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What is PET CT?

Clinical Indications

Cardiac applications

Neuropsychiatric applications


Patient preparation/instructions

The procedure

After Care

What is PET/CT?

PET is a tomographic scintigraphic technique in which a computer-generated image of local radioactive tracer distribution in tissues is produced through the detection of annihilation photons that are emitted when radionuclides introduced into the body decay and release positrons.


PET is a tomographic imaging technique that uses a radiolabeled analog of glucose, 18F-FDG, to image relative glucose use rates in various tissues. Because glucose use is increased in many malignancies, PET is a sensitive method for detecting, staging, and monitoring the effects of therapy of many malignancies.


CT is a tomographic imaging technique that uses an x-ray beam to produce anatomic images. This anatomic information is used to detect and to help determine the location and extent of malignancies. Combined PET/CT devices provide both the metabolic information from PET and the anatomic information from CT in a single examination.


As shown in some clinical scenarios, the information obtained by PET/CT appears to be more accurate in evaluating patients with known or suspected malignancies than does the information obtained from either PET or CT alone or the results obtained from PET and CT separately but interpreted side by side. PET and CT are proven diagnostic procedures.


Although techniques for registration and fusion of images obtained from separate PET and CT scanners have been available for several years, the readily apparent and documented advantages of having PET and CT in a single device have resulted in the rapid dissemination of this technology in the United States.

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Clinical Indications:

  • Oncology Applications

    • Distinguishing benign from malignant disease

    • Establishing the grade of malignancy e.g. brain, soft tissue tumours

    • Establishing the stage of disease e.g. lung cancer, lymphoma etc.

    • Establishing whether there is recurrent or residual disease e.g. lymphoma,teratoma, seminoma, etc

    • Establishing the site of disease in the face of rising tumour markers e.g. colorectal, germ cell tumours etc.

    • Establishing the response to therapy pre, during & post therapy.

    • Identifying the primary site of a tumour for biopsy (either when site is unknown but clinical indications are strongly pointing to a tumour e.g. paraneoplastic syndrome) or therapeutic purposes.

    • Identifying the site to biopsy within a large tumour

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  • Brain and Spinal cord

    • Suspected tumour recurrence when anatomical imaging is difficult or equivocal and management will be affected.

    • Benign versus malignant lesions, where there is uncertainty on anatomical imaging and a relative contraindication to biopsy.

    • Identifying the grade of brain malignancy Investigation of the extent of tumour within the brain or spinal cord

    • Secondary tumours in the brain to identify primary site

    • Assess tumour response to therapy.

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  • Malignancies of oropharyx and larynx

    • Identify tumour recurrence in previously treated carcinoma

    • Identify extent of the primary disease

    • Preoperative staging of known oropharyngeal tumours with equivocal findings on other imaging or where clinical examination difficult e.g. trismus

    • Search for primary with nodal metastases.

    • Staging known laryngeal tumours with equivocal findings on other imaging

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  • Parotid gland

    • Indicated

      • Identification of metastatic disease in the neck from a diagnosed malignancy

    • Not indicated

      • Differentiation of Sjogrens Syndrome from malignancy in the salivary glands.

      • Primary tumour of the parotid to distinguish benign from malignant disease.

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  • Thyroid

    • Indicated

      • Assessment of patients with elevated thyroglobulin and negative iodine scans for recurrent disease

      • Assessment of tumour recurrence or suspected tumour recurrence in medullary carcinoma of the thyroid

    • Not indicated

      • Routine assessment of thyroglobulin positive recurrence with radioiodine uptake

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  • Lung

    • Differentiation of benign versus malignant lesions where anatomical imaging or biopsy are inconclusive or there is a relative contraindication to biopsy.

    • Preoperative staging of non small cell lung cancer.

    • Staging of lung cancer prior to radical radiotherapy

    • Assessment of recurrent disease in previously treated areas where anatomical imaging is unhelpful.

    • Assessment of response to treatment.

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  • Pancreas

    • Indicated

      • Staging a known primary.

    • Not indicated

      • Differentiation of chronic pancreatitis from pancreatic carcinoma

      • Assessment of pancreatic masses to determine benign or malignant status

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  • Malignancies of the GIT

    • Indicated

      • Staging of primary cancer

      • Assessment of disease recurrence in previously treated cancers

      • Assessment of neoadjuvant chemotherapy

      • Assessment of gastro-oesophageal malignancy and local metastases

      • Proven small bowel lymphoma to assess extent of disease

      • Prior to metastectomy for colorectal cancer

    • Not indicated

      • Assessment of polyps

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  • Breast Cancer

    • Indicated

      • Assessment and localisation of brachial plexus lesions in breast cancer

      • Assessment of the extent of recurrent or disseminated breast cancer

      • Axillary node status (breast cancer) especially where there is a relative contraindication to axillary dissection.

