myocardial perfusion imaging

The history of nuclear cardiology began in 1927 when Dr. Herrmann Blumgart developed the first method for measuring cardiac strength by injecting subjects with a radioactive compound known as Radium C (²¹⁴Bi).{{cite journal | vauthors = Blumgart HL, Yens OC | title = Studies on the velocity of blood flow: I. The method utilized | journal = The Journal of Clinical Investigation | volume = 4 | issue = 1 | pages = 1–13 | date = April 1927 | pmid = 16693741 | pmc = 434654 | doi = 10.1172/JCI100106 | url = }}{{cite journal | vauthors = Love WD | title = Isotope Technics in Clinical Cardiology | journal = Circulation | volume = 32 | issue = 2 | pages = 309–315 | date = August 1965 | pmid = 14340959 | doi = 10.1161/01.CIR.32.2.309 | doi-access = free }} The substance was injected into the venous system and travelled through the right heart into the lungs, then into the left heart and out into the arterial system where it was then detected through a Wilson chamber. The Wilson chamber represented a primitive scintillation counter which could measure radioactivity. Measured over time, this sequential acquisition of radioactivity produced what was known as "circulation time". The longer the "circulation time", the weaker the heart. Blumgart's emphasis was twofold. First, radioactive substances could be used to determine cardiac physiology (function) and should be done so with the least amount of radioactivity necessary to do so. Secondly, to accomplish this task, one needs to obtain multiple counts over time.{{citation needed|date=January 2022}}

For decades no substantial work was done, until 1959. Dr. Richard Gorlin's work on "resting" studies of the heart and nitroglycerin emphasized several points.{{cite journal | vauthors = Gorlin R, Brachfeld N, MacLeod C, Bopp P | title = Effect of nitroglycerin on the coronary circulation in patients with coronary artery disease or increased left ventricular work | journal = Circulation | volume = 19 | issue = 5 | pages = 705–18 | date = May 1959 | pmid = 13652363 | doi = 10.1161/01.cir.19.5.705 }} First, like Blumgart, he emphasized that evaluation of cardiac function required multiple measurements of change over time and these measurements must be performed under same state conditions, without changing the function of the heart in between measurements. If one is to evaluate ischemia (reductions in coronary blood flow resulting from coronary artery disease) then individuals must be studied under "stress" conditions and comparisons require "stress-stress" comparisons. Similarly, if tissue damage (heart attack, myocardial infarction, cardiac stunning or hibernation) is to be determined, this is done under "resting" conditions. Rest-stress comparisons do not yield adequate determination of either ischemia or infarction. By 1963, Dr. William Bruce, aware of the tendency of people with coronary artery disease to experience angina (cardiac chest discomfort) during exercise, developed the first standardized method of "stressing" the heart, where serial measurements of changes in blood pressure, heart rate and electrocardiographic (ECG/EKG) changes could be measured under "stress-stress" conditions. By 1965 Dr. William Love demonstrated that the cumbersome cloud chamber could be replaced by a Geiger counter, which was more practical to use. However, Love had expressed the same concern as many of his colleagues, namely that there were no suitable radioisotopes available for human use in the clinical setting.

By the mid-1970s, scientists and clinicians alike began using thallium-201 as the radioisotope of choice for human studies.{{cite book| vauthors = DePuey EG, Garcia EV, Berman DS |title=Cardiac SPECT Imaging|date=2001|publisher=Lippincott Williams & Wilkins|isbn=9780781720076|page=117|url=https://books.google.com/books?id=CqQgnHrDxrUC&pg=PA117|language=en}} Individuals could be placed on a treadmill and be "stressed" by the "Bruce protocol" and when near peak performance, could be injected with thallium-201. The isotope required exercise for an additional minute to enhance circulation of the isotope. Using nuclear cameras of the day and given the limitations of Tl-201, the first "stress" image could not be taken until 1 hour after "stress". In keeping with the concept of comparison images, the second "stress" image was taken 4 hours after "stress" and compared with the first. The movement of Tl-201 reflected differences in tissue delivery (blood flow) and function (mitochondrial activity). The relatively long half-life of Tl-201 (73 hours) forced doctors to use relatively small ({{convert|2|-|3|mCi|MBq|abbr=on|order=flip|disp=or}}) doses of Tl-201, albeit with relatively large dose exposure and tissue effects (20 mSv). The poor quality images resulted in the search for isotopes which would produce better results.{{cite journal | vauthors = Strauss HW, Bailey D | title = Resurrection of thallium-201 for myocardial perfusion imaging | journal = JACC. Cardiovascular Imaging | volume = 2 | issue = 3 | pages = 283–285 | date = March 2009 | pmid = 19356572 | doi = 10.1016/j.jcmg.2009.01.002 | doi-access = free }}

