Martin G. Mack

Cochlear Implantation Via the Round Window Membrane Minimizes Trauma to Cochlear Structures: A Histologically Controlled Insertion Study

Objective To evaluate cochlear implant trauma to intracochlear structures when inserting the electrode via the round window membrane. Material and methods Eight fresh human temporal bones were evaluated histologically after insertion using two types of cochlear implant array. Bones underwent a special fixation and embedding procedure that allowed sectioning of undecalcified bone with the electrode in situ. Insertions depths were evaluated radiologically and histologically. Results All arrays were found in the scala tympani of the cochlea. Basal trauma could be avoided in all but one specimen. The mean depth of insertion was 382.5°. Apically, only one implanted bone showed cochlear trauma exceeding lifting of the basilar membrane. Conclusion Insertions through the round window membrane were shown to be atraumatic, even in basal cochlear regions. This route of insertion might be very effective for combined electric and acoustic stimulation of the auditory system.

Liver metastases: interventional therapeutic techniques and results, state of the art.

Abstract. The liver is the most common site of metastatic tumour deposits. Hepatic metastases are the major cause of morbidity and mortality in patients with gastrointestinal carcinomas and other malignant tumours. The rationale and results for interventional therapeutic techniques in the treatment of liver metastases are presented. For the treatment of patients with irresectable liver metastases, alternative local ablative therapeutic modalities have been developed. Technique and results of local interventional therapies are presented such as microwave-, radiofrequency (RF)- and ultrasound ablation, and laser-induced interstitial therapy (LITT), cryotherapy and local drug administration such as alcohol injection, endotumoral chemotherapy and regional chemoembolisation. In addition to cryotherapy, all ablative techniques can be performed percutaneously with low morbidity and mortality. Cryotherapy is an effective and precise technique for inducing tumour necrosis, but it is currently performed via laparotomy. Percutaneous local alcohol injection results in an inhomogeneous distribution in liver metastases with unreliable control rates. Local chemotherapeutic drug instillation and regional chemoembolisation produces relevant but non-reproducible lesions. Laser-induced interstitial thermotherapy (LITT) performed under MRI guidance results in precise and reproducible areas of induced necrosis with a local control of 94 %, and with an improved survival rate. Interventional therapeutic techniques of liver metastases do result in a remarkable local tumour control rate with improved survival results.

Percutaneous MRI-guided laser-induced thermotherapy for hepatic metastases for colorectal cancer

procedure. LITT was done after agreement from the local ethics committee and with the patients’ informed consent. All patients tolerated the procedure well; six had mild nausea and a symptomless right subphrenic haemorrhage developed in one. No deaths, infections, or liver or bile-duct injury occurred. During follow-up, 23 of 99 treated patients died: one of myocardial infarction, one from a stroke, 13 from tumour progression in the liver, and eight from tumour progression in other locations. The cumulative survival rate was 0·88 after 12 months, 0·70 after 24 months, and 0·42 after 36 months. Median survival time, calculated by the Kaplan-Meier method, was 36·4 months (figure). In patients with liver metastases of colorectal cancer, local tumour destruction with LITT under local anaesthesia is well tolerated and results in improved clinical outcome and survival. Our data can be a basis for a randomised comparison of LITT versus surgery.

Laser-induced thermotherapy of malignant liver tumors: general principals, equipment(s), procedure(s) - side effects, complications and results

PURPOSE To prospectively evaluate the therapeutic potential of MR-guided and ultrasound-guided laser-induced thermotherapy (LITT) in patients with liver metastases and oligonodular hepatocellular carcinoma (HCC). MATERIAL AND METHODS Between June 1993 and June 2000 a total of 1608 LITT sessions was performed to treat 1914 lesions in 676 consecutive patients. The Nd-YAG laser fiber was introduced with a percutaneously positioned cooled application set. Qualitative and quantitative ultrasound and magnetic resonance (MR) parameters, as well as clinical data were evaluated. RESULTS All patients tolerated the procedure well under local anesthesia; no relevant clinical complications were observed. The mean laser power was 25 W and the mean duration was 25 min. MR proved to be superior over computed tomography and ultrasound due the thermosensitivity of the MR sequences allowing a better visualization of the volume of laser-induced changes and their relation to the neighboring geographical structures. The ultrasound-guided LITT should be restricted for patients with contraindications for MR imaging monitoring and for selected patients with low diameter oligonodular HCC. In 95% of cases, we achieved a complete necrosis of the tumor and a 5-mm safety margin, resulting in a complete destruction of the tumor without local recurrences. Mean survival in this group was 35 months (calculated with the Kaplan-Meier method). CONCLUSION MR-guided, or ultrasound-guided, LITT appears to be a safe and effective treatment protocol for liver metastases and oligonodular HCC.

Interventional MR: interstitial therapy

Abstract. 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.

Quantitative measurements of perfusion and permeability of oropharyngeal and oral cavity cancer, recurrent disease, and associated lymph nodes using first-pass contrast-enhanced computed tomography studies.

