THE SUBMANDIBULAR GLAND

Contouring Accuracy Program

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Outline

1. Refresher Course on the Submandibular GlandA. What are the submandibular glands?

B. The functions of the submandibular glands

C. “Did you know?”

2. Locating the Submandibular Glands in Medical ImagesA. Limits and borders

B. Relationship to other anatomy

C. Contouring on axial images

D. Window and level considerations

3. Special Considerations for Radiation TherapyA. Radiosensitivity

B. Notable Protocols & Publications

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1A. What are the Submandibular Glands?

The submandibular glands are

paired salivary glands.

The submandibular glands are

located bilaterally below the floor

of the mouth, just under the jaw

and towards the back of the

mouth.

They are the second largest of the

salivary glands (the largest being

the parotid glands).

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http://rsnaeducation.blogspot.com/2011/09/cervical-lns.html

1B. The Functions of the Submandibular Glands

The primary function of the submandibular glands is to control

the release of saliva into the area of the mouth that is just

under the tongue.

Each gland weighs ~15 grams. Together, the two glands

contribute up anywhere from 60-75% of unstimulated saliva

secretion. On stimulation, their relative contribution %

decreases as the parotid glands’ secretion rises up to 50%.

https://en.wikipedia.org/wiki/Submandibular_gland

https://en.wikipedia.org/wiki/Saliva#Daily_salivary_output

Secretions are delivered through submandibular duct, or

Wharton’s duct.

https://en.wikipedia.org/wiki/Submandibular_duct

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1C. “Did You Know…?”

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Summary fun fact statement here…A few fun facts about saliva…

Humans produce 0.75 to 2.0 liters of saliva per day. The

submandibular glands are the workhorse of this saliva

production in terms of volume.

Our saliva is rich with a painkiller six times more powerful than

morphine, called opiorphin.

Scientific studies suggest that a person’s age can be estimated

within five years by analyzing the saliva (i.e. by measuring the

degree of methylation in DNA).

Here is a neat link with more fun-facts about saliva.

2A. Limits and Borders

Superior - medial surface of

the mandible.

Inferior - soft tissue of the

neck, often down to the level

of the hyoid bone.

Medial/anterior - floor of the

mouth.

Posterior - submandibular LN

and carotid sheath

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2B. Relationship to Muscles

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Ramus of

mandible

2B. Relationship to Other Anatomy

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2B. Relationship to Other Anatomy

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2B. Relationship to Hyoid Bone

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GLAND

HYOID BONE

2C. Contouring Step-by-Step Guide

1. Locate the ramus of the mandible and identify the

medial pterygoid on its medial surface.

2. Scrolling inferiorly, the superior aspect of the

submandibular gland should become apparent

either medial or inferior to the inferior aspect of

the medial pterygoid/mandible.

3. Contour gland inferiorly as it continues in the soft

tissue of the neck, ending approximately at the

level of the hyoid.

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2D. Window and Level Considerations

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Gland tissue = less radio-dense than muscle

Gland tissue = more radio-dense than fat

Low Contrast, i.e. Wide Window

W = 3000, L = 500

MUSCLE

GLAND

FAT

High Contrast, i.e. Narrow Window

W = 240, L = 20

3A. Radiosensitivity

Structure Name Metric Goal Note

Submandibular Gland Mean Dose ≤ 39 Gy Suggested dose limit;should not compromise

tumor coverage

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Link to RTOG 0912

Comments

It is not entirely clear whether the parotid and submandibular glands share similar dose-

volume responses. Murdoch-Kinch et al. showed that there was recovery of stimulated and

unstimulated salivary flow up to a threshold of 39 Gy.

Submandibular gland sparing is an area of debate. Limited retrospective evidence suggests

that it can be safely done in appropriately selected patients (Gensheimer et al.)

3B. Notable Protocols & Publications

RTOG 0912: A Randomized Phase II Study of Concurrent Intensity Modulated Radiation Therapy (IMRT), Paclitaxel and Pazopanib (NSC 737754)/Placebo, for The Treatment of Anaplastic Thyroid Cancer

Grundmann O, Mitchell GC, Limesand KH. Sensitivity of Salivary Glands to Radiation: from Animal Models to Therapies. Journal of Dental Research,2009; 88(10):894-903.

Terhaard CH,et al. The role of radiotherapy in the treatment of malignant salivary gland tumors. Int J Radiat Oncol Biol Phys, 2005 Jan 1;61(1):103-11

Murdoch-Kinch C-A, Kim HM, Vineberg KA, Ship JA, Eisbruch A. Dose-Effect Relationships for the Submandibular Salivary Glands and Implications for Their Sparing by Intensity Modulated Radiotherapy. Int J Radiat Oncol Biol Phys, 2008; 72(2):373-382. DOI:10.1016/j.ijrobp.2007.12.033.

Gensheimer et al. Submandibular gland-sparing radiation therapy for locally advanced oropharyngeal squamous cell carcinoma: patterns of failure and xerostomia outcomes. Radiation Oncology, 2014; 9:255. DOI:10.1186/s13014-014-0255-x

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