ORIGINAL ARTICLE
Multidetector computed tomography evaluation
in neonatal respiratory distress: Clinical implication
Eman Abo Elhamd
a, Gehan S. Seifeldein
a,*
, Nafisa H.R. AbdelAziz
ba
Department of Radiology, Assiut University Hospital, Egypt
b
Department of Pediatrics, Assiut University Children Hospital, Egypt Received 8 June 2012; accepted 11 December 2012
Available online 16 January 2013
KEYWORDS
Neonatal respiratory dis-tress;
MDCT;
Multiplanar images; 3D images
Abstract Objective: To assess the value of multiplanar reformation (MPR) and three-dimensional multidetector computed tomography (MDCT) images in evaluating respiratory distress in neonates. Materials and methods: Sixteen neonates (630 days) who presented with respiratory distress (RD) and admitted in the neonatal intensive care unit of the Assuit university children hospital who were selected from a total of 1295 patients presented with RD in whom chest X-ray was inconclusive, so those 16 neonates underwent 64-rows MDCT in the period between November 2010 and November 2011. The recruited patients were sedated before examination and IV contrast medium administra-tion was needed when there was suspected vascular anomaly. Scans were performed in supine posi-tion to cover the root of the neck down to the level of the adrenal glands. The images were sent to the workstation to be reviewed in the multiplanar and 3D images.
Results: The final radiologic diagnoses included cystic adenomatoid malformation (n = 4, 25%), congenital lobar emphysema (n = 1, 7%), pneumonia (n = 5, 36%), hypoplastic lung (n = 3, 22%), diaphragmatic hernia (n = 2, 14%) and postoperative hydro-pneumothorax (n = 1, 7%). Conclusion: The combination of fast speed, high spatial resolution, and enhanced quality of MPR and 3D images makes MDCT an ideal non-invasive method for evaluating surgical causes of neo-natal respiratory distress.
2012 Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier B.V.
1. Introduction
The clinical presentation of respiratory distress in the newborn includes apnea, cyanosis, grunting, inspiratory stridor, nasal flaring, poor feeding, and tachypnea (more than 60 breaths per minute). There may also be retractions in the intercostal, subcostal, or supracostal spaces. Respiratory distress occurs in approximately seven percent of infants(1). Most cases are caused by transient tachypnea of the newborn, respiratory distress syndrome, or meconium aspiration syndrome, but
* Corresponding author. Address: Radiodiagnosis Department, Fac-ulty of Medicine, Assiut university Hospital, Assiut, Egypt.
E-mail address:[email protected](G.S. Seifeldein). Peer review under responsibility of the Egyptian Society of Radiology and Nuclear Medicine.
Production and hosting by Elsevier
Egyptian Society of Radiology and Nuclear Medicine
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0378-603X 2012 Egyptian Society of Radiology and Nuclear Medicine. Production and hosting by Elsevier B.V. All rights reserved.
Open access under CC BY-NC-ND license.
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various other causes are possible such as pneumothorax, delayed transition ,infection (e.g., pneumonia, sepsis), nonpul-monary causes (e.g., anemia, congenital heart disease, musculoskeletal abnormalities of the chest, lesions of the dia-phragm and abdomen, medications, neurologic or metabolic abnormalities, polycythemia, upper airway obstruction), and persistent pulmonary hypertension of the newborn(2).Chest radiograph can help to differentiate between them. These in-clude primary pulmonary disease, which can be divided into those that can be treated medically and those requiring surgery. In general, medical conditions in the newborn cause bilateral pulmonary disease, whereas surgical problems are often unilateral and frequently produce contralateral shift of the mediastinum. Cardiac disease is an important cause of respiratory symptomatology in the neonate, for which ultra-sound (US) is particularly useful. Extrapulmonary lesions are also important and should be suspected if the chest radiograph is normal or only mildly abnormal in the presence of respira-tory distress. Cross-sectional imaging such as computed tomography (CT) is frequently required for the confirmation of diagnosis, further characterization, and preoperative evalu-ation in the case of surgical lesions(3).
