untitled 21 SA JOURNAL OF RADIOLOGY • December 2005 Introduction A higher proportion of paediatric interstitial lung diseases can be diagnosed with high-resolution computed tomogra- phy (HRCT) scan than plain radiography, with the diagnosis being made with more confidence and higher accuracy.1 HRCT is probably easier to interpret in the child than in the adult. There is less pressure to reach a definitive diagnosis from the HRCT alone, because many entities resulting in diffuse lung disease are rare in childhood and do not require consideration. In addi- tion, endstage fibrosis, which has nonspe- cific appearances, is rare. Lastly, infection is the most likely cause of most positive stud- ies. When to perform a HRCT (indications are similar to those in adults)2,3 (i) When the patient is symptomatic but the chest X-ray (CXR) is normal; (ii) to confirm an interstitial pattern seen on CXR; (iii) to determine the severity of dis- ease; (iv) to look for bronchiectasis; (v) to look for predisposing factors; (vi) to identi- fy the main abnormality and possibly come close to a diagnosis; (vii) to look for seque- lae of infection; and (viii) to show a site for biopsy. How to approach HRCT4 Look for the following: AAiirrwwaayy ddiisseeaassee:: nodules, mosaic pat- tern, bronchiectasis, bronchial wall thick- ening, and air trapping. AAiirrssppaaccee ddiisseeaassee:: nodules, ground glass, mosaic pattern, and consolidation. IInntteerrssttiittiiaall ddiisseeaassee:: nodules, ground glass, mosaic pattern, septal thickening, parenchymal bands, air-filled cysts, honey- combing, and architectural distortion. Features on HRCT Nodules Nodules are focal oval densities of a variety of sizes that can be ‘well defined’ or ‘ill defined’ and are interpreted according to their predominant distribution and size (Table I). A good example of ‘fluffy’ or ill-defined PICTORIAL ESSAY Paediatric HRCT of the chest – help for the general radiologist S Andronikou MB BCh, FCRad (D) (SA), FRCR Department of Radiology Tygerberg Hospital and University of Stellenbosch; N Wieselthaler MB BCh, FCRad (D) (SA) J Bertelsmann Diploma in Radiology Department of Radiology Red Cross Children’s Hospital and University of Cape Town Table I. Causes of pulmonary nodules in children3,4 Small ill-defined CLOs Small soft-tissue nodules Larger masses Halo sign Bronchogenic TB* Miliary TB TB TB Aspiration* Fungi Fungi Pulmonary aspergillosis Bronchiectasis* Metastases Metastases Lymphoproliferative Asthma* Langerhans cell histiocytosis Septic emboli Wegener’s granulomatosis Cystic fibrosis* Pulmonary haemosiderosis Lymphoma Pulmonary haemorrhage Infective bronchiolitis* AVM Osteosarcoma metastases LIP* LCH LCH Papillomatosis Hypersensitivity pneumonitis Vasculitis Pulmonary capillary haemoangiomatosis BOOP/COP Pulmonary haemosiderosis Pulmonary arterial aneurysm Follicular bronchiolitis Bleomycin BO Lipoid granuloma (TPN) Congenital lymphangiectasia Immotile cilia *Common causes. LIP = lymphoid interstitial pneumonitis; LCH = Langerhans cell histiocytosis; BO = bronchiolitis obliterans; AVM = arteriovenous malformation; BOOP/ COP = bronchiolitis obliterans organising pneumonia / cryptogenic organising pneumonia; TPN = total parenteral nutrition Article - Andronikou 11/30/05 10:46 AM Page 21 22 SA JOURNAL OF RADIOLOGY • December 2005 nodules is in pulmonary oedema where they tend to coalesce and form areas of consolidation. True interstitial nodules are ‘well-defined’ and are well represented by military tuberculosis (TB) (Fig. 1a and b). Even though there are innumerable nod- ules, they remain discreet and ‘can be picked off the page individually with tweez- ers’. Nodules of varying sizes, which are randomly distributed, especially in the periphery and usually affect both lungs, are characteristic of metastatic disease (Fig. 2a). A special type of nodule is the cen- trilobular opacity (CLO). These are about 5 mm in size and are seen within the sec- ondary lobule as nodules, branching ‘Y’ structures or ‘trees in bud’ (Fig. 2b). They represent material within the central bron- chiole of the secondary lobule. 