Nuclear Medicine Nuclear Medicine Imaging
Integrated Block Clinical Skill Sessions - Diagnostic Radiology Dr WY Ho, Cons(NM)
Medical specialty that uses unsealed radioactive substances
Nuclear Medicine
Therapy
Diagnostic
Laboratory
Imaging
Gamma Camera
Positron Emission Tomography
Nuclear Medicine Imaging
• Administration of radiopharmaceuticals
– intravenous – oral – inhalation – subcutaneous
Nuclear Medicine vs. X-ray
• Nuclear Medicine
– Physiology (Function) – Poor spatial resolution – Good temporal resolution – Low radiation dose
• X-ray
– Anatomy (Structure) – Good spatial resolution – Poor temporal resolution – Low to moderate radiation dose
• Distribution depends on physiological process • Image = reflection of physiological process
Radioactive Decay
Nuclear Decay Processes
• Alpha transitions • Isobaric transitions
– Beta emission – Positron emission – Electron capture
• Isomeric transitions
– Excited state transitions – Metastable state transitions – Internal conversion
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Ideal Physical Properties of Radioactive Substances
• • • • Readily available & cheap High specific activity Short half-life (few hours) For gamma camera imaging: Decay by isomeric transition with mono-energetic gamma emission of approx. 150 keV • For PET imaging: Decay by isobaric transition with positron emission
Radiopharmaceuticals
• Distribution depends on:
– Radionuclide (e.g. iodine) – Carrier molecule (e.g. DTPA, MDP)
Supply of Radiopharmaceuticals
• Technetium-99m radiopharmaceutcials
– (1) Elution of generator and preparation in laboratory inside hospital – (2) Unit dose (purchased on demand)
Generator and Unit Dose
• Other radiopharmaceuticals
– E.g. Thallium-201, Iodine-131 – Purchased on demand
• PET radiopharmaceuticals
– Medical cyclotron (inside or near the hospital)
Gamma Camera
Computer and Collimators
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Technegas Generator for Lung Ventilation Scan
Dose Calibrator & Fume Cupboard
Radiation Warning Signs
Radiation Protection Devices
Radiation Monitoring Device & Alarm
Musculoskeletal system
Indications Metastases Infection Trauma Avascular necrosis Ga-67 gallium citrate Infection Tc-99m / In-111 WBC Infection Radiopharmaceutical Tc-99m MDP
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Normal Bone Scan
Bone Scan
Multiple bony metastases
Solitary Bony Metastasis
Bone scan (left) & x-ray (right)
Osteosacroma
Increased uptake in primary tumour and lung metastases
Non-ossifying fibroma
Bone scan (left) & x-ray (right)
Bone Scan
Benign osteoporosis collapse
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Osteomyelitis
Bone scan : perfusion & blood pool (left); delayed (right)
Soft Tissue Infection
Bone scan : blood pool & delayed ; Gallium scan
Normal White Blood Cell Scan
Fracture & Osteomyelitis
Bone Scan
Fracture Neck of Left Femur
Pelvic Insufficiency Fracture
Bone scan (left) & x-ray (right)
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Cardiovascular system
Radiopharmaceutical Indications
Mechanisms of myocardial thallium uptake and redistribution
• Uptake
– Actively transported into tissue by sodium-potassium adenosine triphosphate system (Na-K ATPase) – 88% extraction in one pass through the coronary circulation
Tl-201 thallous chloride / Ischaemic heart Tc-99m MIBI / disease Tc-99m tetrofosmin Tc-99m red blood cell LV ejection fraction Wall motion
• Redistribution
– different in clearance of thallium – normally perfused zones clearing more rapidly than ischaemic areas
Indications of Myocardial Perfusion Scan
• Detection of coronary artery disease • Prognostication of the likelihood of a major ischaemic event • Post-therapy follow up study
Normal Myocardial Perfusion Scan
Thallium Scan
Antero-apical reversible ichaemia
Thallium Scan
Polar map display
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Thallium Scan
Myocardial Infarction
Renal Scan
Radiopharmaceuticals • Tc-99m DTPA Tc-99m MAG3 Indications
• • • • • • • • • • GFR / ERPF Differential function Obstruction Renal artery stenosis Transplant Acute pyelonephritis Scarring Horseshoe kidneys Ectopic kidney Space occupying lesion
• Tc-99m DMSA
Causes of Hydronephrosis
• • • • • • Vesico-ureteric reflux Urinary tract infection Previous obstruction Congenital malformation Non-compliant bladder Obstruction
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Diuretic Renogram
• T1/2 < 10 min No obstruction • T1/2 = 10 to 20 min Indeterminate • T1/2 > 20 min Significant obstruction
Renal DTPA Scan
Dilated non-obstructed pelvicalyceal systems
Renal DTPA Scan
Right renal artery stenosis
Renal DMSA Scan
Right upper pole scarring
Renal DMSA Scan
Horseshoe kidneys with hydronephrosis of left moiety
Metaiodobenzylguanide (MIBG)
Uptake mechanisms • Analogue of adrenergic blocking agent guanethidine • share same uptake and storage mechanisms as norepinephrine • not metabolized by monoamine oxidase or catechol-o-methyl transferase
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Metaiodobenzylguanide (MIBG)
Clinical uses • • • • • Phaeochromocytoma Neuroblastoma Carcinoid Medullary carcinoma of thyroid Other neuroectodermal tumours
MIBG Scan
Right phaeochromocytoma
MIBG Scan
Extra-adrenal phaeochromocytoma
Parathyroid Scan
• Radionuclides
– Tc-99m MIBI
• Indications
– Parathyroid adenoma – Parathyroid hyperplasia
Parathyroid MIBI Scan
Normal (left) & parathyroid adenoma (right)
15 min 3 hour 15 min 3 hour
Parathyroid MIBI Scan
Parathyroid hyperplasia
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Thyroid Scan
• Radionuclides
– Tc-99m – Iodine-131 – Iodine-123
Normal Tc-99m Thyroid Scan
• Indications
– Thyrotoxicosis – Thyroid nodule – Congenital hypothyroidism – Ectopic thyroid – Carcinoma of thyroid
Thyroid Scan
Graves’ disease (left) & Autonomous nodule (right)
Thyroid Scan
Subacute thyroiditis
Thyroid Scan
Cold nodule
Thyroid Scan
Thyroglossal cyst (left) & ectopic thyroid (right)
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Carcinoma of Thyroid
Bone scan (left) and iodine-131 scan (right)
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