1. ANSWER: C. Technetium-99m is used to radiolabel the patient’s RBCs. There are three methods for radiolabeling: in vivo, in vitro, and in vivitro. For in vivo labeling, the patient receives intravenous stannous pyrophosphate 15 minutes prior to injection of 15 to 30 millicuries of technetium-99m pertechnetate. This method is the fastest and least expensive but has the lowest labeling efficiency of the RBCs and has a high background due to non-specific labeling of circulating proteins. For the in vitro method, 10 to 15 mL of the patient’s blood is drawn, and the stannous pyrophosphate and technetium-99m are added outside the body. Once labeling has been completed, the RBCs are reinjected into the patient. A commercial kit called Ultratag is available. This technique results in the highest labeling efficiency and lowest background activity but is more expensive and time consuming. The third method involves intravenous injection of the stannous pyrophosphate prior to removal of 10 to 15 mL of the patient’s RBCs that are then mixed with the technetium-99m pertechnetate.

There are many frequently used medications (hydralazine, prazosin, heparin, and digoxin) that inhibit binding of the technetium-99m pertechnetate to the hemoglobin molecule inside the RBCs. Poor binding is easily detected by finding free technetium-99m pertechnetate in the mucosa of the stomach and in the thyroid gland.

LVEF is calculated by measuring LV counts at end systole and end diastole and correcting for background activity due to overlying radioactivity and background scatter adjacent to the lateral or inferoapical walls of the ventricle. Failure to correct for background activity results in a lower ejection fraction measurement.

LVEF = Background corrected end diastolic counts-Background corrected end systolic counts/Background corrected end diastolic counts.

Heart/lung ratio can be calculated by this technique. This ratio measures how well the ventricles compensate by comparing the counts in the heart and lung. Pooling of blood in the lungs has been reported to be present in heart failure.

The assessment of left ventricle and right ventricle (RV) using ERNA is a class I indication in the ACC/AHA Radionuclide Guidelines. The majority of other indications fall in the class II and III categories.

Corbett JR, Akinboboye OO, Bacharach SL, et al.; Quality Assurance Committee of the American Society of Nuclear Cardiology. Equilibrium radionuclide angiocardiography. J Nucl Cardiol. 2006;13(6):e56-e79.

2. ANSWER: E. In addition to measuring LV and RV function, FPRNA can also detect and quantify atrial and ventricular shunts. DTPA, cleared by the kidneys, and technetium-99m sulfur colloid, cleared by the liver, give accurate results. Technetium-99m sestamibi and tetrofosmin used to assess myocardial perfusion at rest or peak stress can be given as a bolus for FPRNA when concentrated in a sufficiently small volume, ideally 0.5 to 1 mL. FPRNA can be performed when doing an ERNA study by the in vivo method but not when labeling is performed by in vitro or in vivitro methods due to the large volume administered. For timing purposes and quality of image (count density), large veins close to the heart are required for the rapid bolus of DTPA. The straight upright anterior view has the advantage of stabilizing the patient’s chest against the detector and positioning the patient so that the right and left ventricles will be in the field of view. FPRNA allows for RV function assessment. A shallow right anterior oblique (RAO) view is recommended to enhance right atrial-RV separation.

Friedman JD, Berman DS, Borges-Neto S, et al.; Quality Assurance Committee of the American Society of Nuclear Cardiology. First-pass radionuclide angiography. J Nucl Cardiol. 2006;13(6):e42-e55.

3. ANSWER: D. A typical LEHR collimator has a sensitivity of around 200 cpm/µCi for technetium-99m, which equals (3.3 cps)/(3.7 × 10⁴ Bq) = 0.9 × 10^-4 cps/Bq. Considering that the crystal efficiency is about 90% and that the 140-keV emission efficiency of technetium-99m is 89%, the collimator efficiency is 1.1 × 10^-4, or about 1 in 10,000.

4. ANSWER: A. Collimator blur increases with distance, and thus, resolution worsens. The number of counts passing through the collimator does not change appreciably as distance increases.