3,4 Ground glass opacification (GG) and consolidation GG is an increased density of the lung where the vascular and bronchial markings are still visible. There may be air bron- chograms. Causes include filling of air spaces, thickening of the interstitium, par- tial collapse of alveoli, expiration in a nor- mal individual or increased capillary vol- ume. GG is seen regularly with infections and is an important but nonspecific HRCT feature of the chronic diffuse interstitial pneumonitides (Table II) (Fig. 3). GG sur- rounding a nodule results in the ‘halo sign’, often seen in fungal disease (Fig. 4a and b).4 Consolidation is caused by filling of the alveoli with fluid or cells or both and differs from GG in that the increased density obscures vascular markings and is usually accompanied by air bronchograms (Figs 5 and 6). PICTORIAL ESSAY Fig.1a. Miliary TB. Fig.1b. Miliary TB. Fig. 2a. Metastases. Fig. 2b. Centrilobar opacity (CLO). Table II. Ground glass / consolidation 3,4 Oedema* Pneumonia* Respiratory distress syndrome* Leukaemia* Contusion* Pulmonary haemorrhage* Alveolar proteinosis Drug toxicity Extrinsic allergic alveolitis Transplant rejection Sarcoid Collagen vascular disease Post lavage Idiopathic interstitial pneumonitides (NSIP) Idiopathic pulmonary fibrosis *Common causes. NSIP = nonspecific interstitial pneumonitis. Fig. 3. Ground glass (GG). Fig. 4a. Halo sign. Fig. 4b. Zoomed ‘halo sign’. Fig. 5. Lobar airspace opacification. Article - Andronikou 11/30/05 10:46 AM Page 22 23 SA JOURNAL OF RADIOLOGY • December 2005 Tip: Focal GG is usually due to air space disease or a vasculitis and diffuse GG is usually representative of an interstitial process.2-4 Tip: GG can cause a ‘mosaic pattern’ on HRCT and requires an expiratory scan to distinguish it from air-trapping.2-4 Mosaic pattern and air-trap- ping (Table III) ‘Mosaic pattern’ is a geographic pattern of varying lung density. It reflects either focal areas of air-trapping (a sign of small airways disease) (Fig. 7a) but is also associ- ated with focal areas of GG (Fig. 7b). The two entities can be differentiated by an expiratory HRCT in which the low-density areas become more exaggerated and vessel calibre decreases if the mosaic pattern is due to air-trapping. Mosaic perfusion is seen with bronchiolitis obliterans and bronchiectasis. Generalised air-trapping may be due to partial or complete airway obstruction or local abnormality in pulmonary compli- ance. Measuring the Hounsfield density of the lung can assess this. Normal lung mea- sures -600 to -750 HU while air-trapping results in density measurements of -900 HU. It can also be assessed with an expira- tory view, which in small children is obtained by a decubitus view of the ‘side- down’ hemithorax (Fig. 8).3,4 Septal lines This is abnormal widening of the inter- lobular septa and can either be seen as lin- ear densities perpendicular to and touching the pleura (equivalent to Kerley B lines) or as a polygonal pattern outlining the sec- ondary lobule more centrally (Fig. 9a and b).4 These are often seen with lymphatic involvement in diseases such as lymphan- giomatosis and lymphangitic spread of malignancy.5 The polygonal pattern of lin- ear densities on a background of GG results in the ‘crazy paving’ pattern best known to occur in alveolar proteinosis.4 Lines may be smooth or irregular helping to differentiate some of the causes of this