Fetal MRI as an extended arm to ultrasound in evaluation of chest anomalies

Transcription

1 Fetal MRI as an extended arm to ultrasound in evaluation of chest anomalies Poster No.: C-1441 Congress: ECR 2014 Type: Educational Exhibit Authors: E. C. nandury, R. Jyothi, A. SRIRAMBHATLA ; Hyderabad/ IN, Hyderabad, andhrapradesh/in, HYDERABAD, ANDHRA PRADESH/IN Keywords: Tissue characterisation, Foetus, Congenital, Intrauterine diagnosis, Diagnostic procedure, Comparative studies, Ultrasound-Colour Doppler, Ultrasound, MR, Thorax, Respiratory system, Foetal imaging DOI: /ecr2014/C-1441 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 22

2 Learning objectives 1. MRI appearances of common chest anomalies 2. Advantages of MRI over ultrasound 3. Role of MRI in decision making Page 2 of 22

3 Background Background Ultrasound is the preferred imaging modality in evaluation of thoracic anomalies in the fetus. However MRI may be necessary in a small percentage where ultrasound is noncontributory or equivocal, where accurate diagnosis is needed in helping make parental decisions about the course of pregnancy and where fetal interventions are contemplated. Accurate prenatal diagnosis of chest lesions is important because the natural history of these lesions and their treatment vary substantially. The most commonly encountered anomalies are congenital pulmonary airway malformation (CPAM), sequestation, bronchogenic cysts and congenital diaphragmatic hernia (CDH). Most prenatally detected lung lesions can be managed successfully during neonatal period. Out of these CPAM, congenital diaphragmatic hernia and hydrothorax require special attention because they are frequent anomalies and require immediate or subsequent special intensive care. Normal Anatomy of the fetal lung on USG At ultrasound, the fetal lungs normally appear homogenous and are slightly more echogenic than the liver (Fig 1). The echogenicity of the lung increases as gestation advances. The presence of cysts or focal increased echogenicity of the lung parenchyma indicates a mass. Cardiomediastinal shift may often be the first clue to the presence of a unilateral chest mass or diaphragmatic hernia. When abnormality is recognized in the lungs a detailed examination of the entire fetus should be performed. Ultrasonography (US) is the primary imaging modality for the evaluation of the fetus. It is safe for both fetus and mother, is relatively inexpensive, allows real-time imaging and is readily available. Nevertheless, a number of lesions have similar echogenicity at ultrasound, leading to low specificity levels. Ultrasound may also be limited in cases of oligohydramnios, large maternal body habitus, or complex fetal anomalies, particularly when scanning is performed late in gestation. Page 3 of 22

4 In these cases, alternative imaging modalities such as MRI provide additional information that can improve diagnostic accuracy and facilitate treatment decisions. Indications and limitations of fetal MRI Despite the well-known advantages of US, including multiplanar imaging and realtime evaluation, the potential advantagesof fetal MR imaging as an adjunct to US are many. Fetal anatomy is well visualized at MR imaging, in part because of large amounts of amniotic fluid, as well as fluid within the fetal lungs, gastrointestinal tract, kidneys, bladder and gallbladder. The multiplanar abilities, large field of view and better tissue characterisation of MR imaging may help determine the origin and extent of lesion. MR imaging is not limited by fetal position, fetal bones or maternal body habitus to the same degree as is US, particularly in the third trimester. It is not operator dependent. MR imaging, however, is limited by fetal motion and as is US, by severe oligohydramnios. MRI remains an expensive method which is not always available. The examination may be affected by such factors as the mother's obesity, claustrophobia or discomfort felt by the mother or by excessive fetus movement. Normal anatomy of fetal lung on MRI At MR imaging, the trachea, bronchi and lungs demonstrate high T2 signal intensity relative to the chest wall muscles since they contain a significant amount of fluid (Fig 2). As the lungs mature, there is increasing production of alveolar fluid, thereby increasing the signal intensity of the lungs relative to the liver. Page 4 of 22

5 On T1-weighted images liver, spleen and meconium are hyperintense compared to lungs. The signal of the thymus is hyperintense compared to the heart and becomes very clear in the third trimester of pregnancy. Flow void is observed in the heart in T2-weighted SSFSE image sequence. Normal lung volumes can be calculated with MR imaging as well and have been shown to increase with gestational age. Page 5 of 22

