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Organisational chart of imaging departments (aka Which department do I arrange this scan with?)

However, most of the hospitals don’t have all three departments. For some scans, they will be done by the radiology department; for others, the patient will have to travel to another hospital.   In addition, the radiology departments in larger hospitals separate their inpatient and outpatient locations (E.g. SGH Inpatient is Blk 6, but outpatient is Blk 2) Back to top

Important people in the department (aka Who do I look for?)

	Who is he?	His role	When you need to look for him!
Radiologist	Medical doctor specialising in imaging	Approve xray requests	Urgent requests
		“Protocols” (gives technical instructions) on how to do the scan. Doesn’t actually do most scans! (except fluoro, U/S and angio)	Not sure which investigation (e.g. CT vs MRI), special circumstances (pregnancy, implants in MRI, post-op anastomotic leak)
		Covers medical emergencies.	Allergic reaction, collapse, resus
		Interprets scans and issues report.	Urgent report, second opinion
		X-ray conferences	Submit list of cases for round
Radiographer	Technologist who runs the xray machines(Diploma holder after ‘A’-level)	Person who actually performs the xray, CT or MRI	If you’ve brought the patient down and can’t find anyone!
		Prints the xray films	Need hardcopy film or CD
Sonographer	Specialised radiographer that does ultrasound	Specialises in ultrasound	-
Clerk	Runs the front desk!	Receives your request form	Check if form has been received
		Schedules appointments	Check appointment date and ask for an earlier one (sometimes works!)
		Issues instruction phamplets, oral contrast, etc.	Collect contrast/prep after urgent request is approved

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Pre-investigation preparation

Contraindications(By modality)

Modality	Absolute C/I	Relative C/I
Plain Xrays	-	Pregnancy
i/v contrast:    -CT    -IVU	Allergy: CT Contrast, Iodine, Fish	Renal disease (Raised Cr) Asthma DM on metformin Allergy: Multiple(> 3)
Ultrasound	-	-
MRI	Cochlear implant Pacemaker Intraocular foreign body Other mobile ferrous objects	Depending on model/operation date Vascular clips Artificial heart valve
Barium swallow / meal / enema	Suspected perforation / leak       (use water-soluble contrast)	Acute Intestinal obstruction Patient unable to stand/weight bear Patient unable to turn over

Preparation (By modality)

Modality	Fasting (8 hours)*	Others
Plain Xrays	No
Mammogram	No	Ideally in first 14 days of menses (will be arranged by the appt desk)
Ultrasound	For HBS and renal arteries
Barium swallow / meal	Yes
Barium enema	Yes, overnight	Bowel preparation 1-2 days before
IVU	Yes	Bowel preparation 1-2 days before
CT abdomen &/or pelvis	Yes	May require oral contrast 1-2 hours before
MRI	For liver, MRCP

*- Implication: Keep the patient nil-by-mouth if you think you need the scan urgently!    

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Consent Taking and Risks of procedure

When is written consent required?
Varies between hospitals, but in general:

1. Age < 21
2. Pregnant women
3. Women who have missed their period, or are in 2nd half of cycle (for high dose Ix)
4. All interventional procedures (including biopsy)

Radiation dose

Risk from radiation is a slope, there is no one “cut-off” point below which it is “perfectly safe” - even small radiation doses may have some risk. Therefore, statutory regulations require the dose to be “as low as reasonably achievable”.      Having said that, there is no absolute “legal” limit to the dose a patient can receive - go ahead and order the scan if you think the investigation is medically indicated, and the benefits outweigh the risk.      What then, is the risk, and how do you explain it to patients in layman terms?

