FAQ
Frequently Asked Questions
General Questions
How should I prepare for an examination?

How should I prepare for an examination?

Please bring along a letter or request form from a physician requesting for the particular examination.

For easy identification, bring along your identity card or passport. This will also assist our staff in expediting the registration process. For follow-up cases, it is necessary to bring previous related scan films in order for the radiologist to compare and report the progress of the condition.

At the clinic, you may be asked to change into a gown and to remove jewellery or ornaments which may obscure the region that is being scanned.

Specific instructions for some scans:

  • Mammotome and breast biopsy:
    For these procedures, written consent is necessary. An informed consent will be taken to the clinic. If the patient is below the legal age of consent, an accompanying adult who is a legal guardian is necessary. Prior to the examination and at least one day before the appointment, the patient will be attended to by the radiologist who will describe the procedure to the patient to allay her fears.
  • CT scan:
    No preparation is required except if the referring physician requires a contrast agent to be given intravenously. In this case, no food or drink is allowed at least four hours before the appointment.
  • MRI:
    No preparation is required. Avoid makeup and mascara as they often contain metallic elements. Patients for abdomen studies and cardiac studies are required to fast for at least four hours. Patients who require sedation will also need to fast for four hours.

    Patients and children who tend to be claustrophobic may be given a sedation to help the patient go through the procedure. If this is the case, an adult may accompany the patient. An informed consent for the sedation will be required. If you have downloaded the appropriate MRI questionnaire , please bring it along with the completed form. This will save you some time at the clinic.

  • Nuclear Medicine:
    Generally, no special preparation is required for most of the tests. In a heart scan, you may be required to discontinue certain medications for a limited time prior to the test. In the case of a renal (kidney) scan, you must drink more water before the test. Generally, drinking more fluids after the procedures will help to eliminate the radiopharmaceuticals quickly from the body.
  • PET:
    • At the time of scheduling, please inform the staff about current medication you are taking and if you have diabetes, are pregnant/nursing or claustrophobic.
    • Bring along all your previous x-rays, ultrasound, CT or MRI films and any blood test reports.
    • Wear comfortable clothing.
    • Leave jewellery at home.
    • Do not eat any caloric food for at least six hours before your scan. You are encouraged to drink more water. Please avoid all drinks with caffeine and sugar.
    • Try not to smoke on the day of the scan.
    • There should be no change in your medication.
    • Diabetic patients need to regulate their blood glucose level to normal and must expect a longer stay in the department.
    • You can expect to be at the department for two to three hours. The actual scan itself takes far less time.

    Please be punctual. If you need to reschedule, notification must be given 48 hours in advance. This is because the radioactive tracer is expensive and is produced according to the number of scheduled patients.

  • Ultrasound – No Special Preparation is Necessary Except:
    • Ultrasound Gall-bladder: No food and drinks at least four hours prior to examination.
    • Ultrasound Pelvis: Patients to drink at least four to six glasses of water before arriving at the clinic. Patient is not to empty the bladder after drinking the water.
Is setting an appointment necessary?

Appointments are necessary for all scans except General Radiography (X-ray). Appointments can be made by doctor clinic by calling our call centre.

What documents do I need to bring along?

Please bring along the letter or request form from a physician requesting for the particular examination.

For easy identification, bring along your identity card or passport. This will also assist in expediting the registration process.

For follow-up cases, it is necessary to bring previous related scan films in order for the radiologist to compare and report on the progress of the condition.

How do I check on costs and fees beforehand?

Call our call centre to check about cost

Will there be any risks during radiation?

Some examinations (X-ray, CT scan, mammography, bone mineral densitometry, PET) require exposure to low doses of radiation. As technology evolves, the radiation risk from these scans is low enough without causing harmful effect. During a single x-ray exposure, a patient is exposed to about 0.06-2mSv of radiation dose. To put this into perspective, we are all exposed to approximately 3mSv of radiation dose each year from sources like the ultraviolet rays of the sun and small traces of radioactive isotopes, such as uranium found in soil.

For female patients, they will be asked to certify that they are not pregnant. If there is any possibility of pregnancy, this should be brought to the attention of the physician or radiographer or nurse attending to you.

How and when can I collect my results?

