Thyrotropin-releasing hormone stimulation test to assess thyroid function in severely sick cats.

Basal serum thyroxine (T4) concentration and the thyrotropin-releasing hormone (TRH) stimulation test were used to assess thyroid function in 36 critically ill cats examined between July 1996 and October 1998. Of the 36 cats. hyperthyroidism (as underlying or complicating disease) was suspected in 22 based on clinical signs, palpable thyroid nodules, and abnormal thyroid gland histology (study group). Hyperthyroidism was not suspected in the remaining 14 cats, which served as the control group. Based on serum T4 concentrations, suppression of thyroid function was documented in 14 (64%) cats of the study group and in 10 (71%) cats of the control group. The TRH stimulation test revealed an increase in serum T4 of less than 50% of the baseline concentration in 18 (82%) cats of the study group, and in 6 (43%) cats of the control group. In conclusion, based on the results of serum T4 determinations and the TRH stimulation tests, it was not possible to differentiate between cats with clinical and histologic evidence of thyroid dysfunction (hyperthyroidism) and cats with severe nonthyroidal illnesses.

[Value of invasive preoperative imaging in kidney tumors of malignant or uncertain character]. / Stellenwert der invasiven präoperativen Bildgebung bei Nierentumoren maligner oder unklarer Dignität.

Preoperative staging of malignant renal tumors or undetermined dignity is mainly performed noninvasively using CT or MRI. In cases with vascular invasion or a solitary kidney extensive invasive evaluation of the tumor can influence preoperative planning. We report two cases of oncocytoma and renal cell carcinoma with extensive imaging using DSA or helical CT-cavography.

Comparison of three dimensional magnetic resonance imaging in conjunction with a blood pool contrast agent and nuclear scintigraphy for the detection of experimentally induced gastrointestinal bleeding.

BACKGROUND AND AIMS: To compare the performance of 3D magnetic resonance imaging (MRI) in conjunction with an intravascular contrast agent with that of scintigraphy, with respect to detection and localisation of gastrointestinal haemorrhage in vivo in pigs. METHODS: Intraluminal bleeding sites were surgically created in the small bowel and colon of six pigs. The animals underwent scintigraphy with (99m)Tc labelled red blood cells and 3D MRI following administration of an intravascular contrast agent (NC100150) at five minute intervals over 30 minutes. For analysis, the intestinal tract was divided into six segments. Based on the two evaluated methods, each segment was characterised on a five point scale regarding the presence of a bleed. At autopsy, the surgically manipulated bowel segments were inspected for the presence of haemorrhage. RESULTS: Bleeding was confirmed at autopsy in 18/36 segments. Contrast extravasation with subsequent movement through the bowel could be documented on MRI data sets. All segments were correctly characterised, resulting in 100% sensitivity and specificity for MRI. Based on scintigraphy, interpretation of seven segments (19%) was false (sensitivity/specificity of 78%/72%). Differences in diagnostic performance were evident in the receiver operator characteristic (ROC) analysis, with an area under the MRI curve of 0.99 and under the scintigraphy curve of 0.85. CONCLUSION: In conjunction with an intravascular contrast agent, 3D MRI permits accurate detection and localisation of gastrointestinal bleeding. The extent and evolution of intestinal bleeding can be determined with repeated data acquisition.

Clinical value of pelvic and penile magnetic resonance angiography in preoperative evaluation of penile revascularization.

Penile angiography is invasive, costly and requires postinterventional surveillance. The aim of this pilot study was to determine whether three dimensional magnetic resonance (3D-MR)-angiography may replace conventional penile angiography in preoperative planning of penile revascularization. Twelve patients with a mean age of 39 (21-59) y were evaluated. All patients underwent evaluation with intracavernous pharmacotesting, color Doppler sonography (CDS), digital subtraction angiography (DSA) and pelvic MR-angiography with gadolinium diethylene-triaminepentaacetic acid (Gd-Dota) 0.2-0.3 mmol/kg body weight. MR-angiography demonstrated the anatomy of the internal iliac arteries in 9 out of 12 patients. Intrapenile vessels were visible in 7 out of 12 patients. In comparison DSA provided complete visualization of all pelvic and penile vessels. Relevant arterial obstruction was found in 10 out of 12 patients. CDS revealed a mean maximal arterial flow of 27 (22-40) cm/s and showed in accordance to angiography arterial insuffiency in 10 out of 12 cases. Indication for revascularization could have been based on MR-angiography alone in only one patient. Therefore, selective penile angiography remains the 'gold standard' for preoperative planning of revascularization procedures.

Interactive MR-guided biopsies of maxillary and skull-base lesions in an open-MR system: first clinical results.

