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Biomedical subjects

M G Mack

Publications and source records attributed to M G Mack.

At least 55 records · Page 3Linked to original sources
PubMed1999

MR imaging of the head and neck.

The purpose of this paper is to describe current imaging protocols for MR imaging of the head and neck region and to define results and clinical impact. Depending on the clinical question, different MRI protocols are presented for imaging of the head and neck. The appearance of different pathologic findings on imaging studies and how adapted imaging protocols help to improve differential diagnosis is discussed. In summary, MRI is the method of choice for imaging of the head and neck.

Diagnosis, Differential↗
PubMed1999

Interventional MR: interstitial therapy.

The rationale and results for interstitial therapies via interventional MRI in the treatment of tumors in various regions are presented. Different interstitial treatment techniques are presented based on varying technologies both for tumor ablation and treatment monitoring. Data are presented based on 335 patients, 29-84 years of age (mean age 59 years, 196 men and 139 women) with a total of 932 liver tumors, 16 head and neck tumors and 14 abdominal recurrent pelvic and lymphatic tumors. All lesions had been treated with MR-guided laser-induced interstitial thermotherapy (LITT) via 2516 laser applications and 1856 cannulations. Data in the literature are extremely varying depending on author experience, treatment technique, and the included patient material. In our patient material we were able to achieve a local tumor control of 96.7% depending on the size of the tumorous lesion, the topographical relationship, and the applied laser parameters. The overall cumulative survival rate of patients with liver metastases was 45.74 months (median 40.97 months, 95 % confidence interval 31.42-50.52). The cumulative survival rate of the patient group with hepatic metastases of colorectal carcinoma was 42.71 months (median 39.33 months, 95% confidence interval 33.26-45.37). In patients with head and neck tumors a relevant reduction in clinically relevant symptoms such as pain, swallowing disorders, or nervous compression was achieved in 11 of 15 patients treated with LITT. In 14 soft tissue tumors, such as pelvic tumor recurrence and lymph node metastases, a local tumor control was obtained in 68% of lesions. Interstitial therapies under interventional MRI guidance, such as LITT, results in a high local tumor control with an improved survival rate.

Abdominal Neoplasms↗
PubMed1999

The prevention of playground injuries.

Playground accidents are the most common cause of injury to children in school. As the health professional who attends to these injured children, school nurses should be aware of safety practices that can help eliminate the risks that children encounter. The National Program for Playground Safety has identified four areas that can reduce the level of risk on school playgrounds: supervision, age-appropriate design of the play area, fall surfaces under and around playground equipment, and equipment and surface maintenance. The article discusses each of these, and recommends leadership methods and practices that nurses can implement that will eliminate or reduce risk factors. In addition, a comprehensive playground risk model is described, and suggestions for policy areas are outlined. Policy areas include assessment, education, and enforcement in relation to each of the risk factors.

Accidental Falls↗
PubMed1998

[Verification of MR thermometry by means of an in vivo intralesional, fluoroptic temperature measurement for laser-induced thermotherapy ov liver metastases].

PURPOSE: To evaluate the correlation of MR-measured changes of signal intensity and invasive fluoroptic temperature measurements during MR-guided LITT of liver metastases. MATERIALS AND METHODS: In 15 patients with proven liver metastases of colorectal carcinoma, MR-guided LITT was performed with a percutaneous approach in a multiapplicator technique. Two temperature sensitive T1-weighted sequences (FLASH-2D- and TurboFLASH-sequences) were used to map the spatial and temporal distribution of Nd:YAG laser effects. Parallel fluoroptic temperature measurements were carried out by means of an inserted probe in a distance of 5-26 mm (mean: 14 mm) from the laser applicator. RESULTS: In both sequences a gradually increasing signal loss could be documented during laser application which proved to be reversible after cessation of energy deposition. the percentage of decrease in signal intensity correlated directly with the measured increase of temperature. Invasive fluoroptical evaluation of temperature distribution after 10 min exposure time showed at 5 mm distance from the applicator an increase of temperature of 35 degrees C, in 10 mm distance a mean increase of 9 degrees C +/- 1.7, in 15 mm a mean increase of 7 degrees C +/- 1.6 and in 20 mm a mean increase of 3 degrees C +/- 0.5. This is evidence of thermal tissue damage up to 3 cm in diameter with laser monoapplication. The qualitative evaluation revealed a reproducible correlation of the extent of signal loss around the applicator and the finally induced degree of necrosis. CONCLUSION: Invasive fluoroptical temperature measurements prove the diagnostic reliability of MR thermometry for the online monitoring of LITT of liver metastases.

