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EDITORIAL Table of Contents   
Year : 2004  |  Volume : 14  |  Issue : 2  |  Page : 123-124
CT - PET - new challenge to radiologists

Editor-in-chief, The Indian Journal of Radiology and Imaging, India

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How to cite this article:
Desai S. CT - PET - new challenge to radiologists. Indian J Radiol Imaging 2004;14:123-4

How to cite this URL:
Desai S. CT - PET - new challenge to radiologists. Indian J Radiol Imaging [serial online] 2004 [cited 2021 Mar 1];14:123-4. Available from:
Cancer is one of the leading causes of mortality and morbidity in the world. Cancer neurosis is probably more common than even cardiac neurosis amongst the population. Most of emerging new technologies aim at very early detection of cancer, the stage at which so called "complete cure" can be achieved. USG, CT and MRI provide excellent mapping of morphology and extent of the tumors. Recent advances in CT /MR perfusion, MR spectroscopy, Functional MR add certain information, even of metabolic activity. PET (Positron Emission Tomography) done with FDG gives us both qualitative and quantitative metabolic information, which is very useful for early diagnosis and follow-up. Historically US/CT/ MRI have been the domain of radiologists while SPECT, PET are managed by our nuclear medicine colleagues. Emergence of PET-CT, a unique combination of cross sectional details provided by CT and metabolic information obtained by PET, has revolutionalized cancer detection work up further, and at the same time, thrown open new issues which may lead to another turf battle.

As we know, malignant cells have characteristics of cellular metaplasia, increasing size, local invasion and distant metastasis. Malignant cells have increased glucose utilization due to upregulation of hexokinase activity. Malignant cells take up glucose, Glycolysis of this results into end products, either pyruvate in aerobic conditions or lactate under hypoxic conditions (necrotic tumour) FDG is analog of glucose and hence taken up by active tumor cells.

Tumors with higher metabolic activity take up higher FDG. This helps in both localizing the tumour and evaluating tumour activity.

MR spectroscopy is highly sensitive and specific in tumour detection, as high choline peaks are seen in cellular metaplasia. Both pyruvate and lactate can be easily detected on MRS, helping to grade the tumour and assess tumor activity.

Both MR and CT perfusion studies have been useful in evaluating viable tumor tissue, which normally shows increased perfusion. CT perfusion is further beneficial as it can quantify blood volume, blood flow and tumor transit time directly. This is of great help in follow up of tumors on different therapeutic regimes.

PET has poor anatomic detail and needs correlation with other imaging tools like CT to accurately localize the lesion and to differentiate normal from abnormal tracer uptake.

PET - CT is one such solution. PET-CT has a single table with a combined gantry of CT and PET. In one single study, high resolution CT of desired organ is obtained with superimposition of PET images on underlying anatomical data, leading to unparalleled imaging acquisition. CT used in PET-CT the same high resolution CT, housed in different imaging departments, capable of doing total body scanning.

CT-PET is already well established in diagnosis, staging and follow-up of colorectal cancer, oesophageal malignancies, lymphomas, lung cancer, melanomas, breast malignancy, head and neck tumors and in characterisation of a pulmonary nodule. CT-PET has been found invaluable in accurate localization of very small areas of increased traced activity, which would have been impossible to localize on PET alone.

It has tremendous advantages of separating normal structures with high metabolic activity from abnormal high activity. CT-PET picks up other diseases in the patient, hitherto not noticed only on PET, which is important for treatment.

Undoubtedly all premier departments across the globe will eventually acquire this facility. The bone of contention would be the location of CT-PET in the hospital. Should that be housed in the radiology department or nuclear medicine department ? Who should control the daily operations on this unit ? Should he be the radiologist or nuclear physician ? Imagine a scenerio where CT-PET is housed in a nuclear medicine department, where a cardiologist will have an access, and rightly so, to CT coronary angio, chest physician will perform his own chest CT studies and so on and so forth.

Time certainly has come for radiologists to understand, take interest and study nuclear medicine, which is essentially a part of imaging. He should master it.

The challenges radiologists will face are unlimited and continuous. If we want to remain in this academic rat race, we have no other option than to master all these newer technological advances.

Correspondence Address:
Shrinivas Desai
Editor-in-chief, The Indian Journal of Radiology and Imaging
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Source of Support: None, Conflict of Interest: None

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