Current Australian diagnostic reference levels for nuclear medicine

Please be aware that DRLs are not recommended doses. They are only a reflection of current practice within Australia. The DRLs should not be used as the basis of calculating paediatric doses or as a starting point for facilities conducting a scan for the first time. Most importantly, if your facility uses a dose lower than the DRL, you should not increase the dose you use to match the DRL.

If the activity your facility routinely administers is higher than the DRL then you should review your protocols. When doing so, ensure that any reduction in dose does not degrade the image quality to the point where diagnosis is compromised. Maintaining diagnostic quality is of paramount importance, even if doing so requires a dose higher than the DRL (which might occur if your facility uses older hardware or regularly images patients with clinical indications that are underrepresented within the NDRLS data).

The nuclear medicine statistics page provides tables of the interquartile ranges for all protocols and the most commonly prescribed activity for nuclear medicine and PET administrations. These tables can help provide context of how your doses compare to the Australian imaging community. Similar statistics and supporting figures can be accessed by clicking the hyperlinks in the tables below.

General nuclear medicine

The DRLs for general nuclear medicine procedures are listed below. A DRL comparison can be conducted by comparing prescribed activities or by comparing the median activity administered to a representative sample of patients to the DRLs. If the former approach is adopted, as part of regular QC procedures, facilities should still audit the activities delivered to patients to ensure that administered activities are close to prescribed activities.

*Unless otherwise specified, all pharmaceuticals are labelled with ^99mTc.
† Quoted DRL is for the total dose delivered, not per injection. The most common approach reported was 4 x 10 MBq injections for same day surgery.

NMCT

The DRLs below are for CT scans conducted for the purposes of attenuation correction or localisation in conjunction with a SPECT scan. DRL comparisons should be conducted by determining the median dose delivered to a representative sample of patients. This should be done separately for each scanner for all regularly conducted scans.

* Excludes scans of the extremities.
CTDI_vol – volume computed tomography dose index
DLP – dose length product

PET

The DRLs for PET are listed below.  The DRLs are expressed as both a fixed activity and in terms of MBq/kg (except for brain FDG scans). The variable DRLs are only intended to apply to patients weighing between 50 and 120 kg. There are additional statistics relating to whole body FDG scan on the nuclear medicine statistics webpage relating to time activity products and breakdowns the submitted data in terms of facility type, detector type and (a small number of) scanner models.

Facilities should compare their prescribed or administered activities against the variable or fixed DRL depending on their own protocol. If comparing administered activities against a variable DRL, a facility should take a sample of patients and determine the proportion that were given an activity below the variable DRL. If half or more patients are below the DRL then the facility can consider its administered activities to be below the DRL.

* Variable DRLs only applicable for patients weighing between 50 and 120 kg.
† Includes oncology, infection, inflammation and vasculitis scans

PETCT

The DRLs below are for CT scans conducted for the purposes of attenuation correction or localisation in conjunction with a PET scan. DRL comparisons should be conducted by determining the median dose delivered to a representative sample of patients. This should be done separately for each scanner for all regularly conducted scans.

CTDI_vol – volume computed tomography dose index
DLP – dose length product

Further information on International Best Practice for Radiation Protection of Patients can be found on the International Atomic Energy Agency Radiation Protection of Patients website, which can be accessed via the following link:

IAEA Radiation Protection of Patients (RPOP)