Research projects

本研究は、MRI・CT・超音波を用いて、フレイルの要因となる筋質・骨質を簡便かつ客観的に評価できる定量的画像バイオマーカーを確立し、臨床や健診で活用可能な指標として提供することを目的とする。これにより、各種疾患の病態把握、予後予測、治療方針決定、さらにはサルコペニアや脆弱性骨折の予防を通じて、健康寿命延伸と医療費削減への貢献を目指す。

本研究は、CTやMRIなどの医用画像から腫瘍の性質や変化を解析し、腫瘍内の再発しやすい部位を可視化する手法の開発を目的とする。さらに、その情報を放射線治療計画に活用し、患者ごとに最適な線量分布を設計することで、治療効果の向上と副作用の低減を目指す。これにより、個々の患者に応じた高精度な個別化放射線治療の実現に貢献する。

本研究では、MRIを用いて膵管の中を流れる膵液の速さと量を体に負担をかけずに調べる新しい方法を開発する。これまで膵液の機能評価には内視鏡など侵襲的な検査が必要であったが、本研究では画像から流れの情報と膵管の形の情報を組み合わせ、より簡便かつ安全に評価できるようにすることを目指す。これにより、慢性膵炎などの膵疾患の診断や病態の理解の向上に役立つことが期待される。

(1) Compared with conventional filtered back projection technique, iterative reconstruction improved the image quality of virtual monochromatic images derived from dual-energy CT data. (2) Virtual monochromatic images (at 70 keV) derived from dual-energy CT data had a higher quantitative image quality and more accurate CT values compared with conventional 120-kVp images. (3) Excellent correlation was observed between the coronary artery calcium (CAC) scores on the virtual unenhanced images (derived from dual-energy CT data) and conventional (true) noncontrast images. Thus, dual-energy coronary CT angiography could allow prediction of the true CAC scores, potentially reducing the total radiation exposure and image acquisition time by obviating the need for true noncontrast CAC scoring CT.

We confirmed that chest upright CT can be used in routine clinical practice. In asymptomatic volunteer cohort, while the inspiratory volumes of the bilateral upper and lower lobes and bilateral lungs were significantly greater in the standing than in the supine position, with lower lobes showing larger changes, the right middle lobe volume did not change significantly between positions. In patients with chronic obstructive pulmonary disease (COPD), whereas the inspiratory volumes of the bilateral upper and lower lobes and bilateral lungs were significantly greater in the standing position than in the supine position, the right middle lobe volume was significantly lower in the standing position than in the supine position. The total lung volume on upright CT in the standing position was more similar to total lung capacity on pulmonary function test than that in the supine position in both asymptomatic volunteer and COPD cohorts.

Using a new diagnostic modality, upright CT, we have shown that the anatomical structures of the whole body, including the head and neck, trunk, upper and lower limbs, are considerably different between the supine and standing positions in healthy volunteers. In addition, in diseases such as chronic obstructive pulmonary disease, scoliosis, knee osteoarthritis, and post-operative neurosurgery, in which symptoms differ between the supine and upright positions, we found that the morphology of the lesions or peri-lesion structures changed considerably between the supine and upright positions, and quantified the lesions or peri-lesion structures in the upright position. Furthermore, we found that various anatomical parameters in the upright CT correlated better with pulmonary function test results, cardiac catheterization results, and clinical findings than in the supine CT.

現在の通常のCTは臥位で撮影するため、ヒトの日常生活の状態(立位/座位) を反映しておらず、立位/座位での様々な病態を3次元的に画像化できていなかった。そこで我々は産学共同で320列立位CTを開発し、当施設に世界第１号機を導入した。これまでの初期検討により、立位と臥位で解剖学的構造や各種病態はかなり異なる事が分かった。この初期結果をふまえ、本研究では、新たな診断機器である立位CTを用いて、立位荷重下でより顕著となる加齢性変化や各種病態を画像的に解明しつつ、立位/座位での新たな疾患早期検出法の確立を目指す。そして立位CTによる早期診断により、超高齢社会における健康寿命の更なる延伸、生活の質の向上を目指す。

This study aimed to establish advanced lymphatic imaging techniques using MR lymphangiography (MRL), photoacoustic imaging (PAI), and upright CT. We developed a novel MRL-based severity classification of lymphedema and published it in an international journal. This system characterizes patterns of dermal backflow and lymphatic visualization based on anatomical region and clinical stage, showing significant correlations with disease severity and duration. It enables a more detailed assessment of individual pathology and supports optimal treatment planning. We also established an improved robust MRL protocol with reduced artifacts and applied MR thoracic ductography to manage refractory lymphatic leakage. Furthermore, comparative analyses of MRL and PAI clarified their complementary roles. Quantitative evaluation of fat tissue changes related to lymphedema was also conducted. These efforts contributed to the standardization of diagnostic approaches in lymphatic disease management.

