AN exciting era in medical imaging has started with the introduction of PET-CT. This state of the art machine combines advanced metabolic imaging with high-resolution rapid anatomic imaging.
PET has been widely accepted by oncologists worldwide in the diagnosis of malignant tumours, looking for spread of already diagnosed tumours, identifying tumour recurrence after treatment and monitoring response to chemotherapy and radiation.
All these can be done in a matter or 20-25 minutes non-invasively with maximum patient comfort. It helps an oncologist get information regarding cancer earlier than with CT or MRI because it identifies tumour at the cellular level. This makes a large difference in patient management.
For example if a patient is found to have distant spread of cancer using PET, he can avoid unnecessary surgery. Conversely, PET can downstage a patient a cancer patient may have enlarged lymph nodes or suspicious lesions on CT/MRI which on PET are shown to have no tumour. A patient can then have more aggressive curative surgery.
In cardiology, perfusion to cardiac tissue can be studied using radioisotopes such as N13 ammonia. Identifying viable tissue will guide cardiologists and cardiothoracic surgeons plan revascularisation procedures such as angioplasty/stenting or bypass surgery. Such procedures are useful only if cardiac tissue is viable.
In neurology, PET can be used to detect tumour recurrence after surgery and radiation of brain tumour. The origin of seizure can be identified in patients who do not respond to medication. Once the seizure focus is found, it can be surgically resected. PET is also useful in diagnosis in cases of patients with dementias, who present with memory loss or behavioural problems.
How does combining PET and CT in one machine help? PET does not always localise lesion precisely as it is more functional so fusing images with CT images will give the exact location and size of an abnormality. Images performed in one sitting will help fusing date accurately.
A practical application is the help it provides radiation oncologists to plan therapy. A fused image of PET and CT will help show which part of a tumour mass has active cancer. The abnormal cancer tissue alone can then be radiated and radiation to normal tissue can be avoided.
Doctors and patients should use this great technology to the maximum, as it will lead to better patient care and management.
Dr. JYOTSANA E. RAO
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