Modality / Procedure	Equivalent of “normal” daily background radiation	Risk of fatal cancer / death
Xray – Limbs	1 day	0.0001% (1 in a million)
* Eating 2 bananas a week for 1 year	1 day
Xray – CXR	3 days	0.0003%
Xray – Skull	9 days	0.001% (1 in 100,000)
* Smoking 1 pack of cigarettes	-	0.001%
* Flight from Singapore to New York	1 month
Mammogram	2 months	0.005%
Xray - Abdomen, Pelvis, Spine	4 months	0.01% (1 in 10,000)
Tc-99m thyroid scan	6 months
IVU	1 year	0.03%
Barium swallow, meal, follow-through	1 – 1.5 years	0.03%
CT Head	10 months	0.03%
Tc-99m dynamic cardiac scan	2 years	0.05%
CT Chest, abdomen or pelvis	3.5 years	0.1% (1 in 1,000)
* Dying in a home accident each year	-	0.1% (1 in 1,000)
* Smoking 1 pack of cigarettes a day x 1 year	-	0.35%

i/v contrast   (IVU and CT scan)

(1) Allergic reaction / anaphylaxis   -  Idiosyncratic, just like all other drugs   -  Increased risk if (1)Multiple drug allergies  (2)Recent asthma (<1 year ago)   -  Prevention: Steroids given AT LEAST 12 hours before the scan.     -  Examples are : Prednisolone 20mg the night before and on the morning of the scan.     -  In emergencies: Hydrocortisone i/v 200mg q4h starting at least 6 hours before the scan. (2) Extravasation   -  Definition: When the contrast is forced outside the vein   -  Background: About 50mls of contrast (which is as viscous as D50%) is injected as fast as 5mls/second under great pressure                        (If you don’t believe, get a 20ml syringe, some D50%, a blue plug, and see if you can inject everything out in 5 seconds!!).   -  Problem: Vein bursts (damn, got to reset the plug ;-) --> Contrast leaks out into tissue --> Draws water from surrounding tissues                        --> (1)Dehydration (& cell death)of surrounding tissues  and (2)Compartment syndrome   -  Prevention:              -   i. Make sure plug works(They check, and you’ll just have to walk down to the department to re-set it if it doesn’t work)              -   ii. Large bore (Pink/Green) plug for procedures requiring high-injection rates (generally anything vascular/arterial).              -   iii. If all else fails, blue plugs (but not in tiny finger veins!) may be acceptable for slow-injection rates (e.g. brain)              -   iv. PICCs are NEVER acceptable. (1) The tiny tip can blast off into the pulmonary arteries and (2) SVC rupture is not a pretty sight.   -  Treatment:              -   i. RICE (Rest, Ice-pack, Compress, Elevate extremity)              -   ii. Watch for compartment syndrome, especially if large volume (3) Contrast induced nephrotoxicity   -   Defined as a 25% increase in serum creatinine (does not always require dialysis though).   -   1% in low risk patients   -   10% in high risk patients (Diabetes, CCF, renal impairment, nephrotoxic drugs, age > 70yrs)   -  Prevention:              -   i. Any high risk factors: Pre-hydrate patient              -   ii. Renal impairment: Consider N-acetylcysteine (600mg bd x 2 day before and on day of scan)              -   iii. Space out contrast studies 72h apart, if possible (e.g. cancer staging)              -   iv. Consider non-contrast CT or alternate studies (e.g. US, MRI)   -   Paradoxically, patients whose kidneys have already failed and are on dialysis can ignore all the above. (4) Metformin-induced lactic acidosis   -   Metformin: Stop on the day, and 2 days after the scan.   -  Once again, do this proactively, if you think patient might be going for a contrast-CT soon!       (Just don’t forget to convert to insulin/another OHGA, and to re-start it later!) (5) Breast feeding   -   Can scan as per normal, but no breast feeding x 24h after the scan

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Radiological investigations

FAQ

Q: How do I know which scan to order?
A: Specifying the modality(i.e. CT, MRI), organ of interest and including an adequate history is usually enough. For example, “CT lung” for “Lung cancer” vs “PE” vs “Interstitial lung disease” will get you three different scans, but as long as you include the diagnosis/history, there is no need to specify the exact technical details. Even suspected clinical diagnosis or the clinical indication, no matter how silly (e.g. “Hemoptysis for Ix”, “right sided rib pain”, “TB x 40 years ago”).

Q: What do I write in the “History” column?
A: The keyword is “relevant”. Include whatever you think might be relevant to the scan, such as Presenting complaint, Duration, Possible causes (e.g. TB, prostate cancer), Physical findings/relevant investigations (e.g. axillary LN, pyloric ulcer on OGD, Hep B carrier), Treatment so far (e.g. Subtotal gastrectomy on 21/4/06), and any previous scans (e.g. U/S Feb 06: 4cm liver mass). Also, include any questions your consultant had (e.g. ?increase in size since 2004, ?anastomotic leak) so that they can be specifically answered in the report (Which may well save you a trip down to bug an irritated, overworked radiologist!).

