[Eye muscle metastasis of neuroendocrine tumor of the pancreas].
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Adult↗
Biomedical subjects
A J Lemke
Publications and source records attributed to A J Lemke.
High resolution magnetic resonance imaging of retinoblastoma.
BACKGROUND/AIMS: Diagnosis of retinoblastoma is mainly based on indirect ophthalmoscopy, but additional imaging techniques are indispensable for the staging of the disease. A new high resolution magnetic resonance imaging (MRI) technique for the examination of the eye was evaluated. A new surface coil with a diameter of 5 cm allows a field of view of 60 mm with an in-plane resolution of 0.8 mm. We compared preoperative MRI scans with the histology after enucleation in 21 cases of retinoblastoma. Parameters studied were appearance of retinoblastoma, choroidal and scleral infiltration, extraocular extension, optic nerve infiltration, and vitreous seeding. RESULTS: All retinoblastomas could be visualised as hypointense to vitreous on T2 weighted images and slightly hyperintense to vitreous on plain T1 weighted images with a moderate enhancement after contrast application. Histology revealed seven cases with infiltration of the optic disc or optic nerve. Preoperative MRI scans depict juxtapapillary tumour masses, but it was impossible to differentiate between a juxtapapillary retinoblastoma, a prelaminar infiltration of the optic disc, or a just postlaminar optic nerve infiltration. In five of 14 cases with a proved tumour infiltration of the choroid, MRI scans showed an inhomogeneous contrast enhancement of the choroid in enhanced T1 weighted sequences beneath the retinoblastoma. Whether this sign is specific for a choroidal infiltration or is just an artefact remains unclear. High resolution MRI scans did not allow the exclusion of this form of intraocular tumour extension. All nine cases with proved vitreous seeding were not detected by MRI scans. None of these cases showed scleral infiltration or orbital tumour extension. Therefore, it is not possible to judge the rank of this technique in detecting orbital tumour growth. CONCLUSION: The new MRI technique is of limited value in visualisation of prelaminar or postlaminar infiltration of the optic nerve. Advanced choroidal infiltration might be visualised by contrast enhanced T1 weighted MRI scans, but the available spatial resolution did not allow the exclusion this critical form of tumour growth by MRI scans. Nevertheless, high resolution MRI with the new surface coil has superior contrast and spatial resolution compared to computed tomograph (CT) or other available imaging techniques. MRI cannot replace CT in detecting tumour calcification but with increasing experience with this new technique it should be possible to renounce CT scans in the majority of cases of retinoblastoma.
Child↗
Contrast-enhanced color Doppler sonography of uveal melanomas.
PURPOSE: The purpose of our study was to evaluate the use of the galactose microbubble-based contrast agent Levovist in color Doppler sonography of uveal melanomas. We also evaluated the use of the resistance index and pulsatility index in differentiating tumor-associated vessels from normal vessels in patients with uveal melanomas. METHODS: In this prospective study, 40 patients with uveal melanoma were examined with color Doppler sonography before and after the administration of the contrast agent Levovist. The Doppler signals were recorded from both the tumor and the orbit and were evaluated quantitatively and qualitatively. RESULTS: Tumor-associated vessels were detected without contrast enhancement in 36 of 40 patients and with contrast enhancement in 38 of 40 patients. The spectral characteristics of the Doppler signals did not change after the injection of Levovist. There were no differences-qualitative or quantitative-in Doppler signals between normal and tumor-associated vessels. CONCLUSIONS: The injection of Levovist slightly improved the detection of small vessels in uveal melanomas and the orbit but did not help to differentiate between normal vessels and tumoral vessels. The differentiation of a solid tumor from subretinal hemorrhage or effusion was improved.
Adult↗
[Sectional diagnosis of orbital tumors. 1: Diagnostic imaging--diseases of the orbits: intraconal compartment].
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Diagnosis, Differential↗
[Sectional diagnosis of orbital tumors. 2: Extra-conal compartment, subperiostal compartment, lacrimal gland, bulbus, preseptal compartment].
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Eye↗
Intraocular metastases: differential diagnosis from uveal melanomas with high-resolution MRI using a surface coil.
