness for several hours or days (Fig. 2D). Historically, tuning tuning the PMTs, the service engineers stated that another been in use for approximately 13 y. (Mark Schmidt, written communication, January 4, 2019). This rec- was the original uniformity correction technique applied to y-cam- tuning might be necessary in several days if the extrinsic This department had 3 other y-cameras to use while the ommendation was followed by the department, and the figures in eras and involved adjusting the high voltage to individual PMTs to produce equal count rates across the field of QC increased. The tubes were given time to stabilize, and Forte was out of service. Upon retrospective review of patient view (6). Manual tuning is performed in- the gel was given time to set; after 4 wk, it was determined studies performed on the last few days before the initial service frequently in modern y-cameras because of that a third tuning was unnecessary (Figs. 4C and 4B). After call, the technologists and physicians did not believe the images the large number of PMTs (6). the second tuning, an extrinsic flood test showed uniform had been affected. So, ultimately, the detector rebuild at this The importance of the photocoupling gel images (Fig. 4A). When the extrinsic QC passed the test, an facility did not have any negative impact on patient care. in an Anger camera can be underappreciated intrinsic flood image was acquired to prove that a third tuning This issue may become of greater importance as Anger by technologists. "Optical coupling grease was unnecessary (Fig. 4C) (no extrinsic image was included y-cameras continue to be used. A recent case report using a (usually some kind of silicon grease) reduces y-camera from a different manufacturer the loss of scintillation photons by preventing reflection at the scintillation crystal/light pipe (an Infinia Hawkeye SPECT/CT system; and light pipe/photocathode interfaces. .. .If Detector 2 UFOV GE Healthcare) described an imaging the coupling gel degrades, the number of artifact that required further investiga- D scintillation photons reaching the PMT is tion (8). The artifact in that case was Cathode excitation greatly diminished" (6). In this case, the QC 3% found to be caused by gradual leakage had discovered part of the problem quanti- of optical coupling grease. Fresh grease When a tube is exposed to even very low levels of ambient light, especially just before the tube is put into operation, tatively (with increasing uniformity values) 1% the dark current in operation can initially be several orders and qualitatively (with nonuniform images), 0% was applied, and the artifact did not appear on later images. of magnitude larger than that when the tube has stabilized and we could detect the issue in view of the 9/18/ 2016 9/15/ 2016 8/13/2016 8/16/2016 8/22/20 1 8 /25 / 2016 several hours or even days in darkness. Coupling gel can degrade and cause rising integral uniformity values. Because the The pulse height spectrum is similar to that for single imaging artifacts that affect image quality. photoelectrons. This phenomenon is very dependent on the coupling gel needed replacement, the photons It is important to communicate with cathode substrate. In normal use, take simple precautions reaching the PMT were reduced and the QC FIGURE 4. (A) Extrinsic QC uniformity image from detector 2 on August 25, 2016 (15 service professionals when such prob- images were affected. million counts, thermal intensity at 91% [printed in gray scale]), after second tuning. (B) to limit exposure. In all cases, avoid fluorescent light and daylight. Line graph showing extrinsic useful field of view on August 25, 2016 (dashed arrow), lems occur, so the department can learn and extrinsic QC uniformity on September 14, 2016 (solid arrow), which is when RESULTS detector 2 might have needed another tuning. Another tuning was not needed per how to properly prepare for servicing FIGURE 2. (A) Photograph of windows and ceiling with fluorescent light in Forte the QC results. (C) Intrinsic QC uniformity image from detector 2 on September 14, of the equipment. If specific conditions y-camera room. (B) Photograph of second window. (C) Photograph of third window The service engineers took this scan- 15 million counts, thermal intensity at 91%). Extrinsic QC image was not such as a darkened room cannot be ac- (5). (D) Excerpt from Photonis PMT manual (7). ner out of service to replace the defective captured on that day (5). UFOV = useful field of view. commodated, the camera may need to 224 JOURNAL OF NUCLEAR MEDICINE TECHNOLOGY . Vol. 47 . No. 3 . September 2019 PROBLEMS WITH AGING y-CAMERAS . Frye et al. 225

