66 Gray


Last Wednesday was the last of my radiation treatments for HNSCC (head/neck squamous cell carcinoma). I got a call in the morning saying the machine had broken down and to come in the afternoon. Anything to drag this out. But now I can retire my mask and mold.

Radiation Mask and Mold
Radiation Mask and Mold

In the last seven weeks I’ve received 66 Gy (gray) of radiation in 33 doses of 2 Gy each.

One gray is the absorption of one joule of energy, in the form of ionizing radiation, divided by one kilogram of matter. The gray measures the deposited energy of radiation. The biological effects vary by the type and energy of the radiation and the organism and tissues involved.

A whole-body exposure to 5 or more gray of high-energy radiation at one time usually leads to death within 14 days. This dosage represents 375 joules for a 75 kg adult. (This is why the dose is divided into multiple treatments.) Since gray are such large amounts of radiation, medical use of radiation is typically measured in milligray (mGy).

The salivary glands and tear glands have a radiation tolerance of about 30 Gy in 2 Gy fractions, a dose which is exceeded by most radical head and neck cancer treatments, potentially causing dryness. Dry mouth (xerostomia) and dry eyes (xerophthalmia) can become irritating long-term problems and severely reduce the patient’s quality of life.

I’m pretty dry now but shouldn’t have long-term problems because of the 360-degree approach of TomoTherapy. At least that’s the theory.

Too bad I can’t blame my dry sense of humor or mental problems on radiation but the beamlets were aimed so as only to pass through the lower part of the brain.

CT Transverse Slice
CT Transverse Slice

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One thought on “66 Gray

  1. Mike, Unfortunately I know exactly what you are going through. My eyes and mouth think I’ve been living in the Sahara! Mine is from meds though. I have much empathy for you!

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