The objective of our study was to assess the value of multiplanar and 3D MDCT images in evaluating respiratory distress in neonates.
2. Patients and methods 2.1. Patients
Within the period between November 2010 and November 2011, 1295 newborn were admitted in neonatal intensive care unit of the Assiut university children hospital with respiratory distress (cyanosis, tachypnea, retraction, grunting, stridor, or feeding difficulties).
Clinical evaluation together with laboratory workup, plain chest X-ray, and/or echocardiography (when it was needed) was done. The final diagnosis was confirmed in 1279 cases as respiratory distress syndrome in 553 cases (42.7%), transient tachypnea of newborn in 435 cases (33.5%), pneumonia & sep-sis in 124 cases (9.5%), meconium aspiration syndrome in 59 cases (4.6%), air leak syndromes in 48 cases (3.8%), diaphrag-matic hernia in 11 cases (0.8%) and extrapulmonary causes in 49 cases (3.9%). However, in 16 cases (1.2%) plain X-ray find-ings were suggestive, but it was not conclusive for congenital surgical pulmonary problems. So they were underwent MDCT.
All patients were receiving supportive care in the form of incubator care, oxygen therapy, partial or total parental nutri-tion, monitoring of vital signs and blood gas analysis, antibac-terial therapy and assisted ventilation when indicated. For patients with proved surgical problems, surgical consultation and management were done.
2.2. MDCT examination
Sixteen neonates were scanned using 64-rows multi detectors CT (Aquillion; Toshiba Corporation, Medical System Com-pany, Tokyo, Japan). MDCT was performed with patients in the supine position. We commonly used oral chloral hydrate as a sedative drug for those neonates according to practice
guidelines for sedation and analgesia published by American society of anesthesia(4). Due to the faster scanning times pos-sible with MDCT scanners, routine sedation is no longer re-quired. In the neonate, recent feeding usually provides tranquillity.
2.2.1. Technical factors
Multidetector CT parameters: using low kilovoltage and tube current appropriately to reduce the radiation dose: 80– 100 kV and approximately 60–90 mAs (following an ALARA [as low as reasonably achievable] principle)(5). Other technical parameters are as follows: detector collimation, 64· 0.5 mm; beam pitches 0.8 and gantry rotation time 0.5 s and image reconstruction matrixes 512· 512.
Intravenous contrast material: it is needed to assess the vas-cular anomalies. Neonates have a smaller than 22- gauge can-nula or central venous line in place, the contrast medium was administered by means of manual injection using non-ionic contrast material (300 mgI/ml). The usual recommended con-trast material dose is 2 mL per kilogram of patient body weight (up to a dose of 125 mL)(6,7).
Oral contrast medium: it was used in suspected cases of dia-phragmatic hernia in order to opacify the bowel. A 60 mL di-lute water-soluble iodine based contrast medium was given by nasogastric tube before the examination.
Timing of CT: regarding the postcontrast scan delay, the scan starts at the end of the injection.
Anatomic scan coverage: Scans are usually acquired from the level of thoracic inlet to the level of the diaphragm. In cer-tain situations, however, CT scan coverage must be modified. More inferior extension to the level of the renal artery should be considered in evaluating extralobar sequestration because the anomalous artery in this situation can arise from the descending aorta below the level of the diaphragm(8,9).
Post processing Techniques: After scanning, the axial images were transferred to an independent workstation (Vir-tea, Toshiba) for post processing. Post processing methods: multiplanar reformation or reconstruction (MPR), and 3-Dimensional (3D) imaging including maximum intensity pro-jection (MIP) and volume rendering (VR) images.
