Rare Applications
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Solve questions (22) →Contents
- 25.1 Dacryoscintigraphy (Lacrimal Drainage)
- 25.2 Salivagraphy (Assessment of Salivary Ducts)
- 25.3 Assessment of LeVeen Shunt
- 25.4 Testicular Scintigraphy
- 25.5 Other Rare Applications
- 25.5.1 Search for Ectopic Gastric Mucosa (Barrett Oesophagus)
- 25.5.2 Assessment of Peritoneal Shunt (VP Shunt)
- 25.5.3 Red Cell and Platelet Kinetic Studies
- 25.5.4 Schilling Test (Historical)
- 25.5.5 Blood Volume Measurement
- 25.5.6 Gastric Mucosa Protection Study (Meckel Scan Variants)
- 25.5.7 Oesophageal Transit and Gastric Reflux (Rare Variants)
- 25.5.8 Brain Shunt Assessment (CSF Flow Studies)
- Key Points for the Board
Learning objectives and modules2 modules · about 1 h 45 min
Learning objectives
After this chapter you will be able to:
- Explain the technique of dacryoscintigraphy and its findings in disorders of lacrimal drainage.
- Interpret uptake and excretion curves in salivary gland scintigraphy.
- Assess the patency of LeVeen and VP shunts.
- Distinguish the patterns of torsion and epididymitis on testicular scintigraphy.
- State the principle and indications of other rarely used studies.
Modules
The chapter is divided into study modules without changing the order of the text: read, watch the animations, then answer the questions linked to those headings.
- Module 125.1–25.3 Dacryoscintigraphy (Lacrimal Drainage) · Salivagraphy (Assessment of Salivary Ducts) · Assessment of LeVeen Shunt55 min · 3 animations · 21 questionsAnswer the questions →
- Module 225.4–25.5 Testicular Scintigraphy · Other Rare Applications · Key Points for the Board50 min · 25 questionsAnswer the questions →
Times are estimates: 130 words per minute, 3 min per animation, 1.5 min per question.
MOST FREQUENTLY ASKED IN THIS CHAPTER
✓
Radiopharmaceutical: Tc-99m pertechnetate/DTPA → drop into the lower conjunctival sac
✓
Non-invasive, physiological assessment (contrast dacryocystography is invasive and anatomical)
✓
Normal drainage: lacrimal sac (2-5 min) → nasolacrimal duct (5-10 min) → nasal cavity (10-15 min) → nasopharynx (15-20 min)
✓
Superior to contrast methods for detecting functional epiphora
✓
Complete obstruction: accumulation proximal to the obstruction, no passage distally
✓
Tc-99m pertechnetate IV → NIS-mediated uptake
✓
Acid stimulation (20 min) → normal: rapid washout
25.1 Dacryoscintigraphy (Lacrimal Drainage)7 questions
Anatomy and Physiology
Lacrimal Drainage System:
•
Tears → punctum (upper and lower) → canaliculus (upper and lower) → common canaliculus → lacrimal sac → nasolacrimal duct → inferior meatus (nasal cavity)
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Tear drainage is driven by both gravity and the blink reflex (lacrimal pump mechanism)
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The lacrimal sac lies behind the medial canthal ligament
Clinical Indications:
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Epiphora (excessive tearing) → obstructive vs functional
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Determining the level of obstruction of the lacrimal drainage system
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Assessment of patency after surgery (dacryocystorhinostomy – DCR)
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Congenital nasolacrimal duct obstruction
•
Functional epiphora (no anatomical obstruction but inadequate drainage)
Technique and Protocol
Radiopharmaceutical:
•
Tc-99m pertechnetate or Tc-99m DTPA
•
Dose: ~1-2 drops per eye (3.7 MBq / ~100 µCi)
•
Non-invasive administration: instilled as a drop into the lower conjunctival sac
•
Unlike invasive methods (contrast dacryocystography), it assesses physiological drainage
Imaging:
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The patient is seated, with the gamma camera positioned anteriorly close to the face
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A pinhole or parallel-hole collimator can be used
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Dynamic images: every 30 seconds, for a total of 30 minutes
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Delayed images if needed (45-60 minutes)
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Preparation and pitfalls: glasses and contact lenses are removed and no eye make-up should be worn. The patient sits with the head fixed; the drop is kept small and gauze is placed under the eye to avoid facial contamination, because activity on the lid or face spoils quantification. To avoid false positives from thickened secretions the lacrimal sac may be emptied by massage before the study (NVNG). The study is not performed in acute infective or allergic eye disease