Adult↗
PubMed1998

Internally cooled power laser for MR-guided interstitial laser-induced thermotherapy of liver lesions: initial clinical results.

PURPOSE: To evaluate experimentally and clinically an internally cooled power laser system for percutaneous treatment of liver metastases, with magnetic resonance (MR) imaging guidance, to increase the volume of coagulative necrosis with single laser beam applications. MATERIALS AND METHODS: The power laser system consisted of standard cannulation paraphernalia and a specially designed 7-F protective catheter for cooling the laser tip during treatment to avoid carbonization. A microdome laser beam applicator with a laser tip diameter of 0.95 mm kept the entire device as small as possible. After the unit was tested in 40 porcine livers, 532 laser beam applications (mean power, 27.5 W [range, 22.1-30.0 W]; mean application time, 19.8 minutes [range, 14-30 minutes]) were performed with MR guidance in 127 patients with 318 liver metastases. The safety of the procedure and the volume of induced necrosis were evaluated. RESULTS: In vitro, cuboid areas of coagulative necrosis with a mean greatest diameter of 4.3 cm +/- 0.5 (SD) were demonstrated after single applications. In vivo, MR thermometry allowed accurate demarcation of changes induced by heat, with a mean diameter of necrosis of 3.3 cm +/- 1.4. No carbonization or vaporization of tissue or damage of equipment occurred during treatment. CONCLUSION: This power laser system can increase the volume of laser-induced necrosis in liver metastases with a single application, thereby simplifying and accelerating the treatment of larger lesions.

Animals↗
PubMed1997

Magnetic resonance imaging--guided abdominal interventional radiology: laser-induced thermotherapy of liver metastases.

The aim of this study was to evaluate the clinical benefit of magnetic resonance imaging--guided laser-induced thermotherapy (LITT) for the minimally invasive treatment of liver metastases, with regard to survival rates and local tumor control. Magnetic resonance--guided LITT under local anesthesia was carried out in 134 consecutive patients aged 28-84 (mean age 69), with a total of 383 liver metastases. The major groups were liver metastases from colorectal cancer (88 patients) and liver metastases from breast cancer (20 patients), as well as metastases of miscellaneous primary tumors (26 patients). A total of 1048 laser applications were carried out. Cumulative survival times were calculated using the Kaplan-Meier method. All of the patients tolerated the procedure under local anesthesia well, and no severe complications or side effects were observed. During the follow-up period, 29 of the 134 patients treated died. The mean survival time was 35 months in the colorectal cancer group, 30 months in the breast cancer group, and 34 months in the group with miscellaneous primary tumors. The statistical assessment of the equality of survival distribution showed no significant differences between the three groups (Breslow test P = 0.35, Tarone-Ware test P = 0.49). These results suggest that in patients with liver metastases, local tumor destruction using minimally invasive percutaneous LITT under local anesthesia results in improved clinical outcomes, independently of the type of primary tumor.

Abdomen↗
PubMed1997

[Dynamic and static MRI using superparamagnetic MRI contrast medium Resovist for visualizing primary and secondary liver tumors].