2.2.2. Image analysis
Axial, MPR, MIP, and VR images were evaluated indepen-dently and retrospectively by two radiologists who reviewed and evaluated all CT studies. The axial images were viewed with standard lung window settings (e.g., width –1,600 to –1,800 H; level, –450 to –550 H) and standard soft-tissue window settings (e.g., width, 400–450 H; level, 40–50 H). Eval-uating MPR in coronal, sagittal, and curved planes. The 3D reconstructed images were presented in two formats––one with more opacity to show the vessels and the other with more transparency to show the airway. The axial CT images were interpreted first, followed by the multiplanar images at the same review session. The 3D volume-rendered images were interpreted independently at a later session in depicting the bronchopulmonary and vascular anomalies as
following:- Pulmonary lesions
Symmetry of hemithorax Decrease CT attenuation Increase CT attenuation
Trachea and bronchial lesions Abnormal reduced caliber External compression. Vascular lesions
Pulmonary arteries and veins Aorta
Any abnormality of pleura, diaphragm and chest cage. 3. Results
Most of the neonates in this study were suffering from respira-tory distress due to medical causes in whom clinical evaluation
Table 1 Pattern of MDCT findings in 16 neonates.
Pulmonary Trachea and bronchi Vascular Associated No (%) Radiological diagnosis Unilateral opacified hemithorax 5/16 (31.25%)
Decrease in volume of right lung
Small caliber of right bronchus
Small pulmonary artery Shift of the mediastinum to the affected right side
1 Primary Pulmonary Hypoplasia
Decrease in volume of left lung
Abrupt tapered left main bronchus
Aneurysmal dilata-tion of the main pul-monary artery and osteal stenosis of left pulmonary artery. Right sided aortic
arch with ALSA.
Compensatory hyperinflation of the right lung with transmediastinal shift.
Opacified left lung
1 Primary Pulmonary Hypoplasia
Decrease in volume of right lung
Abrupt tapered right main bronchus
The mediastinum is displaced to the Contralateral side. Presence of contrast filled bowel loops in the right hemithorax. 2 Secondary pulmonary hypoplasia due to congenital diaphragmatic hernia-Bochdalek Type
Total opacified right hemithorax
NA Ipsilateral mediastinal shift
1 Atelectasis
Hyper lucent lesions 6/16 (37.5%)
Multiple bilateral air filled cysts communicate with each and with the airway. More than 2 cm in diameter.
NA Segmental atelectasis of the right upper lobe.
4 Congenital cystic adenomatoid malformation (CCAM)type I
Unilocular Left upper lung air filled cyst about 10 cm
NA Contralateral
mediastinal shift
Multilocular large air filled cyst occupying almost of the left lower lung lobe that has thick wall.
NA Alveolar patches of the surrounding lung parenchyma
Air-filled distension of the upper lobe of the left lung.
NA Rightward shift of
mediastinum.
1 Congenital lobar emphysema
Presence of both air and fluid in the left pleural space
NA Partial collapse of
left lung (passive atelectasis)
Fixed left intercostal tube.
1 Left postoperative hydro-pneumothorax
Different alveolar pattern: 5/16 (31.25%)
Bilateral patchy area of consolidation
Air bronchogram 4 Pneumonia
Right upper lobe collapse.
1 NA = No Abnormality
together with laboratory work, plain chest X-ray, and/or echo-cardiography when it was needed, were sufficient and they were managed accordingly.
Only 16 neonates were included in whom plain chest X-ray findings were suggestive, and it were not conclusive for con-genital surgical pulmonary problems. Their radiologic diagno-sis is summarized inTable 1.
Hyperlucent lesions are encountered in 6 neonates includ-ing congenital cystic adenomatoid malformation (CCAM), congenital lobar emphysema (CLE) and postoperative hydropneumothorax.
In four neonates presented with CCAM, CT demonstrates multiple air filled cysts that vary greatly in size and shape. 2– 8 cm cysts were scattered in both lung lobes mainly the upper lobes in one neonate (Fig. 1). In another neonate, CT depicts a large unilocular air-filled cyst measured 10 cm in maximum diameter occupying almost all of the right lower lobe and the posterior segment of the upper lobe with internal septa-tions and it is associated with mass effect as mediastinal shift to the contralateral side. In the remaining two neonates, a mul-tilocular large air filled cyst occupies almost of the left lower lung lobe that has a thick wall and it is accompanied with alve-olar patches involving the surrounding lung parenchyma.
