Lacrimal system and salivary glands

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Chapter 15 Lacrimal system and salivary glands

Methods of imaging the lacrimal system

1. Conventional/digital subtraction dacryocystography.
2. Conventional/digital subtraction dacryocystography + computed tomography (CT) dacryocystography
3. Magnetic resonance imaging.

Further reading

Ansari S.A., Pak J., Shields M. Pathology and imaging of the lacrimal drainage system. Neuroimaging Clin. N. Am.. 2005;15(1):221-237.

Digital Subtraction and CT Dacryocystography

Dacryocystography allows visualization of the lacrimal system by direct injection of contrast into the cannalicus of the eyelid. It may be combined with CT imaging performed immediately after lacrimal system contrast injection. CT imaging gives additional diagnostic information, particularly about adjacent structures.1

Indications

Epiphora – to demonstrate the site and degree of obstruction.

Contraindications

None.

Contrast medium

Low osmolar contrast material (LOCM) 300, 0.5–2.0 ml per side.

The use of lipiodol is to be discouraged.

Equipment

1. Digital subtraction radiography unit
2. Silver dilator and lacrimal cannula, or 18G blunt needle with polythene catheter (the catheter technique has the advantage that the examination can be performed on both sides simultaneously).

Patient preparation

0.5 % bupivacaine eye drops.

Technique

1. The lacrimal sac is massaged to express its contents prior to injection of the contrast medium. The lower eyelid is everted to locate the lower canaliculus at the medial end of the lid. The lower canaliculus is dilated and the cannula or catheter is inserted. The lower lid should be drawn laterally during insertion to straighten the bend in the canaliculus, and so avoid perforation by the cannula.
The upper canaliculus may also be cannulated if there is difficulty with the lower canaliculus.
2. The contrast medium is injected and a digital subtraction run at one image per second is obtained. This allows for a dynamic study in real time.

Images

Appropriate images are filmed /digitally stored.

Aftercare

A protective eye patch for 30–60 min may be necessary in view of the local anaesthetic used.

Complications

Perforation of the canaliculus.

Reference

1 Freitag S.K., Woog J.J., Kousoubris P.D., et al. Helical computed tomographic dacryocystography with three dimensional reconstruction: a new view of the lacrimal drainage system. Opthal. Plast. Reconstr. Surg.. 2002;18(2):121-132.

MRI of Lacrimal System

The lacrimal system can be assessed with MRI (MR dacryocystography) either following topical administration of eye drops containing a dilute gadolinium solution (sterile 0.9% NaCl solution containing 1:100 diluted gadolinium chelate) or by direct injection of a dilute gadolinium solution into the lacrimal canaliculus.1 The less invasive, topical administration technique is more widely used. MR is useful in the diagnosis of obstruction level in the lacrimal system for patients with epiphora and in assessment of surrounding soft tissues.

Reference

Manfrè L., de Maria M., Todaro E., et al. MR dacryocystography: comparison with dacryocystography and CT dacryocystography. Am. J. Neuroradiol.. 2000;21(6):1145-1150.

Methods of imaging the salivary glands

1. Plain films: for calculus disease (sialithiasis)
2. Conventional sialography: less commonly performed than in the past; many indications replaced by non-invasive cross-sectional imaging
3. CT: thin-section unenhanced CT for diagnosis of sialithiasis ± intravenous (i.v.) contrast medium, e.g. in suspected tumour or abscess
4. Ultrasound (US): ideal investigation for superficial salivary gland disease and a sensitive test for sialithiasis
5. MRI: ± i.v. contrast medium for assessment of inflammatory or malignant disease, may include MR spectroscopy for characterization of focal mass and MR sialography
6. Radionuclide imaging (sialoscintigraphy).

Further reading

Bialek E.J., Jakubowski W., Zajkowski P., et al. US of the major salivary glands: anatomy and spatial relatinships, pathological conditions and pitfalls. Radiographics. 2006;26(3):745-763.