6 Images for this section: Fig. 1: Ultrasound images of normal fetal thorax. Transverse (Fig 1 a), coronal (Fig 1b) and sagittal (Fig 1c) ultrasound images of normal fetal thorax demonstrate homogeneous and symmetric intermediate echogenicity of the lungs. The heart occupies 25%-30% of the thoracic volume. dept of radiology, kamineni hospital - Hyderabad/IN Fig. 2: Normal MR images of fetal lungs. Fig 2a(Axial),2b(Sagittal)& 2c(Coronal. T2weighted MR images of the fetal lungs at 28 weeks gestation reveals the lungs of uniform symmetric high signal intensity relative to the chest wall muscles. dept of radiology, kamineni hospital - Hyderabad/IN Page 6 of 22

7 Findings and procedure details IMAGING OF VARIOUS ANOMALIES Congenital pulmonary airway malformation (CPAM) It is a focal pulmonary dysplasia defined as a multicystic mass of pulmonary tissue in which there is proliferation of immature bronchial structures at the expense of alveolar development. More than 80% of fetal thoracic lesions are CPAM Though the classification scheme includes five types, only three types of CPAMs are distinguished at imaging. Large cyst (>2 cm) CPAM (type I) demonstrates numerous variable-sized anechoic spaces intermixed with echogenic soft tissue at ultrasound. At fetal MR imaging, large cyst CPAMs manifest as hyperintense unilocular or multilocular lesions with discrete walls on T2-weighted images (Fig3). It has better prognosis. A small cyst (<2 cm) CPAM (type II), which constitute macro cystic CPAM is identified as an echogenic mass with multiple small cysts at prenatal US. At T2weighted MR imaging, it has a variable appearance that depends on the cystic and solid components. It is associated with other anomalies and micro-cystic or solid type (type III) lesions, which have cysts that are smaller than 5 mm in diameter, with no discernible cystic spaces. Type IV usually appears as the large cyst type at imaging and is indistinguishable from a predominantly cystic pleuropulmonary blastoma. Indicators of a poor prognosis include large lesions, bilateral lung involvement and hydrops. Quantitative measurements of mass size that help predict development of hydrops and poor outcome include a mass-thorax ratio of more than 0.56 or a CPAM volume ratio (ie, volume of the mass divided by head circumference) greater than 1.6. Page 7 of 22

8 Typically, CPAMs with a volume of less than 57% of total lung volume resolve completely, whereas CPAMs with a volume of more than 84% of total lung volume do not resolve completely. Broncho Pulmonary sequestration (BPS) BPS is the second most common lung lesion found at prenatal diagnosis. Pulmonary sequestration consists of a mass of pulmonary tissue disconnected from the bronchial tree that receives its blood supply from the systemic circulation. It is divided into two groups: intralobar sequestration,in which the tissue is surrounded by normal lung and found in the interior of the visceral pleura and extra lobar sequestration, in which the tissue is disconnected from the bronchial tree and has its own pleural covering. The most frequent location is in the left lower lobe (more than two-thirds), 90% are supradiaphragmatic, and less than 10% are infradiaphragmatic. Intralobar BPS is rarely diagnosed prenatally and is usually associated with type II CPAM (hybrid lesions). These lesions have an excellent prognosis when they occur as an isolated event and more than 50% disappear in utero. Extralobar sequestration is usually located between the lower lobe and the diaphragm, more frequently at the left thoracic base, in 77% of cases. Rare locations include mediastinum, pericardium, diaphragm or retroperitoneum. At prenatal US, extralobar pulmonary sequestration is seen as a homogeneous hyperechoic mass in a paraspinal location, most often in the left lower thorax. The feeding artery originating from the descending aorta may be seen at color Doppler US. Occasionally, these vessels may not be identified at Doppler US, making extralobar sequestration indistinguishable from a microcystic CPAM. Large lesions can compress the esophagus and thoracic veins and subsequently cause hydrops, which is an indication for fetal intervention or early delivery. Prenatal MR imaging shows a solid, well-defined, uniformly hyperintense mass on T2-weighted images, and the feeding artery may be identified (Fig4). In cases of infradiaphragmatic sequestration, the differential diagnosis includes neuroblastoma and adrenal hemorrhage. Page 8 of 22

