Single-Shot MR Cholangiopancreatography Neonates, Infants, and Young Children

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1 Toshiyuki Miyazaki Yasuyuki Yamashita1 ViTang Tadatoshi Tsuchigame1 Mutsumasa Takahashi1 Yoshihisa Sera2 Received November 21, 1996: accepted after revision July29, Department of Radiology, Kumamoto University School of Medicine, Honjo, Kumamoto 860, Japan. Address correspondence to Y.Yamashita. 2Department of Pediatric Surgery, Kumamoto University School of Medicine, Kumamoto 860, Japan. AJR 1998:170: X/98/ American Roentgen Ray Society Single-Shot MR Cholangiopancreatography of Neonates, Infants, and Young Children OBJECTIVE. This study was undertaken to assess the usefulness of MR cholangiopancreatography (MRCP) with a half-fourier acquisition single-shot turbo spin-echo (HASTE) sequence as a noninvasive imaging technique to evaluate biliary or pancreatic disease in young children. SUBJECTS AND METHODS. We prospectively examined 45 children (mean age. 3 years) with MRCP using HASTE on a I.5-T MR imaging unit. MRCP images were obtained in I.4 sec without breath-hold. A body phased array coil and fat saturation technique were used for data collection. On the basis of the surgical (n = 19) and ERCP (n = 7) findings, clinical data. and followup observation, 21 children were deemed to have no significant abnormality. The other 24 children were found to have pancreaticobiliary disease, including congenital biliary atresia in five neonates, choledochal cyst in six infants, and anomalous connections between the bile and pancreatic ducts in four infants and nine young children. In children without abnormality. the MRCP images were graded for the depiction of normal structures. The findings obtained by MRCP were correlated with the surgical or ERCP results. RESULTS. HASTE MRCP showed the first branch of the intrahepatic duct, the common hepatic duct. the gallbladder, and the common bile duct in most children. In the 21 children with no abnormalities, the main pancreatic duct was visible in two of six neonates, in four of five infants, and in all 10 young children. The diagnostic accuracy of MRCP was 100% in patients with choledochal cysts. 100% in those with congenital biliary atresia. and 69% in those with anomalous connections between the bile and pancreatic ducts. CONCLUSION. MRCP using HASTE with a phased array coil is a noninvasive technique for revealing the pancreaticobiliary tract in young children. C ongenital biliary atresia is one of In the early l990s, several investigators the most serious conditions affecting neonates and infants. Surgical to generate three-dimensional data sets of demonstrated that MR imaging could be used the exploration may be necessary to differentiate between neonatal hepatitis and congenital obstructive lesions of the biliary tract [1]. Detecting idiopathic dilatation of the common bile duct (choledochal cyst) in the early stage is important because of the risk of development of malignancy in the future. These diseases have been diagnosed using surgical cholangiograms. If the imaging results are not definitive, a presumptive diagnosis can be made using a combination of sonography and scintigraphy [2, 3]. Radionuclides are retained for prolonged periods in the liver of infants with atresia of the bile ducts. Sonography does not reliably identify small extrahepatic bile ducts or the gallbladder. Therefore, surgical cholangiography, although invasive, is still performed in most patients. biliary tree and pancreatic duct(mr cholangiopancreatography [MRCP]) in an adult population [4-8]. Improved imaging techniques in MRCP have enabled us to obtain high-resolution MRCP images in a few seconds [9-12]. To our knowledge, however, imaging of abnormalities in young children using the MRCP technique has not been reported. In our prospective study, we investigated the usefulness of MRCP with half-fourier acquisition single-shot turbo spin-echo (HASTE) sequences for the detection and characterization of suspected biliary and pancreatic diseases in neonates, infants, and young children. Subjects and Methods Patients We prospectively examined 45 consecutive children (25 boys and 20 girls. mean age 3 ± 2 AJR:170, January

