PETCT provides the referring physicians superior diagnostic information for their patients with cancer, ischemic heart disease and certain neurologic conditions. In the three decades since its development, PET has been demonstrated to be a clinically proven and safe method for imaging a variety of disorders. In recent years, the advantages of PET have been augmented by the addition of CT in the same gantry.
Hailed as the “Investigation of this century” PET CT has revolutionized the cancer care and the availability of PET CT scanners in India will especially help the oncologists of our state to provide the best cancer cure care.
Early stage cancer detection is the main aim of most of the existing diagnostic procedures in field of modern medicine. Although anatomical (structural) investigations like CT, MRI etc. are more commonly & widely performed, physiological (functional) nuclear medicine gamma camera investigations are more sensitive to detect early cancer.
The ultimate investigation to detect early cancer is PET – Positron Emitting Tomography. Simultaneously performing a CT scan & fusing these two scans – PET CT scan, further enhance PET scan’s cancer detection capability.
A PET scan is performed by injecting minute amounts of a radioactive substance i.e. 18 F Fluoro Deoxy Glucose (18F FDG) which has a structural & functional similarity to glucose - the substrate of any living cell. It is a phenomenon that cancerous cells concentrate, utilize more glucose thereby they show increased concentration of 18FDG. While even the smallest cancer focus is detected by a PET study, the simultaneously acquired CT scan helps to localize precisely to a particular organ (like lung tissue, Lymph nodes, Bones etc).
PET CT is a whole-body imaging procedure, clinically proven, cost-effective and safe method used in the staging, follow-up for most cancers, including lymphomas, lung, colorectal, gynaecological, Head, Neck and breast cancers etc. It is also used to evaluate treatment response to various chemotherapy regimes & radiotherapy in cancer patients. PET CT scan also has immense potential in the Radiotherapy planning of a patient.
The PET scan is different from an x-ray or CT image in that it looks at the body’s metabolic activity and provides important information about the body’s internal physiology. Almost all diseases alter the body’s biological processes. PET is able to discover these changes in their earliest stages, often before any symptoms appear. With this information on early developing cancers, effective treatment plans can be initiated sooner. PET can sometimes eliminate the need for other invasive procedures and, by correctly staging cancers, may prevent unnecessary surgical procedures. Cancer cells have higher metabolic rates than normal cells, and show up as denser areas on a PET scan, which are overlayed on CT and to differentiate easily, are highlighted by different colour codes.
Unlike the PET, the CT scan very accurately evaluates anatomy. By combining these studies, physicians can take advantage of the strengths of both modalities. Before the scan begins, a radiopharmaceutical (tracer), which is comprised of a radiolabeled form of glucose, is injected into the patient. The patient then waits about an hour for the tracer to distribute within the body.
HOW DOES PET CT WORK ?
An injected patient is placed on a table that moves into the scanner and first undergoes a very fast CT scan. This takes less than a minute in most circumstances. The table then moves the patient into the PET scanning portion of the camera. The PET scanner consists of hundreds of radiation detectors that surround the patient. Using the emissions given off by the injected radionuclide, the PET scanner measures the amount of metabolic activity at a site in the body and a computer reassembles the signals into three-dimensional images of tissue function. The PET scan portion of the exam takes a little more than 15 minutes. The entire exam lasts for about 20 minutes in most patients.
PET CT INDICATIONS:
PET/CT is particularly effective in identifying whether cancer is present or not, if it has spread, if it is responding to treatment, and if a person is cancer free after treatment. Cancers for which PET/CT is considered particularly effective include lung, head and neck, colorectal, esophageal, lymphoma, melanoma and breast, as well as a variety of other tumors.
Because PET/CT images biochemical activity, it can accurately characterize some tumors as benign or malignant, thereby avoiding surgical biopsy when the PET/CT scan is negative. Conversely, because a PET/CT scan images the entire body, confirmation of distant metastases can alter treatment plans, in certain cases, from surgical intervention to chemotherapy. PET/CT is extremely sensitive in determining the full extent of disease, especially in lymphoma, malignant melanoma, breast, lung and colon cancers. Confirmation of the presence or absence of metastatic disease allows the physician to more effectively decide how to proceed with the patient’s management.
Checking for Recurrences
PET/CT is currently considered to be the most accurate diagnostic procedure to differentiate tumor recurrences from radiation necrosis or post-surgical changes in many types of cancer. Such an approach allows for the development of a more rational treatment plan for the patient.
Assessing the Effectiveness of Chemotherapy
The level of tumor metabolism is compared on PET/CT scans taken before and after a chemotherapy cycle. PET/CT can provide important information about the effectiveness of a chemotherapy treatment plan. Treatment regime can be altered or modified according to the PET CT scan evidence of treatment response.
PET/CT’s ability to measure metabolism has significant implications in localizing the site or origin of epilepsy, because it can vividly illustrate areas where brain activity differs from the normal. PET/CT can also be used to differentiate Alzheimer’s disease from other causes of dementia in cases where the clinical picture is atypical.
By measuring both perfusion and metabolic activity within the heart, PET/CT scans can pinpoint areas of decreased blood flow such as that caused by artery blockages and can differentiate infracted non viable myocardium from viable one. This information is particularly important in patients who have had previous myocardial infarction and who are being considered for a revascularization procedure.
