Oral Exam - Miscellaneous

Question 1

Dacroscintigraphy protocol

Answer 1

○ Radiopharmaceutical
– Tc-99m pertechnetate: 0.1 mCi/mL normal saline

□ 1-2 drops per eye
– Examine less symptomatic eye first
– Capture radioactive tears with tissue paper to
decrease contamination of skin over lacrimal complex

Question 2

Nasolacriminal obstruction findings

Answer 2

○ Normal
– Symmetrical passage of radiotracer through lacrimal sac, lacrimal duct, valve of Hasner, into nasal cavity

○ Abnormal
– Passage of radiotracer distal to pooling=partial
obstruction

– No passage of radiotracer distal to pooling=complete
obstruction

Question 3

Salivary gland scintigraphy

Answer 3

Demonstrates function of parotid and submandibular
glands, including blood flow and excretion

• Normal scan
○ Radiotracer uptake should occur within 1 min of injection, peak activity within 10-21 min
○ After administration of lemon juice, radiotracer excretion should occur immediately, with radiotracer evident in oral cavity

Question 4

SG protocol

Answer 4

○ Patient preparation
– No thyroid-blocking agents prior to scan

– 15mCi Tc-99m pertechnetate

Question 5

DDx salivary gland obstruction

Answer 5

Acute Sialadenitis - increased blood flow with marked uptake and retention of radiotracer

Chronic Sialadenitis - Low grade, chronic salivary gland infection

Sjögren Syndrome
• Decreased uptake and excretion of radiotracer
• Most commonly affects all salivary glands

Warthin Tumor
• Takes up Tc-99m pertechnetate and retains it after lemon juice administration
• Many salivary gland masses take up Tc-99m pertechnetate nonspecifically

Question 6

Obstruction findings

Answer 6

Obstruction
• Prior to lemon juice: Uptake may be increased (acute inflammation), normal, or decreased (functional deterioration due to obstruction)
• After lemon juice: Poor or absent radiotracer excretion; dilated ducts may be seen

Question 7

Increased blood pool on WBC imaging

Answer 7

Some non-specific labelling of RBCs and platelets

Can also have free pertechnetate if see SG, thyroid, and gastric uptake

In111-oxine binds to all leukocytes

Tc99-HMPAO binds only to neutrophils - not usually used for intra-abdominal disease unless imaged < 2 hrs and get normal urinary and GI clearance

Question 8

PMT defect

Answer 8

Rounded area of decreased or increased intensity on uniformity image

Question 9

False positives on Ga67 and In111WBC studies

Answer 9

Ostomy sites
Drains
Surgical scars
Open wounds