9 Lymphangioma Lymphangiomas are focal proliferations of well differentiated lymphatic tissue that present as multicystic or sponge like accumulations. Isolated anterior mediastinal lymphangiomas are uncommon, with an occurrence less than 1% of all the lymphangiomas and most of them are asymptomatic during childhood. They can lead to compression of vital structures, even life-threatening airway compromise. Once diagnosed, they should be resected, typically by thoracotomy or median sternotomy. It is suspected when the sonographic examination shows a single or multilocated paracardiac anterior mediastinal cystic mass. These masses tend to be uniformly hyperintense on T2W MRI with varied septations. The intra cystic septations, the degree of great vessel and airway displacement and mediastinal infiltration can be better evaluated at coronal and sagittal MR sections (Fig5). Oesophageal duplication cyst It accounts for 10%-15% of all duplication cysts of GIT. The lesion usually appears as a well-marginated, homogeneous, spherical mediastinal mass ranging in size from 2 to 10 cm. Cysts typically occur in the paratracheal or subcarinal region but may be found anywhere within the thorax. On antenatal US, esophageal duplication cysts are seen as posterior mediastinal cysts and appear as smooth, spherical or tubular structures with well-defined walls. Antenatal MRI is very useful for further evaluation as it can show abdominal extension better. The cysts appear as hyperintense on T2W images due to the predominant water content. A right-sided or posteroinferior mediastinal location favors the diagnosis of an esophageal duplication cyst (Fig6). Page 9 of 22

10 The differential diagnoses include other foregut cysts such as bronchogenic cyst and neuroenteric cyst. Bronchogenic cysts are usually located around the tracheobronchial tree and have a relatively thinner wall. Congenital Diaphragmatic Hernia (CDH) CDH is the main indication for fetal thoracic MR imaging. 85% are left-sided (Bochdalek hernia), 13% right-sided and 2% bilateral. Congenital diaphragmatic hernia constitutes a major surgical emergency in the new born which needs prompt diagnosis and treatment. Bochdalek hernia constitutes the most common type of hernia which occurs through foramen of Bochdalek, which is located posterolaterally caused by a defect in the fusion of pleuroperitoneal membranes during embryonic life. It is most commonly seen on left side lateral to the spine, where in stomach, bowel, spleen and kidneys herniate into the left hemithorax. It is rarely seen on the right side where part of the liver herniates in to the right hemithorax. The degree of pulmonary hypoplasia and liver herniation are major prognostic factors. The sonographic features are scaphoid shape of abdomen secondary to displacement of viscera into the chest, abnormal position of gall bladder, hepatic and umbilical veins within the abdomen, mediastinal shift and paradoxical motion of the abdominal contents into the ipsilateral hemithorax with fetal breathing movements. MR imaging can also be used to assess lung maturity, in addition to confirmation of the diagnosis and evaluation of the contents (Fig 7). Pulmonary maturity correlates with high signal intensity of lung on T2-weighted images. The signal ratio between lung and cerebrospinal fluid, lung and gastric fluid, or lung and liver can be used to assess lung maturity. Signal intensity of lung increases with gestation time. Low intensity of the fetal lung suggests the presence of pulmonary hypoplasia, whereas high intensity is consistent with normal pulmonary development. The supradiaphragmatic position of the liver is difficult to visualize with US. MR imaging can identify the diaphragmatic defect (discontinuity of the hypointense band on T2-weighted images) and the anomalous position of the liver, Page 10 of 22

