Biomedical subjects
Publications and source records attributed to Martin G Mack.
This article critically evaluates the role of multidetector-row CT before and after cardiosurgical procedures. In addition, technical aspects, such as scan protocols, optimal image reconstruction intervals, image reformation techniques, and data evaluation, are presented and briefly discussed.
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Joint effusions are common after sports injuries. In a specific form they can be very accurate for the diagnosis of intraarticular fractures; however, assessment can be tricky. Several imaging means are compared which outline the advantages and disadvantages of each technique.
We report a case of a 52-year-old woman with a palpable recurrent metastasis of a neuroendocrine carcinoma to the upper outer quadrant of the right breast. For the treatment of this lesion, MR-guided laser-induced thermotherapy was performed with a cooled power laser system (Nd:YAG-Laser). An open 0.2-T MR unit was used for the monitoring of the laser energy delivery to the breast; thus, a thermosensitive fast low-angle shot 2D sequence for MR thermometry was used, so the ablation of the tumor and the increase of laser-induced necrosis could be interactively visualized with the repetitive use of this sequence. The postinterventional MR control exams 1 day and 4 months after laser-induced thermotherapy at the 1.5-T MR unit (Magnetom Symphony Quantum, Siemens, Erlangen, Germany) verified the complete ablation of the tumor without any signs of residual or relapsing tumor.
The purpose of this study was to evaluate the clinical impact of MRI in the early diagnosis of wrist trauma. High-resolution MR imaging was performed on a 1.5-T unit (Symphony Quantum, Siemens, Erlangen, Germany) using coronal and axial T1- and T2-weighted fat-saturated turbo-spin-echo sequence via a dedicated wrist coil within a mean of 6.6 days after initial radiographs in 54 patients (56 wrists) with clinical suspicion of wrist fractures and normal plain or indistinct radiographs. Initial radiographs were evaluated independently by two senior radiologists and the hand surgeon without knowledge of the MRI findings. The initial treatment protocol was based on evaluation of plain films and clinical findings by the hand surgeon. Treatment protocol was changed after MRI examination if necessary. In 31 of 56 wrists MRI findings resulted in a change of diagnosis. There were false-positive diagnoses on plain radiographs in nearly one half ( n=25) of the patients. False-negative diagnoses on plain radiographs resulted in 6 cases. Magnetic resonance imaging detected additional injuries of soft tissue in more than one third ( n=20). In 22 of 56 wrists the period of immobilization could be shortened or ended, in 12 of 56 it was prolonged, and in 3 of 56 a surgical intervention was necessary. In 19 wrists MRI had no therapeutic consequences. Our data demonstrate the high clinical impact of MRI in the detection of acute wrist fractures. We recommend MRI of the wrist immediately on the day of trauma if there is clinical suspicion and normal plain radiographs. Accurate diagnosis by MRI examination within the first days following trauma may reduce economic costs due to shortened immobilization time in cases with a suspected fracture but plain radiographs.
Our objective was to evaluate the feasibility of a hybrid system consisting of a high-field MR and fully equipped digital subtraction angiography (DSA) unit for MR-guided vascular interventions. In a newly built hybrid system, consisting of a high-field MRI and a fully equipped DSA unit, elective interventional hybrid procedures were performed. Between May 2000 and November 2001, 30 patients with liver tumors underwent MR-guided chemoembolization using the hybrid system. During the intervention accurate catheter position was monitored with real-time and dynamic MR imaging. Elective hybrid interventional vascular procedures were performed successfully in 23 patients with liver metastases and hepatocellular carcinoma ( n=7). Patients could be transferred between the MRI and angiographic units on a carbon fiber tabletop within 10 s. Initial clinical trials demonstrated that in the chemoembolization of primary and secondary liver tumors the hybrid approach resulted in a change of catheter position in 40% of procedures. In combining high-field MR system and a fully equipped interventional vascular angiographic unit as backup, this hybrid system improves the therapeutic capabilities of interventional vascular procedures in the liver.
Interstitial laser-induced thermotherapy (LITT) is a minimally invasive technique for local tumor destruction within solid organs using optical fibers to deliver a high-energy laser to the target lesion. MR imaging is used both for placement of the laser in the tumor and for monitoring progress of thermocoagulation caused by the laser The success of LITT is dependent on the delivery of the optical fibers to the target area, real-time monitoring of the effects of the treatment, and subsequent evaluation of the extent of thermal damage. The key to achieving these objectives is the imaging methods used. The thermosensitivity of certain MR sequences is the key to real-time monitoring, allowing accurate estimation of the extent of thermal damage.
