What is Nuclear Medicine (NM)?

Nuclear Medicine is a specialty which uses very small amount of radiopharmaceuticals to diagnose or treat disease(s). Radiopharmaceuticals are called ‘Magic Bullets’ that are attracted to specific organs, bones, or tissues. A gamma camera is used to detect the gamma rays that are emitted by the radiopharmaceuticals. These cameras work in conjunction with computers to transform such emissions into images and data which provide information about the area of the body being imaged. SPECT/CT scanner incorporates CT imaging technique and gamma camera to provide additional anatomical information in an NM image.

NM • Preparation & Procedure

Preparation & Procedure vary in different examination. Please contact our staff for details.


Below information applies to examination of Myocardial Perfusion Scan only.


General Information 

  1. Female patient should not be pregnant.
  2. Stop medication according to your doctor’s instruction.
  3. Stop food and beverages containing caffeine (coffee, tea, etc.) for at least 12 hours before the exam.
  4. Patients taking long-acting aminophylline should discontinue its use for 48-72 hours before the exam. (Patients taking pentoxifylline [Trental] do not need to discontinue the medication.)
  5. Fasting for 4 hours before exam (except water).
  6. The whole process of the exam takes about 4-6 hours.

Information for female of childbearing age 

  1. Please inform your doctor and our staff when making appointment if you are/may be pregnant or if you are breast-feeding before the exam.
  2. The date of your last menstrual period (LMP) will be asked for our record.

Information for infants / children (who require medication for sedation) 

  1. Wake them up early on the day of exam.
  2. Please keep them awake 4 hours before exam.
  3. Fasting for 4 hours (except water) before exam (skipping 1 meal for infants).

Information for patients under the age of 18

  1. Need to be accompanied by parent or legal guardian for examination.
  2. The written consent form must be signed by parent or legal guardian.
  3. Please bring patient’s birth certificate or relevant identification document for registration.


  1. Arrive at Scanning Department at appointment schedule.
  2. Present the following documents to Front Desk for registration.
    • Doctor’s referral letter
    • Appointment Sheet (if any)
    • Identification document, e.g. HKID card
    • Previous imaging reports, DVDs and films (except those examinations completed in Scanning Department)


  1. Meet our nurse / radiographer to review medical history and explain procedures.
  2. Get changed into hospital gown and take off all personal possessions (e.g. watches, jewellery, hairpins, mobile phones, etc.).
  3. Prepare injection site.


  1. Inject radioactive isotope.
  2. Rest in uptake room for 30-60 mins for isotope uptakes before the first scan starts.
  3. Entire scanning procedure is conducted by our well-trained radiographers.
  4. Lie on the scanner table and stay still throughout the exam.
  5. The table carries you slowly into the scanner gantry.
  6. Intercom system and call bell are available for communication.
  7. It takes about 15-20 mins for this resting scan.


  1. The test will be either an exercise test on a treadmill; or pharmaceutical stress test.


  1. Second injection of radioactive isotope.
  2. Rest in uptake room for 30-60 mins for isotope uptakes before the second scan starts.
  3. Repeat the procedures of the first scan – Resting Scan.
  4. It takes about 15-20 mins for this stress scan.


  1. Stay for about 20 mins for any adverse reactions.
  2. Resume your usual diet and activities thereafter unless your doctor advises you differently.


  1. Our radiologists interpret the images and issue an imaging report to your referring doctor.
  2. Your referring doctor explains the findings and diagnosis to you.


Q: Are there any side effects after a Nuclear Medicine examination?

A: Nuclear Medicine examinations involve injection of radioactive isotope. The radiation dose is small and will not affect your body function or cause discomfort during the procedure. Besides, the residual radiation inside your body will diminish through natural half-life decay. You will be encouraged to drink plenty of water after the examination to facilitate the excretion of radioactivity. You can get rid of radiation usually within a few hours. You can then resume all daily activities. Avoidance of unnecessary contact with pregnant women and infants on the day of examination is suggested.

Q: Can I have NM scan if I am PREGNANT?

A: Pregnancy is relatively contraindicated. Please consult our staff if you are pregnant or may be pregnant.

Q: Can I have NM scan if I am BREAST-FEEDING?

A: Breast-feeding mother may be requested to stop breast-feeding within 48 hours after the examination. Please consult our staff for the precautions of different studies.

Q: Do I need to provide a requisition form from my doctor for NM scan?

A: Yes, a requisition form signed by your doctor will provide us with your necessary clinical information; and we will tailor the examination accordingly.

Q: Why do you need my previous X-Ray, CT, MRI and other imaging scans?

A: The more information that our radiologist has when he reviews your study, the more specific the interpretation will be. Correlations with other studies are often helpful.

Q: How will I get the NM examination results?

A: After the NM examination, our radiologist will interpret your scan and issue an imaging report to your doctor who will then explain the findings and diagnosis to you.