[en] The development of coalition techniques has a high computational cost and they demand, for the use that is given of them, excellent results. This work compares the application of two retro-projection techniques (projection of maximum intensity and average) for the sinograms obtainment, which will be used as analytic tool inside the procedure, together with a couple of correlation methods that they allow to unite two images of the same type; these results constitute the main material of the proposed automatic coalition of images. This procedure doesn't require the use of external markers, neither of corporal markers. The essential principles applied in this article have been previously used in the fusion of images

[en] The invention has been aimed at performing the optoelectronic scanning of the secondary screen of the X-ray image intensifier in such a way that light-sensitive sensors of improved sensitivity-time-behaviour and most suitable for digital processing of image signals can be used

[en] The possibilities of CT image modification which had existed so far for given matrix of attenuation values (window setting, highlighting, black-and-white or colour reversal and logarithmic distortion of the video signal) are supplemented by the method of attenuation value transformation. As a specific case a linear interval by interval attenuation value transformation is described. First of all, the intirety of the measured CT values is transformed into the corresponding CT quotients (CTQ) and then subdivided into 5 optional intervals. Each one freely selected CTQ value can be allocated to the first and to the last interval; the intermediate 3 intervals can be linearly transformed at random. The article discusses the influence of such a manipulation on CT image reproduction; this is of particular importance for the image visualisation of the results of quantitative organ analyses by means of computed tomography. The presented paper also points to the possibility of effecting further attenuation value transformations. (orig.)

No abstract available

[en] Half pulse excitation plays an important role in imaging with ultra-short echo times (UTE imaging) of the order of TE<100 μs. Based on half RF-pulses this method was theoretically modeled and experimentally applied in 1991 for the first time. Following this work, measurements of slice profiles produced by half pulses were performed and results were compared to the slice profiles produced by the original full pulse. Furthermore, the hypothesis was tested that short RF pulses may be of advantage in minimizing the relaxation effects during the pulse. Within the scope of these measurements no dependency of slice profile on the pulse duration could be found. (orig.)

[en] Purpose: Fusing information from multiple correlated realizations (e.g., 4DCT) can improve image quality. This process often involves ill-conditioned and asymmetric nonlinear registration and the proper selection of a reference image is important. This work proposes to examine post-registration variation indirectly for such selection, and develops further insights to reduce the number of cross-registrations needed. Methods: We consider each individual scan as a noisy point in the vicinity of an image manifold, related by motion. Nonrigid registration “transports” a scan along the manifold to the reference neighborhood, and the residual is a surrogate for local variation. To test this conjecture, 10 thoracic scans from the same session were reconstructed from a recently developed low-dose helical 4DCT protocol. Pairwise registration was repeated bi-directionally (81 times) and fusion was performed with each candidate reference. The fused image quality was assessed with SNR and CNR. Registration residuals in SSD, harmonic energy, and deformation Jacobian behavior were examined. The semi-symmetry is further utilized to reduce the number of registration needed. Results: The comparison of image quality between single image and fused ones identified reduction of local intensity variance as the major contributor of image quality, boosting SNR and CNR by 5 to 7 folds. This observation further suggests the criticality of good agreement across post-registration images. Triangle inequality on the SSD metric provides a proficient upper-bound and surrogate on such disagreement. Empirical observation also confirms that fused images with high residual SSD have lower SNR and CNR than the ones with low or intermediate SSDs. Registration SSD is structurally close enough to symmetry for reduced computation. Conclusion: Registration residual is shown to be a good predictor of post-fusion image quality and can be used to identify good reference centers. Semi-symmetry of the registration residual further reduces computation cost. Supported by in part by NIH R01 CA096679

[en] A new multi-modality imaging tool is under development in the framework of the INSERT (Integrated SPECT/MRI for Enhanced Stratification in Radio-chemo Therapy) project, supported by the European Community. The final goal is to develop a custom SPECT apparatus that can be used as an insert for commercially available MRI systems. INSERT is expected to offer more effective and earlier diagnosis with potentially better outcome in survival for the treatment of brain tumors, primarily glioma. Two SPECT prototypes are being developed, one dedicated to preclinical imaging (7 and 9.4 T), the second one dedicated to clinical imaging (3 T).

[en] Purpose: detection of metastasis in the whole body is important for sufficient the staging of malignant melanoma. Sufficient imaging of the brain is particularly important. Although there is evidence that clinical examination is not sufficient for prediction of cerebral metastasis, MRI scan is not always regarded as reasonable in neurological asymptomatic patients. Therefore, we explored the incidence of cerebral metastasis in our patient population in relation to the stage of disease to estimate the reasonability of this examination. Materials and methods: 120 consecutive patients with malignant melanoma were retrospectively evaluated. All patients were neurologically without pathological findings and received routine staging by cranial MRI. The incidence of brain metastasis was evaluated. The examination protocol consisted of an axial orientated flair and a T1 sequence. Ten minutes after administration of contrast agent, a T1 sequence in axial and coronal orientation was performed using the magnetization transfer technique. The type of melanoma, the thickness of the tumor, the Clark level, the location of the primary tumor, and the clinical stage were recorded from the clinical records. Results: 15 (12.5%) of the 120 patients (clinical stage I: 27 patients, stage II: 29 patients, stage III: 25 patients, stage IV: 39 patients) had cerebral metastasis in MRI. 14 patients were in stage III or IV at this time. Consequently 21.8% of the patients in stage III and IV had cerebral metastasis. Only one patient in stage He had cerebral metastasis. (orig.)

[en] The primary aim of this dissertation was to investigate the possibilities of developing a clinically useful imaging device to be used in nuclear medicine and based on the principles of coded-aperture imaging. At the onset of this research the field of coded-aperture imaging was in its infancy. Since that time many investigators other than this author have studied the technique in detail. Some of their results have proven successful and some have not, but all have contributed to the basic knowledge of coded-apertures. In this dissertation, two forms of coded-apertures were investigated, the on-axis Fresnel zone plate and the pseudo-random pinhole array. Important innovations in each of the two systems are reported along with detail analysis of system performance

[en] In recent years continuous advancements in software and hardware technology of modern MRI systems have contributed to substantial progress in the field of pancreatic tumor imaging. Despite technical advances in abdominal MRI, multislice CT still remains the preferential diagnostic tool for pancreatic lesions. In the majority of cases the essential clinical questions can thereby be answered with a high degree of accuracy. However, in dilemma cases state-of-the-art MR imaging can provide relevant information for the diagnosis allowing an optimal therapeutic concept. This report gives an overview on possible applications for MRI in the diagnostic evaluation of malignant pancreatic tumors. (orig.)