Toshiyuki Gotoh

Magnetic resonance analysis of abnormal diaphragmatic motion in patients with emphysema

The purpose of this study was to quantitatively evaluate paradoxical diaphragmatic motion using magnetic resonance (MR) imaging. A total of 27 subjects were examined, including 12 normal young adults, six control individuals, and nine patients with emphysema. With subjects in the supine position, 30 sequential sagittal MR images of the entire right lung were obtained during tidal and deep slow breathing. Diaphragmatic movement between sequential images was estimated as the displacement area and the total diaphragmatic movement in a respiratory cycle was calculated. The paradoxical motion of the diaphragm, representing the inverted movement to increase or decrease lung area, since paradoxical movement ratio (Mpr=(total paradoxical diaphragmatic movement/total diaphragmatic movement)×100), was evaluated. In patients with emphysema, paradoxical diaphragmatic motion was observed on MR images during deep breathing. The mean Mpr in emphysematous patients during deep breathing was 10±4%, which was significantly higher than 0.5±0.2% in young adults (p<0.05), and 1.2±0.6% in aged-matched controls (p<0.05). The present results indicate that magnetic resonance images could be used to detect paradoxical diaphragmatic motion in patients with emphysema.

CT analysis of the effect of pirfenidone in patients with idiopathic pulmonary fibrosis

PURPOSE Pirfenidone is a new, anti-fibrotic drug used for the treatment of idiopathic pulmonary fibrosis (IPF). The aim of this study was to evaluate the utility of computed tomography (CT) in the imaging assessment of the response to pirfenidone therapy. MATERIALS AND METHODS Subjects were 78 patients with IPF who underwent CT on two occasions with one-year interval (38 consecutive patients treated with pirfenidone and 40 age-matched control). Changes in the fibrous lesion on sequential CTs were assessed as visual score by two radiologists. We measured the volume and change per year of fibrous pattern (F-pattern) quantitatively using a computer-aided system on sequential CTs. RESULTS The baseline vital capacity (%pred VC) was 74.0 ± 14.0% in the pirfenidone group and 74.6 ± 16.6% in controls (p=NS). Deterioration of respiratory status was defined as 10% or greater decline in %pred VC value after 12-month treatment. A significantly larger proportion of pirfenidone-treated patients showed stable respiratory status (21 of 38, 65.6%) than the control (15 of 40, 37.5%). The change in fibrous lesion was significantly smaller in the pirfenidone group than the control in both of visual score (p=0.006) and computer analysis (p<0.001). The decline in VC correlated significantly with the increase in fibrotic lesion (p<0.001). CONCLUSION CT can be used to assess pirfenidone-induced slowing of progression of pulmonary fibrosis.

Paradoxical motion of the hemidiaphragm in patients with emphysema.

The authors evaluate paradoxical diaphragmatic motion using magnetic resonance (MR) imaging in patients with emphysema. The subjects were 12 healthy volunteers and 10 male patients with moderate to severe air flow obstruction. With subjects in the supine position, 30 sequential sagittal images of the bilateral lungs were obtained during quiet and forced breathing using a 1.5T MR unit with a body coil. The sequence was single shot fast spin echo (SSFSE) with half Fourier transformation. Subtraction images were made from the original images (by subtracting a given image from the preceding image), which visualized the chest wall motion as white or black bands on the edge of the lung fields. The authors evaluated both the original and subtraction images. MR imaging showed abnormal hemidiaphragmatic motion during forced breathing: the ventral portion of the hemidiaphragm moved downward while the dorsal part moved upward like a seesaw in 6 patients. MR images also revealed abnormal ribcage motion; the ventral ribcage moved anteriorly when the hemidiaphragm moved upward in 7 patients. No abnormal motion was observed in healthy volunteers. MR is a noninvasive and useful tool for evaluating the asynchronous respiratory motion in patients with emphysema.

Correlation of lung parenchymal MR signal intensity with pulmonary function tests and quantitative computed tomography (CT) evaluation: a pilot study.

To evaluate the effect of ventilatory impairment on MR signal intensity of the lung parenchyma.

Influence of the distribution of emphysema on diaphragmatic motion in patients with chronic obstructive pulmonary disease.

