A.-J. Lemke

Value of image fusion using single photon emission computed tomography with integrated low dose computed tomography in comparison with a retrospective voxel-based method in neuroendocrine tumours

The objective was the evaluation of single photon emission computed tomography (SPECT) with integrated low dose computed tomography (CT) in comparison with a retrospective fusion of SPECT and high-resolution CT and a side-by-side analysis for lesion localisation in patients with neuroendocrine tumours. Twenty-seven patients were examined by multidetector CT. Additionally, as part of somatostatin receptor scintigraphy (SRS), an integrated SPECT–CT was performed. SPECT and CT data were fused using software with a registration algorithm based on normalised mutual information. The reliability of the topographic assignment of lesions in SPECT–CT, retrospective fusion and side-by-side analysis was evaluated by two blinded readers. Two patients were not enrolled in the final analysis because of misregistrations in the retrospective fusion. Eighty-seven foci were included in the analysis. For the anatomical assignment of foci, SPECT–CT and retrospective fusion revealed overall accuracies of 91 and 94% (side-by-side analysis 86%). The correct identification of foci as lymph node manifestations (n=25) was more accurate by retrospective fusion (88%) than from SPECT–CT images (76%) or by side-by-side analysis (60%). Both modalities of image fusion appear to be well suited for the localisation of SRS foci and are superior to side-by-side analysis of non-fused images especially concerning lymph node manifestations.

Preoperative localization of parathyroid glands Use of MRI, scintigraphy, and image fusion

AIM Minimally invasive resection of hyperfunctional parathyroid glands is an alternative to open surgery. However, it requires a precise preoperative localization. This study evaluated the diagnostic use of magnetic resonance (MR) imaging, parathyroid scintigraphy, and consecutive image fusion. PATIENTS, METHODS 17 patients (9 women, 8 men; age: 29-72 years; mean: 51.2 years) with primary hyperparathyroidism were included. Examination by MRI used unenhanced T1- and T2-weighted sequences as well as contrast-enhanced T1-weighted sequences. (99m)Tc-MIBI scintigraphy consisted of planar and SPECT (single photon emission tomography) imaging techniques. In order to improve the anatomical localization of a scintigraphic focus, SPECT-data were fused with the corresponding MR-data using a modified version of the Express 5.0 software (Advanced Visual Systems, Waltham, MA). Results of image fusion were then compared to histopathology. RESULTS In 14/17 patients, a single parathyroid adenoma was found. There were 3 cases with hyperplastic glands. MRI detected 10 (71%), scintigraphy 12 (86%) adenomas. Both modalities detected 1/3 patients with hyperplasia. Image fusion improved the anatomical assignment of the 13 scintigraphic foci in five patients and was helpful in the interpretation of inconclusive MR-findings in two patients. CONCLUSIONS Both MRI and (99m)Tc-MIBI scintigraphy sensitively detect parathyroid adenomas but are less reliable in case of hyperplastic glands. In case of a scintigraphic focus, image fusion considerably improves its topographic assignment. Furthermore, it facilitates the evaluation of inconclusive MRI findings.

Magnetic resonance imaging of orbital tumors.

This contribution provides an overview of diseases of eye and orbit and their appearance on magnetic resonance imaging. In recent years the diagnosis of eye and orbit pathology has profited significantly from increasingly sophisticated technical developments in the field of tomographic methods. Due to the small size of the examination area the improvement in spatial resolution and soft tissue contrast leads to an increase in image quality. In most clinical questions concerning eye and orbit pathologies magnetic resonance imaging is superior to computed tomography and should be early performed.

Assessment of the vascularization of neuroendocrine tumors by stimulated acoustic emission of SH U 508A ultrasound contrast agent and color or power Doppler sonography.

