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M G Mack

Publications and source records attributed to M G Mack.

69 records · Page 4Linked to original sources
PubMed1996

[High-resolution magnetic resonance tomography by means of an endorectal coil--the results in rectal tumors].

PURPOSE: To assess the value of high-resolution MRI of the rectum using an endorectal coil. METHODS: 10 volunteers and in 31 patients with suspected rectal tumors were examined. In 17 patients (n = 17) with rectal carcinoma, of which 15 subsequently underwent radical surgery, the preoperatively obtained tumor stage was compared with histology. In 12 patients (n = 12) with rectal adenoma (severe and medium graded epithelial dysplasias according to the WHO) who underwent endoscopy the results of the endorectal surface coil examination were compared with endoscopy and histology. In 4 patients (n = 4) with large rectal adenomas the surface coil was used before and as follow-up after endoscopic electro laser resection and the absence of adenoma after therapy also in the deeper layers of the rectal wall could be confirmed. RESULTS: Visualization of anatomical structures of rectum and adjacent structures is improved by the use of the endorectal surface coil. The diagnosis of carcinoma and adenoma of the rectum and the documentation of the exact extension can be reached with high accuracy (85%). CONCLUSION: MRI with an endorectal surface coil may play an important role in the preoperative diagnosis of rectal carcinoma. This method is useful for primary diagnosis and follow-up of large rectal adenoma after endoscopic electro laser resection.

Adenoma↗
PubMed1996

[Early clinical experiences with MR-guided laser-induced thermotherapy (LITT) of liver metastases in preoperative care].

PURPOSE: To evaluate the LITT-induced changes with the aid of MRT and correlate these with histopathological findings. MATERIAL AND METHODS: Five patients with solitary colorectal liver metastases were treated by means of MR-guided LITT before liver resection. Application time and energy of the Nd:YAG laser (1064 nm) was 10-20 minutes and 4.5-8.8 W. MRT monitoring during the LITT was carried out with temperature-sensitive T1 weighted sequences (FLASH-2-D, turbo FLASH). The extent of the induced necrosis as seen on MR was compared with the unfixed specimen and with the histopathological findings. RESULTS: The extent of necrosis visible by MRT correlated with the histopathological findings with an accuracy of 95.3% +/- 4.2%. Following single treatments (three cases) the metastases suffered a reduction of 24%-55% of their original volume. In two patients a second application produced laser-induced necrosis of 78% and 98% of volume. In these two patients a temperature sound was used for measuring regional heating and showed an exact correlation with MR thermometry. CONCLUSION: The results of pre-operative MR-guided LITT indicates the potential of this form of treatment for obtaining reproducible tumor necrosis of liver metastases.

Aged↗
PubMed1996

Magnetic resonance imaging of focal liver lesions. Comparison of the superparamagnetic iron oxide resovist versus gadolinium-DTPA in the same patient.

RATIONALE AND OBJECTIVES: The authors assess the efficacy of static and dynamic magnetic resonance (MR) imaging using the superparamagnetic iron oxide SHU-555A (Resovist) versus standard dose of gadolinium (Gd)-DTPA in patients with focal liver lesions. METHODS: Magnetic resonance imaging was performed in 30 patients suffering from histopathologically verified malignant (n = 22) and benign (n = 8) liver lesions. T2-weighted conventional and fat-suppressed as well as T1-weighted sequences were used before, during, and after fast intravenous administration of Resovist (1 mL/minute) at three doses of 4, 8, and 16 mumol/kg body weight. One week before the Resovist-enhanced MR imaging study 20 patients underwent Gd-DTPA-enhanced MR imaging. RESULTS: Detection rate was improved for metastatic lesions revealing 36 lesions unenhanced versus 53 focal lesions using Resovist-enhanced MR imaging. Gadolinium-DTPA-enhanced scans showed no additional lesion versus unenhanced and Resovist-enhanced MR imaging. Static and dynamic imaging demonstrated no measurable percentage signal intensity loss (PSIL) using Resovist-enhanced MR imaging versus a percentage enhancement of 79.7% in Gd-DTPA enhanced scans. In the dynamic T2-weighted sequences, hepatocellular carcinoma nodules (n = 4) showed a rapid decrease in signal intensity starting at 44 seconds. Postinfusion of Resovist followed by a low, constant increase in signal intensity. Gadolinium-DTPA enhanced scans showed a percentage enhancement of 73.4 focal nodular hyperplasia (FNH) and hemangioma revealed a strong and early dose-dependent PSIL 44 to 60 seconds postinfusion with a prolonged signal loss for the FNH in the late study. Statistical evaluation revealed a statistically significant superiority of Resovist-enhanced MR imaging concerning the detection and delineation of focal liver lesions compared with unenhanced and Gd-DTPA enhanced scans (P < 0.05). CONCLUSIONS: The fast infusion of the new superparamagnetic contrast agent Resovist shows advantages for dynamic and static MR imaging of focal liver lesions.