–
Delayed transit is common even in older asymptomatic people (low specificity); an image after nose blowing and lid massage at the end of the study removes most false positives. Both eyes are studied together; in unilateral epiphora the other eye provides a comparison. With complete sac obstruction a high (horizontal canal) and low level cannot be distinguished, and after DCR the sac cannot be separated from the surgical opening. Agreement of scintigraphic findings with syringing (Anel) test and symptoms is poor
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Bilateral simultaneous assessment is possible → advantage of comparison
Normal Findings:
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Within 2-5 minutes of instillation → passage into the lacrimal sac
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Within 5-10 minutes → passage into the nasolacrimal duct
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Within 10-15 minutes → passage into the nasal cavity (inferior meatus)
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Within 15-20 minutes → passage into the nasopharynx
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Symmetric bilateral drainage is expected
Left: the lacrimal drainage system of both eyes (punctum, canaliculus, lacrimal sac, nasolacrimal duct, inferior meatus, nasopharynx) with activity changing over time. Right: time curves of sac and nose activity with normal transit times; in step two complete and partial obstruction and functional epiphora in the left eye.
Continuous stream · no seeking
Dacryoscintigraphy shows drainage physiologically: pooling proximal to a block, delay without a block in functional epiphora.
Source: protocol and normal times from the book (25.1); anatomy from OpenStax A&P 2e §14.1 and StatPearls. Kinetic model representative.
How to use: a single click on the drawing pauses and resumes; in the second step ↑ ↓ or the buttons below change the scenario; use the time bar below to go to any minute; ← → change steps.
Did this animation help you understand the topic?
Figure 25.1: Anatomy of the lacrimal drainage system and normal transit times on dacryoscintigraphy.
Pathological Findings
Complete Obstruction:
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Accumulation of activity proximal to the level of obstruction
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No passage of activity distally
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The level of obstruction is determined: punctum, canaliculus, lacrimal sac, nasolacrimal duct
Partial Obstruction:
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Delayed but present drainage
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Asymmetric drainage (comparison with the other side)
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Prolonged retention in the lacrimal sac
Functional Epiphora:
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No anatomical obstruction → activity passes through the whole system
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But drainage is delayed → lacrimal pump mechanism insufficient
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Contrast dacryocystography may be normal → scintigraphy is more sensitive
BOARD TIP
▸
"Difference between dacryoscintigraphy and contrast dacryocystography?"
→ Dacryoscintigraphy assesses physiological drainage (non-invasive, drop); dacryocystography shows anatomical structure (invasive, cannula injection).
▸
"Which is more sensitive in functional epiphora?"
→ Dacryoscintigraphy → no anatomical obstruction, but functional drainage is impaired.
Left: the lacrimal drainage system of both eyes (punctum, canaliculus, lacrimal sac, nasolacrimal duct, inferior meatus, nasopharynx) with activity changing over time. Right: time curves of sac and nose activity with normal transit times; in step two complete and partial obstruction and functional epiphora in the left eye.
Continuous stream · no seeking
Dacryoscintigraphy shows drainage physiologically: pooling proximal to a block, delay without a block in functional epiphora.
Source: protocol and normal times from the book (25.1); anatomy from OpenStax A&P 2e §14.1 and StatPearls. Kinetic model representative.
How to use: a single click on the drawing pauses and resumes; in the second step ↑ ↓ or the buttons below change the scenario; use the time bar below to go to any minute; ← → change steps.
Did this animation help you understand the topic?
Figure 25.2: Normal drainage, complete and partial obstruction and functional epiphora patterns on dacryoscintigraphy; NLD: nasolacrimal duct (schematic).
