T1w Spin Echo Research Articles

Diagnostic Accuracy of Limited Protocol MRI for Diagnosis of Lumbar Disc Degeneration

Objective: To determine the accuracy of limited protocol Magnetic resonance imaging of lumbar spine in determination of lumbar disc herniation, nerve root compression and annular tear taking findings of routine MRI as a reference standard. Methodology: A descriptive cross-sectional study was conducted from August 2016 to February 2017 at Dow Institute of Radiology (DIR), Dow University of Health Sciences (DUHS). All patients of either gender aged 20 years or more presenting for MRI with low back pain were included. Routine complete protocol included T1W spin echo (SE) images on the sagittal plane, fat suppression sequence on the sagittal plane and T2W fast spin echo (FSE) images on the sagittal and axial planes, while limited protocol included T2W fast spin echo images on the sagittal and axial planes. Statistical analysis for social sciences (SPSS version 24), Inc, USA was used for the purpose of statistical analysis.Results: The sensitivity and specificity of limited protocol of disc herniation, nerve root compression, and AT were found to be 100% taking full protocol for disc herniation, nerve root compression, and AT as a gold standard. A significant difference of disc herniation was observed with age (p-value: <0.001), gender (p-value: 0.011), NRC (p-value: <0.001), and AT (p-value: <0.001).Conclusion: Limited protocol MRI of lumbar spine can lead to a definite diagnosis of LDH, NRC and AT without causing any loss of information.Keywords: Low back pain, diagnostic accuracy, limited protocol MRI, disc herniation, nerve root compression

Prospective Imaging Trial Assessing Gadoteridol Retention in the Deep Brain Nuclei of Women Undergoing Breast MRI

To assess for indirect evidence of gadoteridol retention in the deep brain nuclei of women undergoing serial screening breast MRI. This HIPAA-compliant prospective observational noninferiority imaging trial was approved by the IRB. From December 2016 to March 2018, 12 consented subjects previously exposed to 0-1 doses of gadoteridol (group 1) and 7 consented subjects previously exposed to ≥4 doses of gadoteridol (group 2) prospectively underwent research-specific unenhanced brain MRI including T1w spin echo imaging and T1 mapping. Inclusion criteria were: (1) planned breast MRI with gadoteridol, (2) no gadolinium exposure other than gadoteridol, (3) able to undergo MRI, (4) no neurological illness, (5) no metastatic disease, (6) no chemotherapy. Regions of interest were manually drawn in the globus pallidus, thalamus, dentate nucleus, and pons. Globus pallidus/thalamus and dentate nucleus/pons signal intensities and T1-time ratios were calculated using established methods and correlated with cumulative gadoteridol dose (mL). All subjects were female (mean age: 50 ± 12 years) and previously had received an average of 0.5 ± 0.5 (group 1) and 5.9 ± 2.1 (group 2) doses of gadoteridol (cumulative dose: 8 ± 8 and 82 ± 31 mL, respectively), with the last dose an average of 492 ± 299 days prior to scanning. There was no significant correlation between cumulative gadoteridol dose (mL) and deep brain nuclei signal intensity at T1w spin echo imaging (p = 0.365-0.512) or T1 mapping (p = 0.197-0.965). We observed no indirect evidence of gadolinium retention in the deep brain nuclei of women undergoing screening breast MRI with gadoteridol.

Assessment of MR imaging during one-lung flooding in a large animal model.

Magnetic resonance imaging (MRI) of the lung remains challenging due to the low tissue density, susceptibility artefacts, unfavourable relaxation times and motion. Previously, we demonstrated in vivo that one-lung flooding (OLF) with saline is a viable and safe approach. This study investigates the feasibility of OLF in an MRI environment and evaluates the flooding process on MR images. OLF of the left lung was performed on five animals using a porcine model. Before, during and after OLF, standard T2w and T1w spin-echo (SE) and gradient-echo (GRE) sequences were applied at 3T. The procedure was successfully performed in all animals. On T1w MRI, the flooded lung appeared homogenous and isointense with muscle tissue. On T2w images, vascular structures were highly hypointense, while the bronchi were clearly demarcated with hypointense wall and hyperintense lumen. The anatomical demarcation of the flooded lung from the surrounding organs was superior on T2w images. No outflow effects were seen, and no respiration triggering was required. OLF can be safely performed in an MR scanner with highly detailed visualization of the pulmonary structures on T2w images. The method provides new approaches to MRI-based image-guided pulmonary interventions using the presented experimental model.