RATIONALE AND OBJECTIVES To assess the vascularization of neuroendocrine tumors by stimulated acoustic emission (SAE) of SH U 508A during the blood pool phase in comparison with contrast-enhanced Doppler sonography. METHODS Thirty-six patients with neuroendocrine tumors received contrast-enhanced Doppler sonography and 21, an additional SAE. To classify tumor perfusion on Doppler sonography, a 4-step rating score was introduced: (1) no vessels (hypoperfusion); (2) one feeding or central vessel (hypoperfusion); (3) some vessels (hyperperfusion); and (4) disseminated vessels (hyperperfusion). In 36 patients, 1 pancreatic primary tumor, 33 liver metastases, 1 splenic metastasis, and 1 lymph node metastasis were examined. Results were correlated with biphasic spiral CT (n = 35) and angiography (n = 2). RESULTS Arterial-phase CT and digital subtraction angiography revealed 18 hyper- and 18 hypoperfused lesions. Contrast-enhanced Doppler correctly classified 15 of 18 patients (83%) with hyperperfused lesions as well as 16 of 18 (89%) hypoperfused tumors by applying the rating score. SAE correctly identified 4 of 9 hyperperfused lesions (44%), 2 were isoperfused compared with normal liver tissue (22%), and 3 were hypoperfused (33%). Of 12 hypoperfused lesions, 11 were classified correctly (92%), and 1 showed isoperfusion. Hence, the positive and negative predictive values for SAE were 80% and 69%, respectively. For contrast-enhanced Doppler sonography, positive and negative predictive values were 88% and 84%, respectively. CONCLUSIONS Blood pool SAE failed to determine subtle tumor perfusion correctly. The rating score for contrast-enhanced Doppler sonography characterized tumor perfusion with high accuracy. The use of a contrast agent significantly improved perfusion characterization.

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.

Diagnosis of IPA in HIV: the role of the chest X-ray and radiologist

The role of clinical information and chest film for the discrimination between invasive pulmonary aspergillosis (IPA) and its differential diagnoses in human immunodeficiency virus (HIV) infection was studied. The diagnostic performance of clinical information and chest film alone and in combination was studied for eight internists and eight radiologists with regular exposure to IPA patients. The multicenter case sample consisted of 25 patients with proven IPA and 25 with other pulmonary diseases typical for HIV. The cases were presented on a CD-ROM. Receiver operating characteristics (ROC) methodology was employed. With clinical information alone, internists achieved the highest diagnostic performance (area under curve/AUC=0.84). Viewing the chest films did not contribute to their performance (AUC=0.80, P=0.26). The radiologist’s performance on the basis of viewing the chest film (AUC=0.75) increased significantly (P=0.012) when clinical information (AUC=0.83) was supplied. IPA cases with characteristic radiological appearance were correctly identified in 90% with chest film. For radiologists with regular exposure to HIV patients, chest films hold relevant information and contribute to the determination in cases with characteristic radiological appearance. Overall and especially in cases with less characteristic radiological appearance, they have significant profit from full access to the clinical data. For internists with regular exposure to HIV patients, chest films do not provide information essential for the verification or differentiation of potential IPA.

Applications of specialized coils for high-resolution MRI on a whole-body scanner

To investigate the application of a mini-coil surface system for high-resolution MRI, 60 volunteers were examined in a 1.5-T whole-body scanner. Two replaceable probe heads were available: a circular 2.5-cm coil and a quadratic 5-cm coil, both of which were placed directly on the skin. The skin layers, Achilles tendon and finger joints were examined with the 2.5-cm coil and a FOV of 25 × 25 mm2. A matrix of 256 × 256 pixels resulted in a pixel size of 0.098 × 0.098 mm2. For imaging of the carpal tunnel, the 5-cm coil was used in transverse orientation. The FOV was 50 × 50 mm2 so that a matrix of 256 × 256 pixels led to a pixel size of 0.195 × 0.195 mm2. The resulting spatial resolution permitted visualization of the epidermis, dermis and subcutis, resulting in clear definition of anatomical detail of the musculoskeletal system. MRI measurement of skin-layer thickness did not correlate with histometric data (p<0.05). This discrepancy was due in part to shrinkage of the tumor specimen on histologic preparation. Other causes include the motion artifacts and the limited accuracy of determining thickness on the MRI display unit.

