Ordering Radiological Exams

Alex Rybkin MD

Assistant Clinical Professor of Radiology

SFGH/UCSF

Nancy Omahen RN MSN NP

Referral Coordinator, Radiology SFGH

How to order?

What to order?

(Assumed: imaging is clinically indicated)

Motivation

• “I never give accurate history to Radiologists: it biases them and makes me trust them less.”

“Blinded” Radiologist

False Negative Rate

37%For PCP Pneumonia!

Radiology Studies

Prevalence(Pre-test prob)

PPV, NPV(Post-test prob)

Sensitivity: xSpecificity: y

PCP Pneumonia

Hx: Hypoxia in an AIDS patient with CD4 = 57

Result: PCP Pna

Hx: SOBResult: ???

Sens & Spec vary!(And it’s a good thing)

• Clinical situation• Experience• Ability/Training• Adaptation to

technique – Techs– Hardware– Display methods

Why Radiologist is not a tool, but a CONSULTANT

• Results not binary• Multiple signs and findings• How to combine prevalence info with complex results• Most important: Radiologist has a brain

Don’t Blind Your Radiologist

• Think Radiologist as a consultant

• Invest time and effort

• Help us help you

• Summarize signs/symptoms/history– Tell us what you want to know– ICD9 (so we can bill)

Do we need clinical info?

• 2 schools of thought:– Radiologists: We need it, but we are not

going to get it– Non-radiologists: They don’t REALLY need

it

REALITY: Not getting enough specific information

Status Quo

• Chest study: “CP”, “SOB”

• Abdominal study: “Abdom Pain”

• Brain study: “HA”, “Weakness”

Useless

Example of CT e-referral sent by PCP(sent the same information for abd/pelvis

CT request)

• Diagnostic Question: R/O malignancy• History: Constitutional Symptoms

Useless

Status Quo

• Scrotal Ultrasound: “R/o Hernia”

Misleading

Why “Rule Outs” are EVIL

• Take us down the wrong path

“R/o Uterine Fibroids vs Enlarged Prostate”

Crohn’s disease with “creeping fat” producing a subtle mass

Why “Rule Outs” are EVIL

• Take us down the wrong path

• Make us second-guess you

R/o Appendicitis

Why “Rule Outs” are EVIL

• Take us down the wrong path

• Make us second-guess you

• Make Radiologists waffle (cannot prove a negative)

• Really bad NPV– Limitations of technique (search)– “The hardest thing to find is the one

that’s not there”

Why “Rule Outs” are EVIL

They will be rejected by billing &

WE DO NOT GET PAID!!Diagnosis with:• R/O diagnosis• MVA• GSW

Broken lines of communication

• Lack of understanding by Providers of what Radiologists need

• Roadblocks to info access– Hybrid written/digital ordering– Lack of unified repository of information– Lack of continuity of care

Need collaboration within the system!

“But how do I choose the right

study?”

Heuristic vs Perscriptive Approach

• “Heuristics are rules of thumb, educated guesses, intuitive judgements, or simply common sense” -- Wikipedia

• “Heuristics stand for strategies using readily accessible, though loosely applicable, information to control problem solving” – Perl, J et al

Heuristic #1

• If you don’t know how to proceed, don’t guess, ask a Radiologist.

• You can also call the Radiology Nurse Practitioner- x4407

On the Menu:• Plain Films• Fluoroscopy• Ultrasound• CT (Computerized Tomography)• MRI (Magnetic Resonance Imaging)• Nuclear Medicine/PET CT• Angiography

ACR Appropriateness Criteria

• acsearch.acr.org

Choosing a study

• Comparative studies• Consensus• Usefulness• Do no harm• Availability• Expense

– patient– system

Heuristic #2

• Use step-wise approach– Start with inexpensive, less risky studies– Escalate to more advanced studies as

needed– No shotgun please!

Imaging Costs (facility fee)

• CXR 1 view$199

• Ultrasound abdominal$627

• CT abdomen with contrast$2279

• MRI brain with and w/o gad$7875

Plain Films

• Economical

• Readily available

• Quick

• Informative

• Good place to start

Chest X-Ray

• First-line study of the chest

• Varieties: AP, PA & lateral, decubs

• PA & lateral: best quality

• AP: standby for immobile patients, portable studies

• Decubs: eval pleural effusion

Heuristic #3

• Radiological investigation of a Chest problem should always start with a CXR

KUB & Abd series

• KUB: supine abdominal film1. Evaluation for obstruction

2. Abnormal calcifications (kidney stones)

• Abd series: KUB, upright chest, +/- decubs

1. Obstruction

2. Calcifications

3. Pneumoperitoneum

• Further eval: CT

Heuristic #4

• Unless looking for obstruction, don’t bother with KUB

Extremity Films

• Good for broken bones, lesions

• Very limited Soft Tissue info: effusions, sq emphysema, foreign bodies

• For better definition of bone: CT

• For better definition of soft tiss: MRI

• For foreign bodies: CT or US

Heuristic #5

• Plain films are more valuable than MRI for bone problems!

(Known limitations: osteomyelitis, stress fractures, etc)

General CT considerations

• Quick• Available• Relatively Affordable• Problems:

– Radiation (children, pregnancy)– Patient Size limit 450 lb– Patient Motion– Pt with ESRD

Radiation Exposure

• Up to 2% of cancer estimated due to CT.– Brenner et al, NEJM 2007

Heuristic #6

• As Low As Reasonably Attainable (ALARA)– US or MRI in children and pregnant women

CT IV Contrast• Benefits:

– Better contrast in soft tissues

– Better delineation of tissue types

– Better sensitivity for tumors/abscesses

• Risks– Kidney damage (eGFR <

60)– Allergic reactions– Fluid overload

IV Contrast (cont)

• Need eGFR/Cr within 30 days

• eGFR < 15 NO CONTRAST

• eGFR bet 15 and 60– Consent– Hydration– Bicarb (Visipaque, N-AC(mucomyst) not

effective)

Allergic Reactions

• Hx of life-threatening reactions is an absolute contraindication for contrast

• Important to know if pt has had prior reaction to intravenous contrast- screen pt for allergies!

• True allergy- anaphylactic (Type I reactions) or mild (delayed Type 4).

• For mild reactions: premedicate– Call CT for protocol x8069

Head CT

• Trauma• Neurosurgical/Neurological

Emergencies• For detailed exam: MRI• Contrast:

– to better characterize abnormalities seen on noncon

– Suspected tumor, abscess etc

– HIV

Spine CT

• Trauma

• Acute Abnormalities

• Chronic Abnormalities: MRI

• Spine compression: MRI

• CT myelogram when MRI not possible

Chest CT

• Routine Chest CT: noncon, 2.5 mm cuts, no skips

– Good for masses, nodules, effusions– Give contrast for better imaging of mediastinum, pleura

• High Res CT (HRCT): noncon, 1mm cuts, 1-2 cm skips– Interstitial lung disease, airways disease– Expiratory images, prone images

• PE Protocol CT: with contrast, 1.25 mm cuts, no skips, bases and apices excluded– PE, vascular abnormalities

Abdominal CT• Routine Abd/Pelvis

– Most abdominal indications– Oral, +/- Rectal and IV

contrast

• Renal Stone protocol– noncon, thin cuts

• Specialized organ protocols: – talk to you friendly

Radiologist

Heuristic #7

• For most abdominal problems requiring imaging, CT is most bang for the buck

Liver studies• Liver Protocol CT: 3

phases– Arterial, Portal, Delayed

• Alternative-- US: – less radiation, less

sensitivity– useless in proven cirrhosis

• Alternative MRI: – better specificity, less

availability

Abdom CT: Enteric Contrast

• Not absorbed– Minimal risks

• Neutral vs Positive contrast– Neutral (hypertonic): better bowel wall

definition– Positive: better for perforation, abscess

MSK CT

• Exquisite definition of fractures

• Usually for preop planning

• For most problems rely on plain films and MRI (bone vs soft tissue problems)

Ultrasound

• Fast, Cheap, NO RADIATION

• Limitations: – Operator dependent– US does not go through bone, air– Labor intensive– Small field of view

