Artificial intelligence (AI) systems for diagnostic assistance in medical imaging are being researched and developed for main diagnostic imaging areas, such as magnetic resonance imaging and computed tomography imaging. These fields have a large number of examinations, and sufficient training data can be obtained for AI training. However, it may be challenging to collect sufficient training data to train AI in some minor areas, such as cystoscopy. In such cases, pre-trained AI models, which are pre-trained on a large, general-purpose image database based on real images, are often used. However, such large image databases containing real images are subject to copyright issues because the images are collected from the Internet, and mislabeling issues arise because annotation is performed manually. When building AI for medical images, the transparency of the training data is more important, and such problems are undesirable for the pre-training data used to build AI for diagnostic support. Therefore, this study proposed a new pre-training method based on automatically generated image databases to train the AI as a pre-training method that does not rely on real images in developing a diagnostic AI system for cystoscopic images. The objective was to build a diagnostic support system with a classification performance equivalent to that of expert urologists. Proposed method mixed two types of formula-driven image databases with the texture and contour features inspired by cystoscopic images. In the conducted experiments, the effectiveness of proposed method was verified for the classification of cystoscopic images.
Computer-aided diagnosis (CAD) has gained considerable attention for breast cancer screening owing to its high diagnostic efficiency and satisfactory accuracy. However, it has been revealed that traditional CAD systems for mammography are vulnerable to dense breast tissue, which could hide underlying tumors. To resolve this issue, we devised a learning scheme that equips the U-Net backbone with a well-designed attention mechanism to suppress the over-detection rate for nongland mammary regions in dense breast tissue and applied to the CAD for breast ultrasound (BUS) images. The proposed method has two stages: initial mammary gland segmentation, which involves the selection of a region in the mammary gland where a tumor may occur; then tumor region segmentation, wherein the attention U-Net detects tumor regions by characterizing the selected mammary gland probability map as a spatial attention map, drawing selective attention to mammary gland tissues. We evaluated the proposed tumor detection scheme on several public BUS image datasets. Comparative results demonstrate that the proposed approach achieves the best performance in most conditions. Notably, when considering the percentage of all actual tumors that were correctly segmented, the proposed method showed a tumorwise accuracy performance of 92.7%.
Convolutional neural networks (CNNs) can effectively detect objects in satellite images. They use a large number of labeled samples for training appropriate feature extractor. However, creating labels requires significant concentration and increases the workload of users, because satellite images cover quite large areas relative to the scale of the objects. We propose a human cooperative semi-self-training (SST) framework to reduce users' burden for training a CNN. The SST cooperatively collects training samples from unlabeled samples by repeating the following two phases: self-training and user intervention. The self-training automatically constructs the training dataset and trains the CNN, while the user intervention expands the number of accurately labeled samples. Notably, the SST requests users to label samples only if the automatic training stagnates. We improve the self-training phase to reduce the frequency of user intervention through the following two modules: intelligent dataset construction and pre-training. The intelligent dataset construction module automatically collects only effective training samples based on automatic labeling and evaluation of the collected samples utilizing tentatively trained CNN, while the pre-training module facilitates training of feature extractor in the CNN by allowing the CNN to learn handcrafted image features. Introducing the pre-training module into the dataset construction can effectively improve the self-training because the quality of the automatic labeling based on the pre-trained CNN can be enhanced. The experimental results demonstrated that the CNN trained by the proposed method yielded 92% of performance with only 2.6% of the labeled samples relative to the model trained with the complete dataset.
This paper proposes a content-based image retrieval method for optical colonoscopy images that can find images similar to ones being diagnosed. Optical colonoscopy is a method of direct observation for colons and rectums to diagnose bowel diseases. It is the most common procedure for screening, surveillance and treatment. However, diagnostic accuracy for intractable inflammatory bowel diseases, such as ulcerative colitis (UC), is highly dependent on the experience and knowledge of the medical doctor, because there is considerable variety in the appearances of colonic mucosa within inflammations with UC. In order to solve this issue, this paper proposes a content-based image retrieval method based on image recognition techniques. The proposed retrieval method can find similar images from a database of images diagnosed as UC, and can potentially furnish the medical records associated with the retrieved images to assist the UC diagnosis. Within the proposed method, color histogram features and higher order local auto-correlation (HLAC) features are adopted to represent the color information and geometrical information of optical colonoscopy images, respectively. Moreover, considering various characteristics of UC colonoscopy images, such as vascular patterns and the roughness of the colonic mucosa, we also propose an image enhancement method to highlight the appearances of colonic mucosa in UC. In an experiment using 161 UC images from 32 patients, we demonstrate that our method improves the accuracy of retrieving similar UC images.
Although a number of factors relating to lithography and material stacking have been investigated to realize hotspot-free wafer images, hotspots are often still found on wafers. For the 22-nm technology node and beyond, the detection and repair of hotspots with lithography simulation models is extremely time-consuming. Thus, hotspots represent a critical problem that not only causes delays to process development but also represents lost business opportunities. In order to solve the time-consumption problem of hotspots, this paper proposes a new method of hotspot prevention and detection using an image recognition technique based on higher-order local autocorrelation, which is adopted to extract geometrical features from a layout pattern. To prevent hotspots, our method can generate proper verification patterns to cover the pattern variations within a chip layout to optimize the lithography conditions. Moreover, our method can realize fast hotspot detection without lithography simulation models. Obtained experimental results for hotspot prevention indicated excellent performance in terms of the similarity between generated proposed patterns and the original chip layout patterns, both geometrically and optically. Moreover, the proposed hotspot detection method could achieve turn-around time reductions of >95% for just one CPU, compared to the conventional simulation-based approach, without accuracy losses.