Einsatz hochauflösender bildgebender Schnittbildverfahren in der Diagnostik von Auge und Orbita

Die Schnittbildverfahren CT und insbesondere MRT sind aus der modernen Orbitadiagnostik nicht mehr wegzudenken. Insbesondere der Einsatz von Oberflächenspulen hat die MRT zur Methode der Wahl bei nahezu allen Fragestellungen im Bereich der Orbita gemacht. Bei der Wertung der MRT für die Orbitadiagnostik sind zwei Bereiche zu trennen, nämlich differentialdiagnostische Überlegungen und das Tumorstaging.Patienten mit Veränderungen im Bereich der Orbita, die von einem Ophthalmologen zur MRT überwiesen werden, haben häufig schon eine sonographische oder computertomographische Diagnostik durchlaufen, sodass die MRT zur Differentialdiagnose nur noch wenig beitragen muss. Durch die Möglichkeit der MRT, Schnittbilder in allen Raumebenen anzufertigen, ist die Zuordnung von orbitalen Prozessen zu einem Orbitakompartiment und damit die differentialdiagnostische Einordnung erheblich leichter und genauer als bei der transversalen CT. So ist z. B. die Zuordnung eines vergrößerten M. rectus inferior im transversalen CT-Bild erheblich schwerer als im koronaren MRT-Bild. Die MRT ist gegenüber der CT darüber hinaus im Vorteil, weil durch den höheren Weichteilkontrast Gewebeinformationen verfügbar sind, die eine Differenzierung verschiedener Pathologien erlaubt. Lediglich beim Nachweis von Kalk ist die CT der MRT überlegen, was beispielsweise bei Veränderungen des Sehnervs (Optikusscheidenmeningeom) wegweisend sein kann. Besonders hervorzuheben für die Bedeutung der MRT ist die Diagnostik der endokrinen Orbitopathie: Hier ist die MRT in der Lage, durch Messung bzw. Berechnung quantitativer Parameter eine Aussage über den Akuitätsgrad der Erkrankung abzugeben, was direkte Auswirkungen auf das therapeutische Procedere hat.Auf der anderen Seite ist bei einem bekannten Tumor das Tumorstaging vor Beginn einer Therapie von entscheidender Bedeutung, so z. B. bei präseptalen Tumoren, Bulbustumoren, aber auch sämtlichen retrobulbären Tumoren. Die MRT ermöglicht hier eine Weichteildifferenzierung, wie sie mit der CT nicht und mit der Sonographie nur zum Teil erreicht wird. Erst im Bereich der Orbitaspitze und bei knöchernen Veränderungen ist die CT der MRT meist überlegen.

Schnittbilddiagnostik von Orbitatumoren Teil 2: Extrakonales Kompartiment, subperiostales Kompartiment, Tränendrüse, Bulbus, präseptales Kompartiment

Das extrakonale Kompartiment nimmt innerhalb der Orbita nur einen kleinen Raum ein und liegt schlauchartig um den Muskelkonus herum. Eine geeignete Schichtebene für Prozesse dieses Kompartimentes ist die koronare, da hier die Abgrenzung zu den Augenmuskeln und der knöchernen Orbita am besten gelingt. Die Untersuchungstechnik für CT und MRT unterscheidet sich nicht von der Technik für das intrakonare Kompartiment.

Appearance of orbital diseases on MRI

ZusammenfassungDie vorliegende Arbeit gibt einen Überblick über die orbitalen Erkrankungen und deren Erscheinungsbild in der MRT. Die MRT hat sich in den letzten Jahren als bildgebendes Verfahren in der Diagnostik von Orbitaerkrankungen zunehmend etablieren können. Für die Untersuchung steht eine Auswahl unterschiedlicher Oberflächenspulen zur Verfügung. Die Wahl der Spule sollte entsprechend der Fragestellung und der Region erfolgen. Des Weiteren wird auf die Aussagekraft der verschiedenen Sequenzen und der Kontrastmittelgabe eingegangen.Abstract We provide an overview of diseases of the orbit and their MR imaging appearance. Over recent years MRI has become established in the diagnosis of orbit diseases. There is a selection of different surface coils for examination. The choice of surface coil depends on the clinical question and the anatomical region under consideration. In addition, the significance of the different sequences and the value of contrast medium administration are discussed.We provide an overview of diseases of the orbit and their MR imaging appearance. Over recent years MRI has become established in the diagnosis of orbit diseases. There is a selection of different surface coils for examination. The choice of surface coil depends on the clinical question and the anatomical region under consideration. In addition, the significance of the different sequences and the value of contrast medium administration are discussed.