Radiological investigations
1. Chest X-ray
A chest X-ray is the basic screening test for patients with respiratory symptoms. It is regarded as standard for patients presenting with chronic problems or acute potentially serious symptoms. It allows visualization of conditions affecting the lung such as: • Pneumothorax—the accumulation of air in the pleural space • Lung mass—such as carcinoma • Collapse (atelectasis)—a loss of volume of a lung, lobe or segment for any cause. The most common cause is obstruction of a major bronchus by a tumour, foreign body or mucus plug • Tuberculosis • Fibrosis • Over-inflation in airways disease such as asthma and COPD • Consolidation—seen as an area of white lung it represents fluid or cellular matter, where there would normally be air. Most commonly seen in infection such as pneumonia or pulmonary oedema
Nursing considerations
What the patient needs to know: • There will be no discomfort during the test and there is very little risk involved • In women of reproductive age, an X-ray should be performed within 10 days of their last menstruation, unless it is an acute situation • They will need to remove any metal objects and jewellery from their neck and chest • They will be asked to stand in front of a photographic plate, with the X-ray beam positioned two metres behind them • They will be asked to inhale fully, and to hold their breath • The X-ray beam fires a short beam of X-rays through the patient onto the photographic plate • These X-ray beams scatter as they pass through the chest structures • This distortion influences the pattern of X-rays hitting the plate, allowing the structures in the chest to be identified • Patients who are too ill or too breathless to stand for an X-ray in the radiology department can have a portable X-ray • The film obtained by portable X-ray may be inferior to the standard X-ray obtained in the radiology department.
Evaluating chest X-rays
• Always view an X-ray on a viewing box or on a Picture Archiving and Communication System (PACS) • Check the name and date on the X-ray • Note that the radiograph contains right or left-side markers • You should be able to count six ribs anterior to the diaphragm if there was sufficient inspiration • Make sure the whole lung field is included Divide the lungs into zones—upper, middle and lower and compare like with like • Examine the area around the rib cage for masses, swelling, air or foreign objects • Observe the diaphragm—normally the right side looks higher than the left. The diaphragm normally curves downward (costophrenic angle) with clear delineated margins • Examine the bony structures, looking for unusual densities or fractures • Look at the heart and check it is of normal shape and size and that the cardiac borders are visible • Look at the trachea, which should be central—if the trachea has shifted this suggests a problem within the mediastinum or pathology within one of the lungs • Compare the lung fields looking for adequate lung expansion, and similar areas of density in both lungs • You generally cannot see the pleura unless they are abnormally thickened.
2. Computerized tomography (CT) scan
Availability of CT scans has greatly enhanced imaging of the chest, and it is now a routine test in specialist clinical practice. It allows a detailed examination of the lung fields and the central chest. It also allows very high quality images of the chest and the contents of the thoracic cavity, by having many X-rays of the same area performed at different angles. These are collected and processed by a computer into a single image.
Nursing considerations
What the patient needs to know: • Why the test needs to be performed • That the test involves exposure to a moderately large dose of X-ray material, approximately 100 times that of a standard chest X-ray • They may be given intravenous contrast • That the test involves lying flat and motionless, often difficult for a patient who is breathless, on a bed inside a tube for approximately 15 mins • They will need to be able to hold their breath for a period of up to 10s • The scanner takes the images quickly and silently • The pictures are then transferred to a computer that processes the information
What the CT scan identifies
• Pulmonary nodules • Mediastinal masses • Carcinoma of the lung • Pleural lesions • Vascular lesions.
High-resolution CT scan (HRCT)
HRCT is used in imaging diffuse lung diseases as it looks at thin sections of 1–2mm, which show greater lung detail. This scan identifies: • Bronchiectasis • Interstitial lung disease such as sarcoidosis, occupational lung disease, and interstitial pneumonia • Atypical infections, where HRCT is used to provide earlier diagnosis, monitoring disease and response to treatment, and evidence of disease activity and destruction.
3. Magnetic resonant imaging (MRI)
MRI is a test that uses a powerful magnet, radio waves, and a computer to help diagnose respiratory diseases. It provides high-resolution, cross sectional images of lung structures and traces blood flow. An MRI scan can be of additional value to a CT in examining spinal and some soft tissue pathologies. Although a CT scan tends to offer similar detail to MRI, the MRI scan can be very helpful in the staging of lung cancer as it looks for spinal and cerebral metastases. Because of the use of magnetic fields, metal objects cannot be placed in the scanner.
Nursing considerations
• The patient needs to know why the test needs to be done • Ask the patient to remove all jewellery and empty their pockets. The magnet may de-magnetize the magnetic strip on debit and credit cards, and stop a watch from working • Inform the doctor if the patient has a heart pacemaker or orthopaedic pins or disks • Tell the patient that he or she will have to lie on a table that slides into a tunnel inside the magnet • The patient should be advised to breathe normally, but not to talk or move during the test to avoid distorting the results • The test can take up to 45 minutes with the patient lying flat throughout, this can be difficult if they are very breathless • Warn the patient that the machinery is very noisy, with sounds ranging from a constant ping to loud bangs. • Provide ear plugs or play music of the patient’s choice • Some patients may feel claustrophobic and sedation may need to be offered.