What is the proper procedure for interpreting a radiograph (x-ray)?

How to Read an X-ray: A Systematic Approach

Use a structured, systematic method to interpret radiographs by evaluating technical quality first, then systematically reviewing all anatomic regions using a consistent search pattern, correlating findings with clinical context, and always comparing to prior studies when available.

Pre-Interpretation: Technical Quality Assessment

Before interpreting any radiograph, verify adequate technical parameters to ensure diagnostic quality:

• Confirm proper patient positioning and detector placement - The image detector should be positioned as close to the patient as possible to minimize magnification and optimize image quality 1
• Assess penetration adequacy - Proper x-ray tube voltage (typically 30-100 kV for biological samples) ensures adequate tissue penetration, with penetration values between 10-90% yielding good scan quality 1
• Evaluate for motion artifact - Movement during exposure degrades image sharpness and diagnostic utility 2
• Check field of view and collimation - The exposed field should be confined to structures of interest, minimizing unnecessary radiation exposure 1

Systematic Interpretation Framework

Step 1: Identify the Examination Type and Clinical Context

• Determine the anatomic region and projection - Different anatomic areas require different interpretation approaches based on expected pathology and normal anatomic backgrounds 2
• Review the clinical indication - Target findings vary based on the clinical question being addressed 2

Step 2: Use a Consistent Search Pattern

Employ a systematic approach to avoid missing findings:

• Scan the entire image periphery first - Many significant findings are missed at image edges
• Evaluate bone structures systematically - Assess cortical margins, trabecular patterns, and alignment
• Review soft tissues methodically - Examine for asymmetry, masses, or abnormal densities
• Assess air-containing structures - Look for abnormal air collections or absence of expected air
• Evaluate visible organs and vessels - Check size, position, and contour of cardiac silhouette, great vessels, and other visible organs

Step 3: Analyze Image Characteristics

Understanding physical parameters aids interpretation:

• Contrast evaluation - Differences in tissue attenuation create diagnostic information, with photoelectric absorption and Compton scattering being the predominant mechanisms in diagnostic energy ranges 3
• Assess sharpness and resolution - Spatial resolution affects detection of small lesions, with typical pixel sizes of 1.5-2 mm for standard radiographs 1
• Recognize noise patterns - Quantum mottle and other noise sources can obscure findings 4, 2

Step 4: Correlate with Prior Imaging

• Compare to previous radiographs - Serial examinations facilitate detection of interval changes 1
• Use consistent windowing techniques - Maintain similar window width between studies while adjusting window level to reference tissues 1

Common Pitfalls to Avoid

Technical Errors That Compromise Interpretation

• Inadequate penetration - If penetration is less than 10%, increase voltage or current; if above 90%, decrease these parameters 1
• Excessive magnification - Use the least degree of magnification required for accurate interpretation, as magnification substantially increases radiation dose 1
• Poor collimation - Wide-open collimation delivers unnecessary radiation and degrades image quality through increased scatter 1

Interpretive Errors

• Satisfaction of search - Continuing systematic review after identifying one abnormality prevents missing additional findings
• Ignoring clinical context - Target findings and their significance vary based on clinical presentation 2
• Overlooking subtle findings - Lesions smaller than 5 mm may be difficult to detect due to spatial resolution limitations 1
• Failing to recognize artifacts - Motion, beam hardening, and other artifacts can mimic or obscure pathology 1

Anatomic Region-Specific Considerations

Chest Radiographs

• Evaluate lung parenchyma systematically - Compare symmetry, assess for nodules, infiltrates, or masses
• Assess mediastinal contours - Evaluate cardiac silhouette size and great vessel margins
• Review pleural spaces - Look for effusions, pneumothorax, or pleural thickening
• Examine bony thorax - Assess ribs, clavicles, and visible spine for fractures or lesions

Musculoskeletal Radiographs

• Evaluate cortical integrity - Look for breaks, periosteal reaction, or erosions
• Assess joint spaces - Measure joint space width and alignment
• Review soft tissues - Look for swelling, calcifications, or foreign bodies
• Check bone density - Assess for osteopenia or focal lucencies

Quality Assurance Principles

• Verify equipment calibration - X-ray systems should be well-maintained and periodically surveyed to ensure operation within appropriate specifications 1
• Use dose-tracking awareness - Be cognizant of radiation exposure parameters, though individual patient dose tracking adds limited practical clinical value 5
• Employ radiation protection principles - Minimize beam-on time, use optimal collimation, and select appropriate imaging parameters 1

Documentation and Reporting

• Record systematic findings - Document normal and abnormal findings in each anatomic region reviewed
• Provide clinical correlation - Relate radiographic findings to clinical presentation
• Recommend appropriate follow-up - Suggest additional imaging or clinical correlation when indicated
• Compare to established quality criteria - Scoring of quality criteria relating to features observed in normal clinical radiographs provides a simple method for quality assessment 4