Search guidelines

• Routine follow-up not required in fully recovered adults <50 with no risk factors.
• Repeat CXR 6 weeks for smokers ≥50 or persistent symptoms — exclude underlying malignancy.
• Consider CT if persistent consolidation or atypical features.

Source: BTS / ACR guidance

• Negative initial scaphoid series with clinical suspicion → immobilize + repeat XR in 10–14 days, or MRI.
• MRI is most sensitive and shortens immobilization in confirmed-negative cases.

Source: ACR Appropriateness Criteria

• Positive fat pad sign on lateral elbow → presume occult supracondylar / radial neck fracture.
• Splint and follow-up 7–10 days for repeat radiographs.

Source: ACR Appropriateness Criteria — Pediatric

• Any new or indeterminate nodule on CXR → low-dose chest CT for characterization.
• Subsequent management follows Fleischner 2017 by size and solid/sub-solid character.

Source: Fleischner Society 2017 / ACR

• Ankle XR indicated only with malleolar pain plus bony tenderness or inability to bear weight.
• Foot XR only with midfoot pain plus tenderness at navicular / 5th metatarsal base or inability to bear weight.
• Validated to reduce unnecessary imaging by ~30% with near-100% sensitivity for clinically significant fractures.

Source: Ottawa Ankle Rules — Stiell et al.

• XR indicated if any: age ≥55, isolated patellar tenderness, fibular head tenderness, inability to flex 90°, or inability to bear weight (4 steps) immediately and in ED.
• Otherwise plain films can be safely deferred.

Source: Ottawa Knee Rule

• Typical mechanism + posture: no XR needed if clinical reduction is attempted first.
• Image if atypical mechanism, swelling, or failed reduction to exclude fracture.

Source: ACR Appropriateness Criteria — Pediatric

• Mandatory skeletal survey in children <2 with suspected abuse; follow-up survey at 2 weeks improves detection.
• High-specificity injuries: classic metaphyseal lesions, posterior rib fractures, scapular/sternal fractures.
• Report to child protection team per local pathway.

Source: ACR–SPR practice parameter

• Aggressive features (wide zone of transition, periosteal reaction, soft-tissue mass) → MRI + oncology referral.
• Classic benign 'don't touch' lesions (NOF, bone island, fibrous cortical defect) need no follow-up.
• Indeterminate solitary lesion in adult → CT chest/abdomen/pelvis and bone scan to assess for metastatic disease.

Source: ACR Appropriateness Criteria

• Age >50 with new fracture and no high-energy trauma → DXA and osteoporosis workup.
• MRI if neurologic symptoms, suspected pathologic fracture, or to date acuity before vertebroplasty.

Source: ACR Appropriateness Criteria

• TR3: FNA if ≥2.5 cm, follow-up if ≥1.5 cm.
• TR4: FNA if ≥1.5 cm, follow-up if ≥1.0 cm.
• TR5: FNA if ≥1.0 cm, follow-up if ≥0.5 cm.

Source: ACR TI-RADS 2017

• Simple cyst: BI-RADS 2 — no follow-up.
• Complicated cyst: BI-RADS 3 — 6-month US follow-up.
• Complex cystic & solid mass: BI-RADS 4 — biopsy.

Source: ACR BI-RADS Atlas

• O-RADS 2 (almost certainly benign): minimal or no follow-up depending on type/size.
• O-RADS 3: US specialist or MRI follow-up.
• O-RADS 4–5: gyn-oncology referral and/or MRI.

Source: ACR O-RADS US 2020

• Solid intratesticular lesion: urology referral; consider tumor markers.
• Sub-centimeter non-palpable lesion: short-interval US (3 months) is reasonable.

Source: ESUR / consensus guidance

• Anechoic, thin-walled, posterior acoustic enhancement → simple cyst, no follow-up.
• Internal echoes, septations, or solid component → contrast-enhanced CT/MRI for Bosniak classification.

Source: Bosniak 2019 / ACR

• <6 mm, no risk factors: no follow-up.
• 6–9 mm: US at 6 months, then yearly to 5 years.
• ≥10 mm or rapid growth (≥2 mm/yr): cholecystectomy.

Source: ESGAR / SAGES 2022 update

• Simple anechoic cyst: no follow-up.
• Hyperechoic well-defined lesion <3 cm in non-cirrhotic, no malignancy history: presume hemangioma, no follow-up.
• Atypical features or known malignancy → MRI for characterization.

Source: ACR Incidental Findings white paper

• ICA PSV ≥125 cm/s or ICA/CCA ratio ≥2: ≥50% stenosis.
• ICA PSV ≥230 cm/s or ICA/CCA ratio ≥4 + EDV ≥100: ≥70% stenosis.
• Symptomatic ≥70% stenosis → vascular surgery referral for CEA/CAS.

Source: SRU consensus 2003 / NASCET

• Negative whole-leg US: DVT effectively excluded; no repeat needed.
• Negative proximal-only US in outpatient with moderate–high pretest probability: repeat US in 5–7 days or D-dimer-guided strategy.
• Isolated distal (calf) DVT: serial US vs. anticoagulation based on symptoms and risk.

