Radioisotope scans

Radioisotope scans


RADIO- ISOTOPE SCANS

  • The gamma camera, also known as the scintillation or Anger camera is a device used in nuclear medicine.
  • The radionuclide emits faint gamma ray signals from inside the body (after administration into body) which are measured by Gamma Camera.
  • Tc-99 is the most common radionuclide used for imaging in nuclear medicine.

 Various Radio- isotope scans-

Bone Scintigraphy-

  • Tc- 99- MDP is the most commonly used for skeletal imaging.
  • Conditions in which increased uptake on bone scan or Hot spot is seen at new bone formation in as-
  1. Osteomyelitis
  2. Bone tumours, Fibrous dysplasia, osteoblastic metastasis
  3. Paget’s disease
  4. Endocrine- Hyperparathyroidism
  • Conditions in which there is no osteoblastic activity and have no radioisotope uptake or cold spot on bone scan are-
  1. Multiple myeloma
  2. Fibrous cortical defect
  3. Pseudarthrosis/ non union 

Cardiac radionuclide scanning-

a) Myocardial imaging

i) Infarct scanning-

  • TC- 99m pyrophosphate is used most commonly.
  • Infarct appears as Hot spot.

ii) Perfusion scanning

  • It is useful in diagnosis of CAD.
  • Used to identify areas of reversibility after MI.
  • Thallium 201is most commonly used for radionuclide for this purpose.

b) Nuclear angiography-

      1. First pass technique- used for study of intracardiac shunts. Technetium- 99 is used.

      2. Multigated equilibrium studies (MUGA/ radionuclide cardiac ventriculography).

  • Tc- 99 – albumin is used most commonly.

iii) Renal radionuclide imaging-

a) Dynamic renal scintigraphy-

  • Also called as functional imaging as it assesses impaired renal function.
  • Radionuclides used are-
  1. Tc- 99- DTPA → GFR estimation
  2. Tc- 99- MAG- 3 (Best for dynamic renal scintigraphy) → effective renal plasma flow

b) Static renal scintigraphy-

  • Used for renal cortical mass & to locate functional renal mass.
  • Tc- 99- DMSA is used for static scintigraphy.

Thyroid scintigraphy-

  • Radiopharmaceuticals used in thyroid scanning are- 123I, 131I, technetium- 99m pertechnate (as Tc 04).
  • I123 – 100- 300 μ curie dose
  • I131 – 50- 100 μ curie dose

Parathyroid scintigraphy-

  • Tc- 99 sestamibi (methoxyisobutylisonitrile, MIBI) is the scanning procedure of choice of parathyroid.
  • Very sensitive to detect parathyroid adenoma and ectopic parathyroid.
  • Tc- Thallium substraction scan was used.
 

Exam Important

  • The radionuclide emits faint gamma ray signals from inside the body (after administration into body) which are measured by Gamma Camera.
  • Tc-99 is the most common radionuclide used for imaging in nuclear medicine.

Various Radio- isotope scans-

Bone Scintigraphy-

  • Tc- 99- MDP is the most commonly used for skeletal imaging.
  • Conditions in which increased uptake on bone scan or Hot spot is seen at new bone formation in as-
  1. Osteomyelitis
  2. Bone tumours, Fibrous dysplasia, osteoblastic metastasis
  3. Paget’s disease
  4. Endocrine- Hyperparathyroidism
  • Conditions in which there is no osteoblastic activity and have no radioisotope uptake or cold spot on bone scan are-
  1. Multiple myeloma
  2. Fibrous cortical defect
  3. Pseudarthrosis/ non union

Cardiac radionuclide scanning-

a) Myocardial imaging

i) Infarct scanning-

  • TC- 99m pyrophosphate is used most commonly.
  • Infarct appears as Hot spot.

ii) Perfusion scanning

  • It is useful in diagnosis of CAD.
  • Used to identify areas of reversibility after MI.
  • Thallium 201is most commonly used for radionuclide for this purpose.

b) Nuclear angiography-

      1. First pass technique- used for study of intracardiac shunts. Technetium- 99 is used.

      2. Multigated equilibrium studies (MUGA/ radionuclide cardiac ventriculography).

  • Tc- 99 – albumin is used most commonly.

iii) Renal radionuclide imaging-

     a) Dynamic renal scintigraphy-

  • Also called as functional imaging as it assesses impaired renal function.
  • Radionuclides used are-
  1. Tc- 99- DTPA -à GFR estimation
  2. Tc- 99- MAG- 3 (Best for dynamic renal scintigraphy)

b) Static renal scintigraphy-

  • Used for renal cortical mass & to locate functional renal mass.
  • Tc- 99- DMSA is used for static scintigraphy.

Thyroid scintigraphy-

  • Radiopharmaceuticals used in thyroid scanning are- 123I, 131I, technetium- 99m pertechnate (as Tc 04).
  • I123 – 100- 300 μ curie dose
  • I131 – 50- 100 μ curie dose

Parathyroid scintigraphy-

  • Tc- 99 sestamibi (methoxyisobutylisonitrile, MIBI) is the scanning procedure of choice of parathyroid.
  • Very sensitive to detect parathyroid adenoma and ectopic parathyroid.
  • Tc- Thallium substraction scan was used.
 

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