Nuclear Medicine
Nuclear Medicine
1. What is Nuclear Medicine?
Nuclear Medicine is a speciality where small quantities of radiopharmaceuticals are administered to the patients for various diagnostic and therapeutic applications. It is broadly divided into “Diagnostic Nuclear Medicine” and “Therapeutic Nuclear Medicine”.
2. What is Diagnostic Nuclear Medicine?
In diagnostic nuclear medicine, small or trace amounts of radiopharmaceutical is administered to the patient for diagnosing abnormalities in the organ or tissues of the body. It provides functional information and detects abnormalities at an early stage of the disease and often much before it can be identified by conventional diagnostic procedures. Early detection of disease makes it possible to treat disease sooner and thereby permitting a favourable outcome
3. What is Therapeutic Nuclear Medicine?
In therapeutic nuclear medicine, radiopharmaceuticals are administered either for curing the disease (e.g. Graves disease and differentiated thyroid cancer treatment where I131 – sodium iodide is used) or for palliative treatment (e.g. to relieve pain from bone metastases where P32-orthophosphate, Sm153 EDTMP, 89Sr-chloride are used).
4. What is a PET scan?
Positron Emission Tomography (PET) is diagnostic imaging modality where positron emitting radiopharmaceuticals are used. It is used to obtain functional information and is widely used in oncology, neurology, cardiology, infection and inflammation imaging.
5. How a PET scan different from CT or MRI scan?
PET scans provide information on metabolic changes at cellular level which cannot be obtain by other imaging tests like CT scan or MRI. Since, disease process often begin with functional changes at the cellular level, a PET scan can often detect the disease in early stages and much before they become evident on CT or MRI scan.
6. What is a PET-CT scan?
When a CT scan is performed along with a PET scan as a part of the same diagnostic work up, it is termed as PET-CT scan. It uniquely combines the functional information provided by the PET scan with the morphological information obtained from CT scan. This increases the ability to detect disease more accurately when compared to PET and CT alone.
7. How does a PET-CT scan help my doctor?
A PET-CT scan helps your doctor in accurate staging (know the extent of spread of disease), assess effectiveness of a treatment regimen, guide biopsy, plan radiotherapy, modify treatment assess disease progression and detect disease recurrence.
8. Which radiotracers are used for PET imaging?
The most widely used PET tracers in India are 18F –Fluoro deoxy glucose (18 F-FDG) & 18F Sodium Fluoride (18F-NaF), 18F- Prostate specific membrane antigen (18 F-PSMA) & 68 Ga-DOTATATE..
18F-Fluorodeoxyglucose (FDG) is similar to glucose with subtle structural differences. The FDG (unlike glucose) gets trapped in the abnormal cells due to these differences. This ‘metabolic trapping’ of 18F-FDG forms the basis of 18F-FDG PET-CT scan.
18F-Sodium Fluoride (18F-NaF) is used for imaging the skeletal system (Bone Scanning). It is incorporated in bones by binding to the hydroxyl group of the Hydroxyapatite. It gives sharper and more informative images as compared to9mTc-Methylene Di Phosphonate (MDP) bone scan done on Gamma camera.
68Ga-DOTATAE are used for imaging of Neuroendocrine tumors. It detects expression of Somatostatin receptors and thus suitability for PRRT (Peptide Receptor Radinuclide Therapy)
9. Are patients required to get admitted for PET-CT scanning?
No! The patients are not required to get admitted for PET-CT scan. The procedure takes approximately 4 hours from the time of arrival till the end of study
10. What are prerequisites for a 18F-FDG PET-CT scan?
Patient should be fasting for at least 6 hrs prior to the scheduled time of appointment. Patient should refrain from any intense and strenuous physical activity or exercise for 24 hours before the scan appointment. No antidiabetic medicines are to be taken on the day of the scan. No dextrose containing intravenous fluids are to be administered for atleast 4-6 hrs prior to the scan. A recent Serum Creatinine report would also be required.
11. How is a PET-CT scan performed?
A detailed history pertaining to the illness and information relevant to the scan is noted by the doctor and all your previous medical records and reports are reviewed. After obtaining consent, the radiopharmaceutical (PET dye) would be administered. After injection, the patient is asked to rest in a dedicated waiting area for about an hour. The patient is asked to drink oral contrast during this period. No attendants or relatives are permitted to stay with the patient. The patient is advised to stay calm, restrict physical movements and avoid talking to others. The patient is asked to void (pass urine) before starting the scanning procedure. The patient is asked to lie down on the bed of the PET-CT scanner and is expected to remain still during the entire scanning period of 15-20 minutes. After the scanning is completed, the patient is permitted to eat and may carry out routine activities. However, it is advisable to avoid prolonged contact with infants, small children and pregnant women for at least 6-8 hrs after the scan.
12. Does PET-CT scan cause any allergic reactions?
The radiotracers used for PET scan are absolutely safe and have no reported allergic reactions.
The CT scan done as a part of PET-CT procedure may be performed with or without injection of a contrast agent. Contrast agents are usually given to extract more information from the study which may not be possible to obtain from a plain CT scan. These contrast agents are known to cause allergic reactions in few patients as seen with any other contrast enhanced CT procedure. The routinely used non-ionic contrast media are safe. However, in very few cases some side effects may be noticed.
13. Can a pregnant lady undergo a PET-CT scan?
No! As a general rule PET-CT scans are not carried out on pregnant women. However, if the referring doctor is of the opinion that performing this scan during pregnancy is justified, PET-CT scan can be considered on a risk-benefit basis.
14. Can a breast-feeding mother undergo a PET-CT scan?
Yes! However, it is recommended that you do not breast-feed your baby for 6-8 hours after the scan has been performed. It is advisable to collect milk before the scan, so that this can be used to provide a feed.
15. How long does it take to get a PET-CT scan report?
A PET-CT report is usually available in a maximum 2 -3 hours.