Nuclear Medicine provides functional information which is often complementary to the anatomical information provided by radiology, Ultrasound and MRI.

CENTRAL NERVOUS SYSTEM

1. Cerebral perfusion scan:  ^99mTc HMPAO ("Ceretec") brain SPECT

Indications:

• Alzheimer’s disease

• To detect hypoperfusion before atrophy or "leuko-araiosis" becomes apparent on CT/MRI

• The classical finding is bilateral hypoperfusion of the temporal and parietal lobes with or without involvement of frontal lobes, with relative sparing of the primary somatosensory cortices, basal ganglia, thalamus, and cerebellum

• At least three studies are being conducted in which prospective brain SPECT is being evaluated against final histopathologic diagnosis. The total number in these series now approaches 150 and preliminary results indicate sensitivity of approximately 90% and specificity of 85-90%

• PET allows better resolution and quantitation of regional cerebral blood flow, while SPECT offers decreased costs and wider availability.

• Differential diagnosis of other forms of dementia: Multi-infarct/vascular dementia (MID), frontal lobe dementia, Pick’s disease, AIDS dementia, dementia associated with Parkinson’s disease and "pseudodementia" associated with depression.

• Functionally significant cerebrovascular disease

• Acetazolamide ("Diamox"): cerebral stress test:

• "Stress test" of brain to establish cerebrovascular perfusion reserve
• A carbonic anhydrase inhibitor and cerebrovascular vasodilator, Diamox increases cerebral blood flow by a factor of 4, but not in the region supplied by significantly stenotic vessels

• Non -stress test

• Determines the vascular territory and extent of cerebrovascular events.
• May be prognostic following cerebrovascular event

• Detection of epileptogenic foci

2. Others

• Ventricular shunt patency study
• Cisternography: study of CSF dynamics
• Brain death
• Blood-brain barrier scintigraphy

CARDIOVASCULAR SYSTEM

1. Stress Myocardial perfusion imaging

Preparing for the test:

Preparation for the tests will depend upon a number of factors, including age, fitness level and pre-existing medical problems

Patient may be asked:

• To fast for 4 hours before the test as stomach and biliary activity may interfere with interpretation of images. No tea, coffee or cola for 24 hours prior to the scan because they contain caffeine and will antagonise the efffects of Persantin (dipyridimole)

• Routine medications such as Beta blockers, ACE inhibitors, calcium channel blockers may interfere with or reduce the efficacy of the test. Patients must check with their private physician to find whether he or she could stop taking these medication(s). It is generally advised to stop beta or calcium channel blockers for 24-48 hours prior to exercise stress test, but this is not mandatory.

• It is important that the patient should dress comfortably. It is advisable to wear shorts or running shoes for the exercise component of the test. During the imaging session of the exam, the patient may need to wear a hospital gown.

Choice of test

• Technetium sestamibi (or tetrofosmin) is usually preferred over thallium, because of better imaging characteristics. Thallium is preferred if myocardial viability is the main issue

• Gated SPECT is routinely performed as part of the test: Accurate estimation of LVEF, LV volume and Wall motion.

Indications

A. Diagnosis of coronary artery disease (CAD) in patients presenting with chest pain

• Sensitivity: 85-95%, Specificity: 70-90%
• Localise ischaemia in the supply regions of the 3 main coronary arteries

B. Risk stratification in known or suspected CAD

• Normal scan: < 0.5% AMI per year
• Reversible Perfusion defects:
  • 2.6 to 4.3% AMI per year, 0.7 to 4.6% cardiac mortality per year
  • Risks proportional to severity of defects

C. Evaluation of therapeutic interventions: PTCA/stent, anti-angina drugs

D. Peri-operative cardiac risk assessment

E. Assessment of myocardial viability

• Similar accuracy with both exercise or pharmacological stress

• Pharmacological stress technique (Persantin)
• Infusion over 4 minutes
• Increases intravascular adenosine level
  • Vasodilation of normal vessels only: "coronary steal"
• Side effects (20%): headache, nausea, dizziness, chest pain.
  • Rapidly reversed by IV aminophylline
• Cardiac events: 0.1%
• Contraindications: bronchospasm, coffee/tea within 24 hours
• Alternative: dobutamine

• Exercise stress technique

• Preferred method: haemodynamic data
• Bruce or Naughton: 100% predicted heart rate = 220 – age
• No Beta or calcium blockers for 24-48 hours, but not mandatory
• Contraindications:
  • Unstable Angina, decompensated CCF, non-diagnostic baseline ECG (eg: LBBB), BP> 220/120

Other tests include

• Gated Heart pool scan: For ventricular function, size and wall motion and ejection fraction.