Carcinoma, Hepatocellular↗
PubMed1996

Superparamagnetic iron oxide--enhanced versus gadolinium-enhanced MR imaging for differential diagnosis of focal liver lesions.

PURPOSE: To assess AMI-25- versus gadolinium-enhanced magnetic resonance (MR) imaging in the differential diagnosis of liver tumors. MATERIALS AND METHODS: Twenty-nine patients with liver tumors underwent unenhanced, AMI-25-enhanced (15 micromol/kg), and gadolinium-enhanced(0.1 mmol/kg) imaging within 2 weeks. RESULTS: A significant (P< .05) difference in percentage signal intensity loss (PSIL) was seen in benign tumors on AMI-25-enhanced proton-density-weighted images (nine focal nodular hyperplasia [FNH], 41%; one adenoma, 32.4%) versus malignant tumors. Gadolinium-enhanced T1-weighted gradient-echo images showed strong enhancement in benign lesions (seven FNH, 147.5%; one adenoma, 91.3%) and moderate enhancement in malignant tumors (eight hepatocellular carcinomas, 116.2%, 11 metastases, 39.7%). Receiver operating characteristic analysis revealed a threshold PSIL of 10% on AMI-25-enhanced images as the most essential criteria to distinguish benign from malignant lesions (sensitivity, 88%; specificity. 89%). Interobserver analysis for two observers revealed specificity of 93% for AMI-25-enhanced imaging versus 81.5% for gadolinium-enhanced MR imaging. CONCLUSION: AMI-25 decreased the SI of benign tumors and helped differentiate benign from malignant tumors.

Adenoma↗
PubMed1996

Liver tumors: comparison of MR imaging with Gd-EOB-DTPA and Gd-DTPA.

PURPOSE: To compare the usefulness of gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) and gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) in the diagnosis of focal liver lesions. MATERIALS AND METHODS: Thirty-one patients with focal liver lesions underwent T2- and T1-weighted spin-echo magnetic resonance (MR) imaging and fast low-angle shot two-dimensional MR imaging before, during, and after intravenous administration of three different doses of Gd-EOB-DTPA (12.5, 25, and 50 mumol per kilogram body weight). Gd-DTPA-enhanced imaging (dose, 0.1 mmol per kilogram body weight) was performed in the same patients within 1 week of Gd-EOB-DTPA imaging. RESULTS: During the perfusion phase (the 3 minutes after injection of contrast material), the dynamic enhancement characteristics seen after injection of 25 and 50 mumol of Gd-EOB-DTPA were similar to those seen with Gd-DTPA. At the lowest dose of Gd-EOB-DTPA (12.5 mumol), the dynamic enhancement characteristics were not comparable to those seen with Gd-DTPA. During the hepatobiliary phase (1.5 minutes to 4 hours after injection), Gd-EOB-DTPA-enhanced images yielded a dose-independent, statistically significant improvement in the detection rate of additional metastases, hepatocellular carcinomas, and hemangiomas compared with unenhanced and Gd-DTPA-enhanced images (P < .05). CONCLUSION: Gd-EOB-DTPA-enhanced MR imaging enables improved detection of hepatic lesions over Gd-DTPA-enhanced MR imaging while providing comparable differential diagnostic information.

Adult↗
PubMed1995

[MR-guided laser-induced thermotherapy in tumors of the head and neck region: initial clinical results].

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.

Adenoma, Pleomorphic↗
PubMed1995

Malignant liver tumors treated with MR imaging-guided laser-induced thermotherapy: technique and prospective results.

PURPOSE: To evaluate magnetic resonance (MR) imaging-guided laser-induced thermotherapy (LITT) of liver metastases. MATERIALS AND METHODS: In a phase II study, 20 patients with 33 metastases from colorectal carcinoma (75%) or other primary tumors (25%) underwent LITT. MR thermometry performed with fast low-angle shot sequences was used to monitor therapy on-line, and dynamic and static contrast material-enhanced MR images enabled estimation of the degree of resultant necrosis. Follow-up studies were performed 3 months after thermotherapy. RESULTS: The thermosequences enabled accurate on-line monitoring in 85% of lesions. In 69% of lesions 20 mm in diameter or smaller, contrast-enhanced MR images depicted substantial necrosis, with a local tumor control rate of 69% after 6 months and 44% after 12 months. Among lesions larger than 20 mm, necrosis was frequently incomplete, with a local control rate of only 41% after 6 months and 27% after 12 months. CONCLUSION: MR imaging-guided LITT of liver metastases is a safe and promising therapy for liver metastases.

