Name /ajnr/21_118 02/02/00 03:31PM Plate # 0 com osite g 162 # 1 AJNR Am J Neuroradiol 21:162±170, January 2000 Vascularization of Head and Neck Paragangliomas: Comparison of Three MR Angiographic Techniques with Digital Subtraction Angiography Rene van den Berg, Martin N.J.M. Wasser, Adrian P.G. van Gils, Andel G.L. van der Mey, Jo Hermans, and Mark A. van Buchem BACKGROUND AND PURPOSE: MR angiography of the head and neck region has been studied widely, but few studies have been performed concerning the ef®cacy of MR angiog- raphy for the identi®cation of the speci®c vascular supply of the highly vascular head and neck paragangliomas. In this study, we compared three MR angiography techniques with respect to visualization of branch arteries in the neck and identi®cation of tumor feeders in patients with paragangliomas. METHODS: Fourteen patients with 29 paragangliomas were examined at 1.5 T using 3D phase-contrast (PC), 2D time-of-¯ight (2D TOF), and multi-slab 3D TOF MR angiography. In the ®rst part of the study, two radiologists independently evaluated the visibility of ®rst-, sec- ond-, and third-order branch arteries in the neck. In the second part of the study, the number of feeding arteries for every paraganglioma was determined and compared with digital sub- traction angiography (DSA), the standard of reference in this study. RESULTS: Three-dimensional TOF angiography was superior to the other MR angiography techniques studied (P , .05) for depicting branch arteries of the external carotid artery in the neck, but only ®rst- and second-order vessels were reliably shown. DSA showed a total of 78 feeding arteries in the group of patients with 29 paragangliomas, which was superior to what was revealed by all MR angiography techniques studied. More tumor feeders were identi®ed with 3D TOF and 2D TOF angiography than with 3D PC MR angiography (P , .05), with a sensitivity/speci®city of 61%/98%, 54%/95%, and 31%/ 95%, respectively. Sensitivity was low- est for carotid body tumors. CONCLUSION: Compared with intra-arterial DSA, the 3D TOF MR angiography technique was superior to 3D PC and 2D TOF MR angiography for identifying the ®rst- and second- order vessels in the neck. With 3D TOF angiography, more tumor feeders were identi®ed than with the other MR angiography techniques studied. The sensitivity of MR angiography, how- ever, is not high enough to reveal important vascularization. The sensitivity of MR angiography is too low to replace DSA, especially in the presence of carotid body tumors. Paragangliomas of the head and neck are highly paragangliomas). Paragangliomas are rarely malig- vascular neoplasms that originate from paragan- nant. In general, they are very slow-growing, be- glionic tissue located at the carotid bifurcation (ca- nign neoplasms. Paraganglioma-associated morbid- rotid body tumors), along the nodose ganglia of the ity occurs because of local tumor growth vagus nerve (vagal paragangliomas), and in the compromising neural and vascular structures in the jugular fossa and tympanic cavity (jugulotympanic neck, skull base, and posterior cranial fossa. Such morbidity may be an indication for treatment, Received January 21, 1999; accepted after revision July 12. which comprises surgical resection with or without From the Departments of Radiology (R.v.d.B., M.N.J.M.W., preceding embolization. M.A.v.B.) and Otolaryngology (A.G.L.v.d.M.), Leiden Uni- Diagnostic radiology plays an important role in versity Medical Center; the Department of Medical Statistics the analysis of a paraganglioma patient. First, the (J.H.), University of Leiden; and the Department of Radiology tumor has to be detected and characterized, and be- (A.P.G.v.G.), Utrecht University Hospital, the Netherlands. cause paragangliomas are multiple in 30% of pa- Address reprint requests to Rene van den Berg, Department of Radiology, Bldg 1, C2-S, Leiden University Medical Center, tients, the presence of concomitant tumors also Albinusdreef 2, 2333 AA Leiden, The Netherlands. should be studied. In addition, tumor extension has to be determined, especially the relation of the tu- q American Society of Neuroradiology mor to the surrounding vascular structures. For 162 MS Name /ajnr/21_118 02/02/00 03:31PM Plate # 0 com osite g 163 # 2 AJNR: 21, January 2000 NECK PARAGANGLIOMAS 163 these tasks, MR imaging is well equipped and has MR Angiography Acquisition proved to be superior to other imaging techniques MR angiography was performed on a Philips NT 15 gyros- (1±4). Once it has been decided that an operation can (Philips Medical Systems, Best, the Netherlands) operating is indicated, detailed information about the vascular at a ®eld strength of 1.5 T and with a standard quadrature neck supply of the tumors is required. When information coil. The imaging protocol included three axial MR angiog- regarding the angioarchitecture of the vascular sup- raphy