PURPOSE: To analyse characteristics of benign and malignant liver tumours in dynamic and static MR imaging with the superparamagnetic MR contrast medium Resovist. MATERIAL AND METHODS: All 30 patients were examined on a 1.5 Tesla MR unit (Magnetom 63 SP, Siemens AG, Erlangen, Germany) using proton density (PD) weighted (w), T2-weighted-spin-echo, a T1-weighted SE, and a T1-weighted FLASH-2 D gradient echo (GRE) sequence before, during and after the application of Resovist. Dynamic imaging was performed using a T2-weighted GRE-sequence (TurboFLASH; TR/TE = 11/30; flip angle = 10 degrees; Tl = 600 ms). Histopathology revealed benign liver lesions in 8 patients and malignant lesions in 22 patients. RESULTS: Dynamic T2-weighted sequence revealed an early loss of signal intensity in normal liver parenchyma (percentage signal intensity loss (PSIL) = 40.0 +/- 12.2% by 4 mumol Fe/kg, 47.2 +/- 18.8% by 8 mumol Fe/kg and 62.7 +/- 13.0% by 16 mumol Fe/kg), in the spleen, as well as in FNH (PSIL = 49.5 +/- 7.3% by 8 mumol Fe/kg), and regenerating nodules in the first minute after application of Resovist. In two of 4 cases with HCC a short drop in signal intensity was immediately observed after the application, whereas signal intensity remained unchanged in all other malignant liver tumours. Enhanced PDw and T2-weighted SE-sequences revealed an improved detection and delineation of malignant liver lesions versus plain MR imaging. 17 liver lesions of a size lower 10 mm were additionally detected in postcontrast T2-weighted SE-sequences in 4 patients. CONCLUSION: Dynamic and static versus plain MR imaging of primary and secondary liver lesions is markedly improved by the superparamagnetic contrast material Resovist, especially in case of intravenous bolus application of this liver-specific contrast medium.

Adult↗
PubMed1997

[In vitro evaluation of MR thermometry in the implementation of laser-induced thermotherapy].

PURPOSE: To optimize the MR sequences parameter for monitoring hyperthermic effects in the tissue during laser induced thermotherapy (LITT). MATERIAL AND METHODS: Experimental studies were performed for the evaluation of MR-thermometry using a contrast-agent-water solution and a pig-liver. A T1-weighted TurboFLASH sequence and a FLASH-2D sequence were used. The TurboFLASH sequence was used with various T1 settings (between 100 and 1250 ms). MR findings were correlated with temperature measurements using a fluoride optical temperature measuring system in a distance of 1, 2, and 5 cm from the laser applicator. RESULTS: Using the contrast-agent-water solution demonstrated the temperature sensitivity of both sequences. In vitro evaluations using pig liver demonstrated a near linear increase of signal versus increasing tissue temperatures in a distance of 1 cm to the tip of the laser applicator. Optimal visualization of the temperature effects was obtained using a T1 between 100 ms and 400 ms. Using the FLASH-2D sequence a signal loss was documented at a TR of 110 ms. CONCLUSION: MR-thermometry using sequentially TurboFLASH and FLASH-2D sequences allowed a non-invasive monitoring of the laser induced temperature changes.

Animals↗
PubMed1997

A descriptive analysis of children's playground injuries in the United States 1990-4.

OBJECTIVES: To review playground injury statistics over a five year period in order to develop an awareness of how and where children in the United States are being injured. METHODS: All data are based on the United States Consumer Product Safety Commission's National Electronic Injury Surveillance System (NEISS) for playground related injuries during 1990-4. The surveillance data includes injuries recorded in more than 90 hospital emergency departments located throughout the United States. RESULTS: Each year there are roughly 211,000 preschool or elementary school-children in the United States who receive emergency department care for injuries associated with playground equipment. On average, 17 of these cases result in death. 70% of all injuries occur on public playgrounds, with nearly one third classified as severe. Swings, climbers, and slides are the pieces of playground equipment associated with 88% of all NEISS reported injuries. Falls to the surface are responsible for 70%. CONCLUSIONS: NEISS playground injury statistics contribute to our understanding of playground injuries. By identifying where and how children are injured, suggestions can be made in an attempt to make playgrounds safer.

Adolescent↗
PubMed1997

Accuracy of staging rectal tumors with contrast-enhanced transrectal MR imaging.

