Final answer:
The collimator used for both rest and stress ERNA is a lead shield with a hole in the center. Its role is to filter out unwanted radiation and allow only the gamma rays from the heart to reach the detector.
Step-by-step explanation:
The collimator used for both rest and stress ERNA (Exercise Radiopharmaceutical Nuclear Angiography) is a lead shield with a hole in the center. This hole allows only the gamma rays coming from the heart to reach the detector, while blocking out other radiation sources in the surroundings.
The collimator acts as a filter, shaping the radiation beam and reducing scatter. It ensures that the detected signal is primarily from the heart, making the images clearer and more accurate.
It is important to use a collimator in ERNA to enhance the diagnostic value of the procedure and provide valuable information about the coronary arteries and blood flow in the heart.