Is exercise necessary for a Positron Emission Tomography (PET) scan?

Exercise Requirements for PET Scans

Exercise is not required for PET scans, but whether you can or should exercise depends on the specific type of PET scan and the radiotracer being used. For cardiac PET myocardial perfusion imaging with rubidium-82 (Rb-82), exercise cannot be used due to the extremely short tracer half-life, and pharmacologic stress is mandatory. However, for cardiac PET with N-13 ammonia, exercise stress is feasible and can be performed. 1

Cardiac PET Imaging: Tracer-Specific Protocols

Rubidium-82 PET

• Rb-82 PET imaging can only be performed with pharmacological stress because the tracer has an extremely short half-life that makes exercise stress technically impossible 1
• Pharmacologic agents used include adenosine, regadenoson, or dipyridamole 1

N-13 Ammonia PET

• N-13 ammonia PET can be performed with either exercise or pharmacological stress, similar to SPECT protocols 1
• Exercise stress is feasible and has been shown to be as repeatable as adenosine stress for assessing coronary flow reserve 2
• Supine bicycle exercise during PET scanning is technically feasible with mean workloads around 130W (70% predicted maximum) 2

When Exercise Should Be Added to Pharmacologic Stress

Adding modest exercise to pharmacologic stress reduces adverse effects and improves diagnostic accuracy 3:

• Supplementary exercise with dipyridamole or adenosine reduces chest discomfort, feelings of impending syncope, flushing, and blood pressure drops 3
• Sinus bradycardia occurs less frequently when exercise is added to adenosine (1.2% vs 4.3% in younger patients, 0.9% vs 6.9% in elderly) 3
• Ischemic ECG changes are as frequent with pharmacologic stress plus exercise as with exercise alone, improving diagnostic yield 3

Patient-Specific Considerations

When Exercise Stress Is Preferred

• Patients <65 years of age who can exercise 1
• When hemodynamic or symptomatic response to exercise is clinically important 1
• Patients able to achieve ≥5 METs and 85% maximum predicted heart rate 1

When Pharmacologic Stress Is Required

• Patients unable to exercise adequately 1
• When using Rb-82 as the PET tracer 1
• Patients with baseline ECG abnormalities (LBBB, paced rhythm, Wolff-Parkinson-White) where exercise ECG is non-diagnostic 1

Absolute Contraindications to Stress PET

Do not perform stress PET imaging in these situations 4:

• High-risk unstable angina, complicated acute coronary syndrome, or acute MI within 2 days
• Significant arrhythmias (ventricular tachycardia, second- or third-degree AV block)
• Significant hypotension (systolic BP <90 mmHg)
• Uncontrolled heart failure
• Sinus bradycardia <45 bpm

Additional Contraindications for Vasodilator Stress

• Known or suspected bronchoconstrictive/bronchospastic disease 4
• Use of dipyridamole or methylxanthines (caffeine) within 12 hours 4
• Known hypersensitivity to adenosine or regadenoson 5

Non-Cardiac PET Scans

For non-cardiac PET scans (brain, oncology, etc.), exercise is not part of the protocol 6, 7:

• FDG-PET for brain or cancer imaging is performed at rest
• Patients should avoid strenuous exercise before FDG-PET as it can alter tracer distribution
• The goal is to image baseline metabolic activity, not stress-induced changes

Safety Profile

Stress testing with PET is safe across all age groups, including elderly patients >75 years 3:

• No deaths or myocardial infarctions occurred in studies of 3,412 patients
• Major complications are extremely rare (death <0.002%, MI <0.02%) 1
• Elderly patients have similar safety profiles to younger patients when appropriately selected 3