PET-CT Weight and Bore Limits: — Can You Have the Scan?

The scan cannot proceed on that machine, and the limit will not be overridden. Your referring doctor and the imaging centre can work together to find a centre with a higher-capacity scanner. If no suitable PET-CT machine is accessible, your oncologist may consider whether a different imaging modality can answer the same clinical question. This is why calling ahead with your weight is important — these alternatives cannot be arranged on the day.

Bore diameter varies between scanner models. Standard modern machines accommodate most patients, but a larger body habitus can mean the bore is too narrow to complete the scan safely. Wide-bore scanners — available at larger centres — give meaningfully more clearance. When you call ahead, ask about bore size separately from the table weight limit. They are two different specifications and both matter.

In most cases, yes. Extended acquisition times and adjusted settings mean images remain diagnostically useful for larger patients. The radiologist notes any quality limitations in the report, and your oncologist interprets the result with that context. If image quality is a serious concern for your specific cancer and the area being imaged, your oncologist will raise it before the scan is booked.

The radiotracer dose is weight-based, but EANM and SNMMI guidelines set a ceiling above which it does not increase. Above that ceiling, giving more tracer adds radiation exposure without adding useful information. The team compensates for higher body mass by extending acquisition time, not by increasing the dose. Your nuclear medicine team calculates this before the injection — you do not need to request it separately.

No. PET-CT is contraindicated in pregnancy because it uses ionising radiation and an injected radiotracer, both of which carry risk to a developing foetus. If there is any possibility you are pregnant, tell your referring doctor and the imaging centre before the scan is booked, not on the day. If imaging is clinically essential during pregnancy, your oncologist will advise on the safest alternative for your situation.

Tell the team before your appointment, not on the day. Knowing in advance lets them talk you through what to expect and use positioning aids where these help. The technologist stays in voice contact throughout the scan. If anxiety is severe, speak to your referring doctor beforehand — there may be options worth discussing before you arrive.