Original Article pISSN 1738-2637 / eISSN 2288-2928 J Korean Soc Radiol 2017;77(6):396-403 https://doi.org/10.3348/jksr.2017.77.6.396 Physiologic Flow Related Signal Intensity in Dural Sinuses on Time of Flight Magnetic Resonance Angiography: Changes Caused by Head Elevation 자기공명영상 혈관촬영술에서 보이는 경막정맥동의 혈류 연관 신호: 두부거상에 의한 변화 관찰 Jieun Roh, MD1, Seung Kug Baik, MD1,2*, Jeong A Yeom, MD1, Young Soo Kim, MD3, Hee Seok Jeong, MD1, Chang Hyo Yoon, MD4, Junhee Han, PhD5 Departments of 1Radiology, 3Neurosurgery, Pusan National University Yangsan Hospital, Pusan National University School of Medicine, Yangsan, Korea 2Research Institute of Convergence for Biomedical Science and Technology, Pusan National University Yangsan Hospital, Pusan National University School of Medicine, Yangsan, Korea 4Department of Neurology, Kyungpook National University Hospital, Kyungpook National University School of Medicine, Daegu, Korea 5Department of Statistics, Hallym University, Chuncheon, Korea Purpose: The presence of a flow-related signal in the normal dural sinus time of Index terms flight magnetic resonance angiography (TOF MRA) is common. This study aimed to Diagnostic Imaging identify changes in signal intensity in the dural sinus caused by changes in patient Magnetic Resonance Imaging position. Magnetic Resonance Angiography Materials and Methods: The researchers performed an elevation TOF MRA of the Cerebral Angiography cerebral region in 52 patients, who showed abnormal flow-related signals in the Cerebral Veins dural sinuses on supine position. Flow-related signal intensity in the dural sinuses was then analyzed. Received May 23, 2017 Results: Flow-related signals were seen in 114 sites (52 patients), specifically in the Revised August 1, 2017 internal jugular vein (IJV), sigmoid sinus (SS), inferior petrosal sinus (IPS), and cav- Accepted September 29, 2017 ernous sinus (CS) in 29 sites, 33 sites, 32 sites, and 20 sites, respectively. After head *Corresponding author: Seung Kug Baik, MD Department of Radiology, Research Institute of Conver- elevation, flow-related signal changes were then observed in the IJV, SS, IPS, and CS gence for Biomedical Science and Technology, Pusan in 107 sites (107/114, 93.9%). There was loss of signal (62/114, 54.4%), or decrease National University Yangsan Hospital, Pusan National (39/114, 34.2%), increase (6/114, 5.3%), or no change (7/114, 6.1%) in the signal in- University School of Medicine, 20 Geumo-ro, Mulgeum-eup, Yangsan 50612, Korea. tensity, and flow related signals were more frequent on the left than on the right. Tel. 82-55-360-1834 Fax. 82-55-360-1848 Conclusion: Flow-related signals in the dural sinuses on TOF MRA were decreased E-mail: [email protected] or disappeared by head elevation in 88.6% of the sites. Head elevation may help This is an Open Access article distributed under the terms distinguish between pathologic and physiologic states. of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distri- bution, and reproduction in any medium, provided the original work is properly cited. INTRODUCTION which runs craniocaudal direction and shows low velocity. Therefore, high signal intensity within a dural sinus may be In the normal population, time of flight magnetic resonance considered abnormal (1-3). However, it is not infrequent to ob- angiography (TOF MRA) images of the dural sinuses show serve flow related signals in large venous structures such as in- isointense signal relative to the brain tissue. TOF MRA is only ternal jugular vein (IJV) and dural sinuses in healthy individu- sensitive to arterial flow and effective to saturate venous flow als (4-7), which may mimic pathologic conditions such as dural 396 Copyrights © 2017 The Korean Society of Radiology Jieun Roh, et al arteriovenous fistula (AVF) (2, 4, 5, 8). The causes of frequent by the ethics committee of Pusan National University Yangsan high signal intensities in the dural sinuses are complex and de- Hospital (05-2015-037), and the requirement for written in- pendent on many factors, i.e., anatomical variations (compres- formed consent was waived. sion by the left brachiocephalic vein), intrathoracic pressure, respiration, and others - some yet undefined (4, 7, 9, 10). These Image Acquisition factors might cause reverse flow in the IJV and sigmoid sinus All MRI examinations were performed with 1.5T or 3T MR (SS), resulting in flow directed contralaterally via the inferior system (Avanto and Verio models; Siemens, Erlangen, Germa- petrosal sinus (IPS) and cavernous sinus (CS) and contributing ny). TOF MRA scans were obtained in the supine position to this abnormal high signal intensity in dural sinuses (4, 5). without head elevation and supine position with head eleva- To clarify physiologic and pathologic flow related signal in- tion. If an educated