Adult↗
PubMed1995

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.

Adenoma, Pleomorphic↗
PubMed1995

[Diagnosis of cerebral metastasis with standard dose gadobutrol vs. a high dose protocol. Intraindividual evaluation of a phase II high dose study].

PURPOSE: To assess the effectiveness and safety of normal and high doses of Gadobutrol versus a standard dose of Gadolinium DTPA in the MR evaluation of patients with brain metastases. MATERIAL AND METHODS: In a clinical phase-II study 20 patients who had been diagnosed as having brain metastases with CT or MRT were studied prospectively with Gadobutrol, a new nonionic, low osmolality contrast agent. Each patient received an initial injection of 0.1 mmol/kg body weight and an additional dose of 0.2 mmol/kg Gadobutrol 10 min later. Spin-echo images were obtained before and after the two applications of Gadobutrol. Dynamic scanning (Turbo-FLASH) was performed for 3 min after each injection of the contrast agent. Both quantitative and qualitative data were intraindividually evaluated. The primary tumor was a bronchial carcinoma in 11 cases; in 9 other cases there were different primary tumors. RESULTS: Forty-eight hours after the use of Gadobutrol there were no adverse signs in the clinical examination, vital signs or blood and urine chemistry. Statistical analysis (Friedman test and Wilcoxon test) of the C/N ratios between tumor and white matter, percentage enhancement, and visual assessment rating revealed statistically significant superiority of high-dose Gadobutrol injection in comparison to the standard dose. The percentage enhancement increased on average from 104% after 0.1 mmol/kg to 162% after 0.3 mmol/kg Gadobutrol. Qualitative delineation and contrast of the lesions increased significantly. The use of high-dose Gadobutrol improved the detection of 36 additional lesions in 6 patients. CONCLUSION: The first in vivo results prove the excellent contrast capacity of the nonionic contrast agent Gadobutrol for the diagnosis of intracerebral metastases.

Adult↗
PubMed1994

[Fat suppression in contrast-enhanced MRT of the base of the skull and of the head-neck area: its clinical value].

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.

Adipose Tissue↗
PubMed1994

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.

Adult↗
PubMed1994

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.

Contrast Media↗
PubMed1993

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.

Drug Combinations↗
PubMedDate not supplied

Percutaneous MR imaging-guided laser-induced thermotherapy of hepatic metastases.

BACKGROUND: Many primary tumors may cause liver metastases, which are generally treated with surgical resection and/or chemotherapy. After resection of liver metastases in patients with colorectal carcinoma, 5-year survival rates are achieved in 25-38%, and two-thirds of patients will experience recurrent metastases. We examined percutaneous, minimally invasive, laser-induced thermotherapy (LITT) as an alternative outpatient procedure. Local tumor control rate and survival data were analyzed prospectively. METHODS: Between June 1993 and August 2000, 7148 laser applications were performed in 1981 lesions in 705 consecutive patients and 1653 treatment sessions. The complications of the procedure were evaluated by clinical examination and magnetic resonance imaging (MRI) and computed tomography. Local tumor control was evaluated by plain and contrast-enhanced follow-up MRI using T1- and T2-weighted spin-echo and gradient-echo sequences every 3 months after treatment. Cumulative survival times were calculated using the Kaplan-Meier method. RESULTS: The overall rate of complications and side effects was 7.5%. The rate of clinically relevant complications was 1.3%. Local tumor control rate after 3 months was 99.3%; 6 months after laser treatment, plain and contrast-enhanced MRI documented a local tumor control rate of 97.9%. In patients treated with MR-guided LITT for unresectable colorectal liver metastases, the mean survival was 41.8 months (95% confidence interval = 37.3-46.4 months). The 1-year survival rate was 93%, the 2-year survival rate was 74%, the 3-year survival rate was 50%, and the 5-year survival was 30%. In patients treated with LITT for liver metastases from breast cancer, the mean survival was 4.3 years (95% confidence interval = 3.6-5.0 years). CONCLUSION: In patients with liver metastases, local tumor destruction using minimally invasive, percutaneous LITT under local anesthesia results in improved clinical outcomes and survival rates and can be a potential alternative to surgical resection.

Adult↗