Although lithography conditions, such as NA, illumination condition, resolution enhancement technique (RET), and
material stack on wafer, have been determined to obtain hotspot-free wafer images, hotspots are still often found on
wafers. This is because the lithography conditions are optimized with a limited variety of patterns. For 40 nm technology
node and beyond, it becomes a critical issue causing not only the delay of process development but also the opportunity
loss of the business. One of the easiest ways to avoid unpredictable hotspots is to verify an enormous variety of patterns
in advance. This, however, is time consuming and cost inefficient.
This paper proposes a new method to create a group of patterns to cover pattern variations in a chip layout based on
Higher-Order Local Autocorrelation (HLAC), which consists of two phases. The first one is the "analyzing phase" and
the second is the "generating phase". In the analyzing phase, geometrical features are extracted from actual layouts using
the HLAC technique. Those extracted features are statistically analyzed and define the "feature space". In the generating
phase, a group of patterns representing actual layout features are generated by correlating the feature space and the
process margin. By verifying the proposed generated patterns, the lithography conditions can be optimized efficiently
and the number of hotspots dramatically reduced.
Below 40nm design node, systematic variation due to lithography must be taken into consideration during
the early stage of design.
So far, litho-aware design using lithography simulation models has been widely applied to assure that
designs are printed on silicon without any error.
However, the lithography simulation approach is very time consuming, and under time-to-market pressure,
repetitive redesign by this approach may result in the missing of the market window.
This paper proposes a fast hotspot detection support method by flexible and intelligent vision system image
pattern recognition based on Higher-Order Local Autocorrelation.
Our method learns the geometrical properties of the given design data without any defects as normal
patterns, and automatically detects the design patterns with hotspots from the test data as abnormal patterns.
The Higher-Order Local Autocorrelation method can extract features from the graphic image of design
pattern, and computational cost of the extraction is constant regardless of the number of design pattern
polygons.
This approach can reduce turnaround time (TAT) dramatically only on 1CPU, compared with the
conventional simulation-based approach, and by distributed processing, this has proven to deliver linear
scalability with each additional CPU.
SRAF (Sub Resolution Assist Feature) technique has been widely used for DOF enhancement. Below 40nm design
node, even in the case of using the SRAF technique, the resolution limit is approached due to the use of hyper NA
imaging or low k1 lithography conditions especially for the contact layer. As a result, complex layout patterns or random
patterns like logic data or intermediate pitch patterns become increasingly sensitive to photo-resist pattern fidelity. This
means that the need for more accurate resolution technique is increasing in order to cope with lithographic patterning
fidelity issues in low k1 lithography conditions. To face with these issues, new SRAF technique like model based SRAF
using an interference map or inverse lithography technique has been proposed. But these approaches don't have enough
assurance for accuracy or performance, because the ideal mask generated by these techniques is lost when switching to a
manufacturable mask with Manhattan structures. As a result it might be very hard to put these things into practice and
production flow.
In this paper, we propose the novel method for extremely accurate SRAF placement using an adaptive search algorithm.
In this method, the initial position of SRAF is generated by the traditional SRAF placement such as rule based SRAF,
and it is adjusted by adaptive algorithm using the evaluation of lithography simulation. This method has three advantages
which are preciseness, efficiency and industrial applicability. That is, firstly, the lithography simulation uses actual
computational model considering process window, thus our proposed method can precisely adjust the SRAF positions,
and consequently we can acquire the best SRAF positions. Secondly, because our adaptive algorithm is based on optimal
gradient method, which is very simple algorithm and rectilinear search, the SRAF positions can be adjusted with high
efficiency. Thirdly, our proposed method, which utilizes the traditional SRAF placement, is easy to be utilized in the
established workflow. These advantages make it possible to give the traditional SRAF placement a new breath of life for
low k1.
This paper proposes an approach to improving pattern extraction efficiency for character projection lithography
(CPL). CPL is a promising technology for electron beam direct-write lithography. The advantage of CPL is
the reduced number of electron beam (EB) shots compared to conventional variably-shaped beam lithography,
because character patterns that frequently appear within a layout can be simultaneously written by a single EB
shot with a CP aperture mask. This means that it is important to extract frequently-used character patterns
and prepare CP aperture masks in order to reduce the number of EB shots. However, with random logic devices,
each character pattern is subject to being deformed into many different patterns that have complicated optical
proximity correction (OPC) features, which cannot be extracted as a unique CP aperture mask. In order to
overcome this problem, we propose a method of improving the efficiency of pattern extraction for CPL with
random logic devices by employing OPC optimization. Our proposed method can reduce the variety in the
deformed patterns with two developed cell-based algorithms: (1) a cell grouping algorithm that categorizes
differentiated cells and extracts some typical cell groups, and (2) an OPC optimization algorithm that regards
the cells in a group as one typical cell and corrects for the OPC features of a typical cell to form a CP aperture
mask. In conducted experiments, we successfully achieved a 30% improvement in extraction efficiency.
This paper proposes a new approach to optical proximity correction (OPC) using an adjustable OPCed cell and genetic algorithms (GA) to achieve optimal OPC feature generation for the full-chip area at fast operational speeds. GA is an efficient optimization technique based on population genetics. In this new approach, an adjustable OPCed cell consists of two parts. The first part is the original design data. The second part consists of two kinds of OPC features. The first kind is referred to as "fixed features", which include OPC feature data from a conventional OPC technique. The second kind, named "adjustable features", are located in the peripheral regions of the cell and include adjustable OPC variables. As the values of these variables are greatly influenced by neighboring cell patterns, the variables are quickly optimized by the GA after chip layout. The effectiveness of this approach, in terms of reduced times for accurate simulations and repeated modification of OPCed features, is demonstrated through computational experiments.
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