Advantages and Limitations
Advantages:
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Non-invasive, physiological assessment
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Bilateral simultaneous comparison
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Detection of functional epiphora (not detectable with contrast methods)
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Low radiation dose
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Easily repeatable for postoperative assessment
Limitations:
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Low spatial resolution → limited anatomical detail
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Small structures (canaliculi) → may not be clearly distinguished
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Patient cooperation needed (not blinking, keeping still)
25.2 Salivagraphy (Assessment of Salivary Ducts)10 questions
Anatomy and Physiology
Salivary Glands:
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Major glands: parotid, submandibular, sublingual
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Minor glands: widespread in the oral mucosa
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Parotid gland → Stensen duct → opens into the oral cavity through the buccal mucosa (opposite the 2nd molar)
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Submandibular gland → Wharton duct → opens in the floor of the mouth (beside the frenulum linguae)
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Saliva production: 1-1.5 litres per day
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Salivary glands concentrate pertechnetate and iodine (NIS – sodium iodide symporter)
Salivary Gland Scintigraphy (Salivagraphy)
EANM Notes:
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In adults 37 MBq pertechnetate (~0.5 mSv); peak uptake is seen at ~30 minutes; rapid emptying of activity after taste stimulation with citric acid is normal
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The test distinguishes loss of parenchymal function from an outflow (duct) problem; it does not identify the cause of xerostomia
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Indications: Sjögren syndrome (American-European Consensus criterion), monitoring of salivary gland damage after RAI therapy, assessment of response after surgery for a blocked duct, sarcoidosis, aplasia, Warthin tumour, trauma and fistulas
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Breastfeeding is interrupted for 12 hours; because mild xerostomia is a subjective complaint, the study is most useful in severe xerostomia
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For preparation, normal values and pitfalls see 18.1 (fasting for at least 2 hours, stopping anticholinergics, no thyroid-blocking agent)
Note: the basic application of salivary gland scintigraphy is described in Chapter 18 (GI – Nuclear Medicine Applications). This chapter covers assessment of the salivary ducts and rare indications. (→ see Chapter 18.1)
Radiopharmaceutical:
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Tc-99m pertechnetate is given IV; according to EANM 37 MBq in adults, while some centres use 185-370 MBq (5-10 mCi)
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Pertechnetate is actively concentrated by NIS → intense uptake in the salivary glands
Protocol:
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Dynamic imaging: anterior position, 30 seconds/frame, 30-40 minutes
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Acid stimulation (lemon juice or citric acid) at 20 minutes → stimulates saliva secretion
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A rapid fall in gland activity is expected after stimulation (normal washout)
Normal Findings:
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Uptake in the glands begins within 5-10 minutes of IV injection
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Uptake increases progressively → plateau at 15-20 minutes
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After acid stimulation → rapid washout (gland activity falls by more than 50%)
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Bilateral symmetric uptake and washout are expected
Pathological Findings and Clinical Applications
Sjögren Syndrome:
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Autoimmune exocrinopathy → chronic inflammation of the salivary and lacrimal glands
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Scintigraphic findings:
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Reduced uptake (impaired gland function)
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Delayed or absent washout (duct obstruction/loss of function)
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Reduced or absent response after stimulation
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Grading (Grade 1-4):
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Grade 1: mildly delayed uptake, normal washout
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Grade 2: delayed uptake, reduced washout
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Grade 3: markedly reduced uptake, minimal washout
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Grade 4: no or very little uptake, no washout → advanced stage
Salivary Duct Obstruction (Sialolithiasis):
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Stone in the salivary duct → duct obstruction
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Most common: submandibular gland (80-90%) → Wharton duct is long and runs upwards
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Scintigraphic findings:
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Normal or increased uptake in the affected gland (gland function preserved)
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Absent or delayed washout after stimulation (duct blocked)
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Asymmetry with the other side
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Difference from Sjögren: uptake is reduced in Sjögren and normal/increased in sialolithiasis
Sialadenitis after Radioiodine Therapy:
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Damage to the salivary glands after I-131 therapy (NIS-mediated uptake)
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Scintigraphic findings: reduced uptake + reduced washout
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Dose-dependent → risk increases with high cumulative I-131 doses
Warthin Tumour:
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The second most common benign tumour of the parotid gland
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Takes up Tc-99m pertechnetate (oncocytic cells → rich in mitochondria)
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On scintigraphy: focal increased uptake within the parotid ("hot" nodule)
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Pleomorphic adenoma → does not take up pertechnetate ("cold" nodule)
BOARD TIP
▸
"Parotid tumour that takes up Tc-99m pertechnetate?"
