Imaging and Dose (mSv)
Table 1.
SPECT
[i]
Low-Res CT
[ii]
High-Res CT
[iii]
Plain Film
[iv]
Pulmonary Nodes Tc-99m Depreotide 6 Chest 1 Chest 5.8 Chest 0.02
Lumber Spine Tc-99m phosphonate 5 Abdo + pelvis 1.5 Abdo + 7.1 Lumber 1.3
Metastases pelvis Spine
Myocardial Imaging Tc-99m sestamibi 4 Chest 1 Chest 5.8 Chest 0.02
[i] Notes for Guidance on the Clinical Administration of Radiopharmaceuticals and Use of Sealed Radioactive Sources Health Protection Agency,
Administration of Radioactive Substances Advisory Committee, March 2006 (Revised 20 April 2006).
[ii] Effective doses to patients from CT acquisitions on the GE Infinia Hawkeye: a comparison of calculation methods. Sawyer, L et al. Nuclear
Medicine Communications. 29(2):144-149, February 2008.
[iii] Doses from computed tomography (CT) examinations in the UK – 2003 review Shrimpton PC et al. NRPB-W67 March 2005.
[iv] RADIATION PROTECTION 118 Referral guidelines for imaging, European Commission 1999.
under both medicines and ionising radiation legislation and the former mandates that replacing first generation SPECT systems with SPECT-CT units, which generally
only a registered dental or medical practitioner may direct the clinical service and, as require a larger physical space. The space required for a SPECT-CT system will
such, provide the clinical justification required under IR(ME)R. For nuclear medicine depend on the type of unit being installed and the nature of the examinations
examinations, with regard to IR(ME)R, only the ARSAC licence holder may justify conducted. The quoted minimum room size for a GE Hawkeye/Hawkeye-
clinical examinations. Radiographers working within nuclear medicine and with specific 4 is 14 feet x 16 feet and the amount of lead shielding required for this
reference to radiopharmaceuticals may only act as operators. environment may be less than a dedicated CT unit. Some departments utilise
mobile lead shielding devices for the GE Hawkeye devices which permits some
Within nuclear medicine departments, legislative arrangements permit radiographers flexibility with the organisation of the imaging environment. The exposure rate
to act as practitioners and referrers for x-ray examinations and acting as referrer from low performance CT units is approximately 20 times less than that from a
for plain x-ray examinations, in association with nuclear medicine procedures, has multislice CT unit
24
and the use of mobile shields are common in departments
become common practice. Using the same legislative arrangements, radiographers with these units.
can, indeed should, act as referrer and practitioner for the CT component of SPECT-CT.
There is logic for both as SPECT-CT has limited routine applications. For many patients, A larger physical room environment (minimum 15 feet x 24 feet) is required for
the decision to make a CT exposure (low or high resolution) will depend on factors SPECT-CT systems employing a dedicated multislice CT unit, and thicker protective
such as the clinical background, physical make up and the nuclear medicine images shielding is required for the use of multislice SPECT/CT units. The weight bearing
themselves. Hence, the decision to refer for CT may only be made at the point of parameters of the floor should also be considered
24
, especially if the unit is not
care within the nuclear medicine department. Therefore, the radiographer is ideally being installed on the ground level within a hospital. Separate operator console
placed to fulfil the role of referrer. In full knowledge of the evidence base and the environments are also becoming common within SPECT-CT rooms, although this
clinical background, a radiographer can act as practitioner, thereby protecting the does remove an element of patient interaction normally associated with nuclear
patient from unnecessary x-radiation exposure. On discussion with several nuclear medicine.
medicine departments, it was found that radiographers have already adopted
formally the roles of referrer, practitioner and operator for the CT component of the Currently the cost of the high end CT components (eg 64 slice) may exceed the
SPECT-CT studies. cost of the SPECT device and the justification for such units will depend upon
the clinical workload of a nuclear medicine department. With current shifts in
Business, practical and educational considerations imaging tools for certain conditions (eg pulmonary embolism), a SPECT-CT unit with
when purchasing a SPECT-CT system
multislice capabilities may be positioned to undertake contrast enhanced CT scans,
A department should consider the physical footprint required for a hybrid such as pulmonary angiography and the assessment of coronary calcification
10,25
SPECT-CT system. This is especially true if the existing gamma camera has a and, potentially, providing a ’one stop‘ approach for patients undergoing their
small footprint. Some clinical departments within the United Kingdom are diagnostic CT and physiological scans, if required.
2009
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