OBJECTIVE: Our objective was to evaluate the accuracy of contrast-enhanced transrectal MR imaging in staging rectal adenoma and carcinoma by correlating with histopathologic findings. SUBJECTS AND METHODS: Thirty-five patients underwent transrectal MR imaging on a 1.5-T superconducting unit using unenhanced T1-weighted and T2-weighted spin-echo and turbo spin-echo sequences, a dynamic gadopentetate dimeglumine-enhanced turbo fast low-angle shot sequence, and enhanced T1-weighted spin-echo sequences. For all patients, histopathologic correlation was available from biopsy (n = 15) or surgical resection (n = 20). Two radiologists unaware of each other's interpretations of the scans interpreted each case from which we evaluated qualitative and quantitative data. RESULTS: Rectal adenomas (n = 15) were identified when imaging revealed an intact muscularis mucosae, a homogeneous internal structure, and high contrast enhancement of the lesion. Carcinomas staged as T1 by TNM criteria (n = 6) were best revealed by dynamic turbo fast low-angle shot sequences, in which an intact muscularis propria could be seen. Visualization of enhancing tumor tissue in the muscularis propria indicated T2 carcinoma (n = 5). All T3 (n = 5) and T4 (n = 4) carcinomas were correctly staged with dynamic and static MR imaging. The stage revealed by MR imaging correlated well with histologic staging results in 89% (observer 1) and 86% (observer 2) of interpretations. However, when interpreting MR imaging, observers tended to overstage and never understaged. CONCLUSION: Transrectal surface-coil MR imaging provided reliable information in staging patients before surgery and in evaluating rectal adenoma and carcinoma.

Adenoma, Villous↗
PubMed1997

Submillimeter imaging and reconstruction of the inner ear.

OBJECTIVE: To present new radiological developments using high-resolution magnetic resonance imaging (MRI). MATERIALS AND METHODS: Using heavily T2-weighted sequences at a 1.5 Tesla scanner, maximum-intensity projections (MIP) of the inner ear were generated. The imaging time was less than 20 minutes, and imaging could be performed with adults and children of all age groups alike. This method enables us to visualize and identify the different neural structures of the internal auditory canal. Aplasia or schwannoma of a single or a variation of nerves could be clearly demonstrated. RESULTS: Three-dimensional reconstruction enabled unprecedented clear and precise presentation of the fluid content of the inner ear. The size and shape of 2 to 2 1/2 turns of the cochlea could be routinely demonstrated and analyzed in 45 subjects. Eight patients subsequently received an intracochlear implant electrode, and the intraoperative findings correlated with the imaging. CONCLUSION: The most recent high-resolution MRI techniques provide reliable visualization of submillimeter anatomical structures of the inner ear and auditory nerve.

Adult↗
PubMed1996

Radiological modalities in the staging of colorectal tumors: new perspectives for increasing accuracy.

The purpose of this study was to evaluate the diagnostic accuracy of contrast-enhanced endorectal MRI for the staging of rectal adenoma versus rectal carcinoma in correlation to findings from biopsy and histopathology. Ten volunteers and 20 patients underwent body-coil and endorectal MRI (1.5T supraconducting unit) using plain, T1-weighted (w) T2-w SE and TSE-w sequences, a dynamic Gd-DTPA enhanced protocol (turboFLASH), and postcontrast T1-w-SE sequences. Histopathological correlation via biopsy (n = 10) and surgical resection (n = 19) were conducted for all patients. An independent, two-observer, reader evaluation was performed and qualitative and quantitative data calculated. In volunteers and all patients endorectal MRI reliably delineated normal wall layers. Rectal adenomas (n = 7) were identified by a visualization of an intact muscularis mucosae, a homogeneous inner structure, and a significant contrast enhancement. T1 carcinomas (n = 4) were best identified in dynamic turboFLASH sequences by delineation of an intact muscularis propria. The visualization of contrast-enhancing tumor tissue was indicative of a T2 carcinoma (n = 4). All T3 (n = 3) and T4 (n = 2) carcinomas were correctly staged on dynamic and static MRI. The endorectal MRI stage agreed with the staging results from pathological study in 16 of 20 (80%) patients. Endorectal surface coil MRI provides reliable data for the preoperative staging and evaluation of rectal lesions.

Adult↗