Three-dimensional T1-weighted gradient echo is a suitable alternative to two-dimensional T1-weighted spin echo for imaging the canine brain.

Volumetric imaging (VOL), a three‐dimensional magnetic resonance imaging (MRI) technique, has been described in the literature for evaluation of the human brain. It offers several advantages over conventional two‐dimensional (2D) spin echo (SE), allowing rapid, whole‐brain, isotropic imaging with submillimeter voxels. This retrospective, observational study compares the use of 2D T1‐weighted SE (T1W SE), with T1W VOL, for the evaluation of dogs with clinical signs of intracranial disease. Brain MRI images from 160 dogs who had T1W SE and T1W VOL sequences acquired pre‐ and postcontrast, were reviewed for presence and characteristics of intracranial lesions. Twenty‐nine of 160 patients were found to have intracranial lesions, all visible on both sequences. Significantly better grey‐white matter (GWM) differentiation was identified with T1W VOL (P < .001), with fair agreement between the two sequences (weighted κ = 0.35). Excluding a mild reduction in lesion intensity in three dogs precontrast on the T1W VOL images compared to T1W SE, and meningeal enhancement noted on the T1W VOL images in one dog, not identified on T1W SE, there was otherwise complete agreement between the two sequences. The T1W VOL sequence provided equivalent lesion evaluation and significantly improved GWM differentiation. Images acquired were of comparable diagnostic quality to those produced using a conventional T1W SE technique, for assessment of lesion appearance, number, location, mass effect, and postcontrast enhancement. T1W VOL, therefore, provides a suitable alternative T1W sequence for canine brain evaluation and can facilitate a reduction in total image acquisition time.

Diagnostic Efficacy of Perfusion Magnetic Resonance Imaging in Supratentorial Glioma Grading

Background: Pre-operative glial brain tumor grading could determine the management. Perfusion weighted magnetic resonance imaging (PWMRI) is a promising modality for assessment and management of brain lesions. Objectives: In this study, we assessed the diagnostic efficacy of this method in the grading of supratentorial gliomas using 3 Tesla MRI. Patients and Methods: Using a 3 Tesla MRI unit, 35 (20 male, and 15 female) patients with glioma were examined one month before surgery. Imaging protocol was: 615 slices, field of view (FOV) 22 × 22 cm2 T1W spin echo: repetition time (TR) 500 -echo time (TE) 30 and (FOV) 22 × 22 cm2 T2W Turbo spin echo: TR 5000 -TE 90. Then 15 cc gadolinium was injected at the rate of 3cc/s and imaging was repeated with: TR: 2360 TE: 45, flip angle 90, band width 1346 echo planar imaging (EPI) 128 measurement 50. Mean transit time (MTT), cerebral blood flow (CBF) and cerebral blood volume (CBV) were measured at enhancing and edematous regions compared to contralateral white matter. Then, an appropriate biopsy was performed from different sites of the tumor during surgical excision. Standard hispathological examination that was assessed in a double-blinded manner, was considered as gold standard. Results: Patients’ tumor distribution was grade IV in 14 (40%), grade II in 14 (40%), grade III in six (17.1%) and grade I in one (2.9%). Relative CBF (rCBF), and rCBV was significantly more in high-grade glioma (HGG) versus low-grade glioma (LGG) (P < 0.001 and P < 0.009, respectively) and rCBF difference was more than rCBV but it was not significant. MTT was statistically the same in both groups and there was no difference between them. A value of rCBV greater than 2 showed a sensitivity of 90% and specificity of 67% and rCBF greater than 1.4 showed a sensitivity of 100% and a specificity of 74% in discrimination of high grade gliomas versus low grade gliomas. Conclusion: PWMRI is more accurate than conventional MRI for noninvasive discrimination of low-grade glioma (LGG) and high-grade glioma (HGG) that could be helpful for neurosurgeons in decision making dealing with the most common tumor of the brain.