PURPOSE: To compare findings on superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) images of the head and neck with those from resected lymph node specimens and to determine the effect of such imaging on surgical planning in patients with histopathologically proved squamous cell carcinoma of the head and neck. MATERIALS AND METHODS: Thirty patients underwent MR imaging with nonenhanced and SPIO-enhanced (2.6 mg Fe/kg intravenously) T1-weighted (500/15 [repetition time msec/echo time msec]) and T2-weighted (1,900/80) spin-echo and T2-weighted gradient-echo (GRE) (500/15, 15 degrees flip angle) sequences. Signal intensity decrease was measured, and visual analysis was performed. Surgical plans were modified, if necessary, according to MR findings. Histopathologic and MR findings were compared. RESULTS: Histopathologic evaluation of 1,029 lymph nodes revealed 69 were metastatic. MR imaging enabled detection of 59 metastases. Regarding lymph node levels, MR diagnosis was correct in 26 of 27 patients who underwent surgery: Only one metastasis was localized in level II with MR imaging, whereas histopathologic evaluation placed it at level III. Extent of surgery was changed in seven patients. SPIO-enhanced T2-weighted GRE was the best sequence for differentiating between benign and malignant lymph nodes. CONCLUSION: SPIO-enhanced MR imaging has an important effect on planning the extent of surgery. On a patient basis, SPIO-enhanced MR images compared well with resected specimens.
PURPOSE: To evaluate the complications from laser-induced thermotherapy (LITT) of malignant liver tumors and demonstrate that LITT is safe as an outpatient procedure. MATERIALS AND METHODS: During 8 years, 899 patients with malignant liver tumors were treated with magnetic resonance (MR) imaging-guided LITT. A total of 2,132 LITT procedures were performed to treat 2,520 lesions. To account for the technical evolution of LITT during this time and the change from performing the procedure on an inpatient basis to performing it on an outpatient basis, patients were assigned to four groups. Overall complication rates and major and minor complications in the inpatient versus outpatient groups were evaluated. Multidimensional contingency table analysis with the chi(2) test was performed. RESULTS: On the basis of a total of 2,132 LITT procedures performed, complications were divided into major and minor categories and detected at clinical or imaging studies. Major complications included three deaths (0.1%) within 30 days after LITT, pleural effusion requiring thoracentesis in 16 (0.8%) cases, hepatic abscess requiring drainage in 15 (0.7%) cases, bile duct injury in four (0.2%) cases, segmental infarction in three (0.1%) cases, and hemorrhage requiring transfusion in one (0.05%) case. Minor complications included postprocedural fever in 710 (33.3%), pleural effusion not requiring thoracentesis in 155 (7.3%), subcapsular hematoma in 69 (3.2%), subcutaneous hematoma in 24 (1.1%), pneumothorax in seven (0.3%), and hemorrhage in two (0.1%) cases. Outpatient management did not significantly affect pleural effusion (P =.96) or subcapsular hematoma (P =.33) rate. CONCLUSION: MR imaging-guided LITT with local anesthesia is safe and yields an acceptably low rate of major complications.
The liver has a central role in human metabolism and represents one of the organ systems most often affected, especially by tumor diseases. The group of colorectal carcinomas metastatically almost exclusively attacks this organ, which, according to studies by Weiss and colleagues, can be attributed to venous drainage of the intestines through the portal vein. A large number of primary tumors often cause liver metastases as well as bone, lung, and brain metastases. After curative sanitation of the primary tumor, the liver infestation has a decisive influence on survival time of affected patients in many instances.
BACKGROUND: The objective was to evaluate the diagnostic accuracy of ultrasmall superparamagnetic iron oxide (USPIO)-enhanced magnetic resonance imaging (MRI) compared to plain MRI in patients with a clinical N+ neck using histology as a gold standard. MATERIALS AND METHODS: Twenty-eight patients underwent unenhanced and USPIO-enhanced MRI using T1-weighted spin echo (SE) sequences and high resolution Turbo-Spin-Echo (TSE) T2-weighted sequences, as well as T2-weighted Gradient Echo (GE) sequences in axial and sagittal slice orientation. The signal intensity (SI) decrease was measured by a region of interest evaluation and visual analysis was performed. RESULTS: Histopathological evaluation of 363 lymph nodes revealed 34 as metastatic. USPIO MRI detected 28 metastases (sensitivity 82.3%) and 329 non-metastatic lymph nodes (specificity 100%). Regarding lymph node size, USPIO MRI was correct in all patients who underwent surgery. One lymph node with microinfiltration of tumor cells was detected by USPIO MRI. CONCLUSION: There were no side-effects during or after application of the contrast agent. This study confirms the efficacy of MRI with USPIO in patients with head and neck cancer. USPIO-enhanced MRI could have an important effect on surgery planning. Because of its high specificity, USPIO-enhanced MRI seems to be a diagnostic modality able to differentiate borderline-sized lymph nodes.