After the films have been processed, the radiologist will report on his/her findings. For urgent cases, the results will be ready for collection in an hour’s time (2 hours for CT scan, MRI, Nuclear Medicine, US, PET) after the completion of the examination at the clinic. For routine cases, the results will be dispatched to the referring physician’s clinic before your next appointment date.

Contrast Media
What is Contrast Media?

Your radiology examination may require the injection of a contrast agent.

The contrast agent is usually administered by injection into a vein through a fine needle or cannula (plastic tube). This allows your organs to be seen more clearly and will assist your doctor with your medical management.

The contrast agent is processed by the kidneys and leaves the body in your urine. For people with completely normal kidney function, the contrast is easily handled.

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General risk

The contrast agent administration is normally quite safe. However, any injection carries a slight risk of harm including injury to a nerve, artery or vein; infection; or reaction to the material being injected.

Injury to a blood vessel will result in the escape of its contents to the surrounding tissue (extravasation). This risk is estimated to be about 0.04% to 1.3%.

The other side effects / complications with injection of the contrast agent may include:

  • Occasionally, mild allergic reactions such as flushes, sneezing, hives, vomiting and dizziness. Mild nausea, which should pass within a few minutes.
  • For iodine-based contrast inject you may experience a metallic taste in the mouth, funny smell and /or hot flush in the body or pelvic region and behind the throat.
  • Rarely, more severe allergic reactions such as asthma, shock and convulsions. Emergency equipment is on hand for these rare events.
  • Death in extremely rare cases – about 1 in 250,000 to 400,000 injections (0.0004%).
  • Although less than 1% of administered dose is excreted into breast milk, patients who are breast feeding are recommended to abstain from breast feeding for 24 hours post injection and to discard breast milk after the contrast injection.

The Procedure

You may be requested to change into an x-ray gown to avoid metallic items, buttons and zippers. You will also be asked to remove jewellery, eyeglasses, and any metal objects that could obscure the image.

Once you are positioned in the required pose with the x-ray plate, you may be asked to take a deep breath and hold it or just to hold your breath and keep still. The radiographer will go to another small room or cubicle and activate the x-ray equipment which will send a beam of x-rays to the positioned area. You need to keep still as any movement will lead to an unsharp picture and an accurate diagnosis cannot be made.

When the x-rays are completed you will be asked to wait until the radiographer and radiologist examine the images to determine if more are needed.

Experience During the Procedure

This is a painless procedure. The only discomfort results from the coldness of the x-ray plate. Sometimes to get a clear image of an injury, you may be asked to hold onto an uncomfortable position for a short time. Any movement could blur the image and make it necessary to repeat the procedure to get a useful, clear picture.

Schedule of Results

The radiologist (specialist doctor) will review the image and the report will be sent to your doctor who will then discuss the scan results with you. If requested by your doctor, the films may be handed directly to you to return to your doctor.

Benefits and Risks

BENEFITS

  • X-ray imaging is useful to diagnose bone and joint injury and disease, such as fractures, infections, arthritis and cancer.
  • Because x-ray imaging is fast and easy, it is particularly useful in emergency diagnosis and treatment.
  • X-ray equipment is relatively inexpensive and widely available in physician offices, ambulatory care centers, nursing homes and other locations, making it convenient for both patients and physicians.

RISKS

  • Exposure to x-radiation. During a single x-ray exposure, a patient is exposed to about 0.06-2mSv of radiation dose. To put this into perspective, we are all exposed to approximately 3mSv of radiation dose each year from sources like the ultraviolet rays of the sun and small traces of radioactive isotopes, such as uranium found in soil.
  • Women should always inform their doctor or x-ray technologist if there is any possibility that they are pregnant.

