[Experimental evaluation of contrast medium enhanced high resolution MR angiography in the animal model. Gd-DTPA compared with Gd-DTPA-polylysine]. / Experimentelle Evaluierung der kontrastmittelverstärkten, hochauflösenden MR-Angiographie am Tiermodell. Gd-DTPA gegenüber Gd-DTPA-Polylysin.

PURPOSE: To evaluate the qualitative and quantitative efficacy of Gd-DTPA and Gd-DTPA polylysine for contrast-enhanced high resolution MRA (CMRA) of the abdominal vessels. MATERIALS AND METHODS: In ten anesthesized rabbits (average weight 4.3 kg) MR angiography was performed using a 1.5 T MR unit (Magnetom SP 63; Siemens Erlangen) and a CP head coil. Arterial MRA (FISP 3D TONE, TR/TE = 33/8, Flip 20 degrees) and venous MRA (FLASH 2D, TR/TE = 37/10, Flip 60 degrees) was performed before and after administration of the paramagnetic contrast agents Gd-DTPA (n = 5) or Gd-DTPA polylysine (n = 5) at a dosage of 0.1 mmol/kg. In all studies the single sections and the MIP reconstructions were evaluated quantitatively by measuring and calculating signal intensity, percentage enhancement, signal-to-noise and contrast-to-noise ratios. All studies were assessed qualitatively for visualization and distinction of the arterial and venous vessel system by three independent observers before and after the administration of contrast agent. RESULTS: Gd-DTPA-enhanced arterial FISP 3D tone led to a percentage enhancement of 30% for the kidneys, 12% for the superior mesenteric artery, 18% for the deep circumfluent iliac artery, and 7% for the internal iliac artery. In FLASH 2D sequences Gd-DTPA led to a good C/N only for venous abdominal vessels like the left renal vein (2.59) and internal iliac vein (1.66); the percentage enhancement of these structures was between 16 and 21%. Qualitative comparison also showed no significant improvement after injection of Gd-DTPA. In FISP 3D TONE sequences Gd-DTPA polylysine led to a strong percentage enhancement of right and left kidney (21 and 40%) and deep circumfluent iliac artery (17%). Qualitative evaluation showed improved delineation and contrast of low-diameter vessels, while the soft tissue was only slightly enhanced and did not impair vessel visualization. CONCLUSION: CMRA using Gd-DTPA and Gd-DTPA polylysine significantly improved the delineation of abdominal vessels, with Gd-DTPA polylysine being superior.

[Perioperative evaluation of internal carotid artery stenoses: value of multislab MR angiography]. / Perioperative Evaluierung von A.-carotis-interna-Stenosen: Stellenwert der Multislab-MR-Angiographie.

PURPOSE: Evaluation of the diagnostic potential of high resolution multislab 3D-TOF-magnetic resonance angiography (MRA) in the pre- and postoperative assessment of carotid artery stenosis in comparison to conventional angiography. METHODS: 120 Patients were evaluated with MRA and DSA prior to carotid endarterectomy (CEA). Additionally 26 patients underwent MRA after CEA. All MRA examinations were carried out on a 1.5 T MR-unit (Siemens Magnetom SP63) using a Helmholtz surface coil. For the visualization of the vascular structures in the head and neck region, flow compensated GE-sequences were employed. Both original MRA data set and MIP angiograms were included in the evaluation. The determination of the extent of stenoses was performed according to the recommendation of NASCET. RESULTS: In 195 (92.9%) of 210 cases included in the review MRA revealed the same results as DSA (grade I+II: 114, grade III: 24, grade IV: 44, grade V: 13). None of the cases showed a deviation higher than one grade. The sensitivity and specificity of hemodynamic relevant stenoses (> 60%) was 0.964 respectively 0.952. 23 out of 26 patients with postoperative follow-up examination revealed regular reperfusion of the former affected internal carotid artery. The remaining 3 patients showed a restenosis of the operated vessel (n = 2) and a reocclusion of the ICA after surgery (n = 1). MRA proofed to be an accurate and reliable method for the perioperative evaluation of vascular structures in the head and neck region. Despite of some drawbacks MRA reached a high accuracy in the diagnostic imaging before and after CEA. MRA is accurate and useful in screening carotid artery diseases. The indication of MRA employment therefore not only covers the screening of vascular structures but also includes pre- and postoperative evaluation of vascular stenoses.

