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Diagnostic Radiology

Radiological Sciences services within the SingHealth cluster are spread across 7 hospitals and national specialty centres, making it the largest radiology affiliation in Singapore, comprising 50% of public sector radiologists. We provide extensive imaging and image-guided intervention services using the latest imaging technology, thus providing specialised services to our patients. Every year, we perform more than 1.3 million imaging studies and over 12,000 image-guided interventions. The nuclear medicine (NM) and molecular imaging service in SingHealth executes more than 17,000 NM and PET scans every year, with over 5000 clinic consultations and radioisotope treatments annually.


Diagnostic Radiology uses various medical imaging techniques and equipment to help in the diagnosis of diseases. Radiologists are medical doctors who are trained to interpret radiographs, ultrasound, Computed Tomography (CT), Magnetic Resonance Imaging (MRI) and other scans to come to an accurate diagnosis, so that the doctor can make plans for treatment. Our radiologists ensure that the most appropriate scan is performed for the patient’s problem and direct radiographers to obtain good quality images.


SingHealth institutions provide a full range of diagnostic imaging examinations and image-guided interventions. Some common services are listed below.

Imaging Services

General radiography or X-ray

General radiography or x-ray is the foundation of all diagnostic imaging using ionising radiation. This technology uses x-rays to produce an image, which is captured by an image receptor. Plain radiographs are commonly requested by doctors as an initial evaluation upon first consultation or as baseline screening. X-rays may be taken in the x-ray rooms, or at the bedside when necessary.

X-ray images
X-ray images courtesy of Sengkang General Hospital.

Fluoroscopy

Fluoroscopy uses a special contrast dye and a continuous stream of x-rays to produce images through which the radiologist can see the body part and its motion in detail. This provides the radiologist with information about the function and movement of the body in real time, which helps them to determine the appropriate diagnosis and treatment for the patient.


Examples of fluoroscopy investigations are: barium-related studies such as barium meal, barium enema, defecating proctography, and video fluoroscopy studies to assess swallowing abnormalities. Water-soluble contrast studies are popular in children and babies to look for congenital gastro-intestinal or urological abnormalities in studies such as water-soluble swallow, micturition cystouretherogram (MCU) etc. Water-soluble contrast scans are also performed in adults, mostly to look for post-surgical status or complications.


Fluoroscopy is also widely used in musculoskeletal imaging whilst performing diagnostic contrast injections for shoulder, wrist and hip joints prior to MRI. Therapeutic joint injections are occasionally performed using fluoroscopy, as are other procedures such as endoscopic retrograde cholangiopancreatography (ERCP), feeding tube insertions, fracture fixations using plates and screws etc.

Intravenous Urography

Intravenous urography is a specialised x-ray examination of the urinary system, including the kidneys, ureters and bladder. A contrast agent (dye) is injected before the scan, and is used to highlight the urinary tract and study the ability of the urinary system to excrete urine. In this procedure, the contrast agent injected into the body will be cleared by the kidneys and excreted out as part of the urine.


Patients are given instructions on how long to fast before the test. Diabetic patients should inform the radiography department before the scan as they may need different instructions on the preparations.

Computed Tomography (CT)

Computed tomography, commonly known as CT scans, combines the use of x-rays and computer systems to generate cross-sectional images of the human body. X-rays that pass through the body are captured and processed by the computer to create clear and detailed images of internal organs and structures. Advances in technology allow the x-ray dose to be tailored to each patient and kept as low as possible.


For certain types of scans, contrast (a special dye) is injected into the body to allow major blood vessels as well as organs to be seen more clearly.

CT colonography
CT Colonography. Photo courtesy of Singapore General Hospital.

Bone Mineral Densitometry (BMD)

Bone Mineral Densitometry (BMD) is also known as Dual X-ray Absorptiometry (DXA). It is used to screen for reduced bone densities, also known as osteopenia or osteoporosis, and predict fracture risk. BMD can be used to monitor patients who are on treatment for such conditions.


BMD may also be used to measure body composition, i.e. the amount of bone, fat and muscle in the body, as part of clinical evaluation for patients who are obese or have muscle wastage. BMD involves a low level of radiation, much lower than standard X-ray examinations.

Angiography

Angiography is the x-ray imaging of blood vessels using contrast agents (dyes) injected into the bloodstream through a thin plastic tube or catheter that is placed directly in the blood vessel, to take images known as angiograms.


Angiography provides information about blood vessel abnormalities, such as narrowing, blockage, inflammation, abnormal widening and bleeding. The contrast agents are injected into the blood vessels to make them visible on X-rays. Angiography is also used to guide procedures that treat blood vessel abnormalities, such as inserting stents.