The purpose of this study was to explore the potential of interactive MR-guided biopsies in the maxillary and skull base region using a 0.5-T open-configuration scanner in patients with tumours affecting the maxilla or skull base. Ten patients with cystic or solid tumours affecting the maxillary and skull base regions underwent MR-guided biopsy in a superconducting, open 0.5-T MR system equipped with an optical frameless stereotaxic system. T2-weighted spin-echo images were acquired prior to and following biopsy, which was performed with 18- or 22-G needles using an enoral or percutaneous approach following infiltration of the skin, mucosa and periosteum with local anaesthetics. The position of the needle tip was continuously updated on fast T1-weighted gradient-recalled-echo images (TR 19 ms, TE 7.1 ms, flip angle 30 degrees, slice thickness 1 cm, field of view 24 x 24 cm) using the frameless stereotaxic system. In addition, the needle was identified based on the associated susceptibility artefact in all three planes. Once the target lesion had been reached, cytology material was aspirated. All ten patients tolerated the interactive MR-guided biopsies well without complications. Vital structures, including the brain, neurovascular bundles, vessels and eyes, were visualized on MR imaging and could be spared. There was no difference in the use of 18- or 22-G non-ferromagnetic needles concerning the susceptibility artefact. Sufficient material for cytological analysis was obtained in nine of ten cases. The mean biopsy time was 15 min. Interactive MR-guided biopsies of the head and neck in an open system are technically feasible and safe. Monitoring of the needle path in multiple planes permits the interactive adjustment of the needle course in near real time. Interactive MR-guided biopsies may well replace open surgical procedures in the maxillary region in selected patients.

Intestinal and peritoneal bleeding: detection with an intravascular contrast agent and fast three-dimensional MR imaging--preliminary experience from an experimental study.

PURPOSE: To assess the ability to detect and localize intestinal and peritoneal bleeding with an intravascular contrast agent and fast three-dimensional (3D) magnetic resonance (MR) imaging. MATERIALS AND METHODS: An intravascular contrast agent (NC100150 Injection) was administered into small-bowel specimens at five flow rates; the specimens were imaged with a 3D gradient-echo (GRE) sequence at 1-minute intervals. Radionuclide studies with technetium-99m pertechnetate were performed in the same manner. Subsequently, the MR imaging technique was assessed in vivo. Two intraluminal intestinal and one hepatic bleeding sites were created in an anesthetized pig. Three-dimensional GRE imaging data sets were acquired after intravenous injection of the contrast agent. Imaging findings were confirmed with macroscopic inspection. RESULTS: Contrast material injected at 0.5-2.0 mL/min was detected with both radionuclide and MR imaging after 1 minute. An accumulated volume of 0.2 mL was necessary to demonstrate the bleeding site. In vivo, all bleeding sites were readily detected on MR images. Contrast material accumulated in the intestines and peritoneal space. CONCLUSION: In conjunction with an intravascular contrast agent, 3D MR imaging allows detection and localization of gastrointestinal bleeding. The extent of the bleeding can be determined with repeat data acquisitions.

[Gastric pouch dilatation: complications after laparoscopic implantation of a silicone gastric band in pathologic obesity]. / Die Magen-Pouch-Dilatation: Komplikationen nach laparoskopisch implantiertem Silikon-Magenband bei pathologischer Adipositas.

In 20 patients with morbid obesity a laparoscopic silicon gastric banding was installed using a LAP-BAND. All patients were examined postoperatively with water-soluble oral contrast material according to the usual protocol. 8 weeks after the operation a second control with thickened barium sulfate was added to measure and adjust the width of the silicon band. There were no early postoperative complications. But in the follow-up three patients presented with a pathologic gastric pouch-dilatation. This severe complication, which can have different etiologies, requires early detection and specific therapy.

Primary angiosarcoma of the pulmonary arteries: dynamic contrast-enhanced MRI.

PURPOSE: Our goal was to assess the MR appearance and histologic correlation of primary pulmonary artery angiosarcoma. METHOD: Four patients with tumorous masses in the pulmonary arteries were evaluated by dynamic contrast-enhanced MRI using T1- and T2-weighted SE images, GE images, as well as coronal 3D MRA in breath-hold technique. The percentage of tumor enhancement was determined by measuring regions of interest before and after Gd-DTPA administration on the 2D multiplanar spoiled GRE images. RESULTS: All four masses showed some contrast enhancement on the dynamically acquired GRE images. The degree of contrast enhancement correlated with the degree of tumor differentiation, content of myxoid matrix, and associated thrombus. Contrast-enhanced 3D MRA was useful for preoperative delineation of the peripheral pulmonary arteries to the subsegmental order. CONCLUSION: Dynamic contrast-enhanced 3D MRA of the pulmonary arteries can be used to delineate pulmonary arterial angiosarcomas preoperatively. Considerable variability of contrast agent uptake reflects the wide histologic behavior of these masses in differentiation from central pulmonary embolism.