[MR-guided laser-induced thermotherapy in tumors of the head and neck region: initial clinical results]. / MR-gesteuerte laserinduzierte Thermotherapie bei Tumoren in der Kopf-Hals-Region: Erste klinische Ergebnisse.

PURPOSE: To analyse the value of MR-guided laser-induced thermotherapy (LITT) for palliative treatment of recurrent tumours of the head and neck region. MATERIAL AND METHODS: 8 patients with recurrent tumours of the head and neck region (squamous cell carcinomas n = 6, pleomorphic adenomas n = 2) underwent MR-controlled LITT. A 7 French laser applicator was inserted under local anaesthesia into the centre of the recurrent tumour. A Nd:YAG laser with a wavelength of 1064 nm was used. Therapy was monitored on-line using special MR thermosequences. RESULTS: Preinterventional contrast-enhanced MRI revealed a recurrent tumour of the head and neck region for all eight patients. All patients tolerated the procedures well under local anaesthesia, with no clinically relevant side effects. The MR thermosequences depicted up to 15 mm diameter areas of less signal near the laser tip. Postinterventional contrast-enhanced MRI revealed hypovascularized areas due to the resulting coagulative necrosis. Coagulative necrosis of 4 cc to 28 cc occurred in all patients, and a reduction of clinical symptoms was achieved in five. CONCLUSION: The results obtained indicate that minimal invasive LITT can be a therapeutic alternative for palliative treatment of head and neck tumours.

Recurrent nasopharyngeal tumors: preliminary clinical results with interventional MR imaging--controlled laser-induced thermotherapy.

PURPOSE: To evaluate magnetic resonance (MR) imaging-controlled laser-induced thermotherapy (LITT) in the treatment of recurrent head and neck tumors. MATERIALS AND METHODS: Six patients with recurrent nasopharyngeal tumors (squamous cell carcinoma [n = 4], pleomorphic adenoma [n = 2]) underwent LITT with local anesthesia. A 7-F introducing sheath was inserted into the center of the tumor followed by a specially designed laser emitter. Therapy was monitored on-line with MR thermometry, and the amount of necrosis was estimated with dynamic and static contrast material-enhanced sequences. RESULTS: All procedures were well tolerated with use of local anesthesia, with no clinically relevant side effects. MR thermometry depicted up to 15-mm-diameter areas of less signal intensity near the laser tip. Coagulative necrosis was achieved in all patients (volume range, 4-28 cm3), and clinical symptoms were reduced in four. CONCLUSION: MR imaging-controlled LITT may be a safe, minimally invasive alternative in the treatment of recurrent head and neck tumors.

[Multiple slab MR angiography of the A. carotis interna: a preoperative comparative study]. / Mehrvolumen-MR-Angiographie der A. carotis interna: Eine präoperative Vergleichsstudie.

PURPOSE: With the introduction of MR angiography (MRA) into clinical routine, arteriosclerotic lesions of the supraaortic vessels may be well demonstrated. MATERIAL AND METHODS: The comparison between Multislab MRA (gradient echo, TOF) and X-ray angiography (XRA) as reference in 70 patients suspicious of stenotic lesions in the internal carotid artery proved the high reliability of these methods. RESULTS: In determining the degree of stenosis, according to the NASCET study (North American Symptomatic Endarterectomy Trial), a correlation between MRA and XRA of 92.3% could be calculated. The principal problem of MRA is the overestimation of high-grade stenoses; we observed 5 false-positive results in severe stenosis. Sensitivity and specificity were 95.6 and 92.6%, respectively, for detection of severe (> 60%) stenosis. CONCLUSION: Despite its limitations, MRA is a clinically important noninvasive technique for preoperative evaluation of patients undergoing carotid endarterectomy.