Comparison of Maximum Signal Intensity of Magnevist Contrast Agent in Modified T1 Weighted Spin Echo, T1 Weighted Fast Spin Echo and T1 Weighted Gradient Echo Sequences

Background: Nowadays MRI examinations have been widely used in clinical applications for many diagnoses. The use of contrast agent in MRI improves lesion detection and characterization and causes more accurate diagnosis. Objectives: The aim of this study was comparing to optimal dose of Magnevist contrast agent in modified T1W SE (Spin Echo), T1W FSE (Fast Spin Echo) and T1W GRE (GRadient Echo) and effect of scan parameters of these sequences on the maximum SI of Magnevist contrast agent. Material and Method: This study was done on a phantom that was containing test tubes. These test tubes were filled with 30ml saline mixed with different doses of Magnevist contrast agent. In this study, some scan parameters of T1W pulse sequences were changed to achieve optimal parameters for maximum SI of contrast agent. In this study maximum signal intensity of each image was measured by ImageJ software. Results: The results of this study show that there are differences in maximum SI in different T1W pulse sequences with changing scan parameters. This study shows that 0.625 mmol/L of Magnevist has maximum SI in all of sequences. The maximum SI can be seen at GRE, SE and FSE sequences, respectively. Conclusion: Using routine and changed scan parameters, each pulse sequence reaches different maximum SI in specific concentration , which is highest in 2D SPGR (SPoiled GRadient) with flip angle = 75˚ and least in T1W SE with TE (Time of Echo) = 40ms.

Comparison of MRI and 18F-FDG PET for Evaluation of the Response to Treatment of Patients Diagnosed with Multiple Myeloma: A Prospective Clinical Study