Magnetic resonance imaging with dedicated surface coils plays a pivotal role in differential diagnosis and staging of intraocular tumors. The purpose of this study was to establish MRI criteria for the differential diagnosis of uveal melanomas and intraocular metastases. In a prospective study 44 eyes in 36 patients with intraocular metastases and 200 patients with uveal melanomas were investigated with MRI using a 1.5-T scanner and a 5-cm surface coil. Both quantitative and qualitative evaluation of the resulting images was performed. The MR signal intensities typically expected for metastases (slightly hyperintense on non-contrast T1-weighted images and hypointense on T2-weighted images compared to the vitreous body) were seen in only 23.1%. The typical melanoma signal of either moderate or strong hyperintensity on T1-weighted images and hypointensity on T2-weighted images was seen in 69.4% of the proven melanomas. Contrast enhancement was observed in both metastases and melanomas. Morphological differences between metastases and melanomas were detected in tumor size, shape, position, frequency of retinal detachment, and homogeneity of the tumor. Differentiation between intraocular metastases and uveal melanoma is limited by overlap of signal intensities. Some improvement is achieved with morphologic criteria.
Adult↗
[Using high resolution sectional imaging in diagnosis of the eye and orbit].
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Eye↗
Combined imaging techniques for pancreatic cancer.
Advanced pancreatic cancer has a poor prognosis. Early detection with imaging techniques can, however, improve the outlook for patients who undergo surgical resection, the only potential curative treatment. Individual techniques, however, have poor sensitivity for small masses and cannot easily differentiate tumour tissue from pancreatic masses associated with chronic pancreatitis. We combined biochemical detection on positron emission tomography with the anatomical accuracy of computed tomography and were able to improve accuracy of interpretation of imaging for patients with pancreatic cancer.
Aged↗
[Fusion of CT and PET data: methods and clinical relevance for planning laser-induced thermotherapy of liver metastases].
AIM: Catheter-placement in liver metastases is difficult when the lesions are not visible on plain images. We evaluated the use of image fusion using CT and PET data, providing information on anatomy and liver lesions, respectively. METHODS: Plain CT of the liver and whole body FDG-PET were performed in 28 patients with colorectal carcinoma in preparation for laser-induced thermotherapy. Fusions of image data and 2D-visualisation were performed and evaluated with regard to quality of the registration, number of detected lesions and influence of the procedure on laser-induced thermotherapy. Image fusion was performed using an algorithm which was developed by our group. RESULTS: 84 focal liver lesions were visible on CT, 107 on PET images. This means that CT guided catheter placement would have to be performed "blindly" in 23 lesions. In 6 patients previously unknown extra-hepatic tumor deposits were seen on PET images (local recurrence, 2 extrahepatic metastases, 2 second primaries). CONCLUSION: Hot spots from metastases, which are difficult to locate on PET images alone, may be identified on images generated by fusion of CT and PET data. These images facilitate an interventional approach to liver lesions which are not visible on plain CT. As PET allows for whole body screening, it helps identifying patients who would not profit from laser-induced thermotherapy.
Algorithms↗
Uveal melanoma: correlation of histopathologic and radiologic findings by using thin-section MR imaging with a surface coil.
PURPOSE: To evaluate whether the different signal intensities at magnetic resonance (MR) imaging of melanoma are associated with a higher content of melanin. MATERIALS AND METHODS: In a prospective study, MR imaging and ophthalmoscopic examination findings in 42 patients (19 women, 23 men; age range, 30-87 years) with uveal melanoma were compared with histopathologic examination findings obtained after enucleation. MR imaging was performed with 2-mm sections by using a 5-cm surface coil. T1- and T2-weighted images were obtained before and after contrast material administration. RESULTS: In 33 (79%) of the patients, there was homogeneous tumor pigmentation, whereas in nine (21%) patients, there was inhomogeneous bipartite tumor pigmentation. Compared with the histopathologic data, the results of qualitative evaluation were accurate in 29 (58%) of 50 and in 26 (53%) of 49 tumorous areas on T1- and T2-weighted images, respectively. Quantitative evaluation yielded better results, especially at T1-weighted imaging; an 86% correlation was found. Because of methodological reasons, only the superficial pigmentation of inhomogeneous tumors could be evaluated with ophthalmoscopy. CONCLUSION: Thin-section MR imaging of the eye enables an accurate prediction of melanomatous pigmentation with quantitative evaluation of plain T1-weighted images and is superior to ophthalmoscopy in cases of inhomogeneous pigmentation.
Adult↗
Signal-enhanced color Doppler sonography of deep venous thrombosis in the lower limbs and pelvis.
