EDITOR’S PAGE

Can we enhance quality in nuclear cardiology?

George A. Beller, MD

Recently, a state-of-the-art article was published inthe Journal of the American College of Cardiologyregarding the issue of achieving quality in cardiovascularimaging.1 This review summarized the proceedings fromthe American College of Cardiology–Duke UniversityMedical Center Think Tank on Quality in CardiovascularImaging. The article was endorsed by multiple societiesincluding the American College of Radiology and theAmerican Society of Nuclear Cardiology. The confer-ence participants developed a framework for evaluatingthe quality of cardiovascular imaging procedures. Thequality evaluation process begins with ensuring appro-priate patient selection for a specific study based onevidence (or consensus) that it is reasonable, will influ-ence medical decision making, and will lead to quanti-fiable benefits for patients. The second step in the processis the acquisition of images by use of well-functioningequipment, trained and accredited laboratory staff, andreproducible imaging protocols that yield diagnostic-quality images optimized for individual patients. Third,the images must be interpreted with high accuracy andreproducibility. Finally, the participants emphasize thattest results must be communicated to the referral physi-cians in a lucid, comprehensive, clinically relevant, andtimely manner to optimize patient therapy with theultimate goal of improving health outcomes. The confer-ence participants advocated that quality measures shouldbe developed for each step in this framework.

This is a very important report, and the principlesapply to all cardiovascular imaging procedures. Signifi-cant advances have been made in establishing criteria foridentifying patients who truly benefit from stress or restimaging, whatever the modality, while minimizing oravoiding inappropriate testing. The authors state that“quality in patient selection means referring the rightpatient for the right test at the right time.” The Appro-priateness Criteria Working Group of the AmericanCollege of Cardiology standards have been a majoradvance in developing the indications for testing.2 Suchguidelines have already been published for nuclear car-diology,3 cardiac computed tomography, and cardiacmagnetic resonance imaging.

The next two steps inherent in the framework forevaluating quality of cardiovascular imaging relate toimage acquisition and image interpretation. The confer-ence participants who developed the consensus docu-ment on quality in cardiovascular imaging noted that

high-quality image acquisition depends on having spe-cific protocols and sequences in place that will optimizethe likelihood that images are of sufficient diagnosticquality.1 Quality indicators can include determining thecauses of inadequate studies such as excessive patientmotion or percent of equivocal or nondiagnostic studiesdue to technical factors. Obviously, state-of-the-artequipment and instrumentation are key elements thatdictate subsequent quality of image acquisition anddisplay, as are the skills, training, and certification of thetechnologists who oversee the process. Accuracy andreproducibility can be evaluated with the use of standardphantoms.

Clearly, the training and expertise of the physicianreaders are vital standards for assessing the quality ofimage interpretations. Specialized examinations testingphysician proficiency are available for all modalities, aswith the test given annually by the Certification Board ofNuclear Cardiology. The conferees stated that “highquality imaging interpretation will not be guaranteedsolely by the certification of imaging specialists, butobjective evidence of accuracy and reproducibility needsto be provided and is considered a major component ofquality in imaging.” Important indicators of quality atany given institution are inter-reader and intra-readervariability among imaging specialists. Another measure-ment of image interpretation quality is the comparison ofthe results of the imaging study with those of a differentimaging modality (eg, coronary angiography).

The last element in evaluating quality in the imagingprocess relates to the communication of results in reportsto referral physicians. Reports should be unambiguouswith respect to conclusions, and imaging results have tobe communicated in a clear and timely fashion—withprompt notification of the ordering physician whenhigh-risk imaging findings are identified. The AmericanSociety of Nuclear Cardiology has defined well the dataelements to be used in nuclear cardiology reports, withthe goal of creating a uniform national database.4

The final metric for quality assessment for anyimaging modality is that appropriate, high-quality imag-ing leads to improved decision making and patient care.The conferees cited the use of the rate of false-positivefindings after comparison with the gold standard (eg, anunnecessary catheterization) and examining the rate offalse-negative results that subsequently led to adversepatient outcomes (eg, a subsequent significant cardiac

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event in someone whose imaging test was read asnormal).

With respect to nuclear cardiology, slow progresshas occurred in the development of robust technicalsolutions that would improve image quality. Attenuationartifacts that are interpreted as true perfusion defects area major factor contributing to false-positive image inter-pretation. This misinterpretation may lead to unnecessarycardiac catheterization with its attendant increases in costand patient morbidity. In this issue of the Journal ofNuclear Cardiology, Singh et al5 provide their viewpointpertaining to the reasons why more progress has not beenmade to further standardize and enhance utilization ofattenuation correction for clinical usage with the goal ofimproving the specificity and overall diagnostic accuracyof myocardial perfusion imaging with single photonemission computed tomography (SPECT). In the priorissue of the Journal, the Emory University and Cedars-Sinai groups provide their views regarding the merits(and drawbacks) of attenuation-corrected SPECT forroutine imaging.6,7 Singh et al review the literature todate as well as citing consensus statements from scien-tific societies and advocate for a “substantive push formuch higher-quality attenuation- and scatter-correctedimages” to enhance SPECT image quality. They arepuzzled by the fact that, despite all of the currentresearch showing that attenuation correction significantlyimproves diagnostic quality when analyzed in conjunc-tion with non–attenuation-gated images, it has not beenembraced by the nuclear cardiology community. Singh etal state that using attenuation correction in SPECT cansave time and reduce costs in stress laboratories bypermitting laboratories to perform more stress-only per-fusion imaging in patients with a low to intermediate riskof coronary artery disease (CAD). In addition to theattenuation problem, which limits SPECT image quality,Singh et al comment that other technical factors degradeimage quality, including poor resolution with filteringthat blurs out natural myocardial variations in thicknessand photon scatter, which degrades image quality byreducing contrast and artificially boosting counts inregions of the heart (eg, inferior wall overcorrection). Iwould also add that little advance has been made inimproving the perfusion imaging agents that we cur-rently use. These agents exhibit a plateau in myocardialuptake with hyperemic blood flow. Vasodilator SPECTimaging can underestimate the extent of CAD in thesituation of balanced ischemia or if flow reserve becomesdiminished globally in the myocardium. Excessive vis-ceral uptake of currently available SPECT tracers inter-feres with interpretation of the inferobasilar segment ofthe heart.