By the late 1980s, two different compounds containing technetium-99m were introduced: teboroxime {{cite journal | vauthors = Bisi G, Sciagrà R, Santoro GM, Cerisano G, Vella A, Zerauschek F, Fazzini PF | title = [Myocardial scintigraphy with Tc-99m-teboroxime: its feasibility and the evaluation of its diagnostic reliability. A comparison with thallium-201 and coronary angiography] | journal = Giornale Italiano di Cardiologia | volume = 22 | issue = 7 | pages = 795–805 | date = July 1992 | pmid = 1473653 }} and sestamibi. The utilization of Tc-99m would allow higher doses (up to {{convert|30|mCi|MBq|abbr=on|order=flip|disp=or}}) due to the shorter physical (6 hours) half life of Tc-99m. This would result in more decay, more scintillation and more information for the nuclear cameras to measure and turn into better pictures for the clinician to interpret.{{citation needed|date=January 2022}}

The use of positron emission tomography (PET) has been limited due to the shorter half-life of the radionuclides used and the need for in-house production. While not as widely available, PET is increasingly used for myocardial perfusion imaging (MPI). Recent guidelines states that PET is the preferred functional imaging test in patients with chronic coronary syndromes and suspected CAD.{{cite journal | vauthors = Vrints C, Andreotti F, Koskinas KC, Rossello X, Adamo M, Ainslie J, Banning AP, Budaj A, Buechel RR, Chiariello GA, Chieffo A, Christodorescu RM, Deaton C, Doenst T, Jones HW, Kunadian V, Mehilli J, Milojevic M, Piek JJ, Pugliese F, Rubboli A, Semb AG, Senior R, Ten Berg JM, Van Belle E, Van Craenenbroeck EM, Vidal-Perez R, Winther S | title = 2024 ESC Guidelines for the management of chronic coronary syndromes | journal = European Heart Journal | volume = 45 | issue = 36 | pages = 3415–3537 | date = September 2024 | pmid = 39210710 | doi = 10.1093/eurheartj/ehae177 | doi-access = free }} The main benefit of performing PET instead of SPECT is absolute quantification of myocardial blood flow (MBF) in terms of ml/g/min rather than assessing relative perfusion defects. PET also provides higher image quality and better tracer properties which allows for more detailed diagnostics, resulting in higher diagnostic accuracy and prognostics implications.{{cite journal | vauthors = Driessen RS, Raijmakers PG, Stuijfzand WJ, Knaapen P | title = Myocardial perfusion imaging with PET | journal = The International Journal of Cardiovascular Imaging | volume = 33 | issue = 7 | pages = 1021–1031 | date = July 2017 | pmid = 28188475 | pmc = 5489578 | doi = 10.1007/s10554-017-1084-4 }} The available tracers in PET MPI is oxygen-15 water, rubidium-82, nitrogen-13 ammonia, and the newly introduced fluorine-18 flurpiridaz.{{cite journal | vauthors = Dahdal J, Jukema RA, Harms HJ, Cramer MJ, Raijmakers PG, Knaapen P, Danad I | title = PET myocardial perfusion imaging: Trends, challenges, and opportunities | journal = Journal of Nuclear Cardiology | volume = 40 | pages = 102011 | date = October 2024 | pmid = 39067504 | doi = 10.1016/j.nuclcard.2024.102011 | doi-access = free }}

• Diagnosis of CAD and various cardiac abnormalities.
• Identifying location and degree of CAD in patients with a history of CAD.
• Prognosis of patients who are at risk of having a myocardial or coronary incident (i.e. myocardial infarction, myocardial ischemia, coronary aneurysm, wall motion abnormalities).
• Assessment of viable myocardium in particular coronary artery territory following heart attacks to justify revascularization
• Post intervention revascularization (coronary artery bypass graft, angioplasty) evaluation of heart.
• Evaluation of shortness of breath of a possible cardiac origin.{{cite journal | vauthors = Wolk MJ, Bailey SR, Doherty JU, Douglas PS, Hendel RC, Kramer CM, Min JK, Patel MR, Rosenbaum L, Shaw LJ, Stainback RF, Allen JM, Brindis RG, Kramer CM, Shaw LJ, Cerqueira MD, Chen J, Dean LS, Fazel R, Hundley WG, Itchhaporia D, Kligfield P, Lockwood R, Marine JE, McCully RB, Messer JV, O'Gara PT, Shemin RJ, Wann LS, Wong JB, Patel MR, Kramer CM, Bailey SR, Brown AS, Doherty JU, Douglas PS, Hendel RC, Lindsay BD, Min JK, Shaw LJ, Stainback RF, Wann LS, Wolk MJ, Allen JM | title = ACCF/AHA/ASE/ASNC/HFSA/HRS/SCAI/SCCT/SCMR/STS 2013 multimodality appropriate use criteria for the detection and risk assessment of stable ischemic heart disease: a report of the American College of Cardiology Foundation Appropriate Use Criteria Task Force, American Heart Association, American Society of Echocardiography, American Society of Nuclear Cardiology, Heart Failure Society of America, Heart Rhythm Society, Society for Cardiovascular Angiography and Interventions, Society of Cardiovascular Computed Tomography, Society for Cardiovascular Magnetic Resonance, and Society of Thoracic Surgeons | journal = Journal of Cardiac Failure | volume = 20 | issue = 2 | pages = 65–90 | date = February 2014 | pmid = 24556531 | doi = 10.1016/j.cardfail.2013.12.002 }}

