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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: x Specificity: y PCP Pneumonia Hx: Hypoxia in an AIDS patient with CD4 = 57 Result: PCP Pna Hx: SOB Result: ??? 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 Ultrasound abdominal CT abdomen with contrast MRI brain with and w/o gad $199 $627 $2279 $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 film 1. 2. • Abd series: KUB, upright chest, +/decubs 1. 2. 3. • Evaluation for obstruction Abnormal calcifications (kidney stones) Obstruction Calcifications 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 5949 CT, PET CT, US, Nuclear Medicine- Mary Cobbins, Supervisor x5498 THANK YOU!