One neonate has CLE; CT depicts the hyperinflation of the left upper lobe with subsequent mass effect upon the adjacent bronchovascular structures (Fig. 2).
One case has left hydro-pneumothorax postoperatively for the repair of the left sided congenital diaphragmatic hernia (Fig. 3).
Unilateral opacified hemithorax was encountered in 5 neo-nates who have unilateral small sized lungs due to unilateral hypoplastic lung in two cases and unilateral right atelectasis in one case and congenital diaphragmatic hernia in two cases. The first case has a small right lung with mediastinal shift to the affected side and narrow right main bronchus that is clearly seen on MPR and 3D VR images. MPR and 3D images for MDCT angiography revealed hypoplastic right pulmonary artery (2 mm) with absent right pulmonary veins (Fig. 4).
The second case has a small left lung with a narrow left main bronchus and MDCT angiography revealed dilatation of the main pulmonary trunk with osteal stenosis of the left pulmonary artery (2.2 mm) that is smaller than the contralat-eral one and this was clearly evident on MPR and 3D VR images (Fig. 5).
In another two neonates, opacified right hemithorax with air filled structures occupy the lower lung zone. Instillation
Fig. 1 MDCT images in 15 days male neonate. Axial (a), sagittal (b) and coronal(c) reformatted images demonstrating multiseptated cystic lesion in both lungs mainly in both the upper lobes. The largest was located in the left side with transmedistinal extension (arrowed) consistent with congenital cystic adenomatoid malformation type 1 as clearly evident on 3DVR image (d).
of gastrograffine through the Ryle tube revealed opacified intestinal loops herniating into the right hemithorax accompa-nied with herniating liver with subsequent decrease or no aer-ation of the right lung clearly evident on MPR and 3D VR images (Fig. 6).
The fifth neonate has a unilateral opacified right hemitho-rax with ipsilateral mediastinal shift. On follow-up radio-graphs, reareation of the right lung occurred and thus it is diagnosed as atelecatsis and MDCT helped to exclude anomalies.
Alveolar opacities were seen in five neonates. Four cases have bilateral patchy areas of consolidation and segmental ate-lectasis. One case has right upper lobe consolidation (Fig. 7)
Regarding the trachea, small caliber of bronchi is encoun-tered in cases of hypoplasia of the lung.
Regarding vascular anomalies, CT angiography in MPR, maximum intensity projection (MIP) and VR images revealed hypoplastic pulmonary artery in one case (Fig. 4) and osteal stenosis of the left pulmonary artery with dilatation of main pulmonary artery in one case. The latter one is associated with a right sided aortic arch with an aberrant left subclavian artery
(Fig. 5). Small pulmonary veins are noticed draining the hypo-plastic lung.
Common associations are found including mediastinal shift, pneumonic alveolar patches and atelectasis.
4. Discussion
The respiratory distress in neonates may be because of a pre-dominantly medical or surgical pathology or may be a medical condition superimposed on surgical pathology(10).
MDCT may be useful in confirming the presence of the le-sion, determining the extent of the lele-sion, and defining associ-ated abnormalities. Reconstructed data from CT examinations displayed in either 3D or multiplanar formats can be particu-larly helpful in delineating abnormalities of the bronchi and associated arterial and venous structures(11,12).
In the present prospective study, 16 neonates; whose plain chest radiographs were equivocal; were included and had undergone MDCT examination for further assessment of radiographic abnormalities of areation. This is also mentioned by Donnelly and Frush (13) who stated that in cases with
Fig. 2 7 days female neonate. MDCT scan in coronal (a, b) reformatted images in lung window demonstrate hyperinflation of the left upper lobe with contralateral shift of the mediastium impressive of CLE. Alveolar patches affecting the right lung seen in axial image (c) in mediastinal window. 3D VR image (d) demonstrates the extent of hyperinflated left upper lobe and area of hypoareation affecting right lung consistent with pneumonic consolidation.
unclear diagnosis, CT often provides diagnostic information about the exact anatomic location of the lesion difficult to determine on chest radiography.