Breast imaging

SingHealth hospitals offer screening mammography, breast ultrasound, breast MRI and breast biopsies. A mammogram is a low-dose x-ray of the breasts to screen for breast abnormalities, especially useful for early breast cancer detection. Mammography may be used with other imaging techniques such as ultrasound and MRI to make a more accurate diagnosis. Breast ultrasound uses sound waves to create images of the internal structures of the breast, whilst breast MRI creates images of higher resolution. Breast biopsies are performed to remove a small amount of breast tissue for testing. Breast imaging services are offered at SGH, CGH, NCCS, KKH and SKH.

Magnetic Resonance Imaging (MRI)

SingHealth hospitals and specialty centres also offer scans without radiation, such as Magnetic Resonance Imaging (MRI), which uses a strong magnetic field and radio waves to take detailed images of organs and tissues in different planes of any part of the human body. This allows radiologists to visualise internal structures, especially soft tissues, in the body.


We perform a wide variety of MRI exams such as brain, spine, prostate, cardiac, breast and musculoskeletal MRI. Unlike x-rays or CT scans, MRI does not use radiation by default. Intravenous contrast dye may be used, which improves clarity of the images to make a more accurate diagnosis.


The strong magnetic field used in MRI attracts magnetic objects, including implants, jewellery and metal zippers which need to be removed prior to scanning. Please inform the radiographer if you have any metal implants.

Magnetic Resonance Imaging (MRI)
Magnetic Resonance Imaging (MRI). Photo courtesy of Sengkang General Hospital.

Ultrasound

Ultrasonographic equipment
Ultrasonographic equipment. Photo courtesy of Sengkang General Hospital.

An ultrasound scan uses high-frequency sound waves to examine structures in the body, including large organs, blood vessels, muscles, tendons and ligaments. A scanning probe is placed on the skin which gives off high-frequency vibration, which enter the body and echo back, creating real time ultrasound images. Ultrasound does not involve radiation, and is a relatively safer imaging technique compared to common scans involving radiation. It is non-invasive and can be used safely in children and pregnant women.

Interventional Radiology

Interventional Radiology is a branch of medicine specialising in the use of modern imaging modalities, including digital subtraction angiography, ultrasound fluoroscopy and computed tomography (CT), to guide the performance of minimally invasive diagnostic procedures and treatments in different parts of the body. These treatments offer less risk, less pain and faster recovery, compared to traditional surgery.


Procedures done by our interventional radiologists include angiography, stent insertion, embolisation, biopsies and drainages, tumour ablation, and more.

Radiation Doses for Common Examinations

The scans and treatments described above use radiation to see inside the body. One of the most common concerns shared by patients in the Radiology department is "How much radiation is involved?"


Effective radiation dose is measured in milli-sieverts (mSv). We are exposed to natural background radiation daily, which is approximately 2.4mSv yearly. This figure varies depending on geographical location, as it depends on the radioactive elements in the air or the radioactive materials present in rocks, soil, or building materials. Nevertheless, we can estimate the effective radiation dose by comparing the average radiation dose from common scans with the dose that we receive daily from background radiation.


The effective doses of a few common examinations are:

Examples of Common ScansApproximate Effective Radiation Dose (mSv)Comparable to natural background dose of:
X-rayChest0.058 days
Abdomen0.502.5 months
Pelvis & hip0.371.9 months
Cervical spine (upper back)0.058 days
Lumbar spine (lower back)0.804 months
CTHead1.78.6 months
Chest7.03 years
Abdomen6.82.9 years
Pelvis7.43.1 years
Spine7.03 years

*Please note that the effective doses listed above are typical values for an average-sized adult. The actual individual dose can vary substantially, depending on a person's size and the differences in imaging practices. This chart attempts to simplify a very complex topic, and hence it can only provide an estimation of the doses for each examination.


Radiation and Pregnant Women

Radiation exposure by pregnant women is avoided as much as possible as it affects the foetus. The increased risk depends on the amount and duration of radiation to the foetus. The radiation risk is highest during the first few weeks of pregnancy, as the foetus is most sensitive during this development stage. Radiation risk decreases as the pregnancy progresses, and is relatively low when the foetus is fully developed, when birth defects due to radiation exposure are not likely to occur.


From past studies, the radiation dose from diagnostic examinations currently presents no risk of causing foetal death or problems in development. For most diagnostic medical procedures where the foetal dose is up to 1 mSv, the associated risk of childhood cancer due to radiation is very low (below 1 in 10,000) compared to the natural risk (approximately 1 in 500).


Even though most radiological examinations result in a low foetal dose, pregnant patients should avoid scans with radiation as far as possible, due to the small risk they have. Diagnostic radiological procedures or examinations are usually recommended during pregnancy when the information gained from the study is necessary for the care of the patient and when information cannot be obtained by other means, especially by ultrasound or MRI.


