Koichi Ogawa

Prognostic factors influencing relapse of squamous cell carcinoma of the maxillary sinus

In 95 surgically staged patients with squamous cell carcinoma of the maxillary sinus, multivariate regression analyses were employed to identify prognostic factors. Possible prognostic factors for local control were TNM stage and type of surgical procedures: T2 or T3 tumors and use of total maxillectomy showed better local control rates (P < 0.01). High radiation doses of 40 Gy or more also seemed to be of prognostic significance: P < 0.2 for 40 to 60 Gy, and P < 0.1 for 60 Gy or more. The risk of cervical relapse increased when the cheek or alveolus was grossly involved (P < 0.2). However, since cervical relapse frequently accompanied uncontrollable primary recurrence or distant spread, and since cervical relapse alone was frequently salvaged by radical neck dissection, prophylactic irradiation to the neck is not recommended. Sex, age, nodal state, addition of chemotherapy, total doses of bleomycin or 5‐fluorouracil (5‐FU), or intra‐arterial administration of chemotherapeutic agents did not appear to be of prognostic significance.

ATTENUATION CORRECTION METHOD FOR SINGLE-PHOTON EMISSION CT WITHOUT ANY ADDITIONAL DATA COLLECTION.

This paper considers the single-photon emission CT (SPECT) for the object containing a large spatial variation of g-ray absorption distribution, and proposes a new correction method for the effect of attenuation. In the past correction of the image degradation by attenuation in the SPECT source distribution image, it is necessary to have an a priori knowledge about the attenuation distribution within the object. However, it should be noted that the emission data measured on the opposite side are not the same when the object has attenuation. By utilizing this property, it seems possible to acquire both the source distribution and the attenuation distribution from the measured emission data. The proposed method is based on this idea, and while estimating in parallel the source distribution and the attenuation distribution from the emission data, makes a correction of the source distribution using the attenuation distribution. A practical and clinical application of the method is expected. As a result of numerical simulation, it was verified that the proposed method is effective even when the emission data contain a noise of the level usually observed in a clinical situation.

Clinical application of a magneto-optical disk image filing system/image save and carry (ISAC) system

We propose the utilization of portable magneto optical disks for image filing. The main problems in PACS are the need for a high-speed local area network (LAN) and a large mass storage device. An image filing system--image save and carry (ISAC)--is one solution for these problems in present PACS and requires minimal additional hardware and cost for the installation. Whenever a patient is examined, the clerk carries the medical record and the ISAC magneto-optical disk for recording image data, and after inspection records the image data into the magneto-optical disk. We investigated the number of image retrievals done for inpatients and outpatients in 1988 at our radiation therapy department. The data storage requirements were on the average 18.5 MB for outpatients and 173.9 MB for inpatients. An ISAC display console needs also an easy-to-use man/machine interface for specifying images and image display characteristics in order to realize the ISAC system.

Clinical Application Of A Magneto-optical Disk Image Filing System A Prototype Of Ct Image Management System

We propose the utilization of portable magneto optical disks for image filing. The main problems in PACS are the need

CORRECTION METHOD FOR COLLIMATOR EFFECT OF ECT.

One of the factors in the deterioration of the reconstructed image of the single-photon emission CT (SPECT) is the respective characteristics of the collimator used in the detection of the γ-ray. The characteristics depend on the shape and material of the collimator, and produce shiftvariant blurs on the reconstructed image. This kind of error cannot be eliminated by the deconvolution, which regards the blur as shift-invariant. This paper discusses the effect in the spatial frequency domain, and it is shown that the effect of the blur by collimator can be approximated analytically by a shift-invariant blur on the annular ring determined for each frequency. A method of improving the quality of the reconstructed image is proposed utilizing this property. By the numerical simulation using a computer, it is verified that the proposed method is effective independently of the attenuation and quantization noise.

Regional adaptive histogram equalization using fuzzy sets

Contrast Limited Adaptive Histogram Equalization (CLAHE) which was developed to enhance regional contrast of an image was improved by using fuzzy sets. In the proposed method gray level transformation of each pixel is performed using each cumulative distribution function calculated from a histogram of pixel values in a contextual region of the target pixel. We optimized two parameters for making the cumulative distribution function that is size of contextual regions and a clipping level of the histogram for each pixel by using fuzzy logic. The results of simulation showed that the method not only yielded optimum contrast at any regions of an image but also reduced boundary artifacts appeared on images processed by a conventional CLAHE algorithm. 1.© (1990) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Longitudinal ECT imaging using Y‐ray camera

Single-photon emission CT is one of the most useful techniques in nuclear medicine, wherein a radioisotope material is injected into the body and by external detection of the radiated y-ray the RI distribution on an arbitrary layer (slice) is reconstructed from the data, permitting visual representation of physiological information. Longitudinal imaging is one of such techniques. The object is regarded as composed of layered RI distributions. From the y-ray projection data obtained by y-ray detectors placed parallel to the layer, the RI distribution at each slice is reconstructed. In longitudinal imaging, however, the projection data are observed only along a particular direction and the working range of the detector is restricted, leading to blur and degradation of the reconstructed image. This paper discusses the quality degradation inherent in longitudinal imaging and proposes a reconstruction algorithm which employs the contour information of the object in the reconstruction computation to make correction for the quality. The result of numerical simulation is also reported.