Q: That’s a lot to write! What can I leave out?
A: More is better than less, especially if you’re unsure! (It’ll save you an angry phone call from the radiologist, or even worse, having to explain to the patient why he needs another $350 CT scan of the same organ when he just had one yesterday, and to the consultant why the scan didn’t include the pelvic anastomosis…). But you can safely leave out irrelevant comorbidities (e.g. schizophrenia in a liver scan), and a summary of the history/physical exam is enough (e.g. “R breast lump x 2/12” vs “Admitted for # NOF. Incidental finding of R breast lump, 4.5cm, hard. L breast NAD. etc. etc.)

Q: Does the scan require i/v contrast (a.k.a Do I need to set a plug)?
A: This is a tricky one. The full list is given below, but in general, the following require contrast:

Most CT scans, including those looking at/for:
      -  Tumour
      -  Inflammation
      -  Blood vessels

Some MRI scans, especially those looking at
      -  Tumour

All interventional studies (except PermCath and Hickman lines, but including PICC lines)
Common scans that do NOT require i/v contrast include:

CT head for stroke, trauma

CT spine and extremities for trauma

CT KUB for renal/ureteric stones

Q: How do I arrange for an “urgent” scan?
A: This varies by hospital, but here is a suggested approach:

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HEAD AND NECK /NEUROLOGY / NEUROSURGERY / ENT

Xray: Skull

Indication	Investigation
Vault #	Skull (AP,Lateral, Towne’s)
Maxilla #	Skull (AP, Lateral, OM)
Mandible #	Mandible X-xray
Orbit #	Orbit X-ray
Orbital foreign body	Orbit X-ray + Look up/down views
Sinusitis (chronic)	X-ray Paransal sinuses

Xray: Non-Skull

Indication	Investigation
FB Throat	Neck xray,lateral (not C-spine)
Cervical spine trauma	C-spine xray (not Neck)   +/- Swimmer / Lat pull-down for C7/T1
Parotid stone	Parotid xray (occlusal view)
Dental	Occlusal / OPG

Fluoroscopy

Indication	Investigation
Swallowing assessment / ?Aspiration	(1)VFS if high % aspiration (2)Barium swallow (not gastrograffin)
FB throat / perforation / post-esophagect	(1)Gastrograffin swallow (2)NB: CT neck better for FB
Nasolacrimal duct stenosis	Dacrocystogram*
Salivary/Parotid duct stenosis	Sialogram*

* - Specialised, rarely performed investigation

Ultrasound

Indication	Investigation
Thyroid lump / goitre	U/S thyroid
Young CVA	U/S carotids

CT

Indication	Investigation	Contrast?
Stroke, hemorrhagic Head injury (see NICE criteria)	CT brain	No
Meningitis	CT brain	Maybe
Fits, brain tumour, mets	CT brain	Yes
Chronic sinusitis	CT paranasal sinuses	No
Hearing loss, conductive	CT temporal bone	No
Foreign body throat	CT neck	Maybe

MRI

Indication	Investigation	Contrast?
Stroke, hyperacute (< 12 hours)	MRI brain (stroke protocol) NB: CT is better to exclude bleed	No
Stroke, brainstem Posterior fossa lesions	MRI brain (more sensitive than CT)	Maybe
Hearing loss, sensorineural	MRI IAM / MRI IAM screening	Yes
Retrobulbar mass, orbital tumor	MRI orbits	Yes

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RESPIRATORY / CARDIOLOGY / CARDIOTHORACIC SURGERY (CTS)

Chest X-ray

Indication	Investigation	Which side?
Basic CXR view	CXR (Erect)
Rib #	CXR (Oblique)	Same side as suspected # i.e. R oblique for R  #
Localise lung lesion	CXR (Lateral)	Same side as lesion
Loculated effusion,    or patient cannot sit up	CXR (Lateral decubitus)	Same side as effusion i.e. R LD for R effusion
Small pneumothorax,    or patient cannot sit up	CXR (Lateral decubitus)	Opposite side of pneumothorax i.e. R LD for L pneumothorax
Sternal #	Sternal Xray

General notes on CXR:

The ‘standard’ CXR view is PA erect, but patient must be able to stand, and it cannot be done portable. AP Sitting is second best, followed by Supine.