Interactive MR-guided biopsies of the thyroid gland: validation of a new method.

The aim of this study was to demonstrate the clinical feasibility and utility of an interactive MR-guidance system to target and biopsy thyroid lesions, and to compare resolution between ultrasound and interventional MR imaging in the evaluation of thyroid lesions. Twenty thyroid lesions of 18 patients were interactively biopsied using a 0.5-T superconducting open magnet system. Stereotactic localization of the needle and imaging was accomplished using T1-weighted gradient-recalled-echo (GRE) images. Representative cytological material was retrieved in 16 of 20 lesions (benign cystic or colloid goiter: n = 14; one de Quervain's thyroiditis and one follicular neoplasia). Lesions smaller than 1.5 cm detected by ultrasound could not be visualized adequately on GRE images. Lesions smaller than 1.5 cm were successfully biopsied by ultrasound (three colloid and haemorrhagic goiters and one adenoma). Magnetic-resonance-guided interactive biopsies and positioning of non-ferromagnetic needles in the thyroid gland are technically feasible and safe. Compared with high-resolution ultrasound, lesions larger than 1.5 cm can be adequately visualized and biopsied. Magnetic-resonance-guided placement of non-ferromagnetic needles is no substitute for high-resolution ultrasound in clinical work-up of thyroid lesions.

Detection of breast cancer with conventional mammography and contrast-enhanced MR imaging.

The aim of this study was to compare the diagnostic performance of conventional mammography and dynamic contrast-enhanced fast 3D gradient-echo (GRE) MRI regarding the detection and characterization of breast lesions relative to histopathologic analysis and to assess the results of a combined evaluation of both methods. fifty consecutive patients with 63 histopathologically verified breast lesions underwent dynamic contrast-enhanced GRE MRI in addition to routine conventional mammography. All lesions were classified by both methods on a five-point scale as benign or malignant, and the results were correlated to histopathology. Conventional mammography and dynamic MRI yielded a sensitivity and specificity of 82 and 64 %, and 92 and 76 %, respectively. The difference between the results was statistically not significant (p > 0.05) with areas under the receiver-operating-characteristics curves of 0.807 for mammography and 0.906 for MR imaging. Combination of the results of both methods slightly increased the sensitivity for detection of breast cancer to 95 % but decreased specificity to 52 %. In this selected patient subset, including only patients referred for excisional biopsy, contrast-enhanced dynamic MRI proved more sensitive and specific than conventional mammography regarding the detection of malignancy. While a combination of both methods yields a slightly improved sensitivity, specificity is vastly reduced.

Focal nodular hyperplasia of the liver: serial MRI with Gd-DOTA, superparamagnetic iron oxide, and Gd-EOB-DTPA.

BACKGROUND: To demonstrate the improved specificity of liver MRI in diagnosis of focal nodular hyperplasia (FNH) using liver specific contrast agents. METHODS: In a patient after resected adenosarcoma of the uterus a focal nodular hyperplasia was followed. Serial MRI of the liver was performed using first Gd-DOTA, followed by superparamagnetic iron oxide (SPIO) as well as Gd-EOB-DTPA. RESULTS: During the follow-up of FNH specificity of liver MRI improved using liver specific contrast agents. The central scar as well as the pseudocapsule showed different typical contrast uptake using all three methods. CONCLUSION: Serial MRI of the liver with Gd-DOTA, SPIO and Gd-EOB-DTPA can exclude a malignant liver lesion. Liver biopsy of FNH can be avoided with increased specificity of MRI for FNH.

Rapid prototyping (stereolithography) in the management of intra-articular calcaneal fractures.

The purpose of this study was to evaluate and compare the diagnostic performance of stereolithography vs workstation-based three-dimensional (3D) reformations in intra-articular calcaneal fractures. A total of 30 intra-articular calcaneal fractures were examined using standard radiographs, coronal CT scans, and 2D and 3D reformations. The CT data were transferred to an outside institution, and stereolithograms were produced from photopolymer resin employing a laser beam system. 3D reformations and stereolithograms were analyzed in a blinded fashion by two staff radiologists. Receiver-operating-characteristic (ROC) curves were obtained for six clinically significant fracture components. Standard radiographs, coronal CT scans, and 2D reformations served as the standard of reference. The area under the ROC curves for 3D reformations and stereolithograms were 1.0 and 0.98 for abnormal tuber angles, 0.91 and 0.91 for anterior and middle talo-calcaneal joint involvement, 0. 90 and 0.95 for involvement of the posterior talo-calcaneal joint, 0. 65 and 0.78 for the presence of a lateral bulge, 0.80 and 0.81 for the involvement of the calcaneocuboidal joint, and 0.62 and 0.67 for the presence of a "tongue-type" fracture. No statistically significant difference was demonstrated for the two methods (Wilcoxon signed-rank test, p = 0.138). Based on our results stereolithograms did not prove to be statistically superior to workstation-based 3D reformations. Stereolithograms may still be useful for teaching purposes and for surgical planning at a thinking-efficacy level.