11 indicated by a hyper intense signal on T1-weighted images and hypointense signal on T2-weighted images, especially in the sagittal and coronal planes. CDH must be differentiated from CPAM, sequestration, bronchogenic cyst and teratoma. Esophageal atresia Esophageal atresia is the most common cause of congenital esophageal obstruction, occurring in approximately one in 3500 births. In more than 80% of cases is associated with a fistula between the gastrointestinal and respiratory tracts. Prenatal diagnosis of esophageal obstruction may improve the outcome of affected neonates by allowing optimization of both prenatal and postnatal care. Prenatal suspicion of esophageal atresia is usually based on the presence of polyhydramnios together with an absent stomach bubble. Visualization of the dilatation of the blind-ending esophagus (esophageal pouch) during fetal swallowing has been proposed as the most reliable sign for predicting esophageal atresia, but is very infrequently seen. Fetal MRI is an accurate and non-invasive way of diagnosing esophageal atresia in fetuses at high risk based on sonographic findings and may show the dilated proximal segment more accurately (Fig 8). Chest wall sarcoma Chest wall tumours constitute 1.8% of solid tumours in childhood. Malignant small round cell tumors comprising of Ewings sarcoma and Askins tumor are the most common entities. At imaging, they all generally manifest as peripheral chest wall masses, with or without associated rib destruction and cannot be separated on imaging criteria alone. On US these lesions are heterogeneously hypoechoic showing increased vascularity. Page 11 of 22

12 The extent of tumour is better demonstrated on MR. These lesions are hyperintense on T2 and of intermediate signal intensity on T1. Multiple flow voids may be seen within the mass lesion (Fig9). Page 12 of 22

13 Images for this section: Fig. 3: CPAM (type II) MR images [Fig 3a(Sag),3b(Axial)& 3c(Coronal)HASTE images,fig 3d (Axial) T1W image and 3e HASTE MRCP image] reveal a large T2 hyperintense lesion with multiple small cysts involving almost the entire left lung dept of radiology, kamineni hospital - Hyderabad/IN Page 13 of 22

14 Fig. 4: Extralobar pulmonary sequestration. Fig 4a(Axial)& 4b(Sag)US images in 27years old primi of 22 weeks gestational age showed echogenic retrocardiac mass. Fig 4c(Axial),Fig 4d(Coronal)& 4e(Sagittal)T2W MR images showed T2 hyperintense retrocardiac lesion extending into upper abdomen. Fig 4f Post natal CECT with angiography showed venous drainage in to left pulmonary vein. Operated and confirmed as extralobar pulmonary sequestration (operative photograph). dept of radiology, kamineni hospital - Hyderabad/IN Page 14 of 22

15 Fig. 5: Mediastinal lymphangioma. Fig 5a(Axial), 5b(Coronal)& 5c(Sagittal)USG images in a 23 years old primi of 24 weeks gestational age revealed anechoic space occupying lesion in anterior mediastinum. Fig 5d(Axial),5e (Coronal)&5f(Sagittal) HASTE MR images showed this lesions as hyperintense cystic mass in the anterior mediastinum causing displacement of great vessels and cardia. dept of radiology, kamineni hospital - Hyderabad/IN Page 15 of 22

16 Fig. 6: Oesophageal duplication cyst. Fig 6a(Axial),6b(Sag)USG images in 27 years primi of 22 wks gestational age reveal a tubular anechoic cystic lesion in the posterior mediastinum posterior to the heart and anterior to aorta extending into left hemi thorax. Fig 6c(Coronal),6d(Sag),6e(Axial) HASTE MR images reveal the lesion as a homogeneous T2 hyperintense tubular lesion extending from the left lung apical region to the level of the GE junction on the right side. Fig 6f(Axial)&6g(Coronal)Postnatal CECT images reveal similar features as that of prenatal MRI dept of radiology, kamineni hospital - Hyderabad/IN Page 16 of 22

17 Fig. 7: Left Bochdalek hernia. Fig 7a (Coronal)&7b(Sag) USG images in 28 Yr old primi of 24 wks gestational age show a mixed echogenic lesion showing cystic areas in left hemithorax. Stomach is seen in the thorax adjacent to the heart. MRI HASTE coronal (Fig 7c), T1 coronal (Fig 7d), T1 axial (Fig 7e) and HASTE sagittal (Fig 7f) show a large diaphragmatic defect involving posterolateral aspect on left side. The anteromedial aspect of left diaphragm and right hemidiaphragm are normal. Herniation of small and large bowel loops in to the left hemithorax is seen with compression over left lung and shift of heart into right hemithorax. dept of radiology, kamineni hospital - Hyderabad/IN Page 17 of 22

