lung nodule size

On a recent cat scan a lung nodule was found to be approx.  1cm.  The sr recommended follow up with a PET scan- howver the insurance company won't aporve it until the nodule is larger.
At what size is a PET scan useful?  At what size is it warranted?  If I get the PET scan now at 1cm will it be useful and able to give more information?

[Kamal S Saini, MD, MRCP (UK), DM]

A CT (Computerized Tomography) scan picks up anatomical and morphological details of a lesion.
A PET (Positron Emmision Tomography) scan detects the presence of metabolic activity of a lesion.
If a lesion is too small, a PET scan may not pick it up as the level of metabolism is too low. Also, some non-cancer lesions may also be metabolically active, leading to a "false-positive" PET scan.
The exact size of lesion above which PET can give a definitely useful information is not clearly defined.
You may like to read the article (containing medical jargon!) titled: "The Role of PET Scan in Diagnosis, Staging, and Management of Non-Small Cell Lung Cancer " at http://theoncologist.alphamedpress.org/cgi/content/full/9/6/633

[Giveypup]

Pay for your PET scan and fight with the insurance company, later.  This is your life, you are posting about, and earlier findings of Lung CA correlate with greater survival.

[BhumikaMD]

Hi,

'Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) imaging have been approved for use in the United States for evaluating pulmonary nodules.

Malignant cells have a higher metabolic rate than normal cells; therefore, glucose uptake is higher. Thoracic PET imaging uses the isotope fluorine-18 bound to a glucose analog to make fluorine-18-fluorodeoxyglucose (FDG). Increased FDG uptake is seen in most malignant tumors and is the basis of the PET study used to differentiate malignant from benign nodules.

FDG uptake can be quantified using the standardized uptake ratio (SUR) to normalize measurements for a patient's weight and injected dose of radioisotope. This allows comparison of uptake between different lesions and patients. SURs greater than 2.5 have been used by some as a marker of malignancy.'

You could read more about the condition at the following link -

http://www.emedicine.com/RADIO/topic782.htm

Regards.