Umar Chaudhry+, Saba Hamid+, Umber Shafique+, Joan Maley+, Bruno Polliceni+, Henry Hoffmman* KNOWING WHAT, WHEN AND HOW TO INTERPRET: GUIDE TO IMAGING.

Umar Chaudhry+, Saba Hamid+, Umber Shafique+, Joan Maley+, Bruno Polliceni+, Henry Hoffmman*

KNOWING WHAT, WHEN AND HOW TO INTERPRET: GUIDE TO IMAGING SALIVARY

GLAND PATHOLOGY

+ Section of Neuroradiology, Department of Diagnostic Radiology, Univeristy of Iowa Hospitals and Clinics. * Department of Otolaryngology,University of Iowa Hospitals and Clinics.

eEdE#: eEdE-127

OUTLINE

• INTRODUCTION

• MODALITIES AVAILABLE

• INDIVIDUAL MODALITIES

• INDICATIONS

• PROTOCOL

• ADVANTAGES

• DISADVATAGES

• PICTORIAL EXAMPLES

• PEARLS

“ The years teach much which the days never knew ” Ralph Waldo Emerson

INTRODUCTION

• Salivary gland pathology is one the most variable amongst the organ system

• Wide variety of imaging modalities used

• It becomes confusing to determine the most optimum modality when encountered with a clinical scenario

• With era of cost effectiveness, ever increasing patient awareness, and extensive clinician interactions, the expectations from a radiologist have increased

• This presentation is intended to be a quick reference guide and refresher for various tools in our arsenal when dealing with such scenarios

MODALITIES

• Computed Tomography

• Magnetic resonance imaging

• Ultrasound

• Conventional Sialography

• Nuclear imaging

COMPUTED TOMOGRAPHY (CT)

INDICATIONS:

Optimal:

Occasional:

- Inflammatory pathologies, infection- Obstructive pathologies: stones

- CT sialography, ductal pathology- Masses- Post radiation

PROTOCOL- Multidetector CT (MDCT)- kVP 80-120 kVP- Dose reduction techniques:

- Thyroid bismuth shields- Automated dose reduction- Lower kV- Studies showed no significant diagnostic difference between 80 and

120 kV protocols - Inflammatory conditions, abscess usually IV contrast- Stones - Non contrast

ADVANTAGES

- Quick- Readily available- Gross anatomical detail of surrounding structuresextent of

inflammation- High sensitivity for Stones/calcifications- 3D reconstructions: CT Sialography

DISADVANTAGES

- Ionizing radiation- pregnant and children- Not ideal for tumors as higher detail from MRI- Perineural spread in malignancies is difficult- Poor ductal anatomical detail with standard CT

Inflammation of left parotid gland

A case of a left parotid gland tumor – pleomorphic adenoma with spilling, structural details and margins not as clear as with MRI

RIGHT SUBMANDIBULAR GLAND DUCT STONE (RECTANGLE) WITH DILATED DUCT (CIRCLE)

PEARLS - CT

- Acute conditions in adult patients- Inflammation- Stones questioned- With radiation awareness, consider dose modulation

MAGNETIC RESONANCE IMAGING (MRI)

INDICATIONS

Salivary gland massesSystemic conditions, usually non acuteDuctal anatomy - Sialography

PROTOCOL

- For masses or major salivary glands, usually gadolinium based contrast

- Varies from one institution to the other - Our institution protocol

- 3 plane localizer - Coronal and axial T2- Axial T1- Diffusion- 3 plane post -contrast T1 images

EXAMPLE OF SCAN VOLUMES FOR PAROTID GLAND

MRI SIALOGRAPHY- Relies on heavily T2 weighted sequences and water property of saliva

- Side of abnormality and duct included in the scan volume for MR Sialography

- Protocol also varies from institution to institution

- 2D pulse sequences used traditionally - Projection and Maximum Intensity projections for Sialography

- 2D pulse sequence techniques to increase quality of images include

- Projection technique by using a microscopic coil improving the quality of the images obtained with larger coils

- Recently 3D pulse sequences utilized for more post processing options

ADVANTAGES

- No radiation- Non invasive- Excellent gland detail- Tumor characterization, using signal intensity, margins,

pattern of spread, diffusion coefficients- Facial nerve characterization in parotid lesions

DISADVANTAGES

- Time consuming - not ideal for acute settings- Expensive - Limited field of view - More susceptible to artifacts- Ductal detail needs careful optimization, otherwise may be

confounded by vessels etc.