→ Warthin tumour (oncocytic cells, rich in mitochondria).
▸
"Does pleomorphic adenoma take it up?"
→ NO → cold nodule.
▸
"Sjögren vs sialolithiasis?"
→ Sjögren: reduced uptake + reduced washout; sialolithiasis: normal/increased uptake + no washout (duct blocked).
Left: anterior head and neck with parotid and submandibular glands, oral cavity and thyroid; lemon juice at 20 minutes. Right: time-activity curves of the right parotid and right submandibular gland; in step two sialolithiasis, post-RAI sialadenitis and advanced Sjögren against normal.
Continuous stream · no seeking
Rapid washout after acid stimulation is normal; a stone preserves uptake but blocks washout, Sjögren and RAI damage reduce uptake.
Source: protocol and patterns from the book (25.2, EANM notes); anatomy from OpenStax A&P 2e §23.3. Curve model representative.
How to use: a single click on the drawing pauses and resumes; in the second step ↑ ↓ or the buttons below change the scenario; ← → change steps.
Did this animation help you understand the topic?
Figure 25.3: Time-activity curves before and after acid stimulation on salivary gland scintigraphy: normal, sialolithiasis, post-RAI sialadenitis and advanced Sjögren (schematic).
Assessment of Xerostomia:
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Dry mouth → after radiotherapy, Sjögren, drugs, ageing
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Scintigraphy → quantitative assessment of gland function
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Comparison before and after radiotherapy → degree of damage
25.3 Assessment of LeVeen Shunt4 questions
General Information
LeVeen (Peritoneovenous) Shunt:
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Surgical shunt used in the treatment of refractory ascites
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Diverts ascitic fluid from the peritoneal cavity into the venous system (superior vena cava or internal jugular vein)
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One-way valve mechanism → opens when peritoneal pressure exceeds venous pressure
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Its use has declined today (because of TIPS and other methods)
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Complications: shunt occlusion, DIC, infection, pulmonary embolism
Assessment of Shunt Patency
Radiopharmaceutical:
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Tc-99m MAA or Tc-99m sulphur colloid
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Intraperitoneal injection (into the peritoneal cavity by paracentesis)
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Dose: 37-74 MBq (1-2 mCi)
Protocol:
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Intraperitoneal injection of Tc-99m MAA
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The patient changes position (sitting, standing) → to raise peritoneal pressure
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Dynamic and static images: abdomen + thorax
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Imaging: immediately after injection and after 1-2 hours
Findings of a Normal (Patent) Shunt:
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Intraperitoneal activity gradually decreases
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Activity is seen in the lungs (when Tc-99m MAA is used) → shunt patent
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MAA passes into the venous system → is trapped in the pulmonary capillaries
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When Tc-99m sulphur colloid is used → activity is seen in the liver and spleen
Findings of an Occluded Shunt:
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Intraperitoneal activity does not decrease (remains in the peritoneal cavity)
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No activity is seen in the lungs (MAA) or liver/spleen (sulphur colloid)
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No progression of activity along the shunt line
Partial Occlusion:
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Delayed but present passage
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Low-level activity in the lungs
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Preparation, administration and pitfalls: (there is no current guideline for this study) No preparation is needed. After local anaesthesia, intraperitoneal needle position is confirmed by aspirating ascitic fluid, then Tc-99m MAA (about 111-185 MBq) is injected; the patient is rolled from side to side to mix it with the ascites. Widespread abdominal distribution on the first image confirms correct injection. With a patent shunt the lungs usually appear within 10 minutes and at the latest within 1 hour; appearance at 25-60 minutes suggests partial obstruction and no lung activity suggests high-grade obstruction. Breathing exercises against resistance may promote flow
–
Lung activity is the only reliable criterion of patency; visualisation of the shunt tubing depends on flow rate and is unreliable. With sulfur colloid, peritoneal activity pooling under the diaphragm can mimic the liver, and liver function may be impaired, so MAA is preferred. In complete obstruction, direct injection into the shunt tubing can show whether the obstruction is at the valve or in the tubing
BOARD TIP
▸
"How is LeVeen shunt patency assessed?"