Detection of Doppler signal tends to be more difficult in peripheral veins owing to low flow velocity. This can be caused by nonoccluding thrombosis, post-thrombotic wall changes, or a deep anatomic location of pelvic veins. The last-mentioned frequently is accompanied by interference by bowel gas. In addition, inappropriate insonation angles adversely affect the outcome of color-coded Doppler interrogation. The purpose of the present study was to evaluate the effectiveness of signal-enhanced color Doppler sonography on peripheral veins in 31 patients clinically suspected of having deep vein thrombosis. As a result of diagnostic uncertainty, additional enhanced studies were performed on 43 venous segments. The enhancement led to a decrease in false-positive results (from four patients to one patient) and false-negative results (from four patients to two patients) compared to unenhanced studies. Evaluation of the deeply located pelvic veins profited the most through signal enhanced Doppler sonography.
Adult↗
Anomalous origin of the right vertebral artery: review of the literature and case report of right vertebral artery origin distal to the left subclavian artery.
We present the case of a 57-year-old patient who was admitted to the hospital for preoperative cerebral angiography because of an intraspinal mass at the level of C1 and C2. Angiographic examination revealed an abnormal origin of the right vertebral artery, which normally originates from the right subclavian artery. Thus, the right vertebral artery was the last branch of the supraaortic vessels. We also review herein the incidence of the various anomalous origins of the right vertebral artery in the literature and discuss their potential embryologic development and clinical significance.
Cerebral Angiography↗
[Appearance of choroidal melanoma on high resolution MRI using 1.5T with a dedicated surface coil in 200 consecutive patients].
PURPOSE: Choroidal melanomas usually present a characteristic appearance in MRI. Differing characteristics can cause problems in differential diagnosis between melanomas and other masses in the globe. The purpose of this study was to evaluate the appearance of choroidal melanomas with MRI in a large consecutive patient group. METHODS: In a prospective study, 200 patients with choroidal melanomas were investigated with MRI using a 1.5 T scanner and a 5 cm surface coil. Both quantitative and qualitative evaluation of the resulting images was performed. RESULTS: 78.5% of the melanomas presented with homogeneous signal intensities within the tumor due to a homogeneous pigmentation whereas 21.5% of the melanomas demonstrated a mixed pigmentation. Signal intensities of the homogeneous melanomas in the plain T1-WI were moderately or markedly hyperintense compared to the vitreous in 29.3% and moderately or markedly hypointense in the T2-WI in 37.1%. An accompanying retinal detachment was found in 65.5% and an extraocular growth in 7.0%. CONCLUSIONS: In 10% to 37% we observed the typical well known MR appearance, including homogeneous high signal in the T1-WI and low signals in the T2-WI. For further differentiation, morphological criteria (e.g. shape, size, and position) were used, which are also discussed.
Choroid Neoplasms↗
[Use of high resolution color Doppler sonography in diagnosis of temporal arteritis].
PURPOSE: To define sonographic signs of arteritis temporalis using color coded duplex sonography. METHODS: 20 patients with clinically suspected temporal arteritis were examined with color coded Doppler ultrasound prior to temporalis biopsy. The investigation included the temporal artery on both sides and documentation was performed with color prints of the longitudinal orientation of both temporal arteries. All patients had an unilateral biopsy of the temporal artery. RESULTS: 6/20 patients had histologically confirmed temporal arteritis. All patients showed a paravasal zone of lower echogenicity (halo-sign) along the temporal artery. 12/14 patients without temporal arteritis showed no halo-sign. However, a halo-sign was found in 2/14 patients without temporal arteritis which could not be distinguished from the halo-sign observed in patients with temporal arteritis. CONCLUSIONS: A halo-sign could be detected in the majority of patients with arteritis temporalis in concordance with the recent published findings of Schmidt et al. However, a definite specificity of this halo-sign must be rejected.
Aged↗
Septum orbitale: high-resolution MR in orbital anatomy.
