New Toys for Nuclear Cardiologists
2011; Lippincott Williams & Wilkins; Volume: 4; Issue: 1 Linguagem: Inglês
10.1161/circimaging.110.961987
ISSN1942-0080
AutoresTodd D. Miller, J. Wells Askew, Michael K. O’Connor,
Tópico(s)Cardiomyopathy and Myosin Studies
ResumoHomeCirculation: Cardiovascular ImagingVol. 4, No. 1New Toys for Nuclear Cardiologists Free AccessEditorialPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessEditorialPDF/EPUBNew Toys for Nuclear Cardiologists Todd D. Miller, MD, FAHA, J. Wells Askew, MD, FAHA and Michael K. O'Connor, PhD Todd D. MillerTodd D. Miller From the Division of Cardiovascular Diseases (T.D.M., J.W.A.) and Department of Radiology (M.K.O.), Mayo Clinic, Rochester, MN. , J. Wells AskewJ. Wells Askew From the Division of Cardiovascular Diseases (T.D.M., J.W.A.) and Department of Radiology (M.K.O.), Mayo Clinic, Rochester, MN. and Michael K. O'ConnorMichael K. O'Connor From the Division of Cardiovascular Diseases (T.D.M., J.W.A.) and Department of Radiology (M.K.O.), Mayo Clinic, Rochester, MN. Originally published1 Jan 2011https://doi.org/10.1161/CIRCIMAGING.110.961987Circulation: Cardiovascular Imaging. 2011;4:5–7Gordon Liljestrand is credited with establishing modern nuclear cardiology as a noninvasive imaging modality in 1939.1Table summarizes major technological advancements in myocardial perfusion imaging over the past 70 years that have led to more accurate assessment of coronary artery disease (CAD). Most of these technical advances have involved radioisotopes and computer software. Camera hardware has undergone relatively little change since the introduction of the gamma camera, also commonly referred to as the scintillation camera, by Hal Anger in 1958.2 The gamma camera has performed admirably as the workhorse for myocardial perfusion imaging over the years but has several limitations. Sensitivity and resolution are modest. Imaging is inefficient as the heart occupies only a small portion of the field of view. Imaging places several demands on the patient, requiring relatively long imaging times (8 to 12 minutes) while lying motionless on a narrow, hard table with one or both arms fully abducted to minimize the distance between the patient's chest and the rotating detectors. The relatively long imaging times require administration of fairly high doses of radioisotopes with attendant higher radiation exposure, an issue of increasing medical and societal concern.3Table. Developments in Nuclear CardiologyDatesInvestigatorDevelopment1939LiljestrandMeasurement of blood volume1950–1960AngerScintillation (gamma) camera1960–1970BingPET Rb-84 myocardial blood flow1970–1980LebowitzTℓ-201 myocardial blood flow…Tomography (SPECT)1980–1990…Tc-99m myocardial blood flow1990–2000…Gated SPECT imaging2000–2010…Iterative, wide-beam reconstruction…Ultrafast camerasArticle see p 51In the past few years, there have been tremendous advances in gamma camera technology due to the replacement of the conventional sodium iodide (NaI)-based systems with solid-state detectors using cesium iodide coupled to photodiodes or novel semiconductor-based detectors using cadmium zinc telluride (CZT). The most promising of these new technologies is the CZT detector, which directly converts gamma radiation to an electronic pulse and thereby eliminates the need for a scintillating crystal and photomultiplier tubes. The CZT detector is substantially smaller than a NaI-based detector. In addition, the CZT detector offers substantially better energy resolution and spatial resolution than the NaI detector. Because of its compact design, new, innovative detector configurations can be used that enable multiple independent detectors to be positioned around the patient. With multiple detectors focused only on the heart, image quality is improved due to the improved sensitivity in detection of activity in the heart. The most obvious direct benefits to the patients are shorter imaging times, which can be reduced by a factor of 5 or greater and require only 2 minutes, and reduced radiation exposure due to smaller administered doses of radioisotope.Currently, there are 2 commercially available ultrafast camera (UFC) systems: the General Electric (GE) Healthcare Discovery NM 530c and the Spectrum Dynamics D-SPECT. The detector configurations used in these UFC systems differ substantially, but they both have in common the use of multiple CZT detectors in place of NaI crystals. Both