feature (Table IV). Parenchymal bands / archi- tectural distortion / honey- combing These findings all represent some form of chronic involvement and scarring / fibrosis of the lung. Parenchymal bands are longer than septal lines measuring between 2 and 5 cm (Fig. 10) and are often associat- ed with a pleural ‘tag’. They can occur with fibrosis and scarring or atelectasis associat- ed with fibrosis and are most often seen in children with bronchopulmonary dysplasia (chronic lung disease). Architectural dis- tortion indicates displaced bronchi, vessels and or fissures and is usually associated with decreased vascularity and bronchial abnormalities (Fig. 11a). Honeycombing is rare in children and represents destroyed lung that becomes cystic and fibrotic (Fig. 11b). HRCT shows air-filled cysts that tend to occur in a subpleural distribution over several layers and are unaffected by expira- tion. This is seen in children with chronic diffuse idiopathic pneumonitides and con- nective tissue diseases. PICTORIAL ESSAY Fig. 6. Patchy airspace opacification. Table III. Air-trapping 3,4 Bronchiolitis obliterans Cystic fibrosis Bronchiectasis Asthma Viral Left to right Follicular bronchial hyperplasia Fig. 7a. Mosaic pattern due to air-trapping. Fig. 7b. Mosaic pattern due to focal areas GG. Fig. 8. Air-trapping in ‘side down’ lung. Fig. 9a. Septal lines. Fig. 9b. Septal lines. Article - Andronikou 11/30/05 10:46 AM Page 23 Bronchiectasis Bronchiectasis can either be a diagnosis or a feature of another disease. It indicates irreversible dilation of a bronchus and the signature feature is the ‘signet ring sign’ (Fig. 12 a and b). This represents a thick- walled bronchus, which is larger than the adjacent pulmonary artery.4,6 Other indica- tors of bronchiectasis include non-tapering of a bronchus, bronchial wall thickening (Fig. 12b) (more than a fine ‘pencil-thin’ line) and visualisation of a bronchus with- in 1 cm of the periphery (including the fis- sures).7 Associated with bronchiectasis are atelectasis, mosaic pattern and CLOs.8 Air- fluid levels may also be present within dilated bronchi. The causes of bronchiecta- sis are many but are most commonly asso- ciated with previous, current or recurrent infection, cystic fibrosis and aspiration (Table V). PICTORIAL ESSAY 24 SA JOURNAL OF RADIOLOGY • December 2005 Table IV. Septal lines 3,4 Smooth Nodular / irregular Crazy paving Pulmonary oedema* Lymphoma Alveolar proteinosis Infection* Sarcoma / neuroblastoma Lipoid pneumonia BPD* Sarcoid ARDS Pulmonary alveolar proteinosis Fibrosis AIP Neoplasms Drug-induced pneu- monia Pulmonary lymphangiectasia Lymphangiomatosis Pulmonary capillary haemangiomatosis Gaucher / Nieman Piek Sarcoid Pulmonary alveolar microlithiasis Pulmonary haemosiderosis Tuberous sclerosis Collagen vascular diseases Fibrosis BPD = bronchopulmonary dysplasia; ARDS = acute respiratory distress syndrome; AIP = acute interstitial pneumonitis. Fig. 10. Parenchymal bands. Fig. 11a. Architectural distortion Fig. 11b. Honeycombing. Table V. Causes of bronchiectasis 3,6,8 Infection TB AIDS Adenovirus Immunodeficiency Aspiration Recurrent infection Sequelae of infection Obstruction Foreign body Neoplasm Lymphadenopathy Cystic fibrosis (most common cause in children) Allergic bronchopulmonary aspergillo- sis Ciliary dyskinesia Fibrosis Williams-Campbell syndrome Fig.12a. Bronchiectasis. Fig.12b. Bronchial wall thickening and ‘signet ring sign’. Article - Andronikou 11/30/05 10:46 AM Page 24 Air-filled cysts These are usually thin-walled and con- tain air. They may be oval with smooth walls as in tuberous sclerosis or have irreg- ular margins as in Langerhans cell histiocy- tosis (Fig. 13). The causes of air-filled cysts in children are listed in Table