Several acquired and congenital causes of localized lung radiolucencies are seen in neonates, including acute pulmonary interstitial emphysema, localized persistent pulmonary emphy-sema, congenital cystic adenomatoid malformation (CCAM), and congenital lobar emphysema (CLE). The radiolucent nat-ure of these lesions is also distinct from other congenital lung masses, such as bronchogenic cyst and sequestration that do not typically contain air when encountered during the neonatal period(13). In the present study, six neonates had radiolucent lesions.
In this study, we had only one case of CLE with hyperinfla-tion of the left upper lobe. MDCT images demonstrated a hyperinflated left upper lobe with attenuating and displaced pulmonary vessels and contralateral mediastinal shift that was clearly depicted on reconstructed volume rendering images of the airways. This is consistent with Ozcelik et al.(14)who stated that CLE is usually present during the neonatal period and infancy with respiratory distress, especially when there is marked hyperinflation in the involved lobe and mass effect on the adjacent lung parenchyma or mediastinum with a lobar
predilection (left upper lobe > right middle lobe > right upper lobe > lower lobes).
Congenital cystic adenomatoid malformation is resulting from disorganized hamartomatous and adenomatoid prolifer-ation of primary bronchioles, which are in communicprolifer-ation with the bronchial tree (15,16). There are three types of CCAM, which have different radiologic appearances, gross pathologic findings, and histologic findings, as described by Stocker et al. (17). The most common subtype is a type 1 CCAM, in which there is at least one dominant cyst that is lar-ger than 2 cm in size. Type 2 CCAM has numerous small cysts of uniform size measuring 1–10 mm in diameter. Type 3 CCAM, the least common, appears solid at imaging; however, at histologic evaluation, it is characterized by numerous micro-cysts. CCAM demonstrates a variety of imaging appearances based on the type of CCAM and the presence or absence of associated superimposed infection(18). This is consistent with MDCT findings in four cases in the present study as they had type 1 CCAM. Bilateral multilocular air-filled cysts about 2–8 cm occupied most of upper lung lobes in one of them. In another case, a large unilateral air-filled cyst with internal sep-tations occupied most of the right lower lobe and posterior segment of the upper lobe (about 10 cm) causing a mediastinal
Fig. 3 25 days male neonate. Contrast enhanced MDCT in axial (a) at upper cuts and sagittal (b) reformate in mediastinal window revealed normal caliber of the pulmonary trunk with symmertical caliber of main pulmonary areteris and evidence of left pleural effusion with fixed intercostal tube. Coronal reformate (c) image in lung window demonstrates normal shape and caliber of the trachea and both bronchi , presence of air in the pleural space and partial aeration of the left lung as clearly evident on VR images (d). Postoperative hydropneumothorax was the diagnosis.
shift to the contralateral side. In the remaining two, unilateral large multilocular thick wall air-filled cysts were seen suggest-ing the presence of associated infection.
Taylor et al. (19)reported that after congenital diaphrag-matic hernia (CDH) repair, a large postoperative pneumotho-rax is not uncommon and should not be rapidly evacuated because of the increased mobility of the neonatal mediastinum. After the resorption of air surrounding the hypoplastic lung, fluid might accumulate in the pleural space. Follow-up chest imaging after surgical repair might be useful. Cross-sectional imaging can be helpful in cases where the diagnosis is still not clear, and to fully elucidate the spectrum of associated ana-tomic defects. CT with multiplanar reconstruction is useful to elucidate associated lung masses and bronchopulmonary fore-gut malformations. The use of intravenous contrast agent and CT arteriography should be considered for depiction of the vascular supply of lung lesions. In the present study, left sided acquired hydropneumothorax secondary to repaired left sided CDH was depicted in one case who was referred to undergo MDCT pulmonary with intravenous contrast administration in order to assess the status of the ipsilateral lung and pulmon-ary vasculature according to pediatric surgeon’s opinion in our institute.
