Which of the following items is not used for patient positioning?

The correct answer is that tissue compensators are not used for patient positioning. Tissue compensators are devices designed to modify the radiation dose distribution by compensating for variations in tissue density. Their primary function is related to radiation therapy rather than physically positioning a patient during treatment.

In contrast, thermoplastic masks, vacuum cushions, and immobilization straps are all specifically intended for patient positioning and immobilization during procedures. Thermoplastic masks are molded to the patient's face or body to provide stability and reproducibility in positioning during radiation therapy. Vacuum cushions conform to the shape of the patient and maintain that position, providing both comfort and support. Immobilization straps help secure the patient in place to prevent movement during critical procedures, thereby enhancing treatment accuracy and effectiveness. Each of these items serves an essential role in ensuring proper alignment and stability for the patient during medical imaging or therapy.