5. ANSWER: D. Thallium-201 decays by electron capture to mercury-201. The mercury-201 is in an excited state and releases x-rays with energies near 70 keV.

6. ANSWER: C. The difference between the net counts (121,344 – 53,311 = 68,033) indicates the activity ejected by the left ventricle. The ejection fraction is (68,033/121,344) = 56%.

7. ANSWER: B. Transmission and CT-based AC use a radioactive source or CT to create density or attenuation maps that are applied to the emission activity from the heart during reconstruction. Calculated AC does not directly measure the attenuation but calculates it based on assumptions of uniform attenuation and has been used successfully for brain SPECT or PET since the attenuation coefficient is approximately constant over the entire slice. However, for cardiac imaging, there is large variance in attenuation coefficient (lungs vs. other tissues such as diaphragm and breast), and calculated methods are not reliable.

8. ANSWER: A. The gamma camera should be checked each day before use to ensure that the energy window has not drifted and the energy spectrum is of the appropriated shape. The energy spectrum of a radionuclide source is acquired, and the photopeak is checked (either automatically or visually) to confirm that it is centered in the energy window.

Early PJ, Sodee DB. Principles and Practice of Nuclear Medicine. 2nd ed. St. Louis, MO: Mosby; 1985.

Saha GB. Fundamentals of Nuclear Medicine. 5th ed. New York, NY: Springer-Verlag; 1993.

Saha GB. Physics and Radiobiology of Nuclear Medicine. 3rd ed. New York, NY: Springer-Verlag; 1993.

9. ANSWER: C. The PMT consists of a photocathode that is light sensitive and a series of metallic plates (dynodes). A high voltage is applied to the plates, and when a light photon strikes the crystal, the photoelectron is absorbed by the photocathode and is multiplied by each dynode and a pulse is generated, which is proportional to the amount of energy of the isotope interacting with the crystal. The voltage to these plates has to be very stable, and a slight variation will greatly affect the pulse generated.

Early PJ, Sodee DB. Principles and Practice of Nuclear Medicine. 2nd ed. St. Louis, MO: Mosby; 1995.

Saha GB. Physics and Radiobiology of Nuclear Medicine. 3rd ed. New York, NY: Springer-Verlag; 1993.

10. ANSWER: C. A uniform source of radioactive source (flood sheet) is placed on the camera detector to check if all the PMTs are operational. If a PMT tube is malfunctioning, then a blank spot is observed on the flood scan. The large white area in the lower right corner shows the abnormality (Fig. 1.1). The rest of the detector is uniform.

Early PJ, Sodee DB. Principles and Practice of Nuclear Medicine. 2nd ed. St. Louis, MO: Mosby; 1995.

Saha GB. Fundamentals of Nuclear Medicine. 5th ed. New York, NY: Springer-Verlag; 1993.

Saha GB. Physics and Radiobiology of Nuclear Medicine. 3rd ed. New York, NY: Springer-Verlag; 1993.

11. ANSWER: B. In photoelectric absorption, the gamma ray transfers all its energy to an orbital electron of the absorbing material and a photoelectron is released. Compton scatter occurs when the gamma photon transfers only part of its energy to an orbital electron. The scattered photon travels in a different direction and may further interact in the material.

Early PJ, Sodee DB. Principles and Practice of Nuclear Medicine. 2nd ed. St. Louis, MO: Mosby; 1995.

Saha GB. Physics and Radiobiology of Nuclear Medicine. 3rd ed. New York, NY: Springer-Verlag; 1993.

12. ANSWER: B. Technetium-99m has a mean photopeak energy of 140 keV. In order to set a 20% window centered on the photopeak, the window width is 140 × 0.2 = 28. This gives a range of 14 keV on either side of 140 keV; thus, the energy window limits are 126 to 154 keV.

Saha GB. Physics and Radiobiology of Nuclear medicine. 3rd ed. New York, NY: Springer-Verlag; 1993.

13. ANSWER: C. A ramp filter is routinely used during reconstruction by filtered backprojection and does not give any information on motion.

