Manuel D. Cerqueira
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1. A 62-year-old male presents with increasing shortness of breath and lower extremity edema. A projection image in the left anterior oblique position from the stress portion of a 1-day rest/stress technetium-99m perfusion single photon emission computed tomography myocardial perfusion imaging (SPECT MPI) study is shown in Figure 5.1. Given the available information, what is the most likely cause of the patient’s symptoms?
A. Pulmonary hypertension
C. Dilated cardiomyopathy
D. Severe ischemia
1. ANSWER: A. The image shows marked right ventricular hypertrophy and enlargement that is most consistent with pulmonary hypertension due to any cause. The relative paucity of lung uptake of the technetium-99m agent suggests possible obstructive airway disease, which is a frequent cause of pulmonary hypertension and right ventricular hypertrophy. The heart and abdominal organs are in the correct anatomical position, which excludes dextrocardia. Since the left ventricle is normal in size, there is no reason to suspect a dilated cardiomyopathy. Although severe ischemia cannot be excluded based on the projection images alone, it is a less likely diagnosis given the available information. When using thallium-201 with stress, there may be increased lung uptake of thallium-201 on the stress images due to severe ischemia, which causes an increase in the lung-to-heart ratio. This is due to a transient elevation of the pulmonary capillary wedge pressure in association with ischemia and the extravasation of thallium-201 from the intravascular into the interstitial space. Such abnormal heart-to-lung ratios in association with serve ischemia have not been reported with technetium-99m agents and ratios are not routinely measured.
2. A patient is referred for a technetium-99m SPECT MPI study. Based on the stress and rest projection images in Figure 5.2, which of the following radioisotope imaging protocols was most likely used?
A. 1-day stress/rest technetium-99m
B. 1-day rest/stress technetium-99m
C. Rest thallium 201/stress technetium-99m
D. 2-day technetium-99m study
2. ANSWER: B. Based on the grainy quality of the rest images due to the low count statistics, we are led to conclude that this is a 1-day study using a low-dose rest, 8 to 12 millicuries, and a high-dose stress, 20 to 30 millicuries, study. In a dual-isotope protocol, the resting thallium-201 images may have a similar granularity due to low counts associated with the lower dose, 2.5 to 4 millicuries, that is administered to avoid high radiation exposure and the slower radioactive decay. We know both agents are technetium-99m based on the biodistribution that includes large amounts of radioactivity in the liver and gastrointestinal (GI) track. Thallium-201 may have some GI uptake but not the high quantity and the linear/tubular pattern that is shown here. This excludes dual-isotope protocol and is most consistent with a low-dose rest/high-dose stress sequence. A 2-day technetium-99m study could theoretically be done using low-dose rest and high-dose stress as shown, but generally, such studies are performed on heavy patients using high and comparable doses to allow high and comparable doses for both the stress and rest in order to achieve optimal image quality.
3. Based on the stress and rest projection images shown in Figure 5.3, what is the most likely cause for the patient’s severe shortness of breath?
A. Chronic obstructive pulmonary disease (COPD)
B. Dilated cardiomyopathy
C. Hypertrophic cardiomyopathy
D. Pulmonary stenosis
3. ANSWER: A. On the rest, but most prominently on the high-dose stress anterior images, there is marked thickening of the diaphragm recognized as a lucency starting from the patient’s right abdominal wall and extending all the way to the heart. Both attenuation by the diaphragm muscle and the contrast between the vascular lungs above and the liver-associated technetium-99m uptake give the dark appearance. With severe COPD, there is marked hypertrophy of the diaphragm resulting in such an appearance on the projection images. On the perfusion images, the hypertrophy of the diaphragm causes marked inferior wall attenuation. On these anterior images, the left ventricle is not dilated and a cardiomyopathy is not a likely cause. Heart size can be compared to the thoracic and the cardiothoracic ratio should be <½. Hypertrophic cardiomyopathy cannot be definitively excluded, but it does not generally cause diaphragmatic hypertrophy. Pulmonary stenosis does not cause pulmonary congestion. Ascites and pulmonary effusions may give a similar appearance on the projection images, but these are not options provided.
4. A 67-year-old male presents with atypical chest pain and an abnormal baseline electrocardiogram (ECG). Serial perfusion images from an exercise stress SPECT MPI at 13.5 METs without anginal symptoms are shown in Figure 5.4. Based on the images, what is the most likely explanation for the findings?
A. Three-vessel coronary artery disease (CAD)
B. Scaling artifact
C. Breast attenuation
D. Ramp filter artifact
4. ANSWER: B. The images show a very hot apical anterior hot spot on the stress images (arrow) that is causing a scaling artifact. This can be recognized by the circumferential decrease in counts that is most prominent on the short-axis slices relative to the resting images. The incorrect scaling decreases the subendocardial counts and may give the appearance of transient ischemic dilation. Three-vessel CAD is unlikely in view of the high workload, absence of symptoms, and the nonanatomic distribution of the perfusion defects. There is no possible combination of anatomic coronary stenosis that would give such diffuse circumferential decrease in midcavity and basal perfusion without involving the apex.
Breast attenuation is less common in a male and the diffuse pattern of decreased perfusion is not typical. A ramp filter artifact is caused by a hot loop of bowel or liver adjacent to the heart that results in decreased counts in the nearby wall when using filtered back projection for reconstruction. There is no liver or bowel visualized on the images shown.
5. A 60-year-old female presents with chest pain to the emergency department and is referred for exercise SPECT MPI. Based on Figure 5.5, what is the next best step for management?
A. Coronary angiography
B. Computed tomography (CT) coronary angiography
C. Hospital admission
D. Discharge for outpatient follow-up
5. ANSWER: D. This is a completely normal study by visual and quantitative analysis. The stress images have focal hot spots in the septum and lateral wall near the apex. The bull’s-eye display shows completely normal perfusion on the stress and rest images (Fig. 5.14). The normal perfusion makes coronary angiography, CT coronary angiography, and hospital admission unnecessary, and discharge is the best option for this patient.
6. A 58-year-old female with progressive chest pain is referred for an outpatient stress myocardial perfusion imaging (MPI). Based on Figure 5.6, what is the next best step for this patient?
A. Aggressive medical therapy
C. CT coronary angiography
D. Coronary angiography
6. ANSWER: D. The images demonstrate a large area of severe ischemia involving the apex, septum, anterior, and the lateral walls. There is transient ischemic dilation of the cavity. This is a high-risk scan consistent with severe tight proximal disease in the left anterior descending or left main or diffuse severe multivessel disease. In view of the progressive symptoms, coronary angiography is the best management option. Aggressive medial therapy is indicated but not the best option given the severity of the ischemia. An echocardiogram is of no value in this situation. Given the physiologic demonstration of severe ischemia by SPECT, the patient is likely to benefit from and require revascularization. CT coronary angiography is capable of demonstrating CAD but since revascularization is likely, coronary angiography is the best option as percutaneous coronary intervention (PCI) can be performed during the same session.
7. A 75-year-old male with a remote myocardial infarction and atypical chest pain is referred for a rubidium-82 vasodilator positron emission tomography (PET) study. The stress and rest images in Figure 5.7 show:
A. Misregistration artifact on the rest images.
B. Severe lateral wall ischemia.
C. Severe lateral wall ischemia and apical infarction.
D. Reconstruction artifact due to gastric uptake.
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