VI. Specific diseases seen in children on HRCT The range of diseases in children differs from adults (Table VII)1,5 and the reported accuracy for a confident first choice diag- nosis on HRCT varies from 56% to 61%.2,5 The diseases diagnosed with the highest degree of confidence in children include alveolar proteinosis, pulmonary lymphang- iectasia and idiopathic pulmonary haemosiderosis.1,2 We will describe the HRCT appearances of the acute infective causes of diffuse lung diseases and diseases affecting the airways that involve the inter- stitium, because these occur most com- monly in our practice. We will also review the appearances of those conditions char- acterised by nodules and septa that are seen less often in paediatric practice. Infections Infection - tuberculosis Miliary nodules are common but not always present, measure 2 - 3 mm and remain discreet (Figs 1a and b, and 14). Bronchogenic spread of TB may result in larger nodules that may confluence. Both GG and consolidation are regular features of primary TB. CLOs, bronchiectasis and air trapping also occur. In addition, the important characteristic association is hilar and mediastinal lymphadenopathy which are the fingerprint of primary TB.9 Infection - AIDS: LIP (lymphoid intersti- tial pneumonitis) LIP is an AIDS-defining feature in chil- dren < 13 years of age. Between 30% and 40% of children with AIDS have LIP. HRCT features involve septal lines and nodules (CLOs and subpleural) (Fig. 15). GG, cysts and bronchiectasis are common associa- tions. Hilar lymphadenopathy and thymic cysts may or may not be present. Effusions are not a feature.3 Infection - AIDS: Pneumocystis carinii This begins as a patchy airspace or GG appearance and progresses to a more homogeneous GG or airspace process that involves both lungs. In addition there are septa and cysts. Effusions are not a feature and there is a notable absence of nodules and lymphadenopathy.3 Infection - invasive aspergillosis This occurs in immunocompromised patients. The most characteristic features are nodules with a ‘halo’ sign that may cav- itate (50%) (Figs 4 and 16) and result in the ‘air crescent’ sign as air collects between normal and infected lung. More wide- spread GG or airspace disease is also noted.3 Bone marrow transplant children may require a HRCT to exclude this disease process. Airways (Table VIII) Airways - cystic fibrosis HRCT is performed to document the presence and extent of disease. The hall- mark is widespread bronchiectasis involv- ing the upper zones (Fig. 12b). Associated features such as peribronchial thickening, CLOs, larger mucoid impactions and mosaic pattern are common.3,6,8 Airways - immotile cilia syndrome Half of these patients have Kartagener’s PICTORIAL ESSAY 25 SA JOURNAL OF RADIOLOGY • December 2005 Fig.13. Air-filled cysts in Lagerhans cell histio- cytosis. Table VI. Air-filled cysts4 Pneumatoceles* (infective, trauma, tox- ins) Pneumonia* Septic emboli* Congenital* Tuberous sclerosis* LCH* Papillomatosis Pseudocysts (barotrauma) Wegener’s granulomatosis Ehlers-Danlos syndrome Marfan’s syndrome Williams-Campbell syndrome *Common causes. LCH = Langerhans cell histiocytosis. Fig.14. Miliary TB. Fig.15. Lymphoid interstitial pneuomonitis. Fig.16. Fungi. Article - Andronikou 11/30/05 10:46 AM Page 25 syndrome (situs inversus, sinusistis and bronchiectasis). Features cannot be differ- entiated from cystic fibrosis but there is a predilection for the right middle lobe.8 Airways - allergic bronchopulmonary aspergillosis This is a hypersensitivity reaction to endobronchial growth of Aspergillus fumi- gatus and results in asthma. The main fea- ture is central bronchiectasis, which in a patient with asthma, clinches the diagno- sis.8 Airways - Swyer-James / Macleod’s syn- drome This is a post-infectious bronchiolitis and signs include a unilateral lucent lung with air-trapping. In reality on HRCT 50% of these patients have bilateral disease with the most affected lung showing low density, mosaic pattern and bronchiectasis, and the less affected lung showing patchy air-trap- ping.3,8 Airways - bronchiolitis obliterans / con- strictive bronchiolitis As expected for diseases of the airways the predominant HRCT findings are bronchial wall thickening and bronchiecta- sis with the associated mucoid impaction and CLOs and resultant mosaic pattern of air-trapping.3,4,8 The causes of bronchiolitis obliterans are listed below (Table IX). Bronchocentric granulomatosis has the above features but also shows septal thick- ening.3 Airways - BOOP (bronchiolitis obliterans organising pneumonia) and COP (crypto- genic organising pneumonia) This is rare in children but is charac- terised by patchy consolidation or a GG pattern (Fig. 17a and b). Bronchial wall thickening and bronchiectasis are also fea- tures (Fig. 17c). Nodules and septa may be seen. Small effusions may also be present.6,8 The causes of BOOP are listed in Table IX. PICTORIAL ESSAY 26 SA JOURNAL OF RADIOLOGY • December 2005 Table VII. Diffuse lung diseases in children 2,3,8 Common Seen in practice Rare Infant-specific Infection LCH Extrinsic allergic alveolitis Persistent tachypnoea of infancy TB Pulmonary lymphangiectasia Sarcoid BPD Pneumocystis Pulmonary haemorrhage Intersitial pneumonitides Cellular interstitial pneumonia Viral Alveolar proteinosis Collagen vascular diseases Infantile pulmonary haemosiderosis Mycoplasma Collagen vascular disease Vasculitides Chronic pneumonitis of infancy Aspergillosis Neurocutaneous syndromes Lymphangiomatosis Surfactant protein B deficiency Chronic/recurrent ` Alveolar microlithiasis Familial DIP LIP (AIDS-related) Gauchers / Nieman Piek Idiopathic pulmonary fibrosis infancy BPD Pulmonary infiltrates with eosinophilia Aspiration Lymphangitis carcinomatosa LIP = lymphoid interstitial pneumonitis; BPD = bronchopulmonary dysplasia; DIP = desquamative interstitial pneumonitis; LCH=Langerhans cell histiocytosis. Table VIII. Airway diseases in children 1-4,8 Infection Sequelae of infection Bronchiectasis Cystic fibrosis Allergic bronchopulmonary aspergillo- sis and asthma Aspiration Foreign body Swyer James / Macleod’s syndrome Bronchiolitis obliterans / BOOP/ follic- ular bonchiolitis Immotile cilia BOOP = bronchiolitis obliterans organising pneumonia. Table IX. Causes of bronchiolitis oblit- erans and bronchiolitis obliterans with organising pneumonia 3,8 Idiopathic Infection Viral (adenovirus, influenza, measles) Bacteria Mycoplasma Transplant (heart/lung 50% and bone marrow 10%) Collagen vascular diseases Toxic fumes Stevens-Johnson syndrome Post chemotherapy Fig.17a. Bronchiolitis obliterans. Article - Andronikou 11/30/05 10:46 AM Page 26 Interstitial disease: nodules and lines Nodules and lines - bronchopulmonary dysplasia / chronic lung disease This occurs as a result of the treatment of premature lungs. Early appearances are characterised by septa, parenchymal bands and cystic spaces forming a ‘cobblestone’ pattern. Later in life a mosaic pattern and architectural distortion are present and even later there is associated bronchiolitis obliterans and traction bronchiectasis. Nodules and lines - Langerhans cell histio- cytosis The predominant features are nodules that cavitate and become cysts. These then become thin-walled and fuse. This results in an irregular cystic appearance and is often complicated by a pneumothorax (Fig. 18). Early on in the disease, the costophrenic angles are spared.2,3,5 The other causes of air-filled cysts in the lungs are listed below (Table