8 Techniques in Thoracic Imaging

DR MUHAMMAD BIN ZULFIQARPGR III FCPS Services institute of Medical

Sciences/ Services Hospital LahoreGRAINGER & ALLISON’S DIAGNOSTIC RADIOLOGY

• FIGURE 8-1 Series of dual-energy subtraction chest ■radiographs in a healthy man. A right apical opacity is seen on a conventional posteroanterior radiograph (A), but a soft-tissue nodule in the left apex only becomes conspicuous on a bone-subtracted image (B). Additionally, a soft-tissue subtracted image (C) reveals that the right apical opacity is actually calcification of the first costochondral junction. (With permission from McAdams HP, Samei E, Dobbins J III, et al 2006 Recent advances in chest radiography. Radiology 241(3): 663–683.)

• FIGURE 8-2 Suspected pulmonary metastases in a man with poorly ■differentiated adenoid cystic carcinoma. On a 1-mm-thin section image (A), a subpleural nodule (black arrow) is easily seen, but a central nodule (white arrow) can be mistaken for a pulmonary vessel. Scrolling through 10-mm-thick maximum intensity projection (MIP) images (B) can show the central nodule as distinct from the adjacent vessel (white arrow), and make the subpleural nodule more conspicuous (black arrow).

• FIGURE 8-3 Geometry of a dual-source CT ■system. The two tubes are positioned at 90° to each other, diametrically opposite their detector arrays.

• FIGURE 8-4 Geometry and dose profile for spiral, 4-, 16- and ■64-slice CT. In spiral CT, the whole dose within the umbral region (U) contributes to image reconstruction with no wastage. In 4-slice CT, wastage occurs within the penumbral regions (P). The relative contribution of the penumbral region decreases with an increasing number of simultaneously acquired sections. The effect of this wastage is minimised in 64-slice CT.

• FIGURE 8-5 Screenshot from volumetric ■analysis of a low-dose CT study in a lung cancer screening trial. The CT parameters were based on the patient’s body weight, with the effective mAs kept at 22 mAs and a tube potential of 120 kVp.

• FIGURE 8-5 Screenshot from volumetric ■analysis of a low-dose CT study in a lung cancer screening trial. The CT parameters were based on the patient’s body weight, with the effective mAs kept at 22 mAs and a tube potential of 120 kVp.

• FIGURE 8-6 (A) ■Unenhanced and (B) intravenously enhanced volumetric 1-mm section HRCT images in a patient with biopsyproven non-specific interstitial pneumonia, taken one week apart. Generally, increased ground-glass opacity is seen in both lungs, but it is difficult to determine whether this represents new parenchymal opacification, or whether it is purely the consequence of contrast enhancement.

• FIGURE 8-7 HRCT for ■suspected asbestosis. (A) HRCT image in the supine position demonstrates fine reticulation and increased subpleural density (arrows). (B) These changes (arrows) persist on the prone image and may represent early asbestosis in this patient who had an appropriate asbestos exposure.

• FIGURE 8-8 Mosaic ■attenuation in a patient with bronchiectasis in the lower lobes (not shown). HRCT image taken in inspiration (A) shows subtle mosaicism, emphasised in the section acquired at end-expiration (B), indicating small airways disease.

• FIGURE 8-9 Ultrasound evaluation of ■empyema. Multiple septations (arrows) are present within the anechoic pleural collection.

• FIGURE 8-10 Endobronchial ultrasound-■transbronchial aspiration (EBUS-TBNA) of a subcarinal node in a patient with mediastinal lymphadenopathy. The needle is visualised as a linear focus of high echoreflectivity (arrow). (Courtesy of Dr Pallav Shah, Royal Brompton Hospital.)

• FIGURE 8-11 Anterior ■mediastinal mass in a 54-year-old woman incidentally discovered during MRI of the thoracolumbar spine. A well-circumscribed ovoid anterior mediastinal lesion is present (arrows) that is hypointense on T1-weighted (A) and markedly hyperintense on T2-weighted (B) sagittal MR images relative to muscle. The appearances are consistent with a thymic cyst.

• FIGURE 8-12 Coronal ■hyperpolarised 3He MR images of 24-yearold (A) and 17-year-old (B) patients with cystic fibrosis, with FEV1 of 109 and 52%, respectively. Both patients demonstrate multiple ventilation defects, but the patient in (B) with the poorer FEV1 shows defects which are both larger and more widespread. (With permission from Ohno Y, Koyama H, Yoshikawa T, et al 2011 Pulmonary magnetic resonance imaging for airway diseases. J Thorac Imaging 26(4): 301–316.)