• Typical indications: RUQ pain, Ob/Gyn imaging, Thyroid, Vascular imaging

Heuristic #8

• US not good for fishing expeditions– Use US for specific indications

• If you are going fishing, go with CT

General MRI

• Uses High Strength Magnetic fields – No ionizing radiation– Pacemaker absolute contraindication– Metal in body relative contraindication

• Better for Soft Tissue imaging

• Slow, scheduling difficult, expensive

MRI Contrast

• Gadolinium compounds• Used for better ST

characterization• Allergic reactions rare• Nephrogenic Systemic

Fibrosis (NSF):– Rare, recently discovered– Chronic Renal Failure– Requires consent 15 < eGFR

< 30

NSF- nephrogenic systemic fibrosis

• Nephrogenic systemic fibrosis is a rare disease of unknown cause that affects patients with renal failure. Single cases led to the suspicion of a causative role of gadolinium that is used for magnetic resonance imaging.

• 1. Marckmann P, Skov L, Rossen K et al (2006) Nephrogenic systemic fibrosis: suspected etiological role of gadodiamide used for contrast-enhanced magnetic resonance imaging. J Am Soc Nephrol 17:2359–2362 [PubMed]

• 2. Grobner T (2006) Gadolinium—a specific trigger for the development of nephrogenic fibrosing dermopathy and nephrogenic systemic fibrosis? Nephrol Dial Transplant 21:1104–1108 [PubMed]

• 3. Flaten H (GE Healthcare) (2006) Dear Healthcare Professional. http://www.fda.gov/medwatch/safety/2006/gadolinium_NFD-NSF_dhcp.pdf. Accessed 07 Sept 2006.

Neuro MRI

• Brain: usually second-line study (following abnl CT)

• Spine: best for cord, paraspinal pathology, degenerative processes

• Needs contrast for tumors, infections

MRA vs CTA

MRA– Non invasive eval of arterial system– Images flow, not anatomy-slow flow may mimic

stenosis/occlusion– Typical applications: intracranial, neck, renal/mesenteric,

peripheral

CTA

Heuristic #9

• There are true MRI emergencies

– Cord compressions– Posterior fossa infarcts– Appendicitis in pregnant pt

Abdominal MRI

• Always second-line study (Except: proven cirrhosis)

• Liver: high specificity for HCC

• MRCP: Noninvasive Bile/pancreatic duct imaging

• Pelvis: GYN pathology characterization, staging of GYN tumors.

MSK MRI

• Soft tissue pathology: tendons, ligaments, menisci, capsules, muscles etc.

• Osteomyelitis

• MSK Tumor staging (plain films for characterization)

Heuristic #10

• MRI is not part of DJD management– Start with plain films

Osteomyelitis

• Plain Film: sens 43-75% spec 75-83% (1)

• Triple phase bone scan: sens 94% spec 95%(1)

• MRI ROC meta-analysis: superior to bone scan (2)

(1) Semin Roentgenol. 2007 Apr;42(2):92-101.(2) Arch Intern Med. 2007 Jan 22;167(2):125-32.

Conclusion

• Don’t Blind your Radiologist

• “Rule Outs” are EVIL

• Participate! Don’t be discouraged.

Choosing Studies

• Don’t guess, ask Radiologist

• Use step-wise approach

• For chest problems, start with CXR

• KUB is for obstruction

• For bone problems start with plain films

• ALARA

• In abdomen CT is most useful

• Ultrasound is not for fishing

• There are rare MRI emergencies

• MRI is not for DJD

Contact numbers

Urgent (within 14 days) MRI requests:– NP x4407 Rads (neuro)x5798 Abd Imaging Rads x5898,

Musculoskeletal Rads x8030

Urgent (within 14 days) CT requests:-NP x4407 CT chief Tech Kevin x8069 (if unable to reach either of the above, you can contact the numbers above for Rads.

For Scheduling problems:

MRI-x 5949CT, PET CT, US, Nuclear Medicine- Mary Cobbins, Supervisor x5498

THANK YOU!