VI). Nodules and lines - alveolar proteinosis This is characterised by septa on a background of GG resulting in an easily recognisable geographic ‘crazy paving’ sign (Fig. 19a and b).2,3 Nodules and lines - lymphangiectasia (Noonan’s) / lymphangiomatosis Here HRCT shows septal thickening and GG often associated with effusions (Fig. 20a and b).2,3,5 Nodules and lines - lymphangitis carcino- matosa This is a rare finding in children but can occur with lymphoma, neuroblastoma, sarcomas and thyroid malignancy. The main feature is septa accompanied by fis- sural and bronchovascular bundle thicken- ing (Fig. 21a and b). It differs from sarcoid where the fissures are beaded with nod- ules.3 PICTORIAL ESSAY 27 SA JOURNAL OF RADIOLOGY • December 2005 Fig.17b. Bronchiolitis obliterans. Fig.17c. Brochiolitis obliterans. Fig. 18. Langerhans cell histiocytosis with bilateral pneumothoraces. Fig. 19a. Alveolar proteinosis. Fig. 19b. Alveolar proteinosis ‘crazy paving’. Fig. 20a. Noonan’s. Fig. 20b. Noonan’s Fig. 21a. Lymphangitis carcinomatosa. Fig. 21b. Lymphangitis carcinomatosa. Article - Andronikou 11/30/05 10:46 AM Page 27 Nodules and lines - extrinsic allergic alve- olitis / hypersensitivity pneumonitis Patchy or diffuse GG, mosaic pattern and CLOs are the prominent HRCT fea- tures.2,3,5 Nodules and lines - pulmonary haemor- rhage / idiopathic pulmonary haemosiderosis Acute haemorrhage appears either as GG or denser consolidation and is usually bilateral on HRCT (Fig. 22 a - c).3,10 More chronic haemorrhage results in nodules (CLOs and other) and septa.2,10 The causes of pulmonary haemorrhage in children are listed below (Table X). Nodules and lines - sarcoid The nodules in sarcoid are described as ‘beeding’ the fissures, bronchovascular bundles and pleura (Fig. 23). Larger dense nodules may represent confluent areas of GG or consolidation, which may cavitate. Lymphadenopathy is a major feature.3 Nodules and lines - systemic sclerosis (vasculitis) Even though vasculitides are rare in children, systemic sclerosis may result in lung changes on HRCT in childhood. The HRCT features are a GG pattern with sub- pleural nodules that may progress to supleural cysts and honeycombing. Septa are not a feature.2,3 Drug-related toxicity and injury Chemotherapy and other insults to the lung may result in airspace and interstitial disease, which may range from GG to sep- tal lines and nodules to endstage fibrosis (Fig. 24). Endobronchial papillomatosis Endobronchial papillomas cause obstruction with bronchial wall thickening and dilation (Fig. 25). Idiopathic / chronic interstitial pneu- monitides and idiopathic pulmonary fibrosis These diseases are rare in children and are distinguished only after biopsy. HRCT is less accurate in the diagnosis.1 They are predominated on HRCT by GG (Fig. 26) that progresses to pulmonary fibrosis (IPF). In children the diagnoses of DIP (desquamative interstitial pneumonitits) and UIP (usual interstitial pneumonitis) should not be listed in the differential diag- PICTORIAL ESSAY 28 SA JOURNAL OF RADIOLOGY • December 2005 Table X. Causes of diffuse pulmonary haemorrhage in children10 Idiopathic pulmonary haemorrhage Heiner’s syndrome Stacybotrys atra Diffuse alveolar haemorrhage with glomerulonephritis Wegener’s granulomatosis Systemic necrotic vasculitis Goodpasture’s syndrome Systemic lupus erythematosis Henoch-Schonlein purpura Idiopathic glomerulonephritis and alveolar haemorrhage Cardiovascular causes Pulmonary venous hypertension Mitral stenosis Eisenmenger’s Congenital pulmonary vein stenosis Congenital pulmonary artery stenosis Pulmonary capillary haemangiomas Fig. 22a. Idiopathic pulmonary haemosiderosis. Fig. 22b. Idiopathic pulmonary haemosiderosis. Fig. 22c. Idiopathic pulmonary