MR diagnosis of head and neck tumors: comparison of contrast enhancement with triple-dose gadodiamide and standard-dose gadopentetate dimeglumine in the same patients.

OBJECTIVE: The purpose of this study was to compare the relative values of MR images obtained with a triple dose of gadodiamide and MR images obtained with the standard dose of gadopentetate dimeglumine for the detection and determination of the extent of tumors of the head and neck. MATERIALS AND METHODS: Forty-two patients with benign and malignant tumors of the head and neck were examined with contrast-enhanced MR imaging in a comparison of a triple dose of gadodiamide (0.3 mmol per kilogram body weight) and a standard dose (0.1 mmol per kilogram body weight) of gadopentetate dimeglumine. All patients underwent MR imaging with both doses of contrast material. Contrast-to-noise ratios and the percentage enhancement of normal and abnormal structures were calculated, and delineation of the lesion and the contrast between tumor and surrounding tissue were evaluated visually. RESULTS: Statistical analysis (Friedman test and Wilcoxon test) of the contrast-to-noise ratios between tumor and white matter, the percentage enhancement, and the visual assessment rating revealed a statistically significant superiority of the triple dose of gadodiamide over the standard dose of gadopentetate dimeglumine. Tumor/muscle contrast-to-noise ratios were not significantly different with the two doses. The detection rate for tumors was no better with the triple dose of gadodiamide than with the standard dose of gadopentetate dimeglumine. CONCLUSION: Use of the triple dose of gadodiamide results in a statistically significant improvement in the visual assessment rating, but it does not increase the number of tumors detected on MR images over the number detected with the standard dose of gadopentetate dimeglumine and does not appear to alter the differential diagnosis.

Glomus tumors of the skull base: combined use of MR angiography and spin-echo imaging.

PURPOSE: To evaluate the use of magnetic resonance (MR) angiography in the diagnosis of glomus tumors of the skull base. MATERIALS AND METHODS: In 40 patients with pulsatile tinnitus, spin-echo (SE) images, single sections, and maximum intensity projections from gradient-echo sequences, including arterial MR angiography and MR venography, were evaluated for tumor detection. Interpretations by two independent observers were correlated with findings from histologic examination, digital subtraction angiography, computed tomography, and clinical follow-up. RESULTS: Glomus tumors were detected near the tympanic plexus (n = 8) and close to the superior (n = 8) and inferior (n = 1) ganglia of the vagus nerve. Sixteen of 18 proved tumors were detected with SE images alone. Although four high-lying jugular bulbs were misinterpreted as tumor due to similar signal intensity, combined evaluation allowed differentiation between tumor and sinusal blood flow in all cases. CONCLUSION: The authors recommend combined SE imaging and MR angiography for ruling out tumor in patients with pulsatile tinnitus.

[MR-angiography in diagnosis and follow-up of therapy: arteria lusoria]. / MR-Angiographie in Diagnostik und Therapiekontrolle: Arteria lusoria.

Diagnostic and therapeutic procedures are presented in a 29-year-old female patient who suffered from severe dysphagia and rapid loss in weight. In the conventional X-ray examination and barium swallow an aberrant right subclavian artery was suspected. MR imaging (MRI) and MR angiography (MRA) were done to plan the surgical correction. Postoperative MRA documented exactly the complex topography after surgical correction and the flow pattern in the implanted Gore-Tex stretch graft prosthesis. Non-invasive MR angiography renders possible the concrete planning of complex corrections of thoracic vessels replacing invasive catheter angiography.

[Fat suppression in contrast-enhanced MRT of the base of the skull and of the head-neck area: its clinical value]. / Fettunterdrückung in der kontrastverstärkten MRT der Schädelbasis und der Kopf-Hals-Region: klinische Wertigkeit.

