Nuclear medicine

Radioactive substances are used for examining the treating diseases.

Some radioactive materials, such as technetium-99m and iodine-123, are used for diagnostic purposes. The radioactive medicinal substance used for diagnostic purposes is injected into the bloodstream, administered orally or the patient inhales it as an aerosol. The radioactive agent attaches itself specifically to the organ being examined. The accumulation of radioactivity in the organ and body can be monitored with a gamma camera. This provides information on the organ being examined. These examinations are known as isotopic studies.

Approximately 50,000 isotopic studies are performed annually in Finland, most of them on the skeletal system. The lungs, kidneys, vascular system cardiovascular system and thyroid gland can also be examined, among others. One isotopic study results in an average exposure of 4.2 mSv to the patient. All isotopic studies result in an average dose of approximately 0.04 mSv per Finn.

Radioactive iodine-131 is used for treating hyperthyroidism and thyroid cancer. Radioiodine attaches itself specifically to the thyroid gland and destroys hyperactive thyroid gland tissue or tumour. The radiation doses caused to patients from these isotopic treatments are considerably higher than the doses from isotopic studies.

Radiation doses of comparison levels of isotopic studies

Isotopic study

Radionuclide

Compound or chemical form

Comparison level (MBq)

Effective dose (mSv)

Skeletal system and soft tissue

Gamma imaging of the skeletal system

99mTc

Phosphates or phosphonates

670

3.8

Gamma imaging of infection site

99mTc

Leukocytes (HMPAO)

300

3.3

Respiratory system

Gamma imaging of pulmonary perfusion

99mTc

MAA

150

1.7

Urogenital system

Gamma imaging of renal function

99mTc

MAG3

100

0.7

Cardiovascular system

Myocardial perfusion SPECT

201Tl

Ion

100

22

Myocardial perfusion SPECT

99mTc

MIBI (rest + stress)

1000 1)

8.5

 

 

 

1200 2)

10.1

Myocardial perfusion SPECT

99mTc

Tetrofosmin (rest + stress)

1000 1)

7.3

 

 

 

1200 2)

8.8

Gamma imaging of cardiac pump function (at equilibrium)

99mTc

Erythrocytes

750

5.3

Nervous system

Dopamine transporter SPECT imaging

123I

β-CIT

180

9.0

 

123I

FP-CIT

180

4.2

Endocrinologic isotope studies

Gamma imaging of thyroid metastases (after ablation)

131I

Iodide

185

11.3

Gamma imaging of parathyroid gland

99mTc

MIBI

740

6.7

PET studies

 

 

 

 

Imaging of tumours

18F

FDG

2803)

5.3

Imaging of tumours

18F

FDG

3704)

7.0

1) Total activity administered to the patient when the stress and rest phases are performed within 24 hours of each other.
2) Total activity administered to the patient when the stress and rest phases are performed on different days.
3) 3D imaging and time-of-flight technology in use
4) 2D imaging in use

 

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