PURPOSE: The purpose of this study was to ascertain whether MR imaging, with the use of a surface coil, can accurately show small intraorbital structures; in particular, the septum orbitale. METHODS: Examinations of 26 patients who underwent unilateral orbital high-resolution MR imaging for different indications were evaluated to differentiate the septum orbitale from related structures, such as the aponeurosis of the levator palpebrae, the superior tarsal (Müller's) muscle, and the superior orbital (Whitnall's) ligament. RESULTS: A subtle differentiation of the septum orbitale was obtained in 23 patients (88%) and of the levator aponeurosis and Müller's muscle in 24 patients (92%). The orbicularis oculi muscle and the submuscular fibroadipose tissue were reliably identified in all patients. CONCLUSIONS: High-resolution MR imaging is suitable for differentiating small intraorbital structures. Nevertheless, an exact depiction of the septum orbitale remains very much dependent on the cooperation of the patient. The site of orbital disease can be determined precisely and in a noninvasive manner in relation to the septum orbitale.
Aged↗
Choroidal hemangioma: MR findings and differentiation from uveal melanoma.
BACKGROUND AND PURPOSE: The aim of this study was to establish the MR imaging characteristics of choroidal hemangioma and to compare them with those of uveal melanoma. METHODS: Among 41 patients examined at 1.5 T (4-cm surface coil, T1-weighted and fast spin-echo T2-weighted sequences), 25 had uveal melanoma and 16 had circumscribed choroidal hemangioma. After i.v. bolus injection of gadopentetate dimeglumine, dynamic and T1-weighted sequences were acquired. RESULTS: In patients with choroidal hemangioma, uniform signal characteristics were detected on fast T2-weighted images. In 15 of 16 patients with choroidal hemangioma, lesions were isointense with vitreous on fast spin-echo T2-weighted images, whereas lesions in 24 of 25 patients with uveal melanoma were hypointense. Signal characteristics of uveal melanoma and hemangioma did not differ significantly on plain T1-weighted images. Enhancement was earlier and much stronger for circumscribed choroidal hemangioma than for uveal melanoma. After i.v. bolus application of gadopentetate dimeglumine, the increase of signal intensity was higher for circumscribed choroidal hemangioma (signal intensity ratio, 5.8) than for uveal melanoma (signal intensity ratio, 2.2). CONCLUSION: Circumscribed choroidal hemangioma may be difficult to differentiate from melanoma by ophthalmologic examination. Differentiation may not be possible if direct viewing of uveal space-occupying lesions is hampered by opaque vitreous media. The characteristic findings on fast spin-echo T2-weighted MR images and early enhanced images aid in differentiating choroidal hemangioma from uveal melanoma.
Adolescent↗
MRI-assisted specification/localization of target volumes. Aspects of quality control.
The transportation of MRI information on tumor extension into CT-based radiation therapy planning is desirable for several reasons. MRI's better contrast resolution is usually considered the most important, as it leads to a more exact definition of target volumes. Unlike diagnostic imaging, where a certain margin of error in depiction of tumor extension seems acceptable, radiation therapy planning makes it absolutely necessary, that the contents of every MR pixel (or voxel) correspond exactly to the corresponding area in the patient examined. This exact correspondence may be disturbed by a variety of influencing factors. Objects like various implants may lead to the most severe image distortions and--even worse--contrast alterations, some of which are not easily visible on the slices which are used for target volume definition. Additionally, MR images may have intrinsic faults which are able to change the correspondence between the voxel and the part of the patient's body it represents. Quality control has therefore to ensure that parameters like slice thickness are correct and kept constant by the imager. Image fusion may then be used to transfer MR information on tumor extension into the CT data. Electron density distribution provided by CT then allows for treatment planning. Implanted markers may then be used to ensure exact correspondence between the examined parts of the patient's body and the representing pixel or voxel. Care should be taken that landmarks themselves do not influence this relationship.
Brain Neoplasms↗
MR anatomy and small lesions of the eye: improved delineation with a special surface coil.
To develop an improved investigation protocol for MRI studies of intraocular lesions, imaging with a small surface coil (diameter 6 cm) was compared with a standard surface coil (diameter 11 cm). Both coils were assessed initially on an eye phantom and then by studying 22 patients with uveal melanoma and similar lesions of the eye. The influence of bandwidth and field or view (FOV) were systematically studied and evaluated quantitatively. A smaller bandwidth improved image quality independent of surface coil size. The subsequent secondary increase in chemical shift artefact was acceptable. Smaller FOVs (60-80 mm) necessitated the use of a smaller surface coil. A smaller bandwidth also proved to be advantageous with the use of the smaller surface coil. In conclusion, a smaller-diameter surface coil improves MR imaging of ocular lesions. Pulse sequences with a small bandwidth maintain an acceptable signal-to-noise ratio when the FOV is reduced.
Artifacts↗