Useful Links

Contrast Media is available at:

Radiology Department,
Gleneagles Hospital
 
6A Napier Road 
Singapore 258500 
Tel: (65) 6470 5730 
Fax: (65) 6470 5749 

Radiology Department,
Mount Elizabeth Hospital
 
3 Mount Elizabeth, Level 2 
Singapore 228510 
Tel: (65) 6731 2100 
Fax: (65) 6732 3368 

Radiology Department,
Mount Elizabeth Novena Hospital
 
38 Irrawady Road, Level 2 
Singapore 329563 
Tel: (65) 6933 1188 
Fax: (65) 6933 0526 

Radiology Department,
Parkway East Hospital
  
321 Joo Chiat Place 
Singapore 427990 
Tel: (65) 6340 8714 
Fax: (65) 6340 8670 

Radiologic Clinic,
Mount Elizabeth Medical Centre
  
3 Mount Elizabeth #01-01/02 
Mount Elizabeth Medical Centre 
Singapore 228510 
Tel: (65) 6731 2727 
Fax: (65) 6235 5279 

Radiologic Clinic,
Breast Imaging Centre
  
290 Orchard Road 
#07-04/05/06 Paragon 
Singapore 238859 
Tel: (65) 6732 1166 
Fax: (65) 6732 5933 

Radiologic Clinic,
Gleneagles 
 
6A Napier Road #02-25/26  
Gleneagles Hospital 
Singapore 258500 
Tel: (65) 6476 1151 
Fax: (65) 6471 1151
Radiologic Clinic,
Novena Medical Center
  
10 Sinaran Drive #08-02/03/04  
Novena Medical Center 
Singapore 307506 
Tel: (65) 6397 6686 
Fax: (65) 6397 6696

 

What is a Radiopharmaceutical Tracer?

Your Nuclear Medicine examination involves the administration of a small amount of a radioactive medication into you. This makes you slightly radioactive for a short time and the images are made from the ionising radiation given off (emitted) from yourself.

The radioactive medication is most commonly injected into the blood stream via a vein, but it may be given to you in many different ways such as:

  • Swallowing
  • Injection to your tissue beneath the skin
  • Injection to a shunt
  • Injection to a joint
  • Inhalation

Many different organs may be imaged depending on the type of radioactive material administered. The medication given to you is a radiopharmaceutical.

Radiopharmaceutical

The radioactive part is an unstable element (radioisotope) which gives off energy as it decays to a different element or energy state. The actual amount of the radioactive substance given for most imaging tests is usually very small.

The dose of ionising radiation received by a patient having a Nuclear Medicine test can be very low or moderate; the dose varies between different studies in a similar range to that received from CT imaging. This radioactive part is sometimes referred to as a radioactive label or a radioactive tracer. The radioactive part is most commonly Technetium 99m, but other radioisotopes such as Iodine 131, Indium 111 and Gallium 67 are also used. Fluorine 18 is an isotope used in PET (Positron Emission Tomography) studies.

What You Should Know

Your body is not able to detect this ionising radiation and it does not make you “warmer” or “glow in the dark”. The dose of ionising radiation received during a Nuclear Medicine test will not be determined by the number of images taken. It is determined from the radioactivity injected in the radiopharmaceutical, the half-life of the radioisotope and how quickly this is eliminated from the body in urine, faeces or breath. The half-life is the time taken for half of the radioactive atoms to decay or change their energy state. For most radioisotopes used in Nuclear Medicine, this half-life is measured in hours so after a day or so there is very little radioactivity remaining.

The pharmaceutical part may be a few atoms or a complex molecule which helps take the radioactive label to the part of the body being imaged in the nuclear medicine test. It is mostly the choice of the pharmaceutical part which determines where the radiopharmaceutical will go in the body and what body part or organ system will be demonstrated, e.g. Technetium 99m HDP will be used in a nuclear bone scan, but Technetium 99m MAG3 will be used in a nuclear renal scan.

Some diseases or conditions can be treated using Nuclear Medicine. In these cases, the amount of radiopharmaceutical given is much greater, and it usually goes mostly to the diseased or abnormal organ. The type of radiopharmaceutical given usually emits ionising radiation that has maximum effect on the organ that is being treated.

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SERVICE IS AVAILABLE AT:

Nuclear Medicine & P.E.T Centre
Mount Elizabeth Hospital
 
3 Mount Elizabeth, Level 1
Singapore 228510
Tel: (65) 6731 2928
Fax: (65) 6734 2928

Radiology Department,
Mount Elizabeth Novena Hospital
 
38 Irrawady Road, Level 2
Singapore 329563
Tel: (65) 6933 1188
Fax: (65) 6933 0526
Bone Mineral Densitometry
How long will the procedure take?