Source: ACCP / ACR Appropriateness Criteria

• Discriminatory β-hCG ~3,500 mIU/mL without intrauterine pregnancy → consider ectopic.
• Yolk sac visible at mean sac diameter ≥10 mm; embryo at ≥25 mm with no cardiac activity → failed pregnancy.
• Hemodynamically unstable or adnexal mass with free fluid → emergent gyn consult.

Source: SRU 2013 consensus

• <6 mm, low risk: no routine follow-up.
• <6 mm, high risk: optional CT at 12 months.
• 6–8 mm: CT at 6–12 months, consider 18–24 months.
• >8 mm: CT at 3 months, PET/CT, or tissue sampling.

Source: Fleischner Society 2017

• Pure GGN <6 mm: no routine follow-up.
• Pure GGN ≥6 mm: CT at 6–12 months, then every 2 years up to 5 years.
• Part-solid ≥6 mm: CT at 3–6 months; persistent solid ≥6 mm → biopsy/resection.

Source: Fleischner Society 2017

• <10 HU on non-contrast: benign adenoma — no follow-up.
• Indeterminate (>10 HU): adrenal protocol CT or MRI in/out-of-phase.
• ≥4 cm or suspicious features: endocrine + surgical referral.

Source: ACR Incidental Adrenal Mass white paper

• Bosniak I–II: no follow-up.
• Bosniak IIF: CT/MRI 6 months, then annually for 5 years.
• Bosniak III–IV: urology referral, consider intervention.

Source: Bosniak 2019

• LR-3 ≥2 cm: repeat multiphase imaging in ≤6 months.
• LR-4: multidisciplinary discussion; biopsy or short-interval follow-up.
• LR-5: diagnostic of HCC — refer to hepatology/transplant.

Source: ACR LI-RADS 2018

• <2.5 cm, asymptomatic: MRI in 12 months, then space out if stable.
• Symptomatic, near critical structures, or growth: neurosurgical referral.

Source: Consensus guidance

• Non-functioning <1 cm: MRI at 1 year, then less frequently if stable.
• Functioning or near optic chiasm: endocrine + neurosurgery referral.

Source: Endocrine Society

• Acute marrow edema on STIR → consider DXA + osteoporosis workup.
• Atypical features (posterior involvement, mass): contrast MRI + oncology referral.

Source: ACR Appropriateness Criteria

• Recall for additional imaging (spot compression, magnification views, or US).
• Compare with prior exams when available before final assessment.
• Aim to complete workup and re-assign a final BI-RADS category within 30 days.

Source: ACR BI-RADS 5th edition

• Routine annual screening mammography (age- and risk-appropriate).
• Document benign findings (calcified fibroadenoma, simple cysts, lipomas) to avoid future recall.

Source: ACR BI-RADS 5th edition

• Short-interval follow-up mammography at 6 months.
• Then 12 and 24 months to confirm 2-year stability.
• <2% malignancy risk; biopsy if any interval change.

Source: ACR BI-RADS 5th edition

• Tissue diagnosis recommended (image-guided core biopsy).
• Subcategories 4A (>2–10%), 4B (>10–50%), 4C (>50–<95%) stratify malignancy risk.
• Radiologic-pathologic concordance review after biopsy is mandatory.

Source: ACR BI-RADS 5th edition

• ≥95% malignancy risk — core biopsy and surgical/oncology referral.
• Discordant benign pathology requires repeat biopsy or excision.

Source: ACR BI-RADS 5th edition

• Assigned after biopsy confirms malignancy, before definitive therapy.
• Used for neoadjuvant chemotherapy response or pre-operative localization workup.

Source: ACR BI-RADS 5th edition

• Fine pleomorphic, fine linear, or linear branching morphology → BI-RADS 4B/4C.
• Stereotactic vacuum-assisted core biopsy is preferred technique.
• Specimen radiograph required to confirm retrieval of calcifications.

Source: ACR BI-RADS lexicon

• Without known surgical/trauma history — biopsy regardless of mammographic correlate.
• If no US correlate, tomosynthesis-guided or stereotactic biopsy is appropriate.
• Radial scar / complex sclerosing lesion on core → consider surgical excision.

Source: ACR BI-RADS / SBI guidance

• Discuss supplemental screening US or MRI based on lifetime risk.
• Consider abbreviated breast MRI in intermediate-to-high-risk women.
• FDA requires breast density notification in screening reports.

Source: ACR / SBI dense breast guidance

• Annual screening MRI in addition to annual mammography starting at age 25–30.
• Includes BRCA1/2, TP53, PALB2, prior chest radiation age 10–30, strong family history.
• Consider risk-reducing strategies and genetic counseling referral.

Source: ACS / ACR high-risk screening guidelines

• Correlate with anatomic imaging (XR, CT, or MRI) of the site.
• If indeterminate, consider SPECT/CT or targeted MRI before treatment change.
• Single lesion in spine/pelvis without correlate → MRI to exclude early metastasis.

