Image Quality in Portable Chest
A portable chest radiograph is ordered for a 55-year-old intubated patient in the ICU. The technologist uses a mobile unit with a computed radiography (CR) cassette. The image shows the endotracheal tube tip at the level of the clavicles, and the lungs are underexposed. The patient is on a ventilator and cannot be moved easily. The technologist is asked to repeat the image.
1. What positioning and technical adjustments should the technologist make for the repeat image?
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Positioning: Ensure the cassette is centered at the level of the T7 vertebra (approximately 2-3 inches below the sternal angle) and the patient is as upright as possible (e.g., using a wedge). The tube should be angled slightly caudad to avoid clipping the costophrenic angles. Technical: Increase mAs to improve exposure (underexposure suggests insufficient mAs), use a higher kVp (100-120) to penetrate the mediastinum, and ensure the CR plate is properly processed. Use a grid if possible. Also, verify the endotracheal tube position and note that it appears too high (should be 3-5 cm above carina).
2. How can the technologist evaluate if the repeat image is adequate?
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Evaluate: visualization of the entire lung fields, including costophrenic angles; adequate penetration (vertebrae visible behind the heart); no rotation (spinous processes centered between clavicles); endotracheal tube tip visible and ideally at least 3 cm above the carina; and proper inspiration (posterior ribs 9-10 visible). Also, check for artifacts and ensure patient identification.