The examination will take about 20 to 30 minutes.

After the procedure, the radiologist will report on his/her findings. For urgent cases, the results will be ready for collection in an hour’s time at the clinic. For routine cases, the results will be dispatched to the referring physician’s clinic before your next appointment date.

Is the examination painful?

The examination is not painful. Similar with photograph taking, any movement during exposure will render the image unclear. Thus, the patient will be asked not to move during the duration of the exposure.

What are the limitations of DEXA scan?

A DEXA test cannot predict who will experience a fracture but can provide indications of a relative risk.

Despite its effectiveness as a method of measuring bone density, DEXA is of limited use in people with a spinal deformity or those who have had previous spinal or heat surgery. The presence of vertebral compression fractures or osteoarthritis may interfere with the accuracy of the test. In such instances, CT scans may be more useful.

A test done on a peripheral location, such as the wrist, may help predict the risk of fracture in the spine or hip. Since bone mass tends to vary from one location to the other, measuring the wrist is not as accurate as measuring the spine or hip.

More about Bone Mineral Densitometry

Breast Imaging Services
How long will the procedure take?

A mammogram will take about 20 to 30 minutes. If a supplementary ultrasound examination is needed, this may take an additional 20 minutes.

The breast biopsy procedure may take about 40 to 50 minutes. The patient will be required to rest in day surgery after this procedure until the surgeon deems it fit for the patient to be discharged.

After all the x-rays have been processed, the radiologist will report on his/her findings. For urgent cases, the results will be ready for collection in an hour’s time at the clinic. For routine cases, the results will be dispatched to the referring physician’s clinic before your next appointment.

Is the examination painful?

The mammography is not painful although it may feel uncomfortable because of the compression. Similar with photograph taking, any movement during exposure will render the image unclear. Thus, the patient may be asked to hold his/her breath and to keep still the entire duration of the exposure which is only about a few seconds.

For breast biopsy, a local anaesthetic will be used to lessen the pain during the procedure.

What are the limitations of mammogram?

While mammography is the best screening tool for breast cancer today, mammograms do not detect all breast cancers. Also, a small portion of mammograms indicates the presence of cancer when it is not (called a false-positive result).

Similarly, ultrasound breast examination, which is usually used as an adjunct to mammography, does not detect all lesions.

Breast implants and mammography

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Mammogram

Mammogram is a low dose x-ray of the breast used to detect early breast cancer in women. It’s also used to diagnose other breast diseases in women experiencing symptoms such as lump, pain, or nipple discharge.

The Health Promotion Board of the Ministry of Health recommends women aged 40-49 years to have regular mammograms every year and every two years for women above 50 years old.

Women who are at higher risk of developing breast cancer should consult a doctor. You may need to go for screening earlier and more frequently.

Performing a Mammogram

A specially trained female radiographer performs the mammogram.

You will be asked to stand next to the x-ray equipment. The radiographer will position your breast on a flat plate which is part of the mammography equipment. Your breast will then be compressed by a plastic paddle.

Why is a Breast Compression necessary?

  • To even out the breast thickness so that all of the tissue can be visualised.
  • To spread out the tissue so that small abnormalities won’t be obscured by overlying breast tissue.
  • To allow the use of a lower x-ray dose since a thinner amount of breast tissue is imaged.
  • To hold the breast still in order to eliminate blurring of the image caused by motion.
  • To reduce x-ray scatter to increase sharpness of the image

The radiographer will stand behind a glass shield during the x-ray exposure. You will be asked to change positions slightly between images. The routine views are a top-to-bottom view and an oblique side view. The process will be repeated for the other breast.

The examination process should take less than half an hour. When the mammography is completed, you will be asked to wait until the radiographer checks the images to determine if more are needed.

Breast Implants

Women with breast implants should also follow the same guidelines for checking their breast as those without implants.