From 1993 to 2001, myocardial perfusion scans in the US increased >6%/y with "no justification".{{cite journal | vauthors = Lauer MS | title = Elements of danger--the case of medical imaging | journal = The New England Journal of Medicine | volume = 361 | issue = 9 | pages = 841–843 | date = August 2009 | pmid = 19710480 | doi = 10.1056/NEJMp0904735 }} Myocardial perfusion imaging scans are "powerful predictors of future clinical events", and in theory may identify patients for whom aggressive therapies should improve outcome. But this is "only a hypothesis, not a proof". However, several trials have indicated the high sensitivity (90%) of the test, regardless of tracer, outweighing any potential detrimental effect of the ionising radiation.{{cite journal | vauthors = Underwood SR, Anagnostopoulos C, Cerqueira M, Ell PJ, Flint EJ, Harbinson M, Kelion AD, Al-Mohammad A, Prvulovich EM, Shaw LJ, Tweddel AC | title = Myocardial perfusion scintigraphy: the evidence | journal = European Journal of Nuclear Medicine and Molecular Imaging | volume = 31 | issue = 2 | pages = 261–291 | date = February 2004 | pmid = 15129710 | pmc = 2562441 | doi = 10.1007/s00259-003-1344-5 }}{{cite journal | vauthors = Applegate KE, Amis ES, Schauer DA | title = Radiation exposure from medical imaging procedures | journal = The New England Journal of Medicine | volume = 361 | issue = 23 | pages = 2289; author reply 2291-2289; author reply 2292 | date = December 2009 | pmid = 19955531 | doi = 10.1056/NEJMc0909579 }} In the UK, NICE guidance recommends myocardial perfusion scans following myocardial infarction or reperfusion interventions.{{cite web|title=Myocardial perfusion scintigraphy for the diagnosis and management of angina and myocardial infarction|url=https://www.nice.org.uk/guidance/ta73/chapter/1-guidance|website=NICE|date=26 November 2003 |access-date=14 December 2017}} The power of prognosis from a myocardial perfusion scan is excellent and has been well tested, and this is "perhaps the area of nuclear cardiology where the evidence is most strong".{{cite journal | vauthors = Shaw LJ, Iskandrian AE | title = Prognostic value of gated myocardial perfusion SPECT | journal = Journal of Nuclear Cardiology | volume = 11 | issue = 2 | pages = 171–185 | date = April 2004 | pmid = 15052249 | doi = 10.1016/j.nuclcard.2003.12.004 | s2cid = 31369868 }}

Many radionuclides used for myocardial perfusion imaging, including rubidium-82, technetium-99m and thallium-201 have similar typical effective doses (15-35 mSv).{{cite journal | vauthors = Berrington de Gonzalez A, Kim KP, Smith-Bindman R, McAreavey D | title = Myocardial perfusion scans: projected population cancer risks from current levels of use in the United States | journal = Circulation | volume = 122 | issue = 23 | pages = 2403–2410 | date = December 2010 | pmid = 21098448 | pmc = 3548424 | doi = 10.1161/CIRCULATIONAHA.110.941625 }} The Cardiac PET tracer nitrogen-13 ammonia, though less widely available, may offer significantly reduced doses (2 mSv).{{cite web|title=Notes for Guidance on the Clinical Administration of Radiopharmaceuticals and use of sealed Radioactive Sources|url=https://www.gov.uk/government/publications/arsac-notes-for-guidance|website=Department of Health|publisher=Public Health England|format=pdf|date=22 February 2017}}{{cite journal | vauthors = deKemp R, Beanlands R | title = A revised effective dose estimate for the PET perfusion tracer Rb-82. | journal = The Journal of Nuclear Medicine | date = 2008 | volume = 49 | issue = supplement 1 | page = 183 | url = https://jnm.snmjournals.org/content/49/supplement_1/183P.3 }}{{cite journal | vauthors = Stabin MG | title = Radiopharmaceuticals for nuclear cardiology: radiation dosimetry, uncertainties, and risk | journal = Journal of Nuclear Medicine | volume = 49 | issue = 9 | pages = 1555–63 | date = September 2008 | pmid = 18765586 | doi = 10.2967/jnumed.108.052241 }} Stress-only protocols may also prove to be effective at reducing costs and patient exposure.{{cite journal | vauthors = Heston TF | title = Stress-only Nuclear Myocardial Perfusion Imaging. | journal = Internet Med J | date = 2012

| url = http://imj.medjournal.com/2012/02/stress-only-nuclear-myocardial.html | url-status=dead | access-date = 17 February 2012 }}

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Category:Cardiac imaging

Category:3D nuclear medical imaging

Category:Scintigraphy

Category:Technetium-99m