2 Miyazaki et al. years old) who were suspected of having pancreaticobiliary tract diseases. The patient cohort included 1 1 neonates (0-4 weeks old), 15 infants (1-12 months old), and 19 young children between 1 and 6 years old. Informed consent regarding the procedures was obtained from the parents of all patients. All children had undergone sonography before MR imaging. On sonography, choledochal cyst was suspected in six children, biliary atresia or infantile hepatitis was considered in nine children, and abnormal findings were not seen in 14 patients. In the remaining 16 patients, sonographic findings were inconclusive because of technical limitations such as obesity, large amount of intestinal gas. or patients lack of cooperation. After informed consent, patients were referred for MR imaging because the sonographic findings were inconclusive or because the clinicians wanted further information as to the relationship between the bile duct and the pancreatic duct regardless of the sonographic results. ERCP was performed in seven children, unenhanced and contrast-enhanced CT was performed in 21 children, and biliary scintigraphy was performed in 12 children. On the basis of the surgical or ERCP results, 24 children were deemed to have pancreaticobiliary diseases. The diagnoses in 19 patients were based on the surgical results, including five neonates with congenital biliary atresia, six infants with choledochal cyst, and three infants and five chilthen with an anomalous connection between the bile and pancreatic ducts. In five of the six infants with choledochal cysts, an anomalous connection between the ducts was also present. The other five patients (one infant and four young children) with an anomalous connection between the bile and pancreatic ducts were diagnosed on the basis of the ERCP findings. The remaining 21 children (six neonates, five infants, and 10 young children) were found to have no significant abnormality in the pancreaticobiliary system on the basis of other radiologic examinations such as CT and biliary scintigraphy. Symptoms, physical findings. and laboratory data returned to normal by follow-up clinical observations performed at a minimum of 1-month intervals for approximately 8 months. Sonographic reexaminations were performed between I and 3 months, and normal status was confirmed. In these 21 children without abnormality in the pancreaticobiliary system, we analyzed the visualization of the various anatomic parts of the pancreaticobiliary system on MRCP. Imaging Technique All MR imaging examinations were performed on a l.5-t unit (Magnetom Vision; Siemens, Erlangen. Germany) using a body phased array coil. Before MRCP, we acquired TI-weighted fast lowangle shot sequences (TRITE, 150/4.8 msec; flip angle, 75#{176}; acquisition matrix, 128 x 256; scan time, 18 sec) and 12-weighted turbo spin-echo sequences (2000/120; echo train length, 15; acquisition matrix, 128 x 256: scan time, 14 sec) to localize the biliary and pancreatic trees. MRCP was performed using a HASTE Sequence with an echo space of 10.9 rnsec, effective TE of 87 rnsec, one excitation, flip angle of 150#{176}, and a 240 x 256 matrix. Because HASTE is a single-shot sequence, no TR occurs. Only half the K- space was measured (echo train length, 128); the K-space was expanded with the half-fourier method to 240 lines. Fat suppression was used to suppress the signal from peritoneal fatty tissue. HASTE sequences enabled us to obtain an MRCP image very quickly (approximately 1.4 sec). Therefore, all images were acquired without breath-holding. Oxygen inhalation and antiperistaltic drugs were not used in any children. Sedation with triclofos sodium syrup or chloral hydrate suppository Results was used in neonates and infants. The results of visualization of the normal Aware of the results of sonography, we initially structures in the 21 children without abnormality performed HASTE MRCP with acquisition ofa single by two reviewers are shown in Table 1. slice at a slice thickness of mm (imaging In the consensus reading, both the common time, 1.4 sec). The slice thickness was large to indude the entire main pancreatic duct and the intra- bile duct and the first branches of the intrahepatic duct were completely visible in most hepatic bile duct. MRCP at a thinner slice thickness children (Fig. 1). Cystic ducts were not seen of 3-5 mm was then performed in all patients to cxamine the details of regions of interest. The MRCP in neonates and infants, but the ducts were imaging required no postprocessing except image reconstruction, partially visible in five of the 10 young chil- which we completed in less than 1 sec. then. The main pancreatic duct was visible in In all patients, coronal and oblique (usually from -30#{176} two of six neonates, in four of five infants, to #{247}30#{176} to the axis) projections were acquired. Several and in all 10 young children. However, the imaging trials were required to visualize the connecting second branches of the pancreatic duct were portion ofthe biliary tree and the pancreatic duct. not seen in any children. The field of view was cm depending on the The entire course of the bile duct or the area of interest and the patient s constitution. Superimpositions of the fluid-containing spinal canal, pancreatic duct could be visualized in a single plane at the 20- to 50-mm slice thickness, bowel contents, and renal pelvis were eliminated by variation of the orientation and by using a saturation but the image contrast was better at the 3- to slab. The total imaging time for all examinations was 5-mm slice thickness. Motion artifacts within 10 mm. All MRCP images were filmed for caused by patients motion, breathing, or fast analysis by the reviewers bowel movements were not apparent in any Image Analysis All MRCP images were randomly and independently evaluated by two gastrointestinal radiologists who were unaware of clinical data and other imaging information. Reviewers had knowledge only of sex and age. All MRCP images acquired with both thick and thin slice thickness were prepared so the observers could mark anatomic and diseased segments (if present) on the ifims. In non-diseased children, MRCP images ohtamed in the children in each age group were graded for the depiction of the intrahepatic duct. common hepatic duct, gallbladder, cystic duct, common bile duct, main pancreatic duct, and the three segments (head, body, and tail) of the main pancreatic duct. Images were rated on a scale of 0-3 as follows: 3 = the entire anatomic part is visible, 2 = more than 50% of the anatomic part is visible, 1 = less than 50% ofthe anatomic part is visible, and 0 = the amatomic part is difficult to detect. The scores were averaged for each anatomic part. In diseased children, MRCP images were evaluated for detection of dilatation of the bile or pancreatic duct in patients with choledochal cyst. for detection of stenosis or occlusion of the bile duct in patients with congenital biliary atresia, and for detection of abnormal confluence in patients with an anomalous connection between the bile and pancreatic ducts. The diagnostic criteria of choledochal cyst were adapted from the work of Alonso-Lej et al. [13]; for congenital biliary atresia, from Bill et al. [14]; and for anomalous connection between the biliary and pancreatic ducts, from the committee of the Japanese Study Group on Pancreaticobiliary Maljunction [15]. Information provided by MRCP but not provided by sonography was also assessed. children with this short acquisition time. The high signal intensity of the fluid in the spinal canal, stomach, bowels, and renal pelvis could not always be eliminated by varying slice thickness or scan projection. However, the high signal intensity did not affect the ability to analyze the anatomy of the pancreaticobiliary system. High signal intensity in the second portion of the duodenum was useful as a landmark for recognizing the relationship between the duodenum and the pancreaticobiliary tree. The comparison of the MRCP images with the surgical or ERCP results in 24 chilthen is summarized in Table 2. Dilatation of the biliary tract was clearly revealed by MRCP in all six patients with choledochal cyst (Figs. 2 and 3). The level of the dilatation determined on the MRCP images corresponded with the results of surgery. In four of six patients with choledochal cyst, an anomalous connection between the ducts was also present. and three of those connections were detected on the MRCP image. The 34 AJR:170, January 1998

3 MR Cholangiopancreatography of Pediatric Patients IvIvJaIIz*don of Normal Pancrss risraedon Sk wesonmrcholaii EchoS.q cssbil tomic part is difficult to detect anomalous connection between the bile and pancreatic ducts was detected on the MRCP images in nine of 13 patients. Three patients had a long common channel (>15 mm) and two patients had an abnormal complex union of the bile and pancreatic ducts. In five patients with congenital biliary atresia, MRCP visualized the focally dilated intrahepatic duct, but neither the common hepatic duct nor the common bile duct could be seen. Only a focal rudimentary extrahepatic bile duct was seen (Fig. 4). In overall comparison between MRCP and the surgical or ERCP results, MRCP had diagnostic accuracy of 100% in choledochal cysts and in congenital biliary atresia and of 69% in the anomalous connections between Fig. 1.