The differential diagnosis of respiratory distress in the new-born associated with marked opacification of one side of the
thorax on radiograph includes atelectasis, congenital diaphrag-matic hernia (CDH), congenital cystic adenomatoid malfor-mation (CCAM), pulmonary sequestration, chylothorax, pulmonary hypoplasia, bronchogenic cyst, and a chest tumor (e.g., neuroblastoma, teratoma, fibrosarcoma)(20). Five cases had unilateral opacified hemithorax in the present study.
Pulmonary hypoplasia refers to the presence of a bronchus and rudimentary lung, with a decrease in the number and size of alveoli, airways, and vessels. CT can show asymmetrically decreased lung parenchyma with narrowed airways and fewer branches in the affected hemithorax and herniation with medi-astinal shift of the contralateral lung. Clinically, infants with unilateral lobar pulmonary hypoplasia may have variable pre-sentations depending on the extent of lung involvement and comorbidities. Some infants present with severe respiratory distress in the first few hours of life whereas some may be com-pletely asymptomatic. However, most cases of pulmonary hypoplasia are secondary to conditions that limit fetal lung growth. Primary pulmonary hypoplasia is rare. It may be caused by an embryologic defect of the lung or vascular tissues or an in utero vascular accident(21,22). In the present study, unilateral primary hypoplastic lung was encountered in two cases and unilateral secondary hypoplastic lung in two cases.
One of the two cases of primary hypoplastic lung had a small sized right lung with very severe hypoplasia of the
Fig. 4 29 days male neonate with primary pulmonary hypoplasia. Contrast-enhanced MDCT scan in axial cut in mediastinal window (a), coronal reformate in lung window (b) and VR images of MDCT angiography (c, d) demonstrates small sized right pulmonary artery (red arrowed), small volume of right lung with subsequent raising of the right hemidiaphragm. Absence of right pulmonary veins with normal left one (blue dashed arrowed).
correspondent pulmonary artery. The second case had hypo-plasia of the left lung with severe osteal stenosis of the left pul-monary artery that arose from the main pulpul-monary artery. This second case was also associated with congenital heart dis-ease (ventricular septal defect), aneurysmal dilation of main pulmonary artery and right pulmonary artery and right sided aortic arch with aberrant left subclavian artery (ALSA) with no associated complete vascular ring causing pressure symp-toms upon the trachea or esophagus. This is consistent with Tu¨rkvatan et al.(23)who reported this anomaly rarely to pro-duce symptoms and is usually an incidental radiological find-ing and a right arch with an ALSA rarely forms a complete vascular ring.
MDCT barely depicted a small hilum and small pulmonary veins in both primary hypoplastic lung cases. This is consistent with Apostolopoulou et al.(24) and Oguz et al.(25) studies who stated that contrast-enhanced CT of the chest produces an anatomic definition of the pulmonary arteries with
consis-tent quality. An advantage of CT over angiography is that the former allows concomitant evaluation of the bronchial tree and lung parenchyma and the major vascular structures. The complex curving anatomy of the pulmonary artery is well dem-onstrated by MDCT angiography using multiplanar and vol-ume-rendered images. Thus, MDCT is the preferable method for studying pulmonary aplasia and hypoplasia.
