Some people with suspected osteoporosis have been told they face an eight-month queue for a scan to investigate their condition at a clinic in Aberdeen.
A total of 550 patients have faced a delay of at least four-and-a-half months after one of two scanners broke down.
The Scottish Government has condemned the long delays as "unacceptable".
"We would expect NHS Grampian to explore all options to reduce exceptionally long waits for patients, including exploring the use of additional capacity from another board or the independent sector."
A spokeswoman for NHS Grampian said: "Regrettably some patients referred on a non-urgent basis will have had to wait up to eight months for a scan, as a result of damage to one of our two scanners. That scanner has been replaced and we are now working towards reducing average waiting times to the 12 to 14 week norm. Urgent referrals are seen within two to six weeks."