-i -year-old female infant without pancreaticobiliary abnormality. Non-breath-hold MR cholangiopancreatography image acquired with half-fourier acquisition single-shot turbo spin-echo sequence (slice thickness, 30 mm) reveals first-level branches of intrahepatic ducts (arrawheads), common hepatic duct (white arrow), gallbladder (asterisk), and common bile duct (black arrow). Cystic duct and main pancreatic duct are not seen. eanatomic part is vi ble 2 mor ian 50% of the anatomic part is visible 1 less than 50% of the anatomic part is visible and 0 the ana the bile and pancreatic ducts. Additional information provided by MRCP and not provided by sonography included visualization of the anomalous pancreaticobiliary connection (n = 13) and no visualization of a patent common bile duct (n = 5), which suggested the diagnosis of biliary atresia. Discussion Jaundice or hyperbilirubinemia is a common problem in neonates and infants. For the diagnosis of the pancreaticobiliary diseases in childhood, sonography is considered the best screening technique, followed by biliary scintigraphy [1]. Nuclear medicine hepatobiliary scanning using technetium- 99m iminodiacetic acid often permits rapid and clear distinction between obstructive and nonobstructive jaundice. However, the radioisotope may be retained up to 24 hr in jaundiced patients, and anatomic details are insufficiently visualized for complete presurgical evaluation [16, 17]. Therefore, this technique should not be used for screening. We found that MRCP provides valuable information regarding the anatomy of the pancreaticobiliary system. In comparison with the surgical or ERCP findings, MRCP showed high accuracy for detecting anomalies of the pancreaticobiliary tree. However, we could not directly compare the diagnostic AJR:170, January

4 Miyazaki et al. Fig. 2-3-year-old boy with choledochal cyst. Arrowheads = common bile duct, arrow = anomalous connection of bile and pancreatic ducts. A, Non-breath-hold MR cholangiopancreatography (MRCP) images acquired using half-fourier acquisition single-shot turbo spin-echo (HASTE) sequence (slice thickness, 3 mm) discloses fusiform dilatation of common bile duct and anomalous connection of bile and pancreatic ducts. B, Non-breath-hold MRCP image acquired using HASTE sequence in slice thickness of 20 mm at center of same slice as in A shows similar findings. This image also reveals both pancreatic duct and dilated biliary system. Dilatation of right ureter is seen. accuracy of MRCP with that of sonography because our study group was composed of selected patients in whom sonographic examinations were inconclusive or for whom clinicians wanted to have further information about the pancreaticobiliary tree. Differentiating neonatal hepatitis from biliary atresia in the early stage is vital. Many patients with biliary atresia can be saved by replacement of the sclerosed bile ducts with a surgically created bile drainage pathway. The role of imaging studies is not only to Fig month-old boy with congenital choledochal cyst Non-breath-hold half-fourier acquisition singleshot turbo spin-echo MR cholangiopancreatography image (slice thickness, 5 mm) reveals fusiform dilatation of common bile duct Dilatation of right and left intrahepatic bile ducts is also seen (long arrows). Anomalous connection of bile and pancreatic ducts is suspected because their connection point (arrowhead) is far from duodenal lumen. Nondilated main pancreatic duct(shortarrows) is completely visible in this projection. show the anatomy of the biliary system but also to exclude other causes of obstruction such as choledochal cyst. We assume MRCP may have potential in the differentiation between biliary atresia and neonatal hepatitis. We found MRCP disclosed focal rudimentary extrahepatic bile ducts and numerous irregularly dilated intrahepatic ducts in patients with congenital biliary atresia. However. the extrahepatic anatomy in biliary atresia is variable, and its accuracy on MRCP needs further investigation. Fig. 4.