Respiratory system

Published on 12/06/2015 by admin

Filed under Radiology

Last modified 12/06/2015

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Respiratory system

Computed tomography of the thorax

Technique

1. Volume scan – usually performed with intravenous contrast enhancement at a rate of 3–5 ml s–1 with a delay of 25–40 s. However, bolus tracking software can be used to trigger the scan more precisely to coincide with optimal contrast enhancement of specific structures, e.g. mediastinum, aorta in suspected aortic dissection or pulmonary artery in suspected pulmonary embolism. (Delayed imaging at 60 s can be useful in cases of large pleural effusion to assess for underlying soft tissue pleural thickening.)

2. High-resolution scan. Non-contrast scan obtained on full inspiration either:

Computed tomography-guided lung biopsy

Indications

All biopsies should be planned after case discussion at a multi-disciplinary meeting with a respiratory physician, radiologist, surgeon and oncologist where the balance of benefit versus risk can best be assessed. Central lesions are preferably biopsied transbronchially either by standard bronchoscopy (where there is endobronchial disease) or, if extrabronchial, by transbronchial needle aspiration (TBNA) either ‘blind’ or with endoscopic ultrasound guidance (EBUS).

Contraindications

Contraindications are not absolute but should be carefully evaluated by the relevant multi-disciplinary team.

Equipment

1. Sampling needle:

• Fine needle aspiration can be performed if there is an on-site cytopathology service. Usually use 20 or 22G needles. Different needles vary by the profile of the needle tip and include Chiba (with a bevelled tip which allows straightforward cytological sample aspiration) and those with modified tips which allow ‘cutting’ to obtain small histological fragments as well as aspiration (suitable for more fibrous lesions), e.g. Franseen® (Cook Medical™) and Westcott® (Becton-Dickinson Medical™).

• Cutting needle biopsy needles are larger gauge (usually 18 or 20G) and obtain a solid core of tissue for histological examination. They usually have adjustable throw of the specimen notch for precise sampling of the lesion. Types include Temno® and Quick-Core® (Cook Medical™). Coaxial needle biopsy systems can be used as these stabilize the cutting needle, allowing resampling without re-puncturing the pleura, aid re-angling of the cutting needle and allow accurate preplanning of depth of passes.

2. Full resuscitation equipment including equipment for pleural aspiration and chest drain insertion.

Staff should be prepared for recognition and treatment of complications of pneumothorax, vasovagal episodes, haemoptysis and (very rarely) air embolus.

Aftercare

1. Close observation post procedure for at least 1 h in a supervised ward or recovery area, with the patient lying in puncture-site-down position (which should be possible for all but anterior approach interventions). (A limited CT at the end of the procedure will have determined if a pneumothorax or parenchymal bleed is present.)

2. Departmental PA chest X-ray at approximately 1–4 h post procedure. If a pneumothorax has developed (or progressed) then the further management will depend on the size of the pneumothorax and clinical condition of the patient. Small pneumothoraces in asymptomatic patients may be observed; larger pneumothoraces in symptomatic patients will require aspiration or chest drain insertion.

3. High-risk and frail patients, particularly those with pre-existing impairment of respiratory function, are best routinely admitted overnight.

Complications2–4

Usually occur early following the procedure: