Previously, 10+ years ago, there was no need for parathyroid localization because in the hands of the experienced parathyroid surgeons bilateral neck exploration for curing primary hyperparathyroidism achieved cure in 95% of patients.

The cause of primary hyperparathyroidism in in 85-90% of patients due to single adenoma (enlarged gland).  Due to this and to minimize the possible complications of parathyroid surgery, investigations have developed in attempt to find this usually one enlarged gland.

Ultrasound 

It is one of the first developed investigations.  It is fast, non-invasive and non-irradiating and relatively inexpensive.  However, ultrasound is dependent on the operator experience and the size and location of enlarged parathyroid.  It localizes parathyroid gland in up to 80% of patients.  Ultrasound guided fine needle aspiration (FNA) is extremely rarely used for investigating parathyroid conditions and/or to confirm the location.

CT scan 

It has been used more and more in localizing enlarged parathyroid glands.  Contrast CT scan with different washout phases (how quickly the contrast leaves tissue) has been particularly useful.  It can confirm the presence of adenoma in up to 80-90% of patients and is excellent in showing exact location of the parathyroid gland, especially for those ones who are in unusual locations (chest, or very high in the neck).  CT scan is relatively fast and not operator dependent.  It is however more expensive then ultrasound, has significant radiation dose and requires experienced radiologist.

Nuclear medicine scans (parathyroid sestamibi or SPECT) 

These use radioactive substance in the diagnosis.  Sestamibi uses technetium-99m isotope while SPECT is single-photon emission CT.  Sestamibi scan takes long time as requires scanning at multiple intervals following injection (usually at 10-15min) and then 2-3 hours later.  It is also very expensive and operator dependent.  SPECT is also long, expensive and operator dependent.

In Wellington region, I have not had a great experience with parathyroid sestamibi or SPECT, as it has localized adenomas less then 50% of patients and it costs around $2,500.00 (double then regular parathyroid CT scan which is more sensitive in Wellington region).  Due to this I preferentially use CT scan in Wellington. 

MRI scan 

It has been used previously for localization of enlarged parathyroid glands, but in the last 10 years it has not been used widely at all.  These days it may be used in re-operative surgery, but in most places has been surpassed by multiple contrast phase CT scan.