NUCLEAR MEDICINE SERVICES:
The Department of Nuclear Medicine comprises diagnostic and therapeutic services. You may contact your nearest service provider for the range of nuclear medicine and PET-CT services. Cases need to be scheduled and certain procedures may need patient preparation. Services usually include oncologic, neurologic, nephro-urology, endocrinology and cardiac imaging. Please find below the entire list of procedures that are usually available.
GAMMA CAMERA PROCEDURES:
||Thyrotoxicosis, Graves disease, Toxic MNG, Thyroiditis, Thyroid nodule evaluation, Lingual thyroid etc
||To assess parathyroid adenoma, hyperplasia, ectopic parathyroid adenomas
||MYOCARDIAL PERFUSION / THALLIUM SCAN
||Tc MIBI, Tetrofosmin, Thallium
||To evaluate IHD, physiological significance of known coronary stenosis, Coronary artery disease, False positive TMT, Baseline ECG changes like LBBB, Risk stratification of CAD, Presurgical cardiac evaluation, To assess myocardial viability before CABG, prior to surgery for congenital heart disease, follow-up of Kawasaki disease
||Tc RBC LABELLING
||To evaluate accurate LVEF, regional wall motion abnormalities in CAD, patients with obesity, COPD, Prior to adriamycin and other cardiotoxic drug therapy
||Tc DTPA, EC
||To assess GFR of individual kidneys esp. in donors, Neonatal hydronephrosis, PUJ Obstructions, obstructed megaureter. Relative function evaluation in patients with renal malignancy prior to nephrectomy, non visualized / ectopic kidneys, post renal transplant evaluations
||To assess UTI (Renal scars), Ectopic kidneys, accurate function assessment of individual kidneys
||DIRECT / INDIRECT RADIONUCLIDE MCU SCAN
||To assess VU reflux, UTI, Hydroureteronephrosis
||WHOLE BODY BONE SCAN
||To evaluate skeletal mets, bone malignancy, low backache, Tuberculosis of bone, Avascular necrosis, Metabolic bone disease, Stress fracture, Osteomyelitis versus cellulitis.
||Assessment of prosthetic infections, evaluation of lymphoma (Hodgkin’s & non Hodgkin’s), Fever of unknown origin
||LUNG PERFUSION & VENTILATION
||Tc MAA , Tc DTPA AEROSOL
||Pulmonary embolism, Lung vascularity assessment in children with congenital heart disease, Predict FEV1 in pts planned for pneumonectomy / lobectomy
||SULPHUR COLLOID, PHYTATE
||Alcoholic hepatitis, Cirrhosis, Portal hypertension, Hemangioma, Jaundice, Budd chiari syndrome
||Differentiate Neonatal hepatitis vs biliary atresia, Postop bile leak, Choledochol cyst, post Liver transplant cases, Gall bladder dyskinesia, acute / chronic cholecystitis.
||Evaluation of meckels diverticulum (Ectopic gastric mucosa), Malena, GI bleed
||GASTRO INTESTINAL BLEEDING
||To evaluate occult GI bleed and localize the site of bleed
||SULPHUR COLLOID, DTPA
||GASTRO ESOPHAGEAL REFLUX
||Recurrent respiratory infections, Heart burns
||To evaluate testicular torsion, epididymo - orchitis
||To evaluate Tear duct patency
PET - CT PROCEDURES:
||WHOLE BODY FDG PET CT SCAN
||18F-FDG ( Fluorodeoxyglucose)
||1. Oncological evaluation for all cancers –(staging, restaging, follow-up) Brain tumor relapse, Head and neck cancer, Ca of Unknown Primary, Thyroid carcinoma, Esophageal carcinoma, Lung cancer, Colorectal carcinomas, Breast cancer, Gynecological cancers, Musculoskeletal tumors, Malignant melanoma, Prostate Carcinoma, Malignant lymphomas, Neuroendocrine tumors
2. To assess RT / Chemo response,
3. For Radiotherapy treatment planning.
4.To evaluate solitary pulmonary nodule (benign vs malignant),
5.Myocardial viability & ischemia evaluation,
6.To evaluate brain tumour, stroke, epilepsy.
||WHOLE BODY PSMA PET CT SCAN
||Gallium PSMA PETCT)
||Highly sensitive and specific investigation for Prostate cancers – staging, response assessment, recurrence evaluation
||WHOLE BODY GALLIUM DOTA PET CT SCAN
||Gallium DOTA PETCT
||In the evaluation of neuroendocrine tumours
THERAPY PROCEDURES :
|LOW DOSE I131 THERAPY
||Treatment of thyrotoxicosis – Graves disease, Toxic MNG, ATN as an outpatient
|HIGH DOSE I131 THERAPY
||Treatment of Differentiated thyroid Ca & metastases.
||STRONTIUM CHLORIDE, SAMARIUM
||Palliative bone pain therapy for cancer patients
||I 131 MIBG
||Malignant Pheochromocytoma, Neuroblastoma
||Treatment of Hepatocellular cancer & mets
|LUTETITUM THERAPY FOR NEUROENDOCRINE TUMOURS
||Lu 177 DOTA THERAPY
||Treatment of Neuroendocrine tumours and metastases
|LUTETIUM PSMA THERAPY
||Lu 177 PSMA THERAPY
||Treatment of metastases from Prostatic cancer
|RADIUM 223 CHLORIDE THERAPY
||Ra 223 ALPHA THERAPY
||Curative therapy for Prostate carcinoma