PEARLS

- Non acute - Ideal for major salivary gland masses and systemic conditions such

as Sjogren characterization- Spread of malignancies- perineural tumor spread- New techniques such as dynamic contrast high potential - After optimization ductal details acquired non invasively

PLEOMORPHIC ADENOMA ON MRI

T1- LOWT2- HIGHPOST CONTRAST HOMOGENOUS

MALIGNANT PAROTID TUMOR WITH PERINEURAL TUMOR SPREAD (CIRCLE)

ULTRASOUND

INDICATIONS:

- Acute inflammations- Pediatric and pregnant population - Image guided procedures- Initial screening of major salivary gland mass

PROTOCOL

- High frequency linear probes- 7.5-12 MHz

- Color doppler

- Real time imaging

Figure: Example of color doppler on a parotid mass

ADVANTAGES

- No ionizing radiations- Quick- Real time imaging- image guided procedures- Less expensive and more readily available than MRI

DISADVANTAGES

- Operator dependence- Ducts especially Parotid duct not well seen unless largely

dilated- Limited field of view- Deeper pathologies such as

parapharyngeal space lesions and deep lobes of parotid glands not well see

- Less specific characterization of masses as compared to MRI

PAROTID PLEOMORPHIC ADENOMA

Normal parotid parenchyma is more echogenic and homogenous

PEARLS

- Children and pregnant patients- Initial screening for acute conditions such as infections- Image guided procedures- One of the most cost effective modalities in cross sectional imaging

CONVENTIONAL SIALOGRAPHY

INDICATIONS:

- Obstructive and ductal salivary gland pathology- Preoperative exam before sialendoscopy

PROTOCOL- Fluoroscopy- real time imaging- Usually Kv range close to 70 kV- Iodine based contrast directly instilled into major salivary gland ducts- Images in two planes- Ductal and glandular phase- Stimulation for glandular phase - Lime/candy

SIALOGRAPHY -TECHNIQUE• Basic principle: Instilling radio-opaque contrast directly into the duct opening

Sialography can be performed with or without digital subtraction - digital subtraction favored, as it removes the confounding bone opacities

Syringe containing contrast

CanulaStenson’s duct

Salivary Gland

Sialography- The Procedure

ADVANTAGES- Resurgence due to preoperative insight before minimally

invasive ENT procedures- Ductal resolution and detail superior to many other

modalities- Lower dose than CT sialography

DISADVANTAGES

- Invasive- Ionizing radiation- Expertize required

SIALOGRAPHY IN SIALOLITHIASIS

Filling defects seen in Stenson’s duct, with dilated ducts upstream from the obstruction

Common pathologies-a sialographic perspective

PEARLS

- Not to be overlooked and seeing a resurgence due to new minimally invasive techniques in ENT

- Ductal pathology well seen- Usually requires close collaboration with ENT

NUCLEAR MEDICINE

INDICATIONS:- Long term dysfunction/sialadenitis- Metastatic workup

PROTOCOL- Salivary scintigraphy

- Tc-99m Planar and SPECT imaging- Mainly for long term dysfunction after radioiodine

- PET- Fluoro-deoxy glucose for metastatic workup and distant lesions

ADVANTAGES

- Functional information - Distant metastatic lesions

DISADVANTAGES

- Non-specific for salivary gland tumors- Non acute pathologies only- Limited use- Cost and availabillity

PET-FDG SCAN IN METASTATIC SALIVARY GLAND TUMOR: NECK NODE AND RIGHT LUNG NODULE

PEARLS

- Overall limited role

- Chronic sialadenitis after radioactive iodine- Tc-99m scintigraphy

- FDG-PET is non specific, can be used for distant metastasis after tissue diagnosis

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REFERENCES

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