In the era of health and longevity, we aimed to promote the early detection and elucidation of functional disorders. To achieve this, we conducted research on the mechanisms of three functions: swallowing, urination, and walking. For swallowing function, we had a specialized chair designed, and developed a protocol for scanning and established a method for this examination. For urination function, we established a scanning protocol, and clarified the mechanism of normal urination. Imaging of patient groups revealed three patterns of urination disorders (benign prostatic hyperplasia, bladder neck sclerosis, neurogenic bladder). Thus, evaluating urination function appears useful in devising treatment strategies. Concerning walking function, the relation with posture was deemed significant, and software for objectively evaluating posture was developed. Additionally, software capable of measuring muscle volume with a 5% margin of error was developed, deemed useful in predicting frailty.

これまでの医療の主な診断対象は生命寿命を規定する器質的疾患であったが、今後、機能性疾患を対象とした健康寿命の延伸の為の医療が重要になる。立位CTの導入により、姿勢・骨盤底の緩み・筋肉量など身体的フレイルの評価、立位で増悪する腰痛の診断・膝関節異常の早期発見・嚥下機能や排尿機能の評価など機能性障害の病態解明や早期診断が可能になる。また、放射線治療を座位の状態で行えればコストや設置面積を大幅に縮小できる。今回は、立位・座位で評価可能な人体の構造・機能を解明し、それに基づき、①身体的フレイルの評価、②機能性障害の病態解明と早期診断、③座位放射線治療の実現、の新たな診断・治療への有効性を明らかにする。

The aim of this study is to verify the non-inferiority of low-radiaton-dose coronary CT angiography (cCTA) reconstructed with iterative reconstruction (IR) methods, compared to conventional CTA reconstructed with filtered back projection (FBP) methods, in terms of short-term clinical outcomes. This is a multicenter randomized comparative trial involving domestic facilities, with 451 cases enrolled. In the interim analysis, no significant difference was observed in short-term prognostic outcomes between both imaging methods. Data collecting for the final analysis is underway.

A study was conducted to develop a method for generating individual human body models that can withstand use in dynamics analysis of body motion. A method was developed to construct an individual human body volume model using a CT image template from an individual's human skin shape obtained from a body scanner. Based on the obtained human body volume model, we also developed a method to identify the human body dynamics properties of an individual using the measurement data of standard movements as input. Furthermore, a whole-body musculoskeletal model of the human body was integrated into the system to estimate the degree of muscle activation during movement.

We planned to evaluate the flow in the peripheral pulmonary arteries (PA) with dual velocity-encoding (VENC) 4D Flow sequence for adapting to flow speed in the wide range. However, the measurement was inaccurate due to misregistration between two sequences with different VENC. As a next step, we applied 4D Flow with single VENC to measure the vortex duration (Tvx%) and compared it to the mean PA pressure (mPAP) derived from the right heart catheter on the patients with chronic thromboembolic pulmonary hypertension (CTEPH). There was a good correlation between Tvx% and mPAP. In the patients with large vortex and/or pulmonary regurgitation, the substantial difference was observed. In patients after the repair of tetralogy of Fallot, we found the substantial difference depending on the measuring plane. We recommend immediately above the pulmonary valve or peripheral in the main PA as the best location for measuring the regurgitation fraction of the pulmonary valve.

The 2D-PC is one of MRI techniques, which enables to measure the flow volume and velocity. In this study, we utilized 4D Flow which acquires flow information as a volume data in five minutes. The mean pulmonary arterial pressure was able to be estimated by measuring the duration of the vertices in the main pulmonary artery, exception of subjects with huge turbulence and/or marked regurgitation. The turbulence might be a cause of inaccuracy of the flow measurement. The observation of the flow pattern is indispensable to minimize the effect from the turbulence.

For fundamental analysis, we took 4D-CT to measure the flow velocity of vascular phantom. The measurements had a linear correlation to those taken by Doppler US, which helped to indicate potential use of 4D-CT in measuring flow velocity. In regards to clinical application, we evaluated the usefulness of 4D-CT in four clinical fields. In otolaryngology, 4D-CT provided quantitative data of the regurgitated area, which will enable the replacement of conventional X-ray and invasive laryngoscopy. In cardiology, 4D-CT data showed higher diagnostic accuracy compared to conventional CT for the evaluation of endoleak after vascular stentgraft, which will help to decrease the use of invasive angiography. In urology, 4D-CT scans taken during the bladder voiding process allows visualization and clarification of the cause of obstruction in patients with dysuria. In orthopedics, with 4D-CT we could achieve quantitative analysis of joint movement, which has been difficult using X-ray.