be out of service for several more days. We believe our service The goal of this article is to educate technologists that engineers were able to repair the issue as quickly as possible; there are a variety of different problems that can occur in they are seasoned engineers who have fixed numerous depart- aging Anger-style y-cameras. The specific problem de- mental issues. The technologists were not fully aware that scribed here ended up being due to bad coupling gel and Journal of specific conditions (a darkened room) were needed during the PMT tuning complications. Such problems can occur, and rebuild, and the room was still used for nonimaging purposes it is important to communicate with everyone involved in the during the maintenance. resolution process to ensure it is completed as efficiently as It is also important for departments seeking or maintaining possible. High-quality patient care is an imperative goal in accreditation to understand that equipment may degrade over which every individual involved in the maintenance, QC, and JNMT NUCLEAR MEDICINE TECHNOLOGY time. Once a department becomes accredited, its y-cameras quality assessment of imaging equipment plays a role. are not guaranteed to continue operating at the same quality in perpetuity. y-camera QC procedures catch problems when quantitative measurements fall outside standard acceptable DISCLOSURE The Need for Increased Awareness About Potential Quality Control Problems in ranges. Technologists reviewing the QC can visually assess No potential conflict of interest relevant to this article was Aging y-Cameras these images daily. Some issues, such as the one with the reported. photocoupling gel discussed in this article, and the one involv- Sarah Frye, Ross Frye, Barbara Sterkel, Razi Muzaffar and Medhat M. Osman ing leakage of coupling gel discussed in the previous article (8), can happen over time and may degrade image quality REFERENCES J. Nucled. Technol. 2019;47:223-226. Published online: April 24, 2019. before becoming quantitative. 1. What is IAC nuclear/PET accreditation? Intersocietal Accreditation Commission Website. https:/www.intersocietal.org/nuclear/main/what_is_accreditation.htm. Accessed Doi: 10.2967/jnmt. 1 18.222489 April 18, 2019. CONCLUSION 2. Malhotra S, Farrell MB, Katz W, Soman P. Increasing equipment vintage predicts poor laboratory quality and delay in accreditation: an evaluation by IAC echocar When determining the quality of an image acquisition on diography and nuclear accreditation status [abstract]. J Am Coll Cardiol. 2017; a y-camera, one must keep in mind that aging equipment 69(supply:11. This article and updated information are available at: 3. About the IAC. Intersocietal Accreditation Commission Website. https:/www. http://tech.snmjournals.org/content/47/3/223 may lead to unexpected QC concerns. During a detector re- intersocietal.org/. Accessed April 18, 2019. build on a y-camera, the service engineers may need to work 4. The gold standard in imaging accreditation. The American College of Radiology in specific lighting conditions such as a darkened room. Website. https:/www.acraccreditation.org/About-Us. Accessed April 18, 2019. 5. Frye R, Frye S, Osman MA. Photopenic circular artifact that resulted in a gamma Performing a recoupling without ambient light may be advan- camera head rebuild: a technologist case study [abstract]. J Nucled. 2017; Information about reproducing figures, tables, or other portions of this article can be found online at: tageous in that the scanner will be out of service a shorter time 58(suppli):792. http://tech.snmjournals.org/site/misc/permission.xhtml (our scanner was out of service 4 d). After a detector rebuild, 6. Prekeges J. Nuclear Medicine Instrumentation. 2nd ed. Burlington, MA: Jones and Bartlett Learning; 2013:21. Information about subscriptions to JNMT can be found at: the integral and differential values must be closely monitored 7. Photonis: photomultiplier tube basics. Paul Scherrer Institute website. http:/lmu.web. psi.ch/docu/manuals/bulk_manuals/PMT’s/Photonis_PMT_basics.pdf. Accessed April http://tech.snmjournals.org/site/subscriptions/online.xhtml on daily QC (5), because if the gel has not had enough time to set or the electronic voltage drifts, the problem may reoccur 18 , 2019. Bashir S, Shahbaz M, Iqbal D. A bizarre ring artifact on SPECT/CT images. and another tuning requiring more downtime be needed (5). J Nuci Med Technol. 2017;45:119-120. Journal of Nuclear Medicine Technology is published quarterly. SNMMI | Society of Nuclear Medicine and Molecular Imaging 1850 Samuel Morse Drive, Reston, VA 20190. 226 JOURNAL OF NUCLEAR MEDICINE TECHNOLOGY . Vol. 47 . No. 3 . September 2019 (Print ISSN: 0091-4916, Online ISSN: 1535-5675) S NM SOCIETY OF NUCLEAR MEDICINE AND MOLECULAR IMAGING

List some of the main challenges associated with older gamma cameras?

What were the QC test results that first showed there was a problem with the Philips Forte gamma camera in the article?

Describe what happens when coupling gel degrades in a gamma camera.

What maintenance needed to be done to correct the first artifact on the camera?

Why is a darkened room sometimes necessary when PM tubes are replaced or serviced?

What maintenance needed to be done to correct the second artifact on the camera?

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