→ Intraperitoneal injection of Tc-99m MAA → if the shunt is patent, lung uptake is seen (MAA passes into the venous system → is trapped in the pulmonary capillaries).
▸
"If the shunt is occluded?"
→ Activity remains in the peritoneal cavity; NO lung uptake.
Figure 25.4: Patent and occluded shunt findings on LeVeen (peritoneovenous) and VP shunt patency scintigraphy (schematic).
Did this figure help you understand the topic?
25.4 Testicular Scintigraphy8 questions
General Information
Clinical Indications:
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Assessment of the acute scrotum → testicular torsion vs epididymitis/orchitis
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Today largely replaced by colour Doppler US
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But may still be used when US is inadequate or unavailable
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Testicular torsion → surgical emergency → high risk of testicular loss if detorsion is not done within 6 hours
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Predisposition: in the "bell clapper" anomaly the tunica vaginalis completely envelops the testis, so it hangs freely; the anomaly is often bilateral
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Intravaginal torsion (on a bell clapper anomaly) occurs in adolescents, extravaginal torsion (rotation of the spermatic cord together with the tunica) in neonates
Technique and Protocol
Radiopharmaceutical:
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Tc-99m pertechnetate (IV, 370-740 MBq / 10-20 mCi)
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Pertechnetate → indicator of blood flow (as a perfusion agent)
Protocol:
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Patient supine
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A lead shield is placed under the scrotum (to reduce background activity)
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The penis is taped upwards (away from the scrotum)
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Phase 1 – Angiographic phase (flow): dynamic images, 2-3 seconds/frame, 60 seconds
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Phase 2 – Blood pool (static): 5-10 minutes later, static images
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Bilateral comparison is made
Normal Findings
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Angiographic phase: bilateral symmetric iliac and femoral arterial flow
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Static phase: bilateral symmetric scrotal activity
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Testicular parenchyma → moderate homogeneous activity
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Mediastinum testis → low activity (avascular area)
Pathological Findings
Acute Testicular Torsion (<6 hours):
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Angiographic phase: reduced or absent arterial flow on the affected side
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Static phase: reduced activity in the affected testis ("cold" area)
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There may be surrounding reactive hyperaemia (later)
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In the intermediate period (~7-24 hours) a peripheral halo due to dartos hyperaemia begins to appear; as the halo becomes more marked, the probability of salvaging the testis falls
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"Nubbin" sign: cut-off of activity at the level of spermatic cord torsion
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False negatives: spontaneous detorsion and incomplete or intermittent torsion. False-positive cold area: hydrocele, haematoma, inguinal hernia
Late (Missed) Testicular Torsion (>24 hours):
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Angiographic phase: increased flow around the affected side (reactive hyperaemia/inflammation)
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Static phase: central cold area (ischaemic/necrotic testis) + surrounding ring of increased activity ("halo" or "bull's eye" sign)
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This pattern → testis cannot be salvaged → orchidectomy may be needed
Epididymitis/Orchitis:
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Angiographic phase: increased flow on the affected side (hyperaemia)
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Static phase: increased activity on the affected side (diffuse or focal)
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The exact opposite of torsion → hot (cold in torsion)
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Torsion of the appendix testis: mimics testicular torsion in prepubertal boys; scintigraphy is normal or shows focal increased activity ('hot dot'). It resolves spontaneously and does not require surgery
Hydrocele:
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Photopenic area around the testis in the static phase (fluid → takes up no activity)
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Testicular activity normal
Testicular Abscess:
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Increased peripheral activity + central cold area (abscess cavity)
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May be difficult to distinguish from late torsion
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The halo (bull's eye) pattern is not specific to late torsion; it is also seen in abscess, haematoma and necrotic tumour
| Condition | Angiographic Phase (Flow) | Static Phase (Blood Pool) |
|---|---|---|
| Normal | Symmetric flow | Symmetric activity |
| Acute torsion (<6 hours) | Reduced/absent flow | Cold area (reduced activity) |
| Late torsion (>24 hours) | Increased peripheral flow | Central cold + peripheral halo |
| Epididymitis/Orchitis | Increased flow | Increased activity (hot) |
| Hydrocele | Normal flow | Peripheral photopenic area |
| Testicular abscess | Increased peripheral flow | Central cold + peripheral increase |
BOARD TIP
▸
"Testicular torsion vs epididymitis in the acute scrotum?"