Source: SNMMI procedure guideline

• Random distribution involving axial and appendicular skeleton supports metastases.
• Oncology referral; baseline scan recommended before systemic therapy for response assessment.
• Consider PSMA PET (prostate) or FDG PET when bone scan is equivocal.

Source: SNMMI / EANM bone scintigraphy guidance

• Diffuse skeletal uptake with absent/faint renal activity — diffuse marrow involvement.
• Common in widespread prostate or breast metastases; correlate with PSA, ALP, CBC.
• Differential: metabolic bone disease (renal osteodystrophy, hyperparathyroidism).

Source: SNMMI consensus

• Transient increase in uptake 2–6 months after initiating effective therapy.
• Reflects osteoblastic healing — do not interpret as progression in isolation.
• Re-image at 6 months or correlate with CT/labs before changing therapy.

Source: PCWG3 / SNMMI guidance

• Linear/focal uptake at single rib most often reflects healed or healing fracture.
• Correlate with history of trauma and chest XR/CT.
• Multiple rib uptake in linear distribution → consider trauma vs. metastases by morphology.

Source: ACR Appropriateness Criteria

• Focal fusiform uptake along long bone cortex (tibia, metatarsals, femoral neck).
• MRI is preferred for early diagnosis and grading; bone scan remains highly sensitive.
• Sacral H-pattern (Honda sign) → pelvic insufficiency fracture, evaluate for osteoporosis.

Source: ACR Appropriateness Criteria

• Intense uptake involving entire bone with expansion (pelvis, spine, skull, femur).
• Correlate with elevated alkaline phosphatase and characteristic XR/CT changes.
• Treatment with bisphosphonates if symptomatic or at risk for complications.

Source: Endocrine Society / SNMMI

• Osteomyelitis: increased uptake on all three phases (flow, blood pool, delayed).
• Cellulitis: increased flow/blood pool but normal delayed bone uptake.
• In post-surgical or diabetic foot, add WBC scan or MRI for specificity.

Source: SNMMI infection imaging guideline

• Degenerative joint disease, healing fractures, and Paget disease are common pitfalls.
• Correlate with XR or CT before recommending oncologic workup.
• Symmetric periarticular uptake favors arthropathy over metastasis.

Source: ACR Appropriateness Criteria

• ~30% malignancy risk — dedicated thyroid US.
• US findings drive FNA per ACR TI-RADS.
• Diffuse uptake suggests thyroiditis — correlate with TSH/antibodies.

Source: Incidental PET/CT thyroid uptake reviews

• High malignancy / adenoma risk — colonoscopy.
• Diffuse uptake is usually physiologic / inflammatory.
• Cecal/right-sided focal uptake especially concerning for adenoma in older adults.

Source: Consensus reviews

• SUV greater than liver: suspicious — dedicated adrenal CT/MRI.
• <10 HU on non-contrast CT correlates with adenoma despite mild uptake.
• In known malignancy, biopsy if imaging features remain indeterminate.

Source: ACR Incidental Adrenal Mass white paper

• Sub-cm nodules can be falsely negative; correlate with Fleischner.
• FDG-avid solid nodule >8 mm → biopsy or short-interval CT.
• Carcinoid and bronchoalveolar carcinoma can be FDG-negative.

Source: Fleischner Society 2017

• Focal uptake → endoscopy to exclude carcinoma or high-grade dysplasia.
• Diffuse linear uptake typically reflects esophagitis or reflux.

Source: SNMMI / consensus reviews

• Solitary focal uptake — dedicated US or contrast-enhanced MRI of the gland.
• Warthin tumor and pleomorphic adenoma are common FDG-avid benign mimics.
• Bilateral symmetric uptake often physiologic; assess for sialadenitis.

Source: EANM head-and-neck guidance

• Focal marrow uptake without CT correlate → MRI to exclude metastasis.
• Diffuse marrow uptake post-G-CSF or chemotherapy is expected (reactive).
• Sclerotic, FDG-negative lesions can still be metastatic (e.g., treated prostate).

Source: EANM/SNMMI FDG PET oncology guideline

• Any focal uptake in a non-lactating breast → diagnostic mammography ± US.
• Biopsy if BI-RADS 4 correlate is identified.
• Bilateral diffuse uptake usually physiologic / lactational.

Source: ACR / EANM consensus

• Focal pancreatic uptake → contrast-enhanced pancreas-protocol CT or MRI/MRCP.
• Autoimmune pancreatitis can mimic malignancy — correlate with IgG4 and morphology.
• Solid mass with uptake → EUS-guided biopsy and oncology referral.

Source: ACR Appropriateness Criteria

• Score 1–2: complete metabolic response.
• Score 3: usually complete response in interim PET (Hodgkin / DLBCL trials).
• Score 4–5: partial / no response — consider biopsy or therapy escalation.

Source: Lugano 2014 / Deauville 5-point scale