167 patients with abnormalities at the skull base and at the cervical-skull junction were examined by MRT in order to compare a FATSAT technique with T1- and T2-weighted SE sequences before and after intravenous injection of 0.1 mmol Gd-DTPA/kg KG. The diagnostic information from corresponding FATSAT and T1-SE sequences was correlated with the histopathological findings. In 10.7% of patients fat suppression was inadequate and in a further 11.3% of patients chemical shift artifacts limited the diagnostic value. The number of detectable lesions was not increased by the use of FATSAT sequences but visualisation of soft tissue lesions was improved, adding to the diagnostic value under specific conditions. Evaluating by the Friedman and Wilcoxon test showed that the postcontrast FATSAT sequences were markedly superior (p < 0.01) in delineating and contrasting the lesions. The additional use of contrast enhanced FATSAT sequences resulted in improved diagnosis of lesions at the skull base and the facial skeleton.

MR imaging with Gd-DTPA in lesions of the head and neck.

The diagnostic value of MR in the head and neck with special emphasis on the contrast medium Gd-DTPA will be demonstrated. A total of 1,260 patients underwent MR with different pulse sequences plain and with Gd-DTPA. The sequences were analyzed and compared with CT. Due to the different pattern of enhancement the contrast medium helped in differentiating malignant and benign tumors from other processes like cysts and inflammatory changes. Except lesions with small bony erosion and inflammatory changes of the salivary glands MR with Gd-DTPA proved to be diagnostically advantageous in all cases. Gd-DTPA improved the delineation of tumor margins. MR in combination with Gd-DTPA offers a lot of new advantages for diagnosing lesions of the head and neck. However, due to the prolonged examination time and the lack of noninvasiveness the use of Gd-DTPA has to be considered critical for every single area of the head and neck.

Skull base tumors: gadodiamide injection--enhanced MR imaging--drop-out effect in the early enhancement pattern of paragangliomas versus different tumors.

A phase III trial was conducted in 40 patients with known or suspected skull base tumors to evaluate the safety and efficacy of high-dose gadodiamide injection for use as a paramagnetic contrast medium in conventional and dynamic magnetic resonance (MR) imaging. Contrast material enhancement was assessed dynamically with use of a gradient-recalled sequence. The time-intensity curve of selected regions of interest showed a reproducible dropout effect in the form of a dip in the curve during the early enhancement of the sigmoid sinus and jugular bulb; the same phenomenon was observed in all glomus tumors of the skull base, regardless of size or location. In contrast, schwannomas, meningiomas, and a variety of other lesions showed a continuous increase in the time-intensity curve. The drop-out sign, which is probably a result of a paramagnetic phenomenon during the early phase of enhancement, seems to be specific for glomus tumors. High-dose gadodiamide injection may show a specific dynamic pattern for glomus tumors, allowing differentiation from other tumors of the middle and posterior skull base.

[MR angiography for tumor diagnosis in the head-neck region: the study technic and clinical results]. / MR-Angiographie für die Tumordiagnostik in der Kopf-Hals-Region: Untersuchungstechnik und klinische Ergebnisse.

40 normal individuals and 153 patients with lesions in the head and neck were examined by conventional imaging methods and by means of MR angiography (1.5-tesla Magnetom). The problems to be solved concerned the relationship between tumors and vessels and vascular anomalies and abnormalities at the skull base (56 cases), the facial skeleton (62 cases) and the neck (35 cases). Digital subtraction angiography was performed in 54 patients and the findings correlated with MR angiography. Optimal results were obtained by using a FISP 3D sequence; in this way arterial structures could be rendered reproducibly down to a diameter of 2 mm. The venous system in the head and neck was best shown by a FLASH 2D sequence. Correlation with arterial DSA showed high accuracy of MR angiography (91%) concerning displacement of vessels, the topography and the recognition of vascular occlusions. Our results indicate that MR angiography is a rapid and reliable procedure for evaluating the arterial and venous changes due to tumors in the head and neck region.