→ Torsion: COLD (reduced perfusion); epididymitis: HOT (increased perfusion).
▸
"'Halo' sign in late torsion?"
→ Central cold area (necrotic testis) + surrounding ring of increased activity (reactive hyperaemia) → testis cannot be salvaged.
▸
"First choice today?"
→ Colour Doppler US → scintigraphy is an alternative when US is inadequate.
Figure 25.5: Angiographic (flow) and static phase patterns of causes of the acute scrotum on testicular scintigraphy (schematic).
Did this figure help you understand the topic?
25.5 Other Rare Applications
25.5.1 Search for Ectopic Gastric Mucosa (Barrett Oesophagus)
•
Tc-99m pertechnetate → taken up by gastric mucosal cells
•
Ectopic gastric mucosa in Barrett oesophagus → focal pertechnetate uptake in the oesophagus
•
Same principle as Meckel diverticulum (→ see Chapter 18.5)
•
Limited clinical use → endoscopy and biopsy are the gold standard
25.5.2 Assessment of Peritoneal Shunt (VP Shunt)5 questions
Ventriculoperitoneal (VP) Shunt:
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Diverts CSF into the peritoneal cavity in the treatment of hydrocephalus
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Shunt dysfunction → recurrence of hydrocephalus
Technique:
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Tc-99m DTPA or Tc-99m pertechnetate
•
Percutaneous injection into the shunt reservoir (Ommaya or Rickham)
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Dynamic imaging: head → neck → thorax → abdomen
Normal Findings:
•
Activity progresses along the shunt line → reaches the peritoneal cavity
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Activity in the ventricle decreases
Occluded Shunt:
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Activity does not progress along the shunt line
•
The level of occlusion is determined (proximal vs distal)
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Activity remains in the ventricle (proximal occlusion)
•
A limited focal collection at the distal tip of the shunt that does not spread into the peritoneal cavity suggests a CSF pseudocyst or loculation (partial distal occlusion); normally activity spreads freely within the peritoneum
EANM Notes (CSF Drainage System):
•
In-111 DTPA is given in a volume of at most 1 mL as 4 MBq; return of CSF from the reservoir shows that the ventricular limb of the shunt is patent
•
If the drain is patent, activity is seen immediately and progresses to the heart (ventriculo-atrial shunt) or to the abdomen
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Pitfall: inadvertent subcutaneous injection may mimic distal occlusion; a vertex view avoids this pitfall
•
Drainage protocol: 64×64 matrix, frames over 2 minutes of 10 s each; anterior and lateral images at 30 minutes and a 10-minute vertex image
25.5.3 Red Cell and Platelet Kinetic Studies4 questions
Red Cell Survival (Cr-51):
•
Red cell labelling with Cr-51 sodium chromate
•
Normal red cell lifespan: 120 days (T½ = 25-35 days)
•
Shortened survival → haemolytic anaemia
•
Spleen/liver ratio → determines the site of sequestration
•
Spleen/liver ratio >2:1 → splenectomy may be beneficial
Platelet Survival (In-111 Oxine):
•
Normal platelet lifespan: 8-10 days
•
Shortened survival → immune thrombocytopenia, DIC, TTP
•
Site of sequestration: spleen vs liver vs diffuse
25.5.4 Schilling Test (Historical)3 questions
•
Vitamin B12 absorption test → diagnosis of pernicious anaemia
•
Co-57 or Co-58 labelled vitamin B12 is given orally
•
24-hour urine is collected → excreted radioactivity is measured
•
Phase 1: labelled B12 alone → low excretion = malabsorption
•
Phase 2: labelled B12 + intrinsic factor → corrected excretion = pernicious anaemia
•
If not corrected → ileal disease, bacterial overgrowth, pancreatic insufficiency
•
No longer used today → production of Co-57/Co-58 has stopped
•
Replaced by: anti-intrinsic factor antibody, anti-parietal cell antibody, methylmalonic acid, homocysteine
BOARD TIP
▸
"Schilling test Phase 1 low + Phase 2 normal?"