[Interactive stereotaxic interventions in superconducting, open 0.5-Tesla MRI tomography]. / Interaktive, stereotaktische Interventionen im supraleitenden, offenen 0.5-Tesla-MR-Tomographen.

PURPOSE: Evaluation of an interactive, stereotactic biopsy device integrated in an open superconductive 0.5 tesla MR-scanner with a vertical gap. MATERIAL AND METHODS: In addition to "in-vitro" experiments performed on a plexiglas phantom with holes of varying diameters (5-20 mm) biopsies on eleven patients (7 women, 4 men; average age 55 years) were performed in the interventional MR-system. Lesions in the abdomen (n = 6), muscle (n = 1), thyroid (n = 3) and breast (n = 1) were targeted with 18-20 G aspiration biopsy needles of 5-15 cm length. The intervention was interactively guided by a fast T1-weighted 2-D gradient echo sequence. RESULTS: All of the 15 and 20 mm holes of the phantom, but only 83% of the 10 and 5 mm holes were hit. No complications occurred during the MR-guided patient procedures. All lesions (mean size 3.5 cm, distance from the skin 2 cm to 10 cm) were biopsied successfully. The fast image acquisition in combination with the stereotactic technique enables interactive control of the needle. CONCLUSIONS: Stereotactic, interactively controlled biopsies in the interventional MR are technical feasible. However, the range of meaningful indications for MR-guided biopsies is limited.

[Puncture with an open-sided, interventional MRI system. Illustration with a case report]. / Punktionen an einem offenen, interventionellen MR-Gerät. Veranschaulichung anhand eines Fallbeispiels.

INTRODUCTION AND METHODS: A 0.5 T open-configuration MR system allows free access to the patient via a 58-cm-wide opening on both sides of the machine. A newly developed system for needle guidance enables the examiner to perform biopsies in combination with real-time imaging and to position laser fibers in the human body. For imaging, a 2D gradient echo sequence is used (TR 19 ms, TE 9 ms, flip angle 30 degrees FOV 24 x 24 cm, slice thickness 10 mm matrix 256 x 128). The acquired images are displayed on two LCD screens localized within the MR system, thus allowing an interactive needle guidance. This procedure is illustrated by a case report. DISCUSSION: The handling of the system for needle guidance was simple, mainly due to a real-time adaption of the scan plane to the needle direction. The possibility of multi-angulated approaches makes biopsies of hardly accessible anatomic regions feasible. CONCLUSION: We think that MR-guided needle positioning will play an important role in combination with thermosensitive therapies. Thermosensitivity of MR imaging allows extensive monitoring of such interventions.

[Thoracic peri-aortic fibrosis and Ormond disease]. / Thorakale periaortale Fibrose und Morbus Ormond.

Two cases of thoracic periaortal fibrosis as a manifestation of retroperitoneal fibrosis (Ormond's disease) are shown on CT and MRI. Thoracic periaortal fibrosis can result in an inflammatory aneurysmo with chronic dissection. Manifestation of thoracic periaortal fibrosis may typically occur intermittently over decades.

[High-resolution magnetic resonance tomography of the lesser pelvis using an endorectal coil]. / Hochauflösende Magnetresonanztomographie des kleinen Beckens mittels Endorektalspule.

Spatial resolution of MRI within the true pelvis can be increased by a factor of 12 using an endorectal coil. The value of this new method for demonstrating the prostate, the rectum, the cervix and vagina and of pathological processes of these organs was examined in 89 patients and the results compared with conventional body coil MRI. In 25 patients who underwent radical surgery the results of the preoperative studies were compared with the histological findings. Detailed recognition of anatomical structures was markedly improved by using the endorectal coil. Diagnosis of carcinoma of the prostate and extension of the tumour was accurately assessed in 33 patients. Preoperative staging was correct in 87%, compared with 73% when using a body coil. The difference was less marked in examinations for carcinomas of the rectum, the cervix and vagina. Nevertheless, staging was more accurate in a few cases with a better recognition of recurrences. MRI with endorectal coils will have an important role in diagnosis of carcinomas of the prostate in the future. Its use in the diagnosis of carcinomas of the rectum and cervix must be subject to further studies.