AbstractAbstract 4004 IntroductionAlthough conventional radiography is still the standard staging procedure for newly diagnosed and relapsed multiple myeloma (MM) patients in clinical practice, magnetic resonance imaging (MRI) using T2- and T1-weighted contrasted enhanced images has proved to have advantages over a conventional skeletal survey. Fluoro-desoxy-glucose positron emission tomography (18F-FDG PET) is not yet validated as an imaging method for MM evaluation. The purpose of this study was to prospectively compare MRI and 18F-FDG PET for short-term evaluation of the response in newly diagnosed MM patients and to correlate the imaging assessment with the biological response. Materials and methodsA group of 15 newly diagnosed myeloma patients were treated in a single center. After induction with bortezomib-lenalidomide-dexamethasone (VRD), they all received high dose cyclophosphamide and G-SCF prior to peripheral stem cell collection. The patients were then randomized to either autologous stem cell transplantation (ASCT) with 2 consolidation VRD cycles or 5 VRD cycles. All patients subsequently received maintenance treatment with low dose lenalidomide for 1 year. Imaging was performed at diagnosis, after the first three VRD cycles and immediately before initiating maintenance treatment. The spinal and pelvic MRI protocol consisted of sagittal T1-weighted (T1-w) spin echo and fat-suppressed T2-weighted (T2-w) STIR sequences of the spine, axial and coronal T1-w spin echo and fat-suppressed T2-w STIR sequences of the pelvis and upper parts of the lower limbs and finally a fat-suppressed T1-w sequence after intravenous gadolinium covering the spine, pelvis and upper parts of the lower limbs. The biological response was evaluated according to IMWG criteria. The presence or absence of diffuse bone marrow infiltration (DI), diffuse patchy bone marrow infiltration (DPI) and focal bone marrow lesions (FL) was recorded prospectively. A hypointense T1, hyperintense STIR and enhanced fat-suppressed T1 lesion were scored as FL on MRI scans. The presence of extra-medullary disease (EMD) and the SUVmax of FDG-avid focal lesions were assessed. Complete response (CR) and partial response (PR) were determined by MRI and 18F-FDG PET after induction and before maintenance. CR was defined as the absence of diffuse infiltration or focal lesions for MRI and as the absence of diffuse and/or focal uptake for 18F-FDG PET. The response was considered to be partial if the image differed from CR. We compared the results of the two techniques with the biological response for every patient. ResultsThe 15 patients (5 females, 10 males; age: 55 ± 6 years (mean, SD)) were classified according to the ISS (1, n=6; 2, n=8; 3, n=1) and DSS (IIIA, n=14; IIIB, n=1). At baseline, MRI showed DI, DPI and FL in 3, 7 and 189 cases respectively; the 18F-FDG PET uptake displayed a diffuse homogeneous pattern in 4 patients and a diffuse heterogeneous pattern in 11 patients with only 55 focal uptakes. Five cases of extra-medullary uptake were observed on baseline 18F-FDG PET scans and remained at the follow-up. On the basis of the biological response, the patients were classified as MR (n=1), PR (n=7), VGPR (n=5) and CR (n=2) after induction and as MR (n=1), PR (n=6), VGPR (n=3) and CR (n=5) before maintenance treatment. Differences in focal lesion detection were observed between MRI and 18F-FDG PET for small lesions (<10 mm). Two false positive focal uptakes were observed (pulmonary infection, sacrum abnormality).The status assessment showed concordant results between the two techniques in only 5/15 (CR, n=2; PR, n=3) and 8/15 (CR, n= 2; PR, n=6) cases at induction and before maintenance respectively. MRI showed residual disease in 7/15 patients before the initiation of maintenance treatment. ConclusionAt diagnosis and during treatment evaluation, both 18-FDG PET and MRI provide information about the extent of the disease, allowing for a more comprehensive assessment of persisting or recurrent myeloma. The morphologic MRI can often be falsely positive due to persistent non-viable lesions. Hence 18-FDG PET might be more suitable than morphologic MRI for determination of the remission status. Disclosures:No relevant conflicts of interest to declare.

Lesions by tissue specific imaging characterize multiple sclerosis patients with more advanced disease

Background: Cerebrospinal fluid tissue specific imaging (CSF-TSI), a newly implemented magnetic resonance imaging (MRI) technique, allows visualization of a subset of chronic black holes (cBHs) with MRI characteristics suggestive of the presence of CSF-like fluid, and representing lesions with extensive tissue destruction. Objective: To investigate the relationship between lesions in CSF-TSI and disease measures in patients with multiple sclerosis (MS). Methods: Twenty-six patients with MS were imaged at 3.0 T, obtaining T1-weighted (T1-w) and T2-w spin echo (SE), T1 volumetric images and CSF-TSI images. We measured: (i) lesion volume (LV) in T1-w (cBH-LV) and T2-w SE images, and in CSF-TSI; (ii) brain parenchyma fraction (BPF). Differences between patients with and without CSF-TSI lesions were analyzed and association between clinical and MRI metrics were investigated. Results: cBHs were seen in 92% of the patients while lesions in CSF-TSI were seen in 40%. Patients with CSF-TSI lesions were older, with longer disease duration, higher disability scores, larger cBH-LV and T2-LV, and lower BPF than patients without CSF-TSI lesions (≤0.047). Partial correlation analysis correcting for T2-LV, cBH-LV and BPF showed an association (p < 0.0001, r = 0.753) between CSF-TSI LV and disability score. Conclusions: CSF-TSI lesions characterize patients with more advanced disease and probably contribute to the progress of disability.