→ Pernicious anaemia (intrinsic factor deficiency → corrected by exogenous IF).
▸
"Phase 1 and Phase 2 low?"
→ Ileal disease (terminal ileal B12 absorption impaired → adding IF does not correct it).
▸
"Is the Schilling test performed today?"
→ NO → radioisotope production has stopped; serological tests are used.
Figure 25.6: Two-phase interpretation algorithm of the Schilling test.
Did this figure help you understand the topic?
25.5.5 Blood Volume Measurement2 questions
Red Cell Mass (Cr-51):
•
Cr-51 labelled red cells are injected IV
•
Red cell mass is calculated by the dilution principle
•
Normal: men 25-35 mL/kg, women 20-30 mL/kg
•
Polycythaemia vera → increased red cell mass (>36 mL/kg in men, >32 mL/kg in women)
•
Relative polycythaemia → normal red cell mass, reduced plasma volume
Plasma Volume (I-125 Albumin):
•
I-125 labelled human serum albumin is injected IV
•
Plasma volume is calculated by the dilution principle
•
Normal: 40-50 mL/kg
•
Less used today → calculated methods are preferred
BOARD TIP
▸
"Polycythaemia vera vs relative polycythaemia?"
→ Cr-51 red cell mass measurement → increased in PV, normal in relative polycythaemia.
▸
"Which radionuclide measures red cell mass?"
→ Cr-51.
▸
"Plasma volume?"
→ I-125 albumin.
25.5.6 Gastric Mucosa Protection Study (Meckel Scan Variants)2 questions
•
In the search for ectopic gastric mucosa, sensitivity can be increased with pentagastrin or cimetidine
•
Pentagastrin: increases pertechnetate secretion from gastric mucosal cells → increases uptake
•
Cimetidine (H2 blocker): inhibits pertechnetate secretion → reduces release into the lumen → increases retention in the gland → target/background ratio increases
•
Cimetidine: started 48 hours before the study
•
Glucagon: reduces bowel motility → reduces artefact
25.5.7 Oesophageal Transit and Gastric Reflux (Rare Variants)1 questions
•
Standard applications are described in Chapter 18 (→ see Chapter 18.2, 18.3)
•
Pulmonary aspiration scintigraphy: assesses whether gastric reflux leads to pulmonary aspiration
–
Tc-99m sulphur colloid is given orally (before going to bed at night)
–
Morning lung imaging → activity in the lungs → evidence of aspiration
–
Especially in paediatric patients (recurrent pneumonia, chronic cough)
25.5.8 Brain Shunt Assessment (CSF Flow Studies)
•
Described in detail in Chapter 19 (→ see Chapter 19.9 Cisternography)
•
Assessment of VP shunt patency is covered in this chapter (25.5.2)
Key Points for the Board
Dacryoscintigraphy:
•
Radiopharmaceutical: Tc-99m pertechnetate/DTPA → drop into the lower conjunctival sac
•
Non-invasive, physiological assessment (contrast dacryocystography is invasive and anatomical)
•
Normal drainage: lacrimal sac (2-5 min) → nasolacrimal duct (5-10 min) → nasal cavity (10-15 min) → nasopharynx (15-20 min)
•
Superior to contrast methods for detecting functional epiphora
•
Complete obstruction: accumulation proximal to the obstruction, no passage distally
Salivary Gland Scintigraphy (Salivagraphy):
•
Tc-99m pertechnetate IV → NIS-mediated uptake
•
Acid stimulation (20 min) → normal: rapid washout
•
Sjögren: reduced uptake + delayed/absent washout (Grade 1-4)
•
Sialolithiasis: normal/increased uptake + NO washout (duct blocked, gland intact)
•
Warthin tumour: TAKES UP pertechnetate ("hot" nodule) → oncocytic cells, rich in mitochondria
•
Pleomorphic adenoma: does NOT take up pertechnetate ("cold" nodule)
•
Sialadenitis after I-131: reduced uptake + reduced washout (dose-dependent)
Assessment of LeVeen Shunt:
•
Intraperitoneal injection of Tc-99m MAA