Freling N.J. Imaging of salivary gland disease. Semin. Roentgenol.. 2000;35(1):12-20.

Rabinov J.D. Imaging of salivary gland pathology. Radiol. Clin. North Am.. 2000;38(5):1047-1057.

.

Yousem D.M., Kraut M.A., Chalian A.A. Major salivary gland imaging. Radiology. 2000;216(1):19-29.

Conventional and CT Sialography

Indications

1. Pain
2. Swelling
3. Sicca syndrome.

Contraindications

Acute infection or inflammation.

Contrast medium

1. LOCM 240–300
2. Lipiodol Ultra Fluid.

Neither contrast medium has a clear advantage over the other.

Equipment

1. Skull unit (using macroradiography technique)
2. Silver lachrymal dilator
3. Silver cannula or 18G blunt needle and polythene catheter.

Patient preparation

Any radio-opaque artifacts are removed (e.g. false teeth).

Preliminary film

Parotid gland

1. Antero-posterior (AP) with the head rotated 5 ° away from the side under investigation. Centre to the mid-line of the lower lip
2. Lateral, centred to the angle of the mandible
3. Lateral oblique, centred to the angle of the mandible, and with the tube angled 20 ° cephalad.

Submandibular gland

1. Inferosuperior using an occlusal film. This is a useful view to show calculi
2. Lateral, with the floor of the mouth depressed by a wooden spatula
3. Lateral oblique, centred 1 cm anterior to the angle of the mandible, and with the tube angled 20 ° cephalad.

Technique

1. The orifice of the parotid duct is adjacent to the crown of the second upper molar, and that of the submandibular duct is at the base of the frenulum of the tongue. If they are not visible, a sialogogue (e.g. citric acid) is placed in the mouth to promote secretion from the gland, and so render the orifice visible.
2. The orifice of the duct is dilated with the silver wire probe and the cannula or polythene catheter is introduced into the duct. The catheter can be held in place by the patient gently biting on it.
3. Up to 2 ml of contrast medium are injected. The injection is terminated immediately if any pain is experienced. The duct must not be overfilled
4. If the cannula method is used, films are taken immediately after the injection. The catheter method has the advantage that films can be taken during the injection, with the catheter in situ, and that both sides can be examined simultaneously.

Films

1. Immediate – the same views as for the preliminary films are repeated. The occlusal film for the submandibular gland may be omitted, as this is only to demonstrate calculi.
2. Post-secretory – the same views are repeated 5 min after the administration of a sialogogue. The purpose of this is to demonstrate sialectasis.

Aftercare

None.

Complications

1. Pain
2. Damage to the duct orifice
3. Rupture of the ducts
4. Infection.

ULTRASOUND AND MRI OF SALIVARY GLANDS

MR is very useful in the diagnosis of lesions of the salivary glands.

A heavily T2-weighted sequence can image the ductal system of the major salivary glands in the diagnosis of sialolithiasis and sialadenitis (MR sialography). Non-contrast studies can be useful in differentiating benign or low-grade malignant from high-grade malignant tumours. Contrast enhancement is useful in the differential diagnosis of cystic from solid lesions, and when determining the degree of perineural spread of malignant disease.1 Diffusion weighted imaging and MR spectroscopy are increasingly used for the characterization of salivary gland masses.2

Pulse sequences

Thin, T1-weighted and T2-weighted unenhanced images are taken. Fast spin-echo T2-weighted images may require fat suppression. Gadolinium-enhanced scans with T1 weighting and fat suppression are obtained in the axial plane; sagittal and coronal images may be obtained at the radiologist’s discretion.

References

1 Yousem D.M., Kraut M.A., Chalian A.A. Major salivary gland imaging. Radiology. 2000;216(1):19-29.

2 Lee Y.Y., Wong K.T., King A.D., et al. Imaging of salivary gland tumours. Eur. J. Radiol.. 2008;66(3):419-436.

Further reading

Shah G.V. MR imaging of salivary glands. Neuroimaging Clin. N. Am.. 2004;14(4):777-808.

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