Objectives:We sought to evaluate the routine clinical use of perfusion computed tomography in the detection and differentiation of primary and recurrent oropharynx and oral cavity tumors as well as of nodal disease. Materials and Methods:A total of 77 patients with primary cancer as well as suspected recurrent disease and lymph nodes were evaluated. A dynamic acquisition (4 × 6-mm slices) of the largest axial tumor surface was performed and the tumor blood flow (BF), blood volume (BV), and mean transit time (MTT) were calculated by using a modified deconvolution-based analysis taking into account the extravasation of the contrast agent for permeability surface area product imaging (PS). Tumor volume was calculated and region of interest analysis was performed on the pathologic and normal tissue. Results:The mean BF, BV, and PS values in the primary tumors (77.48 mL/min/100 g tissue; 5.29 mL/min; 13.33 mL/min/100 g tissue, respectively) were highly significantly different (P < 0.01) than those obtained in the normal structures. Mean MTT values (9.01 seconds) also were significantly lowered in the tumors compared with normal tissue (P < 0.05). There was no statistical difference in the perfusion values between the primary and the recurrent tumors. Recurrent disease could be differentiated on the basis of BF (P < 0.05) from tissue changes after chemo-radiation-treatment (mean BF: 69.71 versus 45.31 mL/min/100 g tissue, respectively). Differentiation of the lymph nodes was not possible by means of perfusion values. Tumor volume did not significantly correlate with any perfusion parameter. Conclusions:Perfusion CT of oropharyngeal and oral cavity cancer in clinical routine is feasible and helps outlining the malignant tissue as well as differentiating recurrent disease from nonspecific post-therapeutic changes.

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.

Percutaneous vertebroplasty in the therapy of osteoporotic vertebral compression fractures: a critical review

Percutaneous vertebroplasty has become an efficient technique for the treatment of painful vertebral fractures. Osteoporotic vertebral compression fractures are characterized by severe back pain and immobilization causing other complications like thrombosis or pneumonia. Vertebral cement augmentation provides increased strength of the vertebral body and an obvious pain relief. Between 1989 and 2004, 30 studies and a total of 2,086 treated patients have been published in literature. A review of these studies has been performed. The number and age of the patients, number of treated vertebrae, pre- and postoperative outcome of pain and complications of the different studies were assessed and analyzed. Percutaneous vertebroplasty is an efficient technique with low complication rates and a significant reduction in pain. It rapidly improves the mobility and quality of life of patients with vertebral compression fractures. With an increasing number of treated patients, experience with this interventional technique has become excellent. But still there are no randomized controlled trials available, showing that percutaneous vertebroplasty has a significantly better outcome than other treatment options, especially after a long-term follow-up.

MR-compatible Assistance System for Biopsy in a High-Field-Strength System: Initial Results in Patients with Suspicious Prostate Lesions

PURPOSE To examine the feasibility and safety of magnetic resonance (MR)-guided biopsy by using a transgluteal approach in patients with suspicious prostate lesions by using an MR-compatible robotic system and a 1.5-T MR system. MATERIALS AND METHODS The study was approved by the institutional review board of University Frankfurt, and informed consent was obtained from each patient. A total of 20 patients (age range, 57.8-71.9 years; mean age, 65.1 years) underwent biopsy in a closed-bore high-field-strength MR system. Biopsy was performed with an MR-compatible pneumatically driven robotic system. T1-weighted gradient-echo fast low-angle shot and T2-weighted true fast imaging with steady-state precession sequences were used to plan and guide the intervention with a transgluteal access on the external planning computer of the assistance system. The system calculated the trajectory and then moved the guiding arm to the insertion point. The cannula was advanced manually, and biopsies were performed with the coaxial technique by using a 15-gauge pencil tip needle. Intervention time, complications, and biopsy findings were documented. RESULTS The MR-compatible robotic system did not interfere with image quality, nor did MR imaging cause dysfunction of the robot. In one patient, the interventionist caused a fail-safe system shutdown. This was due to inadvertent displacement of the guiding arm during cannula insertion. This problem was solved by increasing the displacement threshold. Accurate coaxial cannula biopsy could be performed in all subsequent patients. Sufficient histopathologic assessment was performed in 19 patients. Insufficient material was retrieved in the patient who experienced fail-safe system shutdown. The median intervention time was 39 minutes (23-65 minutes). No procedure-related complications were observed. CONCLUSION Preliminary results indicate that MR-guided robot-assisted biopsy is feasible and can be performed safely with highly accurate cannula placement.

Image Quality and Radiation Dose of Dual-Energy CT of the Head and Neck Compared with a Standard 120-kVp Acquisition

BACKGROUND AND PURPOSE: DECT offers additional image datasets with potential benefits, but its use for H&N imaging is not justified unless image quality is preserved without increased radiation dose. The aim of this work was to compare image quality and radiation dose between a DE-derived WA image dataset and a standard SECT acquisition of the H&N. MATERIALS AND METHODS: Thirty-two patients underwent DECT of the H&N (tube voltages 80 and Sn140 kVp) and were compared with the last 32 patients who underwent standard SECT (120 kVp) on the same dual-source scanner. WA images from the 2 DE tubes were compared with images obtained with an SE mode. Radiation doses and attenuation measurements of the internal jugular vein, submandibular gland, and sternomastoid and tongue muscles were compared. Objective image noise was compared at 5 anatomic levels. Two blinded readers compared subjective image quality by using 5-point grading scales. RESULTS: CTDIvol was 12% lower with DE than with SECT, a difference of 1.5 mGy, (P < .0001). Objective noise was not significantly different between DE and SECT at any of the anatomic levels (P > .05). No significant differences in attenuation measurements were observed between DE and SECT (P > .05). No significant differences in subjective image quality scores were observed between DE and SECT at any of the 5 anatomic levels (P > .05). CONCLUSIONS: DE-derived WA images of the H&N are equivalent to standard SE acquisitions and thus can be used for routine diagnostic purposes. Multiple additional image datasets can be obtained with no radiation dose penalty.