systems also apply either a wide cushioned table or a cushioned chair to support the patient during imaging in place of the narrow hard tables used by conventional imaging systems.Claims of reduced imaging times, lower radiation exposure, and increased patient comfort are desirable but by themselves cannot be used to justify replacing conventional cameras with UFCs if imaging quality is sacrificed. To evaluate this issue, several studies have been performed using the GE Healthcare Discovery NM 530c4–6 or Spectrum Dynamics D-SPECT7–10 to compare images acquired by a UFC to those acquired by a conventional gamma camera. All of these studies reported comparable myocardial perfusion image quality with the benefit of significantly shorter image acquisition times. Some of these studies4,6,8,10 also evaluated left ventricular ejection fraction and volumes and reported similar results between the UFC and conventional systems.Although these studies focused on demonstrating comparable imaging results between UFCs and conventional cameras, any observer who has had the opportunity to directly compare images acquired using both approaches in the same patient is impressed by the general superior image quality of the UFC system. In most patients, the images appear sharper with more precise edge definition. In this issue of Circulation: Cardiovascular Imaging, Gimelli et al11 sought to determine whether this improved image quality translates into more accurate assessment of patients with CAD. These investigators evaluated 34 patients who underwent 1-day low-dose (370 MBq) stress/high-dose (740 MBq) rest Tc-99m tetrofosmin conventional and UFC SPECT. Images were interpreted both subjectively by applying the standardized 17-segment model scoring system and objectively by using normalized polar maps. Global and segmental radiotracer uptake were quantified. Coronary anatomy was assessed in all patients by quantitative invasive coronary angiography (n=27) or 64-slice CT angiography (n=7). Twenty-nine of the patients had significant CAD, including 9 with 1-vessel, 11 with 2-vessel, and 9 with 3-vessel CAD.In the overall per-patient analysis based on the summed stress score, there was a trend toward a higher area under the receiver operating characteristic curve for UFC versus conventional SPECT (98% versus 86%; P=0.078). By individual vessel analysis, the area under the curve was significantly higher for UFC for the left circumflex artery (97% versus 85%; P=0.039) and right coronary artery (99% versus 88%; P=0.045) territories. In the 29 patients with CAD, mean summed stress score was significantly higher for UFC versus conventional SPECT (10.1±4.4 versus 6.4±2.9; P<0.001). By quantitative analysis, mean tracer uptake on the stress images in each coronary territory was significantly lower by UFC SPECT (left anterior descending artery, 60±2% versus 70±3%; left circumflex artery, 65±4% versus 73±4%; right coronary artery, 63±5% versus 71±2%; P<0.001 for all comparisons). Analysis of the gated images revealed similar values by each method for stress left ventricular ejection fraction and volumes.This study by Gimelli et al11 is the first publication to compare UFC versus conventional SPECT using coronary angiography as the gold standard in a group of patients. Our nuclear cardiology laboratory has acquired experience with both the GE Healthcare Discovery NM 530c and the Spectrum Dynamics D-SPECT cameras. The results of the present study confirm our subjective impression that these UFC systems more accurately identify perfusion defects. We have had the opportunity to directly compare in a side-by-side manner SPECT images acquired with a conventional NaI system to the images acquired with both of these new UFC systems. We have seen several instances where equivocal perfusion defects on the conventional system that we would have passed off as imaging artifacts appear as real defects on the UFC systems and are confirmed as secondary to CAD on subsequent cardiac testing. The higher-count statistics with better image resolution and improved image contrast should lead to higher test sensitivity with UFC systems. Sometimes, better sensitivity is achieved at the cost of poorer specificity; however, with the UFC systems, specificity also appears to be improved. A major cause of false-positive studies is image artifacts. The improved energy resolution of the UFC systems also should result in less scatter in the image