Radiofrequency-induced Heating near Fixed Orthodontic Appliances in High Field MRI Systems at 3.0 Tesla

To assess radiofrequency (RF)-induced heating of fixed orthodontic appliances during acquisition of three different sequences in magnetic resonance imaging (MRI) at 3 Tesla. Ten commonly used fixed orthodontic appliances were investigated utilizing a phantom head and simulating the in vivo intraoral situation. A 3 Tesla MRI system (Intera, Philips Medical Systems, Best, The Netherlands) was used to acquire T1w spin-echo (T1 SE), T1w turbo spin-echo (T1 TSE) and T1w gradient-echo (T1 GRE) sequences in axial orientation. Continuous temperature measurement was performed with a dedicated four channel fluoroptic thermometry system. For each orthodontic appliance temperature probes were placed at three predefined sites in order to perform temperature measurements during MR imaging. The fourth temperature probe was fixed to the neck of the phantom head and served as the reference. Mean temperature alterations were determined for all appliances. Temperature elevations ranged from -0.3 degrees C to 0.2 degrees C and were negligible for all orthodontic appliances investigated. There was no difference in mean temperature alteration for any of the three imaging sequences. Based on the data of our experimental study the radiofrequency-induced heating of orthodontic brackets during high field MRI at 3 Tesla can be categorized as negligibly low. Even the clinical routine examination of the head at 3 Tesla using high-energetic pulse sequences can be applied without hesitation in patients with fixed orthodontic appliances.

Abstract 5765: 3T MRI Molecular Imaging of Benfluorex Treatment of Metabolic Syndrome with α v β 3 -Integrin Targeted Nanoparticles

1.5T MRI with α v β 3 -integrin targeted gadolinium nanoparticle contrast agents (NP) can detect stage I atherosclerosis in experimental animals by localizing specifically to inflammatory plaque components within minutes after injection. We hypothesized that NP could serve as an early surrogate biomarker of therapeutic efficacy for benfluorex treatment of metabolic syndrome in diabetic JCR-LA:cp rats on a 3T clinical scanner. Six week old JCR-LA:cp rats (n=6) received benfluorex in their feed (0.069% wt/wt) for 16 weeks, while control animals (n=5) received regular diet. The abdominal aorta was imaged (T1w spin echo) in 4 cross-sections at baseline and 2-hour post-injection (IV, 1.0 ml/kg NP) every 4 wks with a 3.0 T whole-body clinical MRI scanner, and total aortic wall signal was computed across all sections. Treatment of diabetic JCR-LA:cp rats with benfluorex reduced food consumption and body weight (16.0%; p&lt;0.05); and fasting plasma insulin, leptin and triglyceride were decreased by 52.6%, 18.2% and 36.2% in treated animals. Aortic wall signal for untreated animals rose progressively, whereas signal in treated animals progressively decreased, indicative of attenuation of angiogenesis and vascular inflammation (Figure , *p&lt;0.05). These observations represent the first report of the use of molecular imaging with an MRI surrogate biomarker at clinical field strength for quantifying therapeutic efficacy in a model of metabolic syndrome. This research has received full or partial funding support from the American Heart Association, AHA Midwest Affiliate (Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, South Dakota &amp; Wisconsin).

USPIO‐enhanced MR imaging for visualization of synovial hyperperfusion and detection of synovial macrophages: Preliminary results in an experimental model of antigen‐induced arthritis

To evaluate whether ultrasmall superparamagnetic iron particles (USPIO)-enhanced MRI is capable of assessing both synovial perfusion characteristics and the presence of synovial macrophages in a model of antigen-induced arthritis. Unilateral arthritis was induced in six knees of six rabbits. The contralateral knees of the rabbits served as control knees. After onset of arthritis, all 12 knees were scanned prior to and immediately following intravenous administration of USPIO using a multiphase T1-weighted (T1w) fast gradient-echo (FGRE) sequence, and T1w spin-echo (SE), T2-weighted (T2w) FSE, T2*w GRE, and short-tau inversion recovery (STIR) sequences prior to and 24 hours following USPIO administration. SI-vs.-time curves (STCs) and the early enhancement rate during the first 56 seconds (REE(56)) were calculated from SI measurements within the synovial tissue of all knees on dynamic T1w images. MR findings were correlated to histopathology. REE(56) was significantly higher in the synovial tissue of arthritic knees than in the control knees (P < 0.01). Significant T1-, T2-, and T2* effects (P = 0.03-0.04) and multiple synovial vessels were visually detectable within the arthritic synovial tissue 24 hours after administration of USPIO, whereas no signal changes or synovial vessels were seen in the control knees. Histopathology revealed widened synovial blood vessels in the arthritic knees, and confirmed iron uptake by macrophages in the arthritic knees. USPIO-enhanced MRI is capable of both assessing synovial hyperperfusion and detecting macrophages in antigen-induced arthritis in rabbits.