18 Fig. 8: Esophageal atresia Fig 8a,8b(Axial)US images in a 22 years old primi of 23 weeks gestational age shows an absent stomach bubble and polyhydramnios. Fig 8c(Coronal) MRI HASTE images show atresia of thoracic esophagus with dilated cervical esophageal pouch and absent stomach bubble. dept of radiology, kamineni hospital - Hyderabad/IN Fig. 9: Chest wall sarcoma. Ultrasound (Fig 9a) & color doppler (Fig 9b) images in a 24 years old 2nd gravida of 23 weeks gestational age reveal a large mixed echogenic mass lesion showing increased vascularity. MRI HASTE sagittal (Fig 9c), HASTE axial (Fig 9d) and T1 axial (Fig 9e) images show large lobulated T1 isointense, T2 heterogeneously hyperintense solid mass lesion arising from left side of chest wall showing multiple flow voids within. The mass lesion is seen extending into upper neck, left axilla, left arm and upper abdominal parietes with no intrathoracic extension. Left chest wall is compressed by the mass. dept of radiology, kamineni hospital - Hyderabad/IN Page 18 of 22

19 Conclusion Ultrasound is the modality of choice for fetal imaging because of its high accuracy, wide availability, relatively low cost and real-time result generation. Prenatal MRI serves as a complementary study to prenatal ultrasound in discerning the various chest anomalies and can be problem-solving in many cases. The differentiation between various lesions is important for patient management to direct appropriate prenatal counseling and postnatal treatment planning especially in congenital diaphragmatic hernia. MR imaging should be considered in fetuses with anomalies for evaluation of structures that are suboptimally visualized at ultrasound. Page 19 of 22

20 Personal information 1.Dr E C Nandury Professor and Head, Department of Radiology, Kamineni Academy of Medical Sciences and Research Centre, Hyderabad, India eshwar.nandury@gmail.com 2. Dr Jyothi RG and Dr A Srirambhatla. Department of Radiology, Kamineni Academy of Medical Sciences and Research Centre, Hyderabad, India Page 20 of 22

21 References (1) Zylak CJ, Eyler WR, Spizarny DL and Stone CH. Developmental lung anomalies in the adult: radiologic- pathologic correlation. Radiographics 2002; 22:S25-S43. (2) Teresa Berrocal Carmen Madrid et al Congenital Anomalies of the Tracheobronchial Tree, Lung, and Mediastinum: Embryology, Radiology, and Pathology. From the Department of Pediatric Radiology, Hospital Infantil La Paz, 261 Paseo de la Castellana, Madrid, Spain RSNA, (3) Coakley FV, Glenn OA, Qayyum A, Barkovich AJ, GoldsteinR, Filly RA Fetal MRI: a developing technique for the developing patient. AJR Am J Roentgenol 2004;182: (4) Stocker JT. Congenital pulmonary airway malformation: a new name for and an expanded classification of congenital cystic adenomatoid malformation of the lung. Symposium 24: non-neoplastic lung disease. Histopathology 2002;41(suppl 2): (5) Azizkhan RG, Crombleholme TM. Congenital cystic lung disease: contemporary antenatal and postnatal management. Pediatr Surg Int 2008;24(6): (6) Enzinger, F. M., and S. W. Weiss Tumors of lymph vessels. InS. M. Gay, editor. Soft Tissue Tumors. Mosby, St. Louis (7) Nain RK, Magu S, Rohilla S. Mediastinal foregut duplication cysts. Indian J Paediatr 2004;71: (8) Skari H, Bjornland K, Haugen G, Egeland T, Emblem R. Congenital diaphragmatic hernia: a meta-analysis of mortality factors. J Pediatr Surg 2000; 35 (8): (9) Centini G, Rosignoli L, Kenanidis A, Petraglia F. Prenatal diagnosis of esophageal atresia with the pouch sign. Ultrasound Obstet Gynecol 2003; 21: (10) Woodward PF, Sohaey R, Kennedy A et al. A comprehensive review of fetal tumors with pathologic correlation. RadioGraphics 2005; 25: Page 21 of 22

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