• Qp/Qs 1^st pass for left to right shunt

• FDG PET: gold standard for myocardial viability

• Myocardial "hotspot" imaging: For diagnosis of myocardial infarct in confounding clinical setting

• Imaging of thrombi or atheroma: Research

GASTRO-INTESTINAL SYSTEM

To diagnose biliary tract, gastrointestinal motility,and inflammatory bowel disorders.

1. HIDA Scan

Patient preparation:Fast for 6 hrs prior to the test

• Iminodiacetic acid (IDA) follows the pathway of bile excretion

Indications

• Acute cholecystitis
• Biliary dyskinesia:
  • CCK infusion over 20 minutes: gall bladder ejection fraction < 35 %
  • Sensitivity: 90-100%, Specificity: 80-100%
• Post surgical biliary leak

2. Gastric emptying

Patient preparation: Fast from midnight prior to the test

• Solid phase only or combined with liquid phase
• Gastroparesis: eg. diabetes

3. Gastro-oesophageal reflux +/- pulmonary aspiration

Patient preparation: Fast from midnight prior to the test

4. Colon transit time

Patient preparation:

• Fast for  6 hrs prior to test.
• No laxatives 48 hrs prior to the test
• No laxatives for duration of scan (ie. all week)

Indication

Obstructive vs. slow-transit constipation

5. Liver/spleen technetium sulphur colloid scan

Patient preparation: Nil

Indications

• Hypersplenism or splenic residue
• Portal hypertension
• Splenic infarcts
• Focal nodular hyperplasia

6. Red Blood Cell liver scan

Patient preparation: Nil

Indications

• Hepatic cavernous haemangiomas: 80-90% sensitivity for lesions > 1.5 cm

7. RBC scan for acute GIT bleeding

Patient preparation: Nil

8. Meckel’s Diverticulum (ectopic gastric mucosa)  Scan

Patient preparation: Nil

PULMONARY SYSTEM

1. V/Q scan

Patient preparation: Nil

• Pulmonary embolism

PIOPED criteria (Prospective Investigation of Pulmonary Embolism Diagnosis), 1990

• 1478 V/Q scans and 1089 angiograms
• >95% accuracy if
  • Normal
  • High probability with risk factors
  • Low probability without risk factors

2. Aerosol DTPA lung clearance study

Patient Preparation: No smoking for at least 1 week, preferably for four weeks.

• Increased alveolar-capillary membrane clearance: Active interstitial lung disease, Pneumocystis Carinii lung disease, Bleomycin lung disease.

3. MAA (Macroaggregated albumin) lung perfusion scan

• To diagnose right-to-left shunting.

SKELETAL SYSTEM

Bone imaging is one of the most commonly performed nuclear medicine tests.

Patient preparation: For most bone imaging studies, patient will be asked to drink as much fluids as possible, both before and after the procedure.

• Eating before the procedure will not interfere with the quality of the images and the patient can continue with their regular activities.

Technique

• Use technetium phosphonate analogues
• 3 phase imaging
  • Dynamic phase

• Follows the bolus injection of tracer
• Assesses vascularity

• Blood pool Phase
  • The first 5-10 minutes after bolus injection of tracer
  • Assesses the intravascular phase

• Delayed Phase
  • > 3 hours post injection
  • assess osteoblasic activity

Indications

• Trauma
  • Stress Fractures: Gold standard
  • Radiographically inapparent fractures
  • Soft tissue injury
  • Enthesopathy: insertion sites of tendons and ligaments.

