Pediatric Imaging
Core concepts
Understand the differences between pediatric and adult imaging: smaller body size, lower radiation tolerance, and the need for child-friendly protocols (ALARA, immobilization, play therapy). Learn the imaging of common pediatric emergencies: intussusception, pyloric stenosis, malrotation/volvulus, and appendicitis. Understand the patterns of pediatric chest disease: bronchiolitis, pneumonia, and the significance of the thymus. Learn the imaging of developmental dysplasia of the hip, Legg-Calvé-Perthes, and slipped capital femoral epiphysis. Understand the pediatric brain: germinal matrix hemorrhage in neonates, and the patterns of pediatric tumors (medulloblastoma, ependymoma, pilocytic astrocytoma). Know the principles of skeletal surveys in non-accidental trauma.
Traps
Do not apply adult dosing to children - use weight-based protocols. The thymus can mimic a mass; the sail sign and normal thymic shape are key. Intussusception is diagnosed by ultrasound (target sign) and treated with air or contrast enema if no perforation. Malrotation is a surgical emergency; upper GI series is the test of choice. Remember that a skeletal survey requires specific views and should be performed by trained radiographers.
Rule of thumb
For pediatric abdominal pain, start with ultrasound when available; it avoids radiation and is excellent for intussusception, pyloric stenosis, and appendicitis. Use the "target sign" for intussusception and the "cervical length" for pyloric stenosis.
Nuclear Medicine and Molecular Imaging
Core concepts
Understand radiopharmaceuticals: technetium-99m, iodine-131, fluorine-18 FDG, and gallium-68, and their mechanisms. Learn the principles of PET imaging: annihilation, coincidence detection, and the role of FDG in oncology, infection, and inflammation. Understand the imaging of thyroid disease (I-131 uptake, thyroid scan), bone scanning (metastasis, fracture, infection), and renal scanning (DTPA, MAG3, DMSA). Know the principles of ventilation-perfusion scanning for PE and the interpretation criteria (PIOPED). Understand sentinel lymph node mapping and the role of molecular imaging in prostate cancer (PSMA). Learn the principles of radiation safety in nuclear medicine and the handling of radioactive patients.
Traps
FDG is not tumor-specific - infection, inflammation, and brown fat can show uptake. Do not interpret a bone scan in isolation; correlate with radiographs. Remember that I-131 is both diagnostic and therapeutic and requires thyroid blocking considerations. V/Q scans are interpreted with clinical probability; a high-probability scan with high clinical probability is treated as PE.
Rule of thumb
For oncologic PET, use maximum standardized uptake value (SUVmax) with caution: it varies with time, blood glucose, and lesion size. Always correlate with anatomic imaging and clinical context.
Interventional Radiology
Core concepts
Understand the principles of image-guided procedures: vascular access (Seldinger technique), catheter selection, and the role of fluoroscopy, CT, and ultrasound guidance. Learn the indications and techniques of angioplasty, stenting, embolization, and thrombolysis. Understand the management of hemorrhage (embolization), tumor ablation (radiofrequency, microwave, cryoablation), and drainage procedures (abscess, biliary, nephrostomy). Know the complications of interventions: contrast reactions, bleeding, infection, and nontarget embolization. Learn the principles of radiation dose reduction during fluoroscopy (pulsed fluoroscopy, collimation, last-image hold). Understand the role of IVC filters, TIPS, and venous access.
Traps
Embolization requires careful selection of the embolic agent (coils, particles, glue) depending on the target. Do not overlook the risk of nontarget embolization. Remember that thrombolysis has bleeding risks and contraindications. TIPS is used for portal hypertension complications, not for all ascites. Always confirm catheter position before embolization.
Rule of thumb
Before any embolization, confirm the target vessel and check for anastomoses that could cause nontarget embolization. Use the smallest embolic agent that achieves the desired effect.