•
Shunt patent → MAA passes into the venous system → lung uptake
•
Shunt occluded → activity remains in the peritoneal cavity → NO lung uptake
•
If Tc-99m sulphur colloid is used → liver/spleen uptake with a patent shunt
Testicular Scintigraphy:
•
Tc-99m pertechnetate IV → angiographic phase + static phase
•
Acute torsion (<6 hours): reduced flow + COLD area
•
Late torsion (>24 hours): central COLD + peripheral HALO (ring of increased activity) → testis cannot be salvaged
•
Epididymitis/orchitis: increased flow + HOT area → the exact opposite of torsion
–
Hydrocele: photopenic area around the testis (fluid) + normal testicular activity
•
The bell clapper anomaly predisposes to torsion and is often bilateral
•
The halo pattern is not specific to late torsion: also seen in abscess, haematoma and necrotic tumour
•
Torsion of the appendix testis: scintigraphy normal or focally increased ('hot dot'); false-negative torsion: spontaneous/intermittent detorsion
•
Today largely replaced by colour Doppler US
Schilling Test (Historical):
•
Oral Co-57/Co-58 labelled vitamin B12 → 24-hour urinary excretion measured
•
Phase 1 low + Phase 2 normal (corrected by adding IF) → pernicious anaemia
•
Phase 1 and Phase 2 low (adding IF does not correct) → ileal disease (Crohn, resection)
•
Not used today → Co-57/Co-58 production stopped → serological tests (anti-IF Ab, methylmalonic acid) are used
Blood Volume and Red Cell Kinetic Studies:
•
Cr-51 → red cell mass measurement + red cell survival
•
Normal red cell lifespan: 120 days (Cr-51 T½ = 25-35 days)
•
Polycythaemia vera vs relative polycythaemia: Cr-51 red cell mass → increased in PV, normal in relative polycythaemia
•
Spleen/liver ratio >2:1 → splenic sequestration → splenectomy beneficial
•
I-125 albumin → plasma volume measurement
•
In-111 oxine → platelet survival (normal: 8-10 days)
Assessment of VP Shunt:
•
Tc-99m DTPA → percutaneous injection into the shunt reservoir (Ommaya/Rickham)
•
Patent shunt: activity progresses along the shunt line to the peritoneal cavity
•
Occluded shunt: activity does not progress → the level of occlusion is determined
•
Localised focal collection at the distal tip (no free spread in the peritoneum) → CSF pseudocyst/loculation
Meckel Scintigraphy – Sensitivity-Enhancing Drugs:
•
Cimetidine (H2 blocker): inhibits pertechnetate secretion → retention in the gland increases → target/background ratio increases (started 48 hours before the study)
•
Pentagastrin: increases pertechnetate uptake by gastric mucosal cells
•
Glucagon: reduces bowel motility → reduces artefact
Pulmonary Aspiration Scintigraphy:
•
Oral Tc-99m sulphur colloid (before going to bed at night) → morning lung imaging
•
Activity in the lungs → evidence of aspiration
•
Especially in paediatric patients (recurrent pneumonia, chronic cough)
General Reminders for Rare Applications:
•
Dacryoscintigraphy → physiological (scintigraphy) vs anatomical (contrast) assessment
•
Salivagraphy → Sjögren vs sialolithiasis (reduced vs normal/increased uptake)
•
Warthin tumour (and oncocytoma) → salivary gland tumours that take up pertechnetate
•
LeVeen shunt → MAA IP → lung uptake if patent
•
Testicular scintigraphy → torsion COLD, epididymitis HOT
•
Schilling test → historical, not used today
Additional Notes from EANM Guidelines:
•
Salivary gland scintigraphy: 37 MBq; parenchyma vs outflow; breastfeeding 12 hours
•
Shunt scintigraphy: subcutaneous injection mimics distal occlusion → vertex view
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