• Osteomyelitis
  • Sensitivity: 90%
  • Abnormalities in all 3 phases of bone scan
• Early diagnosis: within 24-48 hours
• Joint prosthesis: Loosening vs. infection

White cell scan

• Improve specificity: eg. Charcot’s joint, orthopaedic prosthesis
• Monitor response to antibiotics

Gallium Scan

• Vertebral osteomyelitis

• Neoplastic disease

• Metastatic bone disease
• Primary bone neoplasm
• Myeloma: abnormal uptake in 50% of cases

• Evaluation of lower back pain

• Metastatic bone disease
• Degenerative disease: Facet joint arthritis, osteophytes
• Fractures: Crush or pars fractures
• Previous spine surgery: eg. pseudoarthrosis at spinal fusion site
• Others: Paget’s disease, osteoma

• Metabolic bone disease

• Renal osteodystrophy
• Paget’s disease
  • Useful in unexplained bone pain and raised ALP
  • Monitor response to therapy
  • Detect fractures or sarcoma

• Avascular necrosis

• Reflex sympathetic dystrophy
  • Exaggerated sympathetic stimulation to an injury in the extremity
  • Diffuse bone pain
  • Bone scan

• Characteristic findings
• Sensitivity: 54-100%,
• Specificity: 85-95%

• Arthropathies

• Rheumatoid arthritis vs. osteoarthritis
• Seronegative inflammatory arthropathy

RENAL SYSTEM

1. DTPA Renal Scan

• Diagnosis of renovascular hypertension
  • Predicts improvement of BP after revascularisation
• Scans with and without captopril or other ACE inhibitors

• 50 mg captopril and oral hydration, then scan 1 hour later
• Captopril decreases GFR and delays DTPA wash out from renal cortex
• Positive study if > 10% deterioration with captopril

• Sensitivity: 80-90%
• Specificity: 70-90%
• Contraindications: Significant renal tract obstruction or renal impairment (Cr >200)

2. DMSA Renal Scan: renal cortical scintigraphy

• Diagnosis of acute pyelonephritis
  • Sensitivity: 90%
  • Specificity: 80-90%
  • Influences decision on prophylactic antibiotics

• Diagnosis of renal scarring
  • Wait for 3 to 6 months after UTI

3. MAG-3 Renal Scan with Lasix: diuresis scintigraphy

• Assess renal tract obstruction: Site (PUJ vs. VUJ), Degree. Differential renal function

4. Radionuclide Cystogram

• Assess vesicoureteric reflux

5. GFR estimation using DTPA

• Serial blood samplings at 1.5 and 2.5 hours

6. Scrotal Scintigraphy

• Testicular torsion

7. Evaluation of renal transplantation

ONCOLOGY / TUMOUR IMAGING

1. Gallium Scan

• Lymphoma
• A variety of solid tumours may also take up gallium
• Lung, hepatoma, oesophagus, melanoma,testicular

2. Thallium

• Low grade Non-Hodgkin’s lymphoma
• Brain tumour: glioma

3. FDG-PET (Positron Emission Tomography)

• Liverpool Hospital is the first hospital in Australia to install a new type of PET camera using a modified conventional dual-head gamma camera (Co-PET) in 1997. We have since performed over 500 studies under several prospective trials

• In United States, both dedicated PET and Co-PET have received medicare reimbursements for staging of a variety of cancer: Pulmonary nodules, lung, colorectal, lymphoma and melanoma

• It is also useful in a variety of other cancer: Brain, Head and Neck, breast, pancreas, oesophagus, testicular, musculoskeletal, ovarian, thyroid

• It may impact on management by:
  • Improve staging by detecting occult foci
  • Monitor response to therapy
  • Early detection of recurrence
  • Differentiation from radiation fibrosis

4. Sestamibi

• Well differentiated thyroid cancer
• Breast: equivocal mammogram or ultrasound findings

5. Neuroendocrine tumour

• Octreotide: best for carcinoid
• I-131 or I-123 MIBG: eg. phaeochromocytoma, neuroblastoma

6. Total body I-131 search

• Post-operative ablation and staging of well differentiated thyroid cancer

7. Sentinel lymphoscintigraphy

• Breast, melanoma, vulva

ENDOCRINE

1. Thyroid Scan

• Investigation of the causes of hyperthyroidism
  • Graves’ diseas
  • Thyroiditis
  • Toxic solitary adenoma
  • Toxic multi-nodular goitre

• Thyroid nodules
  • "Cold" nodule:
    • Solitary nodule: 5 to 10 % malignant
    • Dominant nodule in MNG: 4 % malignant
  • "Hot" nodule:
    • Autonomous functioning thyroid adenoma

2. Parathyroid study

• Investigation of hyperparathyroidisms: Localisation of functioning parathyroid adenoma
• We have developed a technique comprising Sestamibi parathyroid washout images, technetium thyroid scan and thyroid ultrasound
• Sensitivity: 80-90%

[Click here to see a parathyroid image]