 

However, due to the implant besides the usual views taken in mammography, several special mammography views can be taken to better visualise the breast tissue. The differences in imaging breast with and without implants are as follows:

 

  • Examination of augmented breasts (breasts with implants) is more time consuming, as more views are required.
  • Breast implants can also delay accurate mammogram readings because both silicone and saline implants are not transparent on x-rays. It can block a clear view of the tissues behind them, especially if the implant has been placed in front of the chest muscles. It Is estimated that about 25% of breast tissue will not be seen on the mammogram as it will be covered by the implant. The radiographer will use special techniques to take clearer x-rays of your breasts. You might find this uncomfortable.
  • As with the usual mammogram, compression is an important aspect of mammography examination. Radiographers take special care to use minimal compression on the breast implant during the breast x-ray procedure. It is highly unlikely, but possible, that this compression could cause or worsen leaking of silicone or change the shape or texture of the breast.

Useful Links

Questionnaire

Prepare yourself for a medical examination by downloading this questionnaire

Computed Tomography
How long will the procedure take?

The examination may take around 15 to 40 minutes.

After the procedure, patient will be asked to wait while the films are being processed and checked to be in order. This may take another 10 minutes.

After the films have been processed, the radiologist will report on his/her findings. For urgent cases, the results will be ready for collection in two hours’ time at the clinic. For routine cases, the results will be dispatched to the referring physician’s clinic before your next appointment date.

Is the examination painful?

The CT examination is not painful. Similar with photograph taking, any movement during the procedure will render the image unclear. Patient may be instructed to hold his/her breath during the duration of the exposure which may only last a few seconds.

A contrast agent may be injected into the patient. If this is done, the patient might feel a sting from the needle prick. Some people report a flushing feeling during the contrast agent injection, but this will disappear within a minute or two. There should be no cause for alarm.

What are the limitations of a CT scan?

CT does involve exposure to radiation in the form of y-ray, but the benefit of an accurate diagnosis far outweighs the risk. The effective radiation dose from this procedure is about 10 mSv, which is about the same as the average person receives from background radiation in three years.

Women should always inform their doctor or nurse or radiographer if there is any possibility that they are pregnant.

Nursing mothers should wait for 24 hours after contrast material injection before resuming breast feeding.

The risk of serious allergic reaction to iodine-containing contrast material is 1%.

The risk of extravasation where injury to blood vessel causes leakage of contrast to surrounding tissues is 0.1% or 1 in 1,000.

More about Computed Tomography (CT)

General Radiography
How long will the procedure take?

Actual procedural time will depend on the number of views of region x-rayed. It may therefore range from about a minute to 20 minutes.

After the procedure, patient will be asked to wait while the x-ray is being processed and checked to be in order. This may take another 10 minutes.

Therefore, please allow around 30 minutes for the entire process.

What will I experience?

This is a painless procedure. The only discomfort results from the coldness of the x-ray plate. Sometimes to get a clear image of an injury, you may be asked to hold onto an uncomfortable position for a short time and hold your breath for a few seconds. Similar to photograph taking, any movement could blur the image and make it necessary to repeat the procedure to get a useful, clear picture.

More about General Radiography

Pregnancy & X-ray

Diagnostic X-rays can give doctors significant and life-saving information about a person’s medical condition.

However, diagnostic X-rays come with risks and benefits too. As such, it’s important to use them only upon a doctor’s recommendation.

X-rays During Pregnancy

You’ll probably never need an abdominal X-ray during pregnancy. Sometimes, however, your physician may feel that this is needed because of a particular medical condition. Don’t worry if this will happen. The risk to you and your unborn child is very small, and the benefit of finding out about your medical condition is far greater. In fact, the risk of not having a needed X-ray could be much greater than the risk from the radiation. But even small risks should not be taken if they are unnecessary.

You can reduce those risks by telling your doctor if you are, or think you might be, pregnant whenever an abdominal X-ray is prescribed. If you are pregnant, the doctor may decide that it would be best to cancel, postpone, or modify the examination to reduce the amount of radiation.

Depending on your medical needs, and realising that the risk is very small, the doctor may also feel that it is best to proceed with the X-ray as planned. In any case, you should feel free to discuss the decision with your doctor.

Health Risks During Pregnancy

While the vast majority of medical X-rays do not pose a critical risk to a developing child, there may be a small likelihood of causing a serious illness or other complication. The actual risk depends on how far along the pregnancy is and on the type of X-ray.

