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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!