Registration and Summation of Respiratory-Gated or Breath-Hold PET Images Based on Deformation Estimation of Lung from CT Image

Lung motion due to respiration causes image degradation in medical imaging, especially in nuclear medicine which requires long acquisition times. We have developed a method for image correction between the respiratory-gated (RG) PET images in different respiration phases or breath-hold (BH) PET images in an inconsistent respiration phase. In the method, the RG or BH-PET images in different respiration phases are deformed under two criteria: similarity of the image intensity distribution and smoothness of the estimated motion vector field (MVF). However, only these criteria may cause unnatural motion estimation of lung. In this paper, assuming the use of a PET-CT scanner, we add another criterion that is the similarity for the motion direction estimated from inhalation and exhalation CT images. The proposed method was first applied to a numerical phantom XCAT with tumors and then applied to BH-PET image data for seven patients. The resultant tumor contrasts and the estimated motion vector fields were compared with those obtained by our previous method. Through those experiments we confirmed that the proposed method can provide an improved and more stable image quality for both RG and BH-PET images

Non-contact imaging of peripheral hemodynamics during cognitive and psychological stressors

Peripheral hemodynamics, measured via the blood volume pulse and vasomotion, provide a valuable way of monitoring physiological state. Camera imaging-based systems can be used to measure these peripheral signals without contact with the body, at distances of multiple meters. While researchers have paid attention to non-contact imaging photoplethysmography, the study of peripheral hemodynamics and the effect of autonomic nervous system activity on these signals has received less attention. Using a method, based on a tissue-like model of the skin, we extract melanin Cm and hemoglobin CHbO concentrations from videos of the hand and face and show that significant decreases in peripheral pulse signal power (by 36% +/- 29%) and vasomotion signal power (by 50% +/- 26%) occur during periods of cognitive and psychological stress. Via three experiments we show that similar results are achieved across different stimuli and regions of skin (face and hand). While changes in peripheral pulse and vasomotion power were significant the changes in pulse rate variability were less consistent across subjects and tasks

Deformable image registration between pathological images and MR image via an optical macro image

Computed tomography (CT) and magnetic resonance (MR) imaging have been widely used for visualizing the inside of the human body. However, in many cases, pathological diagnosis is conducted through a biopsy or resection of an organ to evaluate the condition of tissues as definitive diagnosis. To provide more advanced information onto CT or MR image, it is necessary to reveal the relationship between tissue information and image signals. We propose a registration scheme for a set of PT images of divided specimens and a 3D-MR image by reference to an optical macro image (OM image) captured by an optical camera. We conducted a fundamental study using a resected human brain after the death of a brain cancer patient. We constructed two kinds of registration processes using the OM image as the base for both registrations to make conversion parameters between the PT and MR images. The aligned PT images had shapes similar to the OM image. On the other hand, the extracted cross-sectional MR image was similar to the OM image. From these resultant conversion parameters, the corresponding region on the PT image could be searched and displayed when an arbitrary pixel on the MR image was selected. The relationship between the PT and MR images of the whole brain can be analyzed using the proposed method. We confirmed that same regions between the PT and MR images could be searched and displayed using resultant information obtained by the proposed method. In terms of the accuracy of proposed method, the TREs were 0.56 ± 0.39 mm and 0.87 ± 0.42 mm. We can analyze the relationship between tissue information and MR signals using the proposed method

Multiple-template matching for direct tracking of tumor mass

第102回日本医学物理学会学術大会 （第6回日韓医学物理学術合同大会（JKMP）、第11回アジア・オセアニア医学物理会議（AOCMP）

Accuracy improvement of Time delay correction method for PET-based tumor tracking

The world\u27s first open type PET, named OpenPET, is being developed at the National Institute Radiological Sciences. We are aiming to employ the OpenPET in radiotherapy and to track the respiratory motion of a tumor in the thoracoabdominal region of a patient. By using PET images, we expect that the tumor itself can be directly visualized without using radio-opaque markers. Our prototype OpenPET system can output reconstructed images at about 2 frames per second with about a 2 s delay; this delay is mainly due to the reconstruction calculation time. Therefore we presented a time delay correction method with belt type piezoelectric sensor for tumor tracking for the OpenPET with support vector regression method (SVR) in the last IEEE NSS-MIC meeting. In this paper, we improved accuracy of this method. In the modified method, we added body surface displacement velocity as a secondary independent variable of the regression line so that it represents hysteresis effect. In addition, to supplement SVR\u27s prediction posterior probability, we introduced hidden Markov model (HMM). As the result, the mean tracking error became within 3 mm.The 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference, and Room-Temperature Semiconductor X-Ray and Gamma-Ray Detectors worksho

Performance Evaluation of a Transformable Axial-Shift Type Single-Ring OpenPET

One of the challenging applications of PET is implementing it for in-beam PET, which is an in situ monitoring method for charged particle therapy. For this purpose, we have previously proposed two geometries for our open-type PET scanners named OpenPET. The original OpenPET had a physically opened field-of-view (FOV) between two detector rings through which irradiation beams pass. This dual-ring OpenPET (DROP) had a wide axial FOV including the gap. But, this geometry is not necessarily the most efficient for application to in-beam PET in which only a limited FOV around the irradiation field is required. Therefore, we proposed a single-ring OpenPET (SROP) geometry which can provide an accessible and observable open space with higher sensitivity and a reduced number of detectors compared to DROP. Also, we proposed two arrangement types, a slanted ellipse (SE) type where oval detector rings are slanted and stacked and an axial shift (AS) type where block detectors originally forming a conventional PET scanner are axially shifted little by little. Previously, we developed the SE-SROP prototype, and showed its good performance for in-beam PET. However, the SE-SROP decreased sensitivity slightly relative to the ring-type PET and needed a large gantry in the axial direction for conventional PET studies. On the other hand, AS-SROP can transform conventional ring-type PET scanners into stacked detectors with a gradual axial shift. In this work, we developed and evaluated a small AS-SROP prototype for proof-of-concept. The AS-SROP prototype was designed with 2 cylinder-shaped detector rings of 16 DOI detectors. The system sensitivity and spatial resolution were measured and were 5.1% and 2.6 mm, respectively, for the OpenPET mode. For the conventional PET mode, the system sensitivity and spatial resolution were 7.3% and 2.2 mm, respectively. We concluded that the AS-SROP geometry has a good potential for not only in-beam imaging but also conventional PET studies.The 2013 IEEE Nuclear Science Symposium and Medical Imaging Conference, and Room-Temperature Semiconductor X-Ray and Gamma-Ray Detectors worksho