Secondary pulmonary hypoplasia was found in two neo-nates due to right sided congenital Bochdaleck hernia and sub-sequently reduced size of the right lung. As Ryan (26) who reported secondary pulmonary hypoplasia is an important fea-ture of congenital diaphragmatic hernia and of oligohydram-nios, such as the Potter sequence. The difficulty in diagnosing these two cases on radiograph was because the characteristic radiologic appearance of diaphragmatic hernia was unclear. Swischuk(27)and Mandell(28)stated that Boch-dalek hernias are more common on the left, while Morgagni hernias occur mostly on the right. If herniation occurs on
Fig. 5 30 days old female neonate. axial contrast-enhanced CT in mediastinal window (a, b), coronal MIP (c) and posterior VR images (d, e) of MDCT angiography revealed osteal stenosis of the left pulmonary artery(arrowhead) and right sided aortic arch with ALSA(dashed arrowed) with main and right pulmonary arteries are massively dilated and small volume of the left lung with subsequent raising of the left hemidiaphragm. Small left pulmonary veins (black arrowed). 3D VR image (d) demonstrates small caliber of the left main bronchus.
the right side, the bowel and liver or liver alone may fill the right hemithorax represented as dense opacity in the lower right hemithorax. Thus CCAM, particularly when it is located in the lower lobes, can be confused with congenital diaphrag-matic hernia. In this situation, CT with coronal and sagittal reconstructions can aid in evaluating the diaphragm thus enabling the radiologist to distinguish CCAM from congenital diaphragmatic hernia(29).
The fifth case had a marked right hemithorax opacification on chest radiography. On follow-up radiographs, neonatal atelectasis was diagnosed and congenital anomalies could be excluded on MDCT.
Five cases in this study were referred to MDCT with pneu-monia to exclude underlying congenital anomalies. The most common radiographic manifestation of neonatal pneumonia is a bilateral coarse pattern of perihilar reticular densities which may also involve scattered areas of air space disease. Isolated lobar pneumonia is uncommon in this age group likely related both to the aspirated route of entry as well as to the inability of the neonate to control infection locally (30). In the present study, MDCT depicted segmental atelecta-sis and alveolar opacities in five neonates. Four cases had bilat-eral patchy area of consolidation without underling congenital anomalies. One case had right upper lobar consolidation who was suspected to have tracheo-esophageal fistula (TOF). The presence of TOF could be excluded on reconstructed multipla-nar reformate and volume rendering images.
4.1. Limitations of MDCT
The main disadvantage of MDCT is radiation exposure, a fac-tor to be considered particularly in regard to children. Even though, to our knowledge, there are no large-scale epidemiol-ogic studies of the cancer risks associated with CT, conscious effort should be taken to keep the radiation exposure as low as possible during scanning (31,32). Thus we use the lowest possible milliamperage (mA) and kilovoltage (kV). Secondly, we agree with Calder and Owens(33) who stated that auto-mated bolus tracking is problematic in neonates, as drawing a region of interest correctly is difficult in these very small patients.
5. Conclusion
Although a few number of cases were referred to MDCT in our institution but we could state that MDCT was problem solving in complicated cases in whom the simpler tests was inconclusive .We found that MDCT was useful in confirming the presence of the lesion, determining the extent of the lesion, and defining associated abnormalities in all our cases. Recon-structed data from MDCT examinations displayed in either 3D or multiplanar formats can be particularly helpful in delin-eating the abnormalities of the bronchi and associated arterial and venous structures and was able to differentiate 1ry and 2ry
Fig. 6 2 days male neonate. axial and sagittal reformate in mediastinal window (a, b), coronal reformate in lung window (c) and VR images (d) of MDCT chest demonstrate dense right hemithorax with upward raise of liver (arrowed) and air-filled bowel loops seen in the right hemithorax with secondary right hypoplastic lung.
cases of hypoplasia. Post- processing is essential to fully clarify the relationship of vascular structures to airways. Multiplanar reformats in axial, coronal and sagittal are an important first step in which the problem of superimposition of densities in the CXR is markedly reduced, and the true distribution of the disease becomes apparent. Maximal intensity projections (MIPS) in thin and thick sections can help to accentuate vas-cular structures, but may obscure the airways. Volume ren-dered (VR) images were very useful to demonstrate overall vascular anatomy and detect associated vascular anomalies. The airways were easily reconstructed with VR images which demonstrated the narrowed and congenitally absent bronchi. Lastly, MDCT techniques have revolutionized the imaging of bronchopulmonary, vascular and tracheobronchial anomalies.
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