Aims Identifying the manufacturer and the type of cardiac implantable electronic devices (CIEDs) is important in emergent clinical settings. Recent studies have illustrated that artificial neural network models can successfully recognize CIEDs from chest X‐ray images. However, all existing methods require a vast amount of medical data to train the classification model. Here, we have proposed a novel method to retrieve an identical CIED image from an image database by employing the feature point matching algorithm. Methods and results A total of 653 unique X‐ray images from 456 patients who visited our pacemaker clinic between April 2012 and August 2020 were collected. The device images were manually square‐shaped, and was thereafter resized to 224 × 224 pixels. A scale‐invariant feature transform (SIFT) algorithm was used to extract the keypoints from the query image and reference images. Paired feature points were selected via brute‐force matching, and the average Euclidean distance was calculated. The image with the shortest average distance was defined as the most similar image. The classification performance was indicated by accuracy, precision, recall, and F1‐score for detecting the manufacturers and model groups, respectively. The average accuracy, precision, recall, and F‐1 score for the manufacturer classification were 97.0%, 0.97, 0.96, and 0.96, respectively. For the model classification task, the average accuracy, precision, recall, and F‐1 score were 93.2%, 0.94, 0.92, and 0.93, respectively, all of which were higher than those of the previously reported machine learning models. Conclusion Feature point matching is useful for identifying CIEDs from X‐ray images.

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A 77-year-old man with symptoms of chest pain was diagnosed with immunoglobulin G4 (IgG4)-related disease. Fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) revealed an intense uptake in the submandibular gland, lymph nodes and abdominal aortic wall. Diffusion-weighted imaging with background body signal suppression (DWIBS) revealed signal enhancements at the same location as those of the FDG-PET/CT findings. The DWIBS signal intensity decreased after steroid treatment, so we decreased the steroid dosage. Relapse did not occur. DWIBS makes it possible to adjust the medicine dosage while confirming the therapeutic effects and will likely be a useful method for monitoring IgG4related disease.

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