 

Ultrasound studies, for example, do not use X-rays and have never demonstrated any potential for risk to a pregnancy. X-ray studies of the head, arms, legs and chest do not usually expose the baby directly to the rays. Typically, the radiographer who takes the X-rays will also implement special precautions to ensure that the baby of a pregnant patient is not directly exposed.

Risks Related to Gestational Age

  • Early Gestation / First Trimester (up to 12 weeks): At this point, the rate of foetal growth is very rapid and the foetus, as an organism, is at its most radiation-sensitive stage. The incidence of foetal wastage following radiation exposure is unknown, since
    • Many women were never aware they were pregnant at the time of the exposure or miscarriage
    • The normal rate of miscarriage for any pregnancy is high (15 to 25% of pregnancies)
  • Second Trimester (12 to 24 weeks): During this period, the overall growth rate of the foetus has slowed. However, the major organ systems are beginning to differentiate. From a standpoint of future development, the foetus is in its most sensitive stage. The incidence of gross congenital malformations and mental retardation are dose-related and appear to have thresholds. In other terms, doses below which the incidence above “background” is not elevated.
  • Third Trimester (after 24 weeks): Diagnostic irradiation during this period will not result in gross organ malformations.

Risks Related to Radiation Dose

The risk of adverse effects increases with increasing dose. Some broad generalizations based on fetal dose ranges may be made.

  • Fetal dose less than 100 mSv: No increased incidence of malformations or fetal death.
  • Fetal dose between 100 mSv and 200 mSv: very low risk of malformations.
  • Fetal dose between 200 mSv and 500 mSv: Effects vary with phase of pregnancy.

 

NOTE: Highest dose to the fetus in diagnostic radiology rarely exceeds 10 mSv and most examinations are under 2 mSv of radiation. The background radiation dose most of us receive every year from the atmosphere and sun is almost 3 mSv.

Minimising the Risks

  • Strictly tell your physician if you are pregnant or think you might be. This is important for many medical decisions, such as drug prescriptions and nuclear medicine procedures, as well as X-rays. Remember that this is critical even in the very early weeks of pregnancy.
  • Occasionally, a woman may mistake the symptoms of pregnancy for the symptoms of a disease. If you have any of the symptoms of pregnancy —nausea, vomiting, breast tenderness, fatigue — consider telling your doctor or radiographer before having an X-ray. A pregnancy test may be called for.
  • If you are pregnant, or think you might be, do not hold a child who is being X-rayed. If you are not pregnant and you are asked to hold a child during an X-ray, be sure to ask for a lead apron to protect your reproductive organs. This is to prevent damage to your genes that could be passed on and cause harmful effects to your future descendants.
  • Whenever an X-ray is requested, tell your doctor about any similar X-rays you have had recently. It may not be necessary to do another. It is a good idea to keep a record of the X-ray examinations you and your family have had taken so you can provide this kind of information accurately.
  • Feel free to talk with your doctor about the need for an X-ray examination. You should understand the reason X-rays are requested in your particular case.

 

Diagnostic X-ray is available at:
Magnetic Resonance Imaging (MRI)
How long will the procedure take?

The examination may take from 30 minutes to one hour.

After the procedure, patient will be asked to wait while the films are being processed and checked to be in order. This may take another 10 minutes.

After the films has been processed, the radiologist will report on his/her findings. For urgent cases, the results will be ready for collection in two hours’ time at the clinic. For routine cases, the results will be dispatched to the referring physician’s clinic before your next appointment date.

Is the examination painful?

The MRI examination is not painful. Similar with photograph taking, any movement during the procedure will render the image unclear. Patient will be comfortably lying down on a padded mattress and must keep still during the scan.

During the scan, intermittent humming and drumming sounds will be heard. Earplugs will be provided.

What are the limitations of MRI?

Bone is better imaged by conventional x-rays. In some cases, CT is preferred for patients with severe bleeding.

MRI may not always distinguish between tumour tissue and oedema fluid.

It does not detect calcium when this is present within a tumour.

In most cases, the examination is safe for patients with metal implants, with the exception of a few types of implants. Therefore, patients should inform the staff of the presence of an implant prior to the test.

The examination must be used cautiously in early pregnancy.

MRI typically costs more than CT scanning.