technician had found an abnormal signal tensities, several studies have been performed on physiologic intensity on TOF, he or she notified the radiologist. Radiologists maneuvers (such as Valsalva or Müller’s maneuver) and breath- assessed flow related signal in the IJV, SS, IPS, and CS. After ing maneuvers (7, 11). However, the results of these studies have confirmation by the radiologist, we decided whether to per- not been entirely satisfactory. Different body positions have dif- form head elevation. A designated soft pillow was used to per- ferent patterns of cerebral venous outflow, and considerable vari- form head elevation. The degree of head elevation was 15–18°, ations in the cerebral venous outflow have been reported (1, 9). which is based on Valdueza et al. (13) and was determined by Positional MRI was recently introduced as a new machine to measuring the angles on the picture archiving and communica- get images of cerebral venous outflow (1, 9, 12). However, despite tion system (PACS). the good results, this type of MR scanner remains largely unpop- Both image sets were acquired using the same MR scanner ular. To our knowledge, no study so far has addressed the issue (1.5T or 3T) and 12 channel head matrix coil [Avanto (Verio): of the changes of sinus flow on conventional MRI by position. length × width × height: 300 × 300 × 280 mm (330 mm)]. We The purpose of our study was to identify flow induced chang- performed our brain three-dimensional (3D) TOF MRA pro- es in signal intensity in the dural sinuses caused by changes in tocol in all cases by using the following sequences: repetition patient position, namely, head elevation. Our hypothesis was that time, 30 ms; echo time, 3.3 ms; and a tilted optimized non-sat- physilologic signal intensity in the dural sinuses would change urating excitation pulse with a central flip angle of 20°. Section after head elevation, which may help distinguish between phys- thickness was 1 mm. A field of view of 180× 180 mm was used iologic and pathologic flow related signals. with a matrix of 384 × 224. The sequence included a spatial sat- uration pulse above the acquisition slab to saturate the venous MATERIALS AND METHODS flow. The acquisition time was 4 min 37 s. Patient Selection and Study Design Image Analysis Between September 2013 and March 2014, 52 patients with A subjective grade of 1 to 3 was given for the magnitude of any abnormal signals of dural sinuses who underwent additional signal in either sinus. The grade system was modified from Saka- MRA were included. The indications of the MR exam for en- moto et al. (14): grade 1 was equal to that of normal dural sinus rolled patients were non-specific neurological symptoms such signal on an MRA source and/or maximum intensity projection as headache. Patients were excluded on the following criteria: (MIP) images; grade 2 was greater than the normal dural sinus poor image quality, venous thrombosis, Moyamoya disease (3 signal and lesser than the internal carotid artery signal on an patients), dural AVF (3 patients), and MR images obtained with MRA source and/or MIP images; and grade 3 was equal to that different machines. To confirm Moyamoya disease and dural of internal carotid artery signal on an MRA source and/or MIP AVF, digital subtraction angiography (DSA) was performed. (Fig. 1). When flow related signal intensity of grade 2 or 3 was The cases consisted of 21 men and 31 women (mean age, 61.3 detected in the IJV, SS, IPS, and/or CS on TOF MRA with su- years; range, 28–86 years). This retrospective study was approved pine position, additional head elevation TOF MRA scans were jksronline.org J Korean Soc Radiol 2017;77(6):396-403 397 Physiologic Signal of Sinus obtained. Two independent radiologists with 6 and 25 years of by visual inspection of 3D TOF MRA images and measuring the experience in neuroradiology assessed the overall images, re- signal intensities in the most proximal and distal areas of the si- spectively. They evaluated the changes in the signal intensity in nus and vein using variable sized regions of interest or subjec- the IJV, SS, IPS, and CS before and after head elevation as follows: tive differences on PACS images. We also assessed the laterality loss, decrease, increase, and no change. Differences in the assess- of signals in the dural sinuses. ments of both readers were resolved by consensus. Source imag- es of the TOF MRA and MIP images were used for the evalua- Statistical Analysis tion. Flow directions of both the sinuses and vein were determined The exact binomial test was used to compare flow related sig- A B C Fig. 1. TOF MRA images demonstrate subjective grade for the magnitude of any signal in left internal jugular vein. A. Grade 1, equal to that of normal dural sinus signal on an MRA source and/or MIP images. B.