Motion during acquisition may give the following artifacts: misalignment of the apex, matching 180-degree areas of decreased intensity in the anterior and inferior walls, hotspots in the septum or lateral wall, and “blobs” or a ring of activity in the anterior wall or an apical nipple. However, seeing such artifacts on the long- and short-axis images does not confirm that there was motion. Review of the raw projection images in a cine format allows visual detection of vertical or up-and-down motion. This can be corrected using motion correction or, if it is excessive, reacquiring the study. Horizontal or side-to-side motion is difficult to detect and cannot be corrected. Rapid or deep breathing may also cause motion like artifacts. Acquisition with a dual-head camera will sometimes give the appearance of motion as the images from each head are displayed in a continuous loop. The last acquisition from one head is displayed next to the first acquisition from the other head. Spatially, these images are adjacent, but temporally, one is at the end and the other at the beginning of acquisition. If the patient moved gradually, such motion may not be detected on individual projections but is seen in the transition from one head to the other. Such motion should not be motion corrected.

The technologist should be questioned, but this in itself is not sufficient as he or she may not have been observing the patient throughout the study.

Christian PE, Waterstram-Rich K. Nuclear Medicine and PET/CT: Technology and Techniques. 6th ed. St. Louis, MO: Mosby/Elsevier; 2007.

14. ANSWER: A. Thirty-two to sixty-four planar projections are acquired 180 degrees around the patient perpendicular to the long axis of the body, and the initial reconstruction is into the transaxial plane. From these transaxial images, the long axis of the heart is defined, and subsequently, the conventional vertical and horizontal long-axis and the short-axis images are reconstructed for analysis.

Christian PE. Nuclear Medicine and PET Technology and Techniques. St. Louis, MO: Mosby; 1981.

60 s/(heart rate × the number of frames)

60/(60 × 20) = 0.05

Christian PE. Nuclear Medicine and PET Technology and Techniques. St. Louis, MO: Mosby; 1981.

16. ANSWER: B. In a cardiac SPECT study, typically 64 projections are obtained over 180 degrees at 3-degree increments, and each projection usually takes about 20 seconds. A total of ˜21 minutes will be required. However, if two detectors at 90-degree orientation are used, the time to acquire the 64 projection will be half (11 minutes).

Christian PE. Nuclear Medicine and PET Technology and Techniques. St. Louis, MO: Mosby; 1981.

17. ANSWER: B. LET is the amount of energy deposited per unit length of the absorber, and units are expressed as keV/µm. Electromagnetic and beta particles have low LET, since they lose little energy per interaction. Alpha particles are heavy particles and lose energy very rapidly and have high LET.

Early PJ, Sodee DB. Principles and Practice of Nuclear Medicine. 2nd ed. St. Louis, MO: Mosby; 1995.

18. ANSWER: B. Inferior wall attenuation is often present in male patients (diaphragmatic attenuation), and anterior attenuation is often seen in female patients (breast attenuation). These artifacts often affect the specificity of diagnosing CAD by introducing false-positive tests. Normal systolic thickening on gated SPECT in a fixed defect on both rest and stress images represents an attenuation artifact rather than a myocardial scar, which is associated with reduced systolic thickening.

19. ANSWER: D. AC significantly improved the normalcy rate compared to uncorrected perfusion data using either the corrected images (96% vs. 86%) or the corrected data and quantitative analysis (97% vs. 86%). There is no impact on overall sensitivity (75% to 78%), although the detection of multivessel disease was reduced.

Hendel RC, Berman DS, Cullom J, et al. Multicenter clinical trial to evaluate the efficacy of correction for photon attenuation and scatter in SPECT myocardial perfusion imaging. Circulation. 1999;99:2742.

Hendel RC, Corbett JR, Cullom SJ, et al. The value and practice of attenuation correction for myocardial perfusion SPECT imaging: a joint position statement from the American Society of Nuclear Cardiology and the Society of Nuclear Medicine. J Nucl Cardiol. 2002;9:135.