More about Magnetic Resonance Imaging

Nuclear Medicine & PET
How long will the procedure take?

After the injection of the radiopharmaceutical, the patient may take a walk and return about 2-3 hours later for the imaging portion of the examination. The imaging will take about half an hour.

Please prepare to be at the clinic for a total of about 3 hours.

After the films has been processed, the radiologist will report on his/her findings. For urgent cases, the results will be ready for collection in two hours’ time at the clinic. For routine cases, the results will be dispatched to the referring physician’s clinic before your next appointment date.

Is the examination painful?

The MRI examination is not painful. Similar with photograph taking, any movement during the procedure will render the image unclear.

Nuclear Medicine uses gamma rays. How do they differ from other types of rays or radiation?

The four common types of radiation are alpha, beta, gamma, and x-rays.

Alpha ray:

A particle ray consisting of two protons and two neutrons (namely, a nucleus of helium).

Alpha rays are produced following spontaneous decay of certain radioactive atoms, such as radium, plutonium, uranium, and radon. Because of its large mass and positive charge, an alpha ray can usually pass only a short distance – less than 1 mm – in water. A single piece of paper can stop an alpha ray effectively.

Beta ray:

A particle ray consisting of a fast electron whose mass is nearly 1/2000 of the mass of a proton or neutron.

Beta rays are produced following spontaneous decay of certain radioactive materials, such as tritium (an isotope of hydrogen), carbon-14, phosphorus-32, and strontium-90. Depending on its energy (ie, speed), a beta ray can traverse different distances in water–less than 1 mm for tritium to nearly 1 cm for phosphorus-32.

Gamma ray:

An electromagnetic wave, a gamma ray is similar to ordinary visible light but differs in energy or wavelength.

Sunlight consists of a mixture of electromagnetic rays of various wavelengths, from the longest, infrared, through red, orange, yellow, green, blue, indigo, and violet, to the shortest in wavelength, ultraviolet. A gamma ray’s wavelength is far shorter than ultraviolet (i.e., it is far higher in energy). Since Gamma rays can pass through body, they are used in Nuclear Medicine for imaging the body.

X-ray:

X-rays have the same characteristics as gamma rays, although they are produced differently. When high-speed electrons hit metals, electrons are stopped and release energy in the form of an electromagnetic wave. Wilhelm Roentgen first observed this in 1895, who considered it a mysterious ray, and thus called it an X-ray. X-rays consist of a mixture of different wavelengths, whereas gamma-ray energy has a fixed value (or two) characteristics to the radioactive material.

Neutrons:

Neutron particles are released following nuclear fission (splitting of an atomic nucleus producing large amounts of energy) of uranium or plutonium. In fact, it is neutrons that trigger the nuclear chain reaction to explode an atomic bomb. Neutrons hardly damage cells because they do not carry any electrical charge. However, the human body contains a large amount of hydrogen (a constituent of water molecules that occupy 70% of the human body), and when neutrons hit the nucleus of hydrogen, (i.e., a proton that is positively charged), the proton causes ionizations in the body, leading to various types of damage.

We hear a lot about the side effects of Nuclear Radiation. How safe is the use of radiation in the diagnosis of diseases?

We are exposed to various types of naturally occurring radiation from cosmic rays, from radioactive substances in the earth and from naturally occurring radiation in our bodies. This is commonly referred to as background radiation. The combined annual dose from these sources is thought to range from 0.001 to 0.002 sievert (or from 1 to 2 millisievert [mSv]).

The radiation dose delivered by most of the medical procedures is low. Such low level of radiation is accepted medically, as they help to diagnose and treat different diseases and does not pose any health hazards. However, there is a hazard to foetus if radiation is administered to a pregnant woman when the foetus is between 8 to 15 weeks old.

The table below shows the average annual radiation doses received per capita in the United States 1,2 from naturally occurring and man-made sources of radioactivity.

Natural background, Radon

2.0 mSv

 

Natural background, other

1.0 mSv

 

Consumer products

0.1 mSv

Medical diagnostics x-rays

0.39 m

Nuclear Medicine

0.14 mSv

 

           

Airline Travel

           

0.06 mSv

 

Total background:

3.69 mSv

(1 – US National Council on Radiation Protection and Measurements, NCRP Report No. 93, pp 53-55, 1987. Bethesda, Maryland, USA, NCRP. 2 – Cameron JR. The BERT: a radiation unit for the public. Physics Society 1991:20:2)

Because radioactive substances are injected into the patient, does the patient pose any threat to others?