haemosiderosis. Fig. 23. Sarcoid with ‘beeding’. Fig. 24. Drug toxicity. Fig. 25. Papillomatosis. Article - Andronikou 11/30/05 10:46 AM Page 28 noses. Instead NSIP (non-specific intersti- tial pneumonitis) and AIP (acute intersti- tial pneumonitis) may be added to a differ- ential diagnosis.2,3,8 The end result of these is pulmonary fibrosis that is characterised on HRCT by cysts, honeycombing, parenchymal bands and traction bronchiectasis. Recommended tech- niques for HRCT in children2,3,5 The aim is to produce images of high spatial resolution with no motion artefact using the least amount of radiation possi- ble. Diffuse disease allows for large inter- slice imaging. Current multi-detector CT allows the acquisition of a volume of con- tiguous data and allows reconstruction of this data on a high-frequency algorithm in fine slices, thereby yielding both contigu- ous thicker-slice CT scans and high-resolu- tion CT scans in one event. mmAAss:: 40 - 80 (Tip: reduces radiation by up to 80%) kkVV:: 120 (Tip: an increase from 120 to 140 kV increases the dose by 40%) Slice thickness: 1- 2 mm (multidetector = 1.25) (Tip: thicker slice = less motion arte- fact) SSlliiccee ssppaacciinngg:: > 10 years = 10 mm, 2 - 10 years = 7 mm, < 2 years = 5 mm (irrelevant for MDCT) FFOOVV:: small as possible, < 25cm (Tip: small FOV = higher resolution) SSccaann ttiimmee:: shortest possible, e.g. 1- 2 s (Tip: shorter time = less motion) RReeccoonnssttrruuccttiioonn:: High frequency, e.g. bone or lung (Tip: increases edge and detail) IInnssppiirraattoorryy:: quiet respiration represents inspiration in children EExxppiirraattoorryy:: use decubitus side down (Tip: flat, half or sliver moon trachea = expira- tion) PPoossiittiioonn:: only rarely require prone position in children VViieewwiinngg:: lung window, width 1 500 HU and level -500 HU References 1. Copley SJ, Coren M, Nicholson AG, Rubens MB, Bush A, Hansell DM. Diagnsotic accuracy of thin- section CT and chest radiography of pediatric interstitial lung disease. Am J Roentgenol 2000; 174: 549-554. 2. Koh DM, Hansell DM. Computed tomography of diffuse interstitial lung disease in children. Clin Radiol 2000; 55: 659-667 3. Kuhn JP, Brody AS. High resolution CT of pedi- atric lung disease. Radiol Clin North Am 2000; 40(1): 89-110. 4. Lucaya J, Le Pointe HD. HRCT features of lung dis- ease. In: Baert AL, Sartor K, eds. Pediatric Chest Imaging. 1st ed. Berlin: Springer-Verlag, 2002: 64 - 73. 5. Lynch DA, Hay T, Newell JD, Divgi VD, Fan LL. Pediatric diffuse lung disease: Diagnosis and classi- fication using high resolution CT. Am J Roentgenol 1999; 173: 713-718. 6. Evans ED, Kramer SS, Kravitz RM. Pediatric dis- eases of the lower airways. Semin Roentgenol 1998; 33: 136-150. 7. Kim JS, Muller NL, Park CS. Cylindrical bronchiectasis: diagnostic findings on thin-section CT. Am J Roentgenol 1997; 168: 751-754. 8. Lucaya J, Le Pointe HD. HRCT features in diagno- sis of airway disease (4.7). HRCT features in spe- cific lung disease (4.8). In: Baert AL, Sartor K, eds. Pediatric Chest Imaging. 1st ed. Berlin: Springer- Verlag, 2002: 74 - 87. 9. Andronikou S, Wieselthaler N. Modern imaging of tuberculosis in children: thoracic, central nervous system and abdominal tuberculosis. Pediatr Radiol 2004; 34: 861-875. 10. States LJ, Fields JM. Pulmonary haemorrhage in children. Semin Roentgenol 1998; 33: 174-186. PICTORIAL ESSAY 29 SA JOURNAL OF RADIOLOGY • December 2005 Fig. 26. Fibrosing alveolitis. PRICE: R399.00 To order contact: The South African Medical Association, Health & Medical Publishing Group 1-2 Lonsdale Building, Gardener Way, Pinelands, 7405. Tel: (021) 530-6520/27 Fax: (021) 531-4126/3539 email: carmena@hmpg.co.za or avrilm@hmpg.co.za Article - Andronikou 11/30/05 10:46 AM Page 29