“What Test is Best”

Choosing Radiology Exams in Emergency Settings

Dr. C. Freeman PGY-4

Dr. A. Olivier

Objectives

• To provide a guide to selecting the appropriate imaging studies in common emergency settings

Please note: the goal of this talk is NOT to review how to read

radiological exams.

Modalities

• Plain Films– Based on differential attenuation of X-rays by different

tissues

• Ultrasound– Uses sound waves

– Real time

– Very accessible

– No radiation

CT

• Computer reconstruction of 2 dimensional X-ray data

• reconstructions in any plane

• Accessible, fast

WHAT IS A “SPIRAL CT”??????

• Helical movement (patient and gantry move at the same time)

• Almost all modern CT’s are helical

– Exceptions: Head CT, High Resolution CT of the chest

MRI

• Soft tissue differentiation (e.g. Soft tissue tumors)

• many other specialized indications (e.g. acute stroke)

• limited accessibility, expensive

• Expanding role in many clinical situations

CHEST “the patient who is short of breath”

Common Causes…– CHF, atelectasis, pneumonia, pneumothorax,

pulmonary embolus

start with a Chest X Ray

Atelectasis

Left diaphragm now seenLeft diaphragm silhouetted

Complete Collapse

Pneumothorax

Inspiration-expiration

may increase

sensitivity

Pneumothorax

Tension pneumothorax

***EMERGENCY

•place needle in 2nd intercostal space (mid clavicular line)

Pneumonia

Silhouette sign

Air bronchograms

Pneumonia: Air Bronchogram

Congestive Heart Failure

Pulmonary Emboli

• CXR– non specific, non sensitive

• V/Q Scan – useful if high probability or low probability

• CT Pulmonary Angiogram

CXR: HAMPTON’S HUMP

•Chest X-ray not useful to rule in or rule out PE

•BUT may help to find other cause of SOB (e.g. CHF)

V/Q Scan

VENTILATIONPOSTERIOR

PERFUSIONLATERAL

•High probability: Treat (anticoagulate)

•Low probability: unlikely to have PE

•Intermediate Probability: ??? CT Angiogram

CT ANGIOGRAPHYACUTE THROMBOEMBOLI

Aortic Dissection

• CT

• Trans-esophageal echo

CT Reconstruction: Aortic Dissection

GI/GU

• Again, begin with a plain film

• Remember utility of upright and decubitus films for identifying free air and air fluid levels

Often move on to another exam depending on plain film findings

^^^^ ^

Free Air

•Upright Chest X-Ray is the most sensitive test for free air

Free Air: Decubitus View

FREE AIR•we see both sides of the bowel wall

“Riegler’s sign”

Renal Colic

•Plain Films

•CT

•IVP

•(ultrasound sometimes useful…e.g. if pregnant)

Ureteric calculus

•note how well a calcified stone is seen on plain films.

“Left flank pain”

IVP

•Shows function and obstruction

•HOWEVER…largely replaced by CT

Renal Colic: CT

Now Preferred Modality

RLQ Pain, Fever, WBC……? Appendicitis

• Plain film of limited utility – may see appendicolith

• Ultrasound– No radiation– In females, can also see adnexa– Especially good in thin patients

• CT– If overweight

..? Appendicitis

•RLQ PAIN•appendicolith

Appendicitis: CT

Bowel Obstruction

“distended abdomen with obstipation and peritoneal signs”

•start with a plain film

•supine and upright views

•lateral decubitus if upright not possible

•Multiple air-fluid levels

•distended bowel loops

•note the value of upright (or decubitus) view

Small Bowel Obstruction

•Confirms the site of abrupt narrowing at the splenic flexure (large arrow)

Large Bowel Obstruction: Contrast Enema

Bowel Obstruction…after the plain film

• Depends on the clinical scenario

• May monitor patient

• May go directly to the Operating Room

• May proceed to CT– helps to define location and cause of

obstruction

Pancreatitis

• Clinical/Biochemical Diagnosis

• Ultrasound to identify cause (i.e. biliary stones)

• CT is used to identify and follow complications ***NOT TO DIAGNOSEWill MISS diagnosis in 30% of cases

Scrotal Pain

•History and Physical firstMay proceed directly to the OR

•Ultrasound is the modality of choice

•Can identify status of blood supply

Testicular Ultrasound

RUQ Pain

• Ultrasound is the modality of choice

• CT can miss acute cholecystitis or cholelithiasis

Ultrasound: Cholelithiasis

Neuroradiological Emergencies

•Start with a CT–**Except cord compression

•May ultimately need an MRI

Clinical Settings

• Seizures

• Trauma

• Headache

• Stroke

Seizures: CT---Neoplasm

Seizure: MRI---Neoplasm

CT: Stroke

•In the USA, many centers MRI is the initial exam

•Some specialized MRI Techniques can identify brain at risk (“penumbra”) vs. dead brain

•Some advanced CT techniques …”CT Perfusion” helpful

CT

Intra - Cranial Bleeds

• Subarachnoid Hemorrhage

• Subdural Hemorrhage

• Epidural Hemorrhage

CT: Subarachnoid Hemorrhage

Epidural Hematoma

Subdural Hematoma

SPINE Emergencies

C-Spine Trauma• Plain films:

– If minor trauma, plain films including flexion and extension views can suffice

• CT– For significant injury– From skull base to T1 – Sagital and coronal reconstructions

• MRI– Unexplained neurologic deficit– Unconscious for prolonged period of time

Normal C-Spine with CT

Axial Sagital Coronal

Hangman’s #

Axial Sagital

C5-6 dislocation

Axial Sagital

C5-6 dislocation withLeft Vertebral Artery dissection

MR Angiogram

Suspected Spine Infection

• Plain films – may be diagnostic– Do not demonstrate compression of thecal sac

• MRI is optimal • CT can be adequate• Fluoroscopic or CT guided

aspiration/biopsy• We follow these cases with MRI

Discitis

Sagital AxialCoronal

Discitis, osteomyelitisprevertebral & epidural phlegmon

Cord Compression: MRI

Metastatic

Melanoma

Spine Emergencies: Summary

• MRI is generally the best exam for the spine

• CT is excellent in many indications

• Plain films have a limited role

• MRI access is quite limited, so we compromise and do a lot more CT

MSK

Fractures

• Remember that acute fractures may not be seen on plain films for up to 7- 10 days.

• Bone scan is more sensitive

Plain Film: Ankle Fracture

Sacral Fracture: CT

? Septic Joint

• Plain film may be suggestive

• MUST aspirate joint– This is a medical emergency

Necrotizing Fasciitis

• Ultimately a clinical diagnosis

• Plain FilmsGas in the soft tissues

• MRIFor surgical planning

• CT may give a false negative (not sufficient to rule out diagnosis)

Summary

• Almost always start with the plain film

• There are some exceptions– Neurological Emergencies

• If you are unsure as to what test is appropriate…talk to the Radiologist

Thank you!!Dr. C. Freeman

Dr. A. Olivier