data. Anecdotally, we have seen spectacular image quality in some very obese patients. The shorter imaging times with more comfortable table or chair designs should lead to less motion artifacts. One standard approach to address imaging artifacts is to image patients in multiple positions. Although prone imaging has been available for years, it is not commonly performed because of time constraints and patient comfort issues. The very short imaging times provided by UFC systems substantially facilitate imaging patients in multiple positions. Using combined supine and upright imaging with the Spectrum Dynamics D-SPECT camera provides more accurate results than imaging patients in either 1 of these positions alone.12The study by Gimelli et al11 does have limitations. The study group was small. A minority of patients underwent only CT angiography, a highly sensitive technique but, nonetheless, not as accurate as the gold standard of invasive coronary angiography. Eighty-five percent of the patients had significant CAD, reflecting a highly selected patient population. It is conceivable that UFC systems may not be superior to conventional cameras in lower-risk populations where a much greater percentage of the population will have normal images. Clearly, more studies are needed.Despite these limitations, Gimelli and colleagues have made a significant contribution by generating data to support the general subjective impression that UFC systems provide not just comparable, but better and more accurate SPECT images compared to conventional systems. The characteristics of UFC systems should result in better diagnostic sensitivity and specificity. The short imaging times provide nuclear cardiology laboratories with greater flexibility to optimize the SPECT study to the individual characteristics of the patient. For instance, in a younger patient where radiation exposure is a primary concern, a lower dose of a radioisotope with a lengthening of imaging time to achieve adequate count statistics could be the protocol of choice. However, in an elderly patient who has difficulty holding still, a higher dose of radioisotope (radiation exposure much less a concern) with short imaging times could be the preferred approach. The short UFC imaging times also have the potential to facilitate dual isotope imaging13; to apply SPECT imaging to optimize pacing parameters for cardiac resynchronization therapy14; and, theoretically, to quantitate myocardial blood flow.15Everyone loves a new toy. An old toy may seem perfectly adequate until compared to a new one, when it quickly loses its luster and appeal. In the movie Toy Story, it did not take Andy long to replace Woody with Buzz Lightyear.16 Nuclear cardiologists will undoubtedly be eager to replace their old Anger camera with a UFC model.DisclosuresThe Mayo Clinic Nuclear Cardiology Laboratory received research funding to support studies to validate the GE Healthcare Discovery NM 530c camera. Drs Miller, Askew, and O'Connor participated in these studies.FootnotesThe opinions expressed in this article are not necessarily those of the editors or of the American Heart Association.Correspondence to Todd D. Miller, MD, FAHA, Mayo Clinic, Gonda 5, 200 First St, SW, Rochester, MN 55905. E-mail miller.[email protected]eduReferences1. Fye WB. President's page: cardiology and technology: an enduring and energizing partnership. J Am Coll Cardiol. 2002; 40:1192–1195.CrossrefMedlineGoogle Scholar2. Anger H. Scintillation camera. Rev Sci Instrum. 1958; 29:27–33.CrossrefGoogle Scholar3. Cerqueira M, Allman K, Ficaro E, Hansen C, Nichols K, Thompson R, Van Decker W, Yakovlevitch M. Recommendations for reducing radiation exposure in myocardial perfusion imaging. J Nucl Cardiol. 2010; 17:709–718.CrossrefMedlineGoogle Scholar4. Esteves F, Raggi P, Folks R, Keidar Z, Askew JW, Rispler S, O'Connor M, Verdes L, Garcia E. Novel solid-state-detector dedicated cardiac camera for fast myocardial perfusion imaging: multicenter comparison with standard dual detector cameras. J Nucl Cardiol. 2009; 16:927–934.CrossrefMedlineGoogle Scholar5. Herzog BA, Buechel RR, Katz R, Brueckner M, Husmann L, Burger IA, Pazhenkottil AP, Valenta I, Gaemperli O, Treyer V, Kaufmann PA. Nuclear myocardial perfusion imaging with a cadmium-zinc-telluride detector technique: optimized protocol for scan time reduction. J Nucl Med. 2010; 51:46–51.CrossrefMedlineGoogle Scholar6. Buechel R, Herzog B, Husmann L, Burger I, Pazhenkottil A, Treyer V, Valenta I, von Schulthess P, Nkoulou R, Wyss C, Kaufmann P. 