MAGNETIC RESONANCE IMAGING FEATURES OF CERVICAL SPINAL CORD MENINGIOMAS

The records of four dogs with cervical spinal cord meningiomas were retrospectively reviewed. Signalment, history, laboratory findings, neurological examination, and histopathological findings were evaluated. Magnetic resonance imaging (MRI) was performed using a 1.0-T superconducting magnet and T2-weighted (W) and noncontrast and postcontrast T1-W spin echo pulse sequences. Meningiomas were located at the level of the second, third, and fifth cervical vertebrae and the C2-3 intervertebral space. All meningiomas appeared as focal masses that were hyperintense to the spinal cord on T2-W images and iso- to hypointense on the T1-W images. They could be identified as intradural and extramedullary in origin based on a broad-based dural margin seen on at least one of the imaging planes and a gradual expansion of the subarachnoid space cranial and caudal to the mass, best noted on the transverse and dorsal plane images. On dorsal plane T2-W images in three dogs, expansion of the subarachnoid space adjacent to the mass appeared similar to the myelographic "golf tee" sign. All meningiomas exhibited moderate, well-defined contrast enhancement with dural tails seen in three of the four dogs. One dog had extension into the intervertebral foramen along the nerve and ipsilateral atrophy of the muscles of the neck. By differentiating the meningiomas from intramedullary tumors and by clearly depicting the extent of the masses, MRI provided valuable information about treatment options and prognosis.

Evaluation of meniscal repair with serial magnetic resonance imaging: a comparative study between conventional MRI and indirect MR arthrography

Objective: To prospectively investigate the healing process of meniscal repair with plain magnetic resonance imaging (MRI) and indirect MR arthrography and to compare the two methods. Materials and methods: Twenty patients with an arthroscopic meniscal repair without clinical symptoms underwent conventional and indirect MR arthrography of the affected knee, 3, 6 and 12 months after the index operation applying a T1-w Spin Echo sequence in three planes. The size of the tear gap was measured on transverse images. The signal-to-noise ratio and the configuration of the abnormal signal were evaluated in the coronal images. Results: All patients demonstrated abnormal signal intensity at the side of the meniscal repair. The size of the gap at the previous tear side, reduced significantly by 45 and 40% on conventional MRI and indirect MR arthrography respectively, from 3 months to 1 year ( P<0.05). The signal-to-noise ratio of the intrameniscal abnormal signal reduced significantly and approximately 50% from 3 to 6 months, and from 6 to 12 months postoperatively, as demonstrated with indirect MR arthrography. However, as opposed to normal meniscus, the signal-to-noise ratio of the abnormal area remains 5.5 times higher 12 months postoperatively. In contrast, the reduction of signal-to-noise ratio of the abnormal area at conventional MRI was not significant even from 3 to 12 months. In 90% of the cases, the indirect MR arthrography showed the intrameniscal abnormal signal on plain MRI, to extend to the articular surface as opposed to 25% on plain MRI. Conclusion: With indirect MR arthrography, the natural process of meniscal healing can be evaluated. Significant reduction of the size of the tear gap and significant reduction of the signal-to-noise ratio of the abnormal signal as well as its configuration are the main parameters interpretating the normal healing process.

