Introduction to Nuclear Medicine

General concept
Advantages and disadvantages
Common studies
Cases describing various different imaging modalities - offering some things to take with you to look good on your interviews

3 Main differences

Take home point

Radio-pharmaceutical
Patient
Gamma Camera
Images

Common radionucleotides

 Tc-99m **
 I-131
 Tl-201
 Ga-67
 In-111

What you're looking for

 Available
 Low cost
 Pure gamma emitter
 Optimal gamma energy (100-200 keV) *140
 Optimal physical half life *6 hr
 Safe
 Chemically active
 Various radiopharmaceuticals

Skeletal system eg. Bone scan

Endocrinology: Thyroid scan, Parathyroid scan

Cardiovascular system: Myocardial perfusion scan, Radionuclide venography

Genitourinary system: Renogram, Testicular scan, Radionuclide cystography

Pulmonary system: Perfusion/ Ventilation lung scan

Gastrointestinal system: Liver scan, Hepatobiliary scan, GE reflux study

Tumor imaging: Ga-67 scan for Lymphoma, I-131 scan for pheochromocytoma, Tc-99m MIBI for parathyroid adenoma

SCOPE OF STUDIES

 Functional

 Sensitive

 Quantitative

 Very safe

 Minimally invasive

 Low radiation exposure

 Screening

 Follow-up

Advantages

 Not widely available

 Radiation (less than you'd expect)

 Generally non-specific

 Require NM instrument & radiopharmaceuticals

 Higher cost than routine X-ray or U/S

Disadvantages

Bone scan

Principles, Indications, and Examples

Principles and indications

 Detection, staging and follow-up of bone metastasis

 Differentiating between osteomyelitis and cellulitis

 Determination of bone viability

 Evaluation of difficult fracture (stress fracture, fracture in battered child)

 Evaluation of prosthetic joint problems (loosening, infected prosthesis)

 Evaluation of bone pain in patient with normal plain radiograph (unexplained bone pain) Radiotracer: 99mTc-MDP (methylene diphosphonate)

Pathophysiology

Chemisorption to the hydroxyapatite crystal

Increased uptake

Increased blood flow

Increased osteoid formation

Increased mineralization of osteoid

Interrupted sympathetic nerve supply

GI Bleeding Scintigraphy (Red blood cell scan)

Principles, Indication, and Examples

Indications : To detect and localize lower GI bleeding (sensitivity 93% & specificity 95%, Laing CJ 2007)
Radiotracer : Tc-99m labelled RBC
Interpretation : Positive = extravasation of the radiotracer into bowel lumen
Criteria for diagnosis of GI bleeding - Focal activity appears & conforms to bowel anatomy - Activity increases overtime - Activity movement along the bowel loop - Movement may be anterograde or retrograde