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Eur J Nucl Med Mol Imaging. 2010; 37:1710–1721.CrossrefMedlineGoogle Scholar10. Sharir T, Slomka PJ, Hayes SW, DiCarli MF, Ziffer JA, Martin WH, Dickman D, Ben-Haim S, Berman DS. Multicenter trial of high-speed versus conventional single-photon emission computed tomography imaging: quantitative results of myocardial perfusion and left ventricular function. J Am Coll Cardiol. 2010; 55:1965–1974.CrossrefMedlineGoogle Scholar11. Gimelli A, Bottai M, Giorgetti A, Genovesi D, Kusch A, Ripoli A, Marzullo P. Comparison between ultrafast and standard SPECT in patients with coronary artery disease: a pilot study. Circ Cardiovasc Imaging. 2011; 4:51–58.LinkGoogle Scholar12. Nakazato R, Tamarappoo BK, Kang X, Wolak A, Kite F, Hayes SW, Thomson LEJ, Friedman JD, Berman DS, Slomka PJ. Quantitative upright-supine high-speed SPECT myocardial perfusion imaging for detection of coronary artery disease: correlation with invasive coronary angiography. J Nucl Med. 2010; 51:1724–1731.CrossrefMedlineGoogle Scholar13. Berman DS, Kang X, Tamarappoo B, Wolak A, Hayes SW, Nakazato R, Thomson LEJ, Kite F, Cohen I, Slomka PJ, Einstein AJ, Friedman JD. Stress thallium-201/rest technetium-99m sequential dual isotope high-speed myocardial perfusion imaging. J Am Coll Cardiol Img. 2009; 2:273–282.CrossrefMedlineGoogle Scholar14. Pazhenkottil A, Buechel R, Herzog B, Nkoulou R, Valenta I, Fehlmann U, Ghadri J-R, Wolfrum M, Husmann L, Kaufmann P. Ultrafast assessment of left ventricular dyssynchrony from nuclear myocardial perfusion imaging on a new high-speed gamma camera. Eur J Nuclear Med Mol Imaging. 2010; 37:2086–2092.CrossrefMedlineGoogle Scholar15. Sharir T, Slomka P, Berman D. Solid-state SPECT technology: fast and furious. J Nucl Cardiol. 2010; 17:890–896.CrossrefMedlineGoogle Scholar16. Lasserter J, Docter P, Stanton A. Toy Story [movie]. Burbank, CA: Walt Disney Studios; 1995.Google Scholar Previous Back to top Next FiguresReferencesRelatedDetailsCited By Okuda K, Nakajima K, Matsuo S, Kondo C, Sarai M, Horiguchi Y, Konishi T, Onoguchi M, Shimizu T and Kinuya S (2017) Creation and characterization of normal myocardial perfusion imaging databases using the IQ·SPECT system, Journal of Nuclear Cardiology, 10.1007/s12350-016-0770-2, 25:4, (1328-1337), Online publication date: 1-Aug-2018. Katsikis A, Theodorakos A, Kouzoumi A, Kitziri E, Georgiou E and Koutelou M (2016) Fast myocardial perfusion imaging with 99mTc in challenging patients using conventional SPECT cameras, Journal of Nuclear Cardiology, 10.1007/s12350-016-0431-5, 24:4, (1314-1327), Online publication date: 1-Aug-2017. Acampa W, Buechel R and Gimelli A (2016) Low dose in nuclear cardiology: state of the art in the era of new cadmium–zinc–telluride cameras, European Heart Journal – Cardiovascular Imaging, 10.1093/ehjci/jew036, 17:6, (591-595), Online publication date: 1-Jun-2016. Miller T, Askew J and Anavekar N (2016) Noninvasive Stress Testing for Coronary Artery Disease, Heart Failure Clinics, 10.1016/j.hfc.2015.08.006, 12:1, (65-82), Online publication date: 1-Jan-2016. Kao Y and Better N (2015) D-SPECT: New technology, old tricks, Journal of Nuclear Cardiology, 10.1007/s12350-015-0290-5, 23:2, (311-312), Online publication date: 1-Apr-2016. Hwang K, Lee B, Kim Y, Lee H and Sun Y (2015) Recent Development in Low Dose Nuclear Medicine Gamma Camera Imaging, Journal of Biomedical Engineering Research, 10.9718/JBER.2015.36.4.123, 36:4, (123-127), Online publication date: 30-Aug-2015. Tweet M, Arruda-Olson A, Anavekar N and Pellikka P (2015) Stress Echocardiography: What Is New and How Does It Compare with Myocardial Perfusion Imaging and Other Modalities?, Current Cardiology Reports, 10.1007/s11886-015-0600-1, 17:6, Online publication date: 1-Jun-2015. Miller T, Askew J and Anavekar N (2014) Noninvasive Stress Testing for Coronary Artery Disease, Cardiology Clinics, 10.1016/j.ccl.2014.04.008, 32:3, (387-404), Online publication date: 1-Aug-2014. January 2011Vol 4, Issue 1 Advertisement Article InformationMetrics © 2011 American Heart Association, Inc.https://doi.org/10.1161/CIRCIMAGING.110.961987PMID: 21245363 Originally publishedJanuary 1, 2011 KeywordsEditorialsnuclear medicinePDF download Advertisement SubjectsNuclear Cardiology and PET
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