      • Assessment of multifocal disease within the difficult breast

      • Assessment of chemotherapy response

    • Not indicated

      • Routine assessment of primary breast cancer.

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  • Liver

    • Indicated

      • Equivocal diagnostic imaging (CT,MRI, Ultrasound) in secondaries

      • Assessment pre and post therapy intervention in secondaries

      • Exclude other metastatic disease prior to metastectomy

    • Not indicated

      • Routine assessment of hepatoma

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  • Renal and adrenal

    • Indicated

      • Assessment of possible adrenal metastases

    • Not indicated routinely (but may be helpful)

      • Paraganglionomas or metastatic phaeochromocytoma to identify sites of disease

      • Screening of family members of patients with genetic disorder predisposing to development of paraganglioma

      • Assessment of renal carcinoma at staging where equivocal findings on other imaging but note ~ 30% of tumours may be non-FDG avid

      • Assessment of metastatic renal carcinoma in difficult management situations

    • Not indicated

      • Phaeochromocytoma MIBG scanning is usually first choice

      • Malignant neuroendocrine tumours Ga-68 somatostatin receptor labeled compounds

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  • Bladder and Prostate

    • Not indicated FDG in prostate cancer assessment may be helpful in equivocal imaging

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  • Testicle

    • Assessment of recurrent disease from seminomas and teratomas.

    • Assessment of residual masses

    • Assessment of primary tumour staging with equivocal findings on other imaging

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  • Ovaries and Uterus

    • Indicated

      • In difficult management situations to assess local and distant spread Uterus: Cervix

      • Primary staging of cervix to assess equivocal lymph node status

      • Assessment of extent of recurrent disease prior to pelvic exenteration

    • Not indicated

      • Cancer body of the uterus

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  • Metastasis of Unknown origin

    • Indicated

      • Determining the site of an unknown primary when this influences management

    • Not indicated

      • Widespread metastatic disease when the determination of the site is only of interest

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  • Lymphoma

    • Staging of Hodgkins lymphoma.

    • Staging of NonHodgkins lymphoma

    • Assessment of residual masses for active disease

    • Response to chemotherapy Identification of disease sites when there is suspicion of relapse from clinical assessment.

    • Pre-transplant assessment

    • Assessment of bowel lymphoma

    • Assessment of bone marrow to guide biopsy  

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  • Skin tumours

    • Indicated

      • Malignant melanoma to assess extent of disease

      • Malignant melanoma in whom a sentinel node biopsy was not or can not be performed in stage II.

      • To exclude systemic involvement in skin lymphomas

      • To exclude primary malignancy in skin conditions that may be paraneoplastic phenomema eg dermatomyositis

    • Not indicated

      • Malignant melanoma with negative sentinel node

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  • Musculoskeletal tumours

    • Soft tissue primary mass assessment to distinguish high grade malignancy from low or benign disease

    • Soft tissue mass biopsy site to direct biopsy to most malignant area

    • Staging of primary soft tissue malignancy to assess metastases

    • Assessment of recurrent abnormalities in operative sites

    • Assessment of osteogenic sarcomas for metastatic disease

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Cardiac applications

  • Indicated

    • Diagnosis of hibernating myocardium in patients with poor left ventricular function prior to revascularisation procedure.

    • Patients with a fixed SPECT deficit who might benefit from revascularisation.

    • Prior to referral for cardiac transplantation.

    • Diagnosis of coronary artery disease or assessment of known coronary stenosis where other investigations (SPECT, ECG etc.) remain equivocal.

    • Differential diagnosis of cardiomyopathy (ischaemic versus other types of dilated cardiomyopathy).

  • Not indicated

    • Patients with confirmed coronary artery disease in whom revascularisation is not contemplated or indicated.

    • Routine screening for coronary artery disease

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Neuropsychiatric applications

  • Indicated

    • Presurgical evaluation of epilepsy.

    • Suspected recurrence or failed primary treatment of primary malignant brain tumours.

    • Early diagnosis of dementia, (especially younger patients)

    • Differential diagnosis of dementia.

    • Localisation of optimal biopsy site. Differentiating malignancy from infection in HIV subjects

  • Not indicated

    • Diagnosis of dementia where MRI is clearly abnormal.

    • Most instances of stroke.

    • Most psychiatric disorders other than early dementia.

    • Pre-symptomatic or at risk Huntingdons disease.

    • Diagnosis of epilepsy

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Please call our hotline 16171 or (202) 3336-3310 (Mohandeseen), (202) 2417 5556 (Heliopolis) or (202) 2528 4888 (Maadi) to speak with a radiologist if you have any questions. It is best to call between 10 a.m. and 10 p.m., Saturday through Thursday.


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Last modified: 17-06-2009