Singh et al5 state that over the past few years, the useof SPECT imaging has grown by 19.5% annually. They

lament that “almost none of the growth can be attributedto significant technical advances.” They also mentionthat there have not been any new commercially availableperfusion tracers for more than 20 years, despite allspecialists in the field understanding full well the prob-lems of myocardial uptake that are not linear with flow,excessive scatter and attenuation of photons, and “unde-sirable tracer uptake in cardiac-adjacent structures.”They assert that the “Anger gamma camera has been theonly commercial offering for more than 40 years.” In thisreview they conclude by asking “why has our subspe-cialty not embraced and insisted on solutions to improveimage quality . . . ?” They lay the blame in several areas.Most importantly, they state that industry has refused toagree on a common approach pertaining to attenuationcorrection, which would make the end product similarregardless of the method used. Singh et al speculate thatindustry has chosen to sell their devices into a “hotmarket of less-skilled providers with lesser performance’demands’ rather than emphasize technologic innovationthat may improve care.” The authors further mention thatindustry has not attempted to educate its consumersabout the importance of attenuation correction hardwareand, with few exceptions, has not supported clinicalresearch for its validation.

I agree with many of the conclusions made by Singhet al5 in their review. The field of nuclear cardiology hasexisted for many years, but we still have not been able tosurmount many of the problems that interfere withoptimizing image quality. If technologic advances of thekind deemed necessary were made, it would lead to moreconsistent and less equivocal image interpretation. This,in turn, would lead to better outcomes for patients.Certainly, we have made great progress in identifyingpatients for whom stress perfusion imaging is mostappropriate, thus enhancing the diagnostic and prognos-tic value of the test. With experience, we have learned tocorrectly interpret images that are of poor technicalquality, making stress perfusion imaging highly usefulfor diagnosing CAD and assessing risk of future events.However, limitations regarding the technical features ofSPECT imaging must be overcome, and a meaningfulunderstanding between providers and industry must beachieved to push the field forward. If this does nothappen, SPECT imaging could lose its influence andmarket share to other emerging new technologies thatseem currently to enjoy more industry investment thandoes nuclear cardiology.

References

1. Douglas P, Iskandrian AE, Krumholz HM, Gillam L, Hendel R,Jollis J, et al. Achieving quality in cardiovascular imaging: proceed-ings from the American College of Cardiology–Duke University

140 Beller Journal of Nuclear CardiologyCan we enhance quality in nuclear cardiology? March/April 2007

Medical Center Think Tank on Quality in Cardiovascular Imaging.J Am Coll Cardiol 2006;48:2141-51.

2. Patel MR, Spertus JA, Brindis RG, Hendel RC, Douglas PS,Peterson ED, et al. ACCF proposed method for evaluating theappropriateness of cardiovascular imaging. J Am Coll Cardiol2005;46:1606-13.

3. Brindis RG, Douglas PS, Hendel RC, Peterson ED, Wolk MJ, AllenJM, et al. ACCF/ASNC appropriateness criteria for single-photonemission computed tomography myocardial perfusion imaging(SPECT MPI): a report of the American College of CardiologyFoundation Quality Strategic Directions Committee Appropriate-ness Criteria Working Group and the American Society of NuclearCardiology. J Am Coll Cardiol 2005;46:1587-605.

4. Cerqueira MD, Weissman NJ, Dilsizian V, Jacobs AK, Kaul S,Laskey WK, et al; American Heart Association Writing Group on

Myocardial Segmentation and Registration for Cardiac Imaging.Standardized myocardial segmentation and nomenclature fortomographic imaging of the heart. A statement for healthcareprofessionals from the Cardiac Imaging Committee of the Councilon Clinical Cardiology of the American Heart Association. Circu-lation 2002;105:539-42.

5. Singh B, Bateman TM, Case JA, Heller G. Attenuation artifact,attenuation correction, and the future of myocardial perfusionSPECT. J Nucl Cardiol 2007;14:153-64.

6. Garcia EV. SPECT attenuation correction: an essential tool torealize nuclear cardiology’s manifest destiny. J Nucl Cardiol 2007;14:16-24.

7. Germano G, Slomka PJ, Berman DS. Attenuation correction incardiac SPECT: The boy who cried wolf? J Nucl Cardiol 2007;14:25-35.

Journal of Nuclear Cardiology Beller 141Volume 14, Number 2;139-41 Can we enhance quality in nuclear cardiology?