Most of the diagnostic Nuclear Medicine procedures utilise minute quantity of radioactive material, which is eliminated from the body quickly. Therefore, the patient can resume normal activities immediately. There is no additional requirement of safety, as the patient is not a threat to family and friends.

I have previously undergone ultrasound, x-ray and CT scan. Why has my doctor referred me for a Nuclear Medicine test?

Nuclear Medicine imaging is unique that it documents organ function (physiology) and structure, as compared to diagnostic radiology, which is based upon structural appearance (anatomy). The physiological information coupled with anatomical findings, help for the better management of the disease.

All these diagnostic procedures are complementary and do not substitute each other.

I am allergic to penicillin. Does the injection used in the Nuclear Medicine procedure induce allergy too?

If you are allergic to other drugs, like penicillin, it does not mean that you will be allergic to radiopharmaceuticals used in Nuclear Medicine procedures.

Allergy/hypersensitivity reactions are extremely rare (less than 10 / year world-wide) in Nuclear Medicine tests. The test will not cause any adverse reaction, nausea, dizziness or blurred vision.

I am currently on prescription drugs. Can the radioactive substances counteract with my medication resulting in an adverse-effect or other side-effects?

There is normally no need to stop your medication except for myocardial perfusion test. In which cases, your referring physician will inform you about this. There are no side effects and you will not have any abnormal feelings during the test.

What are the common Nuclear Medicine procedures? Can children also undergo these tests too?

Common nuclear medicine applications include diagnosis of thyroid disease, bone scans for cancer patients and orthopaedic injuries, renal scan to assess kidney function/scar, lung scans for blood clots, liver and gall bladder procedures to diagnose abnormal function or blockages, and cardiac perfusion stress tests to analyse heart function.

Children commonly undergo nuclear medicine procedures to evaluate bone pain, injuries, infection and kidney function.

Nuclear Medicine & PET
How long will the procedure take?
Is the examination painful?
What are the limitations of PET?

A negative FDG PET scan does not necessarily rule out presence of malignancy. A few tumour types depend upon protein metabolism rather than glucose. In such cases, FDG PET scan can be a false negative.

PET can underestimate the severity of the disease if blood sugar is too high.
PET should not be used alone as a diagnostic tool. Its value is enhanced when it is part of a larger diagnostic work-up.

What are the limitations of PET-MR?

PET-MR can underestimate the severity of disease, if blood sugar is too high.
PET-MR is ideal for evaluation of disease distribution, however small incidental lesion(s) and calcified lesions may not be fully evaluated.
If a lesion is detected, dedicated scans and contrast enhancement may be required for better visualization.

The outer portion of both arms may not be completely included, depending on your body size.

In most cases the examination is safe for patients with metal implants, with the exception of a few implants. So patients should inform the staff of the presence of an implant prior to the test.

The examination must be used cautiously in early pregnancy.

More about Nuclear Medicine & PET Scan

Ultrasound
How long will the procedure take?

The examination may take about 30 minutes.

For doppler studies, it may take a longer time of approximately 45 minutes.

After the procedure, patient will be asked to wait while the films are being processed and checked to be in order. This may take another 10 minutes.

Please be prepared to be at the clinic for at least 45 to 60 minutes.
After the films have been processed, the radiologist will report on his/her findings. For urgent cases, the results will be ready for collection in two hours’ time at the clinic. For routine cases, the results will be dispatched to the referring physician’s clinic before your next appointment date.

Is the examination painful?

Painless, fast, and easy, no harmful effects from diagnostic ultrasound have been identified.

The radiographer will spread some gel on your skin and then press the transducer firmly against your back, moving it until the desired images are captured. There may be varying degrees of discomfort from pressure as the radiographer guides the transducer over your abdomen, especially if you are required to have a full bladder.

Ultrasound imaging will take around 30 minutes. If a blood flow visualisation is required, this may take up to 60 minutes.

More about Ultrasound

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