sequences using thin-section gradient-echo pulse se- ply of paragangliomas has been obtained, a thera- quences covering an area of 10 centimeters from the distal peutic decision can be determined based on wheth- common carotid artery upward. Field of view (200 mm) and matrix size (196 3 256) were identical for all techniques. The er such a lesion can be embolized. This also results scan parameters for 3D PC MR angiography were 26/9/2 (TR/ in a reduction of operative risk. Digital subtraction TE/excitations); ¯ip angle, 208; 50 over-contiguous slices; and angiography (DSA) is the diagnostic method of slice thickness, 4 mm with 2-mm overlap. A band to suppress choice for obtaining this vascular information. venous ¯ow signal was placed cranially to the imaging vol- MR angiography has several advantages over ume. Scan time was 11 minutes 39 seconds. Both magnitude DSA. The most obvious is its lack of morbidity and and phase images were evaluated. In a pilot study, we assessed mortality. In addition, because of the availability of the optimal velocity encoding for the PC MR angiography the source images as well as the possibility of gen- technique. Using an encoded velocity of 20 cm/s, we found some signal loss in the carotid bifurcation due to aliasing, but erating maximum-intensity projections (MIPs), no signal loss in the external carotid artery itself. This velocity spatial relationships between blood vessels and sur- encoding value was chosen to optimize visualization of the rounding structures can be assessed optimally. Two small feeding arteries. Two-dimensional TOF scan parameters previous investigations (5, 6), both studying six pa- were 28/5.1/2 (TR/TE/excitations); ¯ip angle, 608; 50 slices; tients, demonstrated that identi®cation of feeders of and slice thickness, 2 mm. A travelling band for saturation of paragangliomas is feasible with MR angiography. venous ¯ow was placed cranially to every slice. The scan time Other articles regarding the role of MR angiog- was 4 minutes 17 seconds. A gradient-echo technique with ®ve raphy for assessment of vascularization of paragan- overlapping slabs was used for 3D TOF MR angiography. Cra- nial to each separate slab, a saturation band was placed to gliomas reported unsuccessful attempts at identi- suppress venous ¯ow. This multi-slab technique reduces the fying feeding vessels (7, 8). saturation of ¯ow signal. Scan parameters were 25/6.9/1 (TR/ Systematic studies on the ef®cacy of MR angi- TE/excitations); ¯ip angle, 208; 135 over-contiguous slices; ography for identifying tumor feeders in patients and slice thickness, 1.5 mm with 0.75 mm overlap. The scan with paragangliomas are lacking in the literature. time was 5 minutes 49 seconds. A prerequisite for establishing the utility of MR From the individual source images of the three MR angi- angiography techniques for identifying tumor feed- ography data sets, MIPs were generated using the software ers is to explore the reliability of this technique for provided by the manufacturer of the MR system. Nine projec- identifying normal branch arteries in the neck. We tions were obtained rotating around the craniocaudal axis at 208 increments. For each case, identical MIPs were generated are not aware of any studies in the literature that of each MR angiography sequence. Subregions of interest on explore this aspect of MR angiography. In this the MIPs were only made for illustrative purposes in this in- study, we attempted to study the ef®cacy of three vestigation; none of them were used during the reading ses- MR angiography techniquesÐ3D phase-contrast sions. MIPs and axial source images were evaluated as de- (PC), 2D time-of-¯ight (TOF), and 3D TOF angi- scribed in the following section. ographyÐto determine which technique enabled optimal visualization of branch arteries in the neck. We also attempted to study the ef®cacy of these MR Angiography Interpretation MR angiography techniques with respect to iden- For each MR angiography technique, the combined set of ti®cation of tumor feeders in patients with axial source images and MIPs were evaluated independently paragangliomas. by two radiologists (APGvG, MNJMW). They had no knowl- edge of the DSA results. Before reviewing the data sets, both readers ®rst were trained to identify the normal vascular anat- Methods omy on MR angiography, both in the axial plane as well as on the MIPs. Correct identi®cation of branch arteries in the Patients neck in the axial plane is possible, because the endpoint is ®xed, and the origin shows only a small number of variations Fourteen patients (seven female, seven male; median age, (9). This is also true in patients with paragangliomas, because 39 years [range, 29±57 years]) with 29 paragangliomas were only the course of these vessels, and not their origin (or end- studied. These 29 paragangliomas included 13 carotid body point), is affected by the tumor.