Type of ScanTypical foetal dose range (mSv)Risk of childhood cancer per examination
X-raySkull0.001 – 0.010<1 in 1,000,000
Chest
Thoracic Spine
Head and/or neck
X-rayAbdomen0.1 – 1.01 in 100,000
to
1 in 10,000
Pelvis
Hip
CTChest & Liver
CTLumbar Spine1.0 - 101 in 10,000
 to
1 in 1,000
Abdomen
CTPelvis10 - 501 in 1,000
 to
1 in 200
Pelvis & Abdomen
Pelvis, Abdomen & Chest

*Foetal doses derived from doses to the uterus seen in UK surveys and Administration of Radioactive Substance Advisory Committee (ARSAC) Notes for Guidance, applied to early stages of pregnancy when the foetus is small.


While exposure to radiation carries a certain amount of risk to the foetus, however, there are times when radiological examination would be the preferred way to obtain essential diagnostic information of the pregnant patient. Diagnostic scans with x-rays or CT have proven to be efficient and holistic in providing information about a patient’s internal injuries or conditions, especially for life-threatening cases.


Thus, the radiological examination will need to be performed as it is deemed necessary and carries greater benefit than risk to the pregnant patient. In such a case, it would be clinically justified to carry out radiological examinations for pregnant patients.


If there is a chance the patient is pregnant, our staff will discuss the benefits and risks of any radiological scans with the patient.

Lead Aprons and Shields for safety in Fluoroscopy / Interventional Radiology

You may notice our staff wearing a lead gown when attending to your scan. Fluoroscopy or interventional radiology (IR) procedures require clinical staff to be inside the room with patients when x-ray exposures are made continuously. Hence, our staff are required to protect themselves from radiation exposure by wearing lead aprons, thyroid shields and lead glasses, which are the standard shields commonly used to protect both staff and patients from unnecessary radiation exposure. The appropriate shielding reduces the amount of radiation exposure received by the body tremendously.

Shield attire
Staff donning a lead gown

Information on radiation dose and protection compiled by Laurentcia Arlany, Medical Physicist, Sengkang General Hospital.


Sources:

  • J Vilar-Palop et. al. Updated effective doses in radiology. J. Radiol. Prot. 2016; 36:975-990
  • B K Cheon et.al Radiation safety: a focus on lead aprons and thyroid shields in interventional pain management. Korean J Pain 2018; 31:244-242
  • Centre for Disease Control and Prevention Radiation Emergency Fact Sheet, Radiation and Pregnancy: A Fact Sheet for the Public, 2011
  • Guidelines for perinatal care. 3d ed. Elk Grove Village, Ill.: American Academy of Pediatrics and American College of Obstetricians and Gynecologists, 1992:210-3
  • Protection of Pregnant Patients during Diagnostic Medical Exposures to Ionising Radiation, Health Protection Agency, The Royal College of Radiologists, 2009

Preparations for scans and interventional procedures

Some scans and procedures involving x-rays or ionising radiation may not be suitable for pregnant patients. Do inform your doctor if the patient may be pregnant. The doctor will carefully weigh the benefits and risks before proceeding with the scan.


Some scans may require specific preparations, such as taking certain medicines, or fasting before the scan. Our care team will inform you of these beforehand. Do ask our care team in advance if you have any queries or concerns about the scans.

 

Diagnostic Radiology and Interventional Radiology services are available at:

 

Related Conditions & Treatments

 

Singapore General Hospital

Nuclear Medicine (NM) services are available at all SingHealth restructured hospital campuses. The Department of Nuclear Medicine and Molecular Imaging (DNMMI) in SGH handles all NM studies within the main department at SGH, and also provides imaging services to other campuses, including CGH, KKH, SKH and TTSH (part of the National Healthcare Group).


DNMMI performs at least 70 therapies per month including radioactive iodine therapy for benign and malignant thyroid conditions, selective internal radiation therapy (SIRT) therapy for malignant hepatic conditions, peptide receptor radionuclide therapy (PRRT) for neuroendocrine cancers, and prostate specific membrane antigen (PSMA) therapy, Radium-223 therapy and radiosynovectomy.


DNMMI performs approximately 450 general nuclear medicine scans and 85 PET-CT studies per week.


Dr Xie Wanying, a nuclear medicine physician, says, “We are privileged to be working in Singapore General Hospital, where our leaders listen to our voices. At our department, we have had the opportunities to introduce modern imaging studies such as I-123 ioflupane, F-18 flutemetamol, as well as novel therapies supported by well published results, such as PRRT and PSMA therapy.” She enjoys coming to work daily as there is a safe and conducive working environment with friendly co-workers without rigid hierarchy within the department. Everyone is free to express their opinions, especially with regards to ideas on improving patient safety and workplace efficiency.


DNMMI holds weekly peer review learning sessions, weekly resident teaching sessions and monthly journal club meetings.