The Use of Open MRI in Otorhinolaryngology: Initial Experience

Intraoperative imaging in head and neck surgery is a useful tool in many situations. In addition to being helpful for intraoperative orientation, real-time imaging enables visualization of the progress of surgery and the completeness of tumor resection. Regions in the head and neck to which access is difficult, and which therefore have a high incidence of morbidity and risk for the patient, can be approached more easily and safely in an open MRI than in a conventional way. Interventions in the open MRI (Signa SP, 0.5 Tesla) were performed with nonmagnetic instruments and an MR-safe microscope. For intraoperative navigation, the integrated FlashPoint system is helpful, because it allows targeting of the tumor by a calculated virtual line. T1W spin-echo, T2W fast spin-echo, and 3D T1W gradient-echo sequences were used for high-resolution imaging. Real-time imaging is achieved by fast multiplanar spoiled gradient-echo sequences or T2 single-shot fast spin-echo sequences. From 1996 to the present, we biopsied 17 petroclival tumors, performed paranasal sinus surgery in five cases, biopsied two neck masses, and inserted tubes for brachytherapy in 12 cases. No complications were observed. In all surgical procedures, a good resolution was obtained with MRI, especially for soft-tissue structures. The tumor could be targeted exactly, and all specimens revealed the relevant histology. In paranasal sinus surgery, however, the success rate was lower because it was difficult to distinguish blood from pathologic tissue. The insertion of tubes for brachytherapy was successful in all cases. It was possible to apply the tubes parallel to each other, 1 cm apart. Relevant biopsies could be taken of both neck masses. The indications for the use of open MRI in otorhinolaryngology are biopsies of tumors in regions that are difficult to approach, such as the petrous apex and petroclival region, the parapharyngeal space, and the orbit. Furthermore, the open MRI can be useful in paranasal sinus surgery, in the evaluation of tissue resection, and in the detection of the anatomy of delicate structures such as the internal carotid artery, the skull base, and the orbit. In addition, active navigation in the open MRI is possible with the integrated FlashPoint system. The advantage over conventional navigation systems lies in the possibility of real-time imaging, which allows detection of tissue changes occurring during the procedure.

The use of open MRI in otorhinolaryngology: initial experience.

Intraoperative imaging in head and neck surgery is a useful tool in many situations. In addition to being helpful for intraoperative orientation, real-time imaging enables visualization of the progress of surgery and the completeness of tumor resection. Regions in the head and neck to which access is difficult, and which therefore have a high incidence of morbidity and risk for the patient, can be approached more easily and safely in an open MRI than in a conventional way. Interventions in the open MRI (Signa SP, 0.5 Tesla) were performed with nonmagnetic instruments and an MR-safe microscope. For intraoperative navigation, the integrated FlashPoint system is helpful, because it allows targeting of the tumor by a calculated virtual line. T1W spin-echo, T2W fast spin-echo, and 3D T1W gradient-echo sequences were used for high-resolution imaging. Real-time imaging is achieved by fast multiplanar spoiled gradient-echo sequences or T2 single-shot fast spin-echo sequences. From 1996 to the present, we biopsied 17 petroclival tumors, performed paranasal sinus surgery in five cases, biopsied two neck masses, and inserted tubes for brachytherapy in 12 cases. No complications were observed. In all surgical procedures, a good resolution was obtained with MRI, especially for soft-tissue structures. The tumor could be targeted exactly, and all specimens revealed the relevant histology. In paranasal sinus surgery, however, the success rate was lower because it was difficult to distinguish blood from pathologic tissue. The insertion of tubes for brachytherapy was successful in all cases. It was possible to apply the tubes parallel to each other, 1 cm apart. Relevant biopsies could be taken of both neck masses. The indications for the use of open MRI in otorhinolaryngology are biopsies of tumors in regions that are difficult to approach, such as the petrous apex and petroclival region, the parapharyngeal space, and the orbit. Furthermore, the open MRI can be useful in paranasal sinus surgery, in the evaluation of tissue resection, and in the detection of the anatomy of delicate structures such as the internal carotid artery, the skull base, and the orbit. In addition, active navigation in the open MRI is possible with the integrated FlashPoint system. The advantage over conventional navigation systems lies in the possibility of real-time imaging, which allows detection of tissue changes occurring during the procedure.