Lateral views are not routinely required. Ask yourself – “how will it affect management?”

Fluoroscopy

Indication	Investigation
Diaphragmatic paralysis	Fluoroscopic sniff test*

* - Specialised, rarely performed investigation  

CT

Indication	Investigation	Contrast
Most lung conditions	CT Thorax / CT Chest
Interstitial lung disease	High resolution CT (HRCT)  (NB: Slices are “skipped” – do not use for tumour detection)	No
Aortic aneurysm / dissection	CT Aortogram / CT Thoracic aorta	Yes (High rate)
Pulmonary embolism (PE)	CT PE / CT Chest (PE protocol)	Yes (High rate)
Coronary arteries	CT Coronary Arteries / Cardiac CT	Yes (High rate)

 

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ABDOMEN / PELVIS / GASTROENTEROLOGY / HBS / UROLOGY / OBSTETRICS / GYNAECOLOGY / BREAST

Abdomen X-ray

Indication	Investigation
Standard AXR view	AXR (Supine)
Air-fluid levels	AXR (Erect) or (Lateral decubitus)
Free air under diaphragm	CXR (Erect) or (AP Sit)
Ureteric/bladder calculi	KUB

General notes on AXR:

The ‘standard’ AXR does not always cover the pelvis. Order a KUB for pelvic pathology.

Erect or decubitus views are not routinely required, even in IO. The supine view shows bowel distribution better, and free gas is better detected on the CXR.  

Ultrasound

Indication	Investigation	Preparation	Notes
Liver, gallbladder	U/S liver / HBS	Fast x 8 hours	Includes a quick look at kidneys
Kidneys	U/S kidneys	-
Kidneys & bladder	U/S kidneys + bladder	Needs to have a full bladder	Not routinely ordered
Renal arteries	U/S renal artery	Fast x 8 hours	Specialised investigation
Aorta	U/S abdominal aorta	Fast x 8 hours	CT preferred, if possible
Uterus/ovaries	U/S pelvis	Needs to have a full bladder	May include endovaginal scan
Testes	U/S testes	-

General notes on ultrasound:

Do NOT order "ultrasound abdomen" – only solid organs can be scanned, and the vast majority of the “abdomen” (including the bowel) is un-scannable.
You will either get a rejected request, a call from an irate radiologist, or a vague scan of the region based on the clinical history in your form.
They will never scan the entire “abdomen”, so you might as well be more specific.

Intravenous urogram (IVU)

Indication	Investigation	Preparation
Hydronephrosis, ?stones	IVU	Fast overnight, bowel prep

General notes on IVU:

IVU as an inpatient is usually suboptimal due to (1)poor bowel preparation or (2)infeasible to keep patient in hospital just for bowel prep.
Alternatives include CT KUB (if looking for hydro and stones, or if renal function is poor) or CT urogram (if looking for renal function or pyelonephritis).
Disadvantages of CT are higher cost and radiation dose.    

Fluoroscopy

Indication	Investigation	Requirements	Notes
Esophagus / swallowing problem	Barium swallow	Be able to stand
Stomach / PUD / reflux / hiatus	Barium meal	Be able to stand and roll over.
Small bowel pathology	Barium follow-through
	Enteroclysis		More invasive than follow-through, but better results
Large bowel	Barium enema	Be able to stand and roll over. No fecal incontinence.
?anastomotic leak	Water-soluble / gastrograffin swallow/ meal/ enema.	As for similar barium study.	Include op details (incl anastomosis type), and exact date study is required on form.
Urethral stricture	Ascending urethrogram		Include op details if any
Vesico-ureteric reflux	MCU		Include op details if any
Post PCN	Check nephrostogram

 

