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Imaging (MRI, PET, CT scans, X rays & ultrasound) in head & neck cancer

Imaging techniques include Magnetic Resonance Imaging (MRI), Positron Emission Tomography (PET) scan, Computed Tomography (CT) scan, plain X rays, and ultrasound.  All are non-invasive medical imaging procedures that enable the visualization of internal body structures. They are also used to detect cancer and follow up its progression and response to therapy.

Magnetic Resonance Imaging (MRI)

MRI can be used for cancer diagnosis, staging, and treatment planning. The main component of most MRI systems is a large tube-shaped or cylindrical magnet.  Using non-ionizing radio frequency waves, powerful magnets, and a computer, this technology produces detailed, cross-sectional pictures of the inside of the body. In some cases, contrast dyes are used to illuminate certain structures in the body. These dyes may be injected directly into the bloodstream with a needle and syringe or they may be swallowed, depending on the area of the body being studied. With MRI, it is possible to distinguish between normal and diseased tissue and precisely pinpoint tumors within the body. It is also useful in detecting metastases.

MRI of the head and neck

Additionally, the MRI provides greater contrast between the different soft tissues of the body than a CT scan. Thus, it is especially useful for imaging the brain, connective tissue, spine, muscles, and the inside of bones. To perform the scan the patient lies within a large device that creates magnetic field that aligns the magnetization of atomic nuclei in the body.  

MRI tests are painless and there is no radiation involved. It takes much longer than a CT scan and is more expensive. Some patients report feelings of mild to severe anxiety and/or restlessness during the test.  A mild sedative before the test can be administered to those who are claustrophobic or find it difficult to lie still for long periods of time. MRI machines produce loud banging, thumping, and humming sounds. Wearing earplugs can reduce the effect of noise.

Computed Tomography (CT ) scan
CT scan is a medical imaging procedure that utilizes computer-processed series of X-rays to generate detailed tomographic images or 'cuts' of specific areas of the patient’s body. These cross-sectional images are used for diagnostic and therapeutic purposes in many medical disciplines. Digital geometry computerized processing is utilized to generate a three-dimensional image of the inside of a body site or organ from a large number of two-dimensional X-ray images taken around a single axis of rotation. Contrast dyes can be used to illuminate certain structures in the body. It is a quick test, but exposes the patient to radiation. Also dental work and movement during the procedure can distort the images.

                             CT  of the head and neck showing a cystic lesion


Positron Emission Tomography (PET) scan

PET scan is a nuclear medicine imaging test that creates a three-dimensional image or picture of the functional metabolic processes in the body.  It uses a radioactive substance called a "tracer" that is administered through a vein to look for disease in the body. The tracer travels through the blood and collects in organs and tissues with high metabolic activity. A single PET scan can accurately image the cellular function of the entire human body.

Since a PET scan detects increased metabolic activity of any cause, such as cancer, infection, or inflammation, it is not specific enough and therefore cannot differentiate between them. This can lead to equivocal interpretation of the results and may create uncertainty that can lead to further tests which may not be needed. In additional to the financial burden this can cause, it may generate anxiety and frustration.

It is also important to realize that these tests are not perfect and can miss a small tumor (less than one inch). A thorough physical examination should also accompany any scanning procedure.

PET and CT scans are often done in the same session and are performed by the same machine. While the PET scan demonstrates the biological function of the body, the CT scan provides information with respect to the location of any increased metabolic activity. By combining these two scanning technologies, a physician can more accurately diagnose and identify existing cancer.

The general recommendation is to perform fewer PET/CT scans the longer the elapsed time from the surgery that removed the cancer. Generally, PET/CT is performed every three to six months during the first year, then every six months during the second and then yearly throughout the fifth year. Some patients are followed yearly throughout life with PET/CT, and others undergo them if recurrence or a new malignancy is suspected. These recommendations, however, are not based on studies and are merely the opinion or consensus among the specialists. More scans are performed if there are concerns or suspicious findings. When scheduling a PET and/or CT scan any potential benefit gained by the information should be weighed against any potential deleterious effects of exposure to ionizing radiation and or X rays.

Normal Pet Scan 

Sometimes physicians do not need a PET scan and only request a CT dedicated to the area in question. Such a CT is more precise compared to a combined PET/CT; the former can also include the injection of contrast material to assist in the diagnosis of the problem.

PET scan showing abnormal lymph nodes

On occasion CT is not helpful, especially in those who had extensive dental work, including filings, crowns or implants that can interfere with the interpretation of the data. Not performing a CT spares the patient from receiving a substantial amount of radiation. Instead an MRI of the area can be done.

CT/PET showing left lesion in the left floor of the mouth and a spread to the lymph glands

When viewing the scans, radiologists compare the new scan(s) with the old ones to determine if there have been any changes. This can be useful in determining if there is new pathology.

A PAT/CT scanning machine

Plain X-rays 

X-radiation is an electromagnetic radiation produced by an X-ray tube. Plain X-rays radiography is an X-ray image generated by placing a body part in front of an X-ray detector and illuminating it with a short X-ray exposure. It is an inexpensive and easy method to evaluate the size of the heart and detect lung anomalies including cancer spread.

                                      Normal plain chest X rays radiography 


An ultrasound machine generates images that enables the examination of various body parts. The machine produces high-frequency sound waves through a hand held probe, which reflect off body structures. The handheld probe (called a transducer) is moved over the area being examined. A computer receives these reflected waves and creates a picture. There is no ionizing radiation exposure with this test. An ultrasound is a method that enables viewing vessels, structures and lymph nodes all over the body, including the neck and thyroid gland. It can also be used to obtain a biopsy of a lymph node or nodule.


                                          Ultrasound image of a neck mass

Ultrasound machine

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