-i-month-old female neonate with congenital biliary atresia. Non-breath-hold half-fourier acquisition single-shot turbo spin-echo-mr cholangiopancreatography image (slice thickness, 5 mm) clearly shows severely stenotic common bile duct Focal faint high-signal-intensity areas, presumably rudimentary extrahepatic bile duct, are seen (arrows), suggesting common bile duct Note high signal intensity caused by gastric and intestinal fluid collection. Choledochal cyst and choledochocele are congenital malformations of the extrahepatic biliary tree that may cause jaundice in the neonate or present later in childhood with right upper quadrant pain and mass. In recent studies, an association with abnormal connection between the pancreatic duct and the common bile duct is considered a cause of these diseases [18]. Revealing this connection has required invasive ERCP studies. Choledochal cyst was not only diagnosed correctly but also classified according to the Alonso-Lej or Todani classification [13, 19] using MRCP with high accuracy in our preliminary study. The anomalous connection between the bile and pancreatic ducts could be visualized on HASTE MRCP with 3- to 5-mm-thin slice thickness in approximately 69% of cases, although several imaging trials were required to visualize the connecting portion of the two ducts. The anomalous connection between the bile and pancreatic ducts was classified as an abnormal confluence of the bile and pancreatic ducts or a long common channel (>15 mm). This classification may be correctly recognized on MRCP. Several MRCP techniques have been applied to image the pancreaticobiliary system with breath-hold or without breath-hold (signal averaging) [201. However, most techniques require a relatively long imaging time of sec even when a breath-hold technique is applied [5-8]. Motion artifacts would make it difficult to obtain MRCP images of diagnostic quality in young children when such a long imaging time is needed. MR cholangiography using a rapid acquisition with relaxation enhancement or HASTE sequence provides excellent images in a few seconds [9-12], and we presumed that the HASTE sequence would be suitable for imaging the pancreaticobiliary system of children 6 years old or younger. Although we did not use any breath-hold technique, oxygen inhalation, or antiperistaltic drug, motion artifacts caused by respiration and bowel movements could be avoided in all children who underwent the MRCP using HASTE techniques. This imaging technique can be completed in a short time (1400 msec) and does not require any postprocessing such as maximum intensity projection. MRCP at 20- to 50-mm thickness provided coverage encompassing the entire main pancreatic duct or intrahepatic bile duct, but the image contrast was somewhat inferior to that at the thinner slice thickness because of partial volume averaging. Thin slices (3- to 5-mm 36 AJR:170, January 1998

5 MR of Pediatric Patients thickness) were required for examination of the details or regions ofinterest. In the neonates and infants, the extent of the main pancreatic duct was not consistently visualized. Evaluation of stenosis or wall irregularity of the main pancreatic duct in neonates and infants was difficult cobiliary system in young children. MRCP also provides information useful for surgical planning because it detects ductal dilatation and biliary atresia with high accuracy. Henning J. Langer M. Breath-hold projection magnetic cholangiopancreatography (MRCP): a new method for the examination of the bile duct and pancreatic ducts. Magn Reson Med 1995:33: Reuther G, Kiefer B, Tuchmann A. Cholangiography before surgery: single-shot MR cholangiography versus intravenous cholangiography. Radiology even at a 3-mm slice thickness because the diameter of these ducts is approximately 1-2 mm atthatage [17, 18]. Regarding the safety of use of the HASTE sequence in young children, three specific areas have been addressed by the British National Radiological Protection Board [21]: the effects of the static magnetic field; the time-varying magnetic field effect of gradient switching (seen in echoplanar imaging), which may cause the induction of electric currents; and heat production by the RF magnetic fields. The guidelines laid down by the board are aimed at preventing these potential hazards [2 1]. In the HASTE sequence, heat production by the RF magnetic fields should be seriously considered because numerous pulses are applied to obtain a single-shot image. The peak specific absorption rates obtained in this study using the HASTE sequence were W/kg, which are well within the limits laid down by the National Radiological Protection Board [21] and compare favorably with the spinecho study peak specific absorption rates of Wfkg. 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