CT

Indication	Investigation	Contrast
Upper abdominal pathology	CT abdomen	Yes
Pelvic / gynae pathology	CT pelvis	Yes
Entire abdominal cavity required	CT abdomen + pelvis (abdo/pelvis)	Yes
Liver (Routine e.g. abscess)	CT liver	Yes
Liver lesion ?HCC	CT liver (triphasic)	Yes (High rate)
Liver HCC post-TACE	CT liver (plain + triphasic)	Yes
Pancreas	CT pancreas (fine cuts)	Yes
Renal /ureteric stone	CT KUB (may differ by hospital)	No
Kidneys	CT kidneys	Yes (High rate)
Kidneys, ureter, bladder	CT urogram(may differ by hospital)	Yes (High rate) and Lasix
Abdominal aorta	CT abdominal aorta	Yes (High rate)
Colon	CT colongraphy	Yes and rectal gas

General notes on CT:

There are many, many different CT protocols for the abdomen (e.g. see CT liver above!). If unsure, it is best to state the organ of interest, and provide sufficient history, rather than guess blindly.

Abdomen and Pelvis (in radiological protocol terminology) are completely different!! Your consultant may casually order a “CT abdomen” for “?sigmoid CA” or “abd pain for ix”, when what he really means is “CT Abdomen + Pelvis”. The radiographers protocoling the scan are not medically qualified, and may or may not catch your meaning, so make sure you fill the form in correctly!  (As an aside, the main reason why the pelvis is not automatically included in a “CT abdomen” is due to the high radiation dose to the gonads and bowel.)

Almost all abdo scans require fasting. If you’re clerking a patient and think he might need an urgent scan, keep him NBM!  

MRI

Indication	Investigation	Contrast
Liver	MRI liver	Yes
Bile duct stones	MRCP	Maybe
Pancreas	MRI pancreas	Yes
Kidneys	MRI kidneys	Yes

General notes on MRI:

There are many, many, many MRI protocols for the abdomen, even more than for CT. MRI liver for HCC alone has 12 sequences. Don’t bother trying to specify them, just state the organ of interest, and provide sufficient history.

Breast

Indication	Investigation	Note
Screening	Mammogram
Evaluation of breast lump	Ultrasound + Mammogram
Biopsy of lump	Ultrasound guided bx	Specialised investigation
Biopsy of lesion on mammogram	Mammotome / Stereotactic biopsy	Specialised investigation
Implant rupture	MRI breast	Specialised investigation

   

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ORTHOPAEDICS / SPINE / EXTERMITIES / TRAUMA
General notes on orthopaedic xrays:

Othopaedic xrays are really easy to order – if you can name the bone that is likely to be fractured, then that's the xray you ask for! So go ahead, and order xrays according to where you think the problem is.

Using radio-opaque markers, especially for foreign bodies, is highly recommended. If you can’t personally accompany the patient and put the marker – just write a “with marker” on the xray form, and make sure the patient  can point out the site of the problem!

Plain x-rays

Skull See head and neck Spine Cervical spine Cervical spine (Swimmers view) or (Lateral pull-down) Open-mouth / Odontoid views Thoracic spine Lumbar spine Oblique views of above Coccyx   Upper limb Clavicle Scapula Shoulder Humerus Elbow Forearm or radius/ulna Wrist Scaphoid Hand x finger Pelvis Pelvis (AP) Pelvis (Inlet / Outlet) Judet views (for acetabulum) Lower limb Hip Femur Knee Skyline (Patella) Tib/Fib Ankle Calcaneum Foot

CT / MRI for tumour or trauma

Specify region as above.

3D-reconstructions are not performed by default at most hospitals, so specify if your consultant needs them.

Ultrasound

Indication	Investigation
Rotator cuff pathology	U/S shoulder
Carpal tunnel, cysts, neuroma	U/S wrist
DDH / CDH (< 4-6 mths)	U/S hip

MRI

Spine (specify region, level, and side of symptoms) Shoulder* Wrist* Hip Knee Ankle

General notes on MRI:

While MRI is highly detailed, it is not cheap, and before ordering one, ask yourself if it will affect subsequent management.

* - These procedures may involve use of intra-articular contrast injection (arthrogram), which depends on indication for the scan, and varies between hospitals. Once again, include all relevant details on the request form (esp. suspicion of tears and any previous operation) and advise patient he may require an injection.    

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