PurposeWe investigated whether the distribution of emphysema on computed tomography (CT) images can affect chest wall motion in patients with chronic obstructive lung disease (COPD).Materials and methodsThe subjects were 35 male patients with COPD (age, 69.7 ± 6.2 years). The RA-950 (the ratio of lung volume under −950 HU to total lung volume on CT) was measured separately for the upper and lower halves of the lung. We analyzed the flatness of the diaphragm (Kdome) and its motion (ΔLappo) using dynamic magnetic resonance imaging. Paradoxical motion (Mpr) represented the ratio of the paradoxical diaphragmatic movement (downward or upward) when the lung area decreased or increased, respectively, to he total diaphragm movement (expressed as a percent). These parameters were analyzed in correlation with pulmonary function tests and St. George Respiratory Questionnaire (SGRQ) scores.ResultsThe RA-950 of the lower lung zone correlated significantly with the Kdome (P = 0.033), ΔLappo (P = 0.006), Mpr (%) (P = 0.001), forced expiratory volume at 1 s (% predicted; P < 0.001), and activity score of the SGRQ (p = 0.017). The RA-950 of the upper lung zone did not correlate with these parameters.ConclusionIn COPD patients, the distribution of emphysema on CT correlates with airflow obstruction and abnormal diaphragmatic motion.

Animated solid model of the lung constructed from unsynchronized MR sequential images

This work discusses a 4D lung reconstruction method from unsynchronized MR sequential images. The lung, differently from the heart, does not have its own muscles, turning impossible to see its real movements. The visualization of the lung in motion is an actual topic of research in medicine. CT (Computerized Tomography) can obtain spatio-temporal images of the heart by synchronizing with electrocardiographic waves. The FOV of the heart is small when compared to the lungs FOV. The lungs movement is not periodic and is susceptible to variations in the degree of respiration. Compared to CT, MR (Magnetic Resonance) imaging involves longer acquisition times and it is not possible to obtain instantaneous 3D images of the lung. For each slice, only one temporal sequence of 2D images can be obtained. However, methods using MR are preferable because they do not involve radiation. In this paper, based on unsynchronized MR images of the lung an animated B-Rep solid model of the lung is created. The 3D animation represents the lungs motion associated to one selected sequence of MR images. The proposed method can be divided in two parts. First, the lungs silhouettes moving in time are extracted by detecting the presence of a respiratory pattern on 2D spatio-temporal MR images. This approach enables us to determine the lungs silhouette for every frame, even on frames with obscure edges. The sequence of extracted lungs silhouettes are unsynchronized sagittal and coronal silhouettes. Using our algorithm it is possible to reconstruct a 3D lung starting from a silhouette of any type (coronal or sagittal) selected from any instant in time. A wire-frame model of the lung is created by composing coronal and sagittal planar silhouettes representing cross-sections. The silhouette composition is severely underconstrained. Many wire-frame models can be created from the observed sequences of silhouettes in time. Finally, a B-Rep solid model is created using a meshing algorithm. Using the B-Rep solid model the volume in time for the right and left lungs were calculated. It was possible to recognize several characteristics of the 3D real right and left lungs in the shaded model.

Pneumothorax and idiopathic pulmonary fibrosis

PurposeWe evaluated the relation between the severity of idiopathic pulmonary fibrosis (IPF) and the incidence of pneumothorax on computed tomography (CT) images.Materials and methodsIn this retrospective study, we evaluated the presence of pneumothorax in 56 consecutive patients who died of IPF from the initial CT to death. We quantitatively analyzed a total of 207 CT images and measured the volume of the normal pattern (N-pattern) and each lesion pattern on the initial CT and their serial changes. The effects of pneumothorax and clinical and CT features on survival were evaluated using Cox regression analysis.ResultsPneumothorax occurred in 17 of 56 patients. Comparison of the pneumothorax (+) and (-) groups showed the initial vital capacity (VC) was lower (P = 0.005) and the follow-up period was shorter (P = 0.03) in the former group. The decrease in the N-pattern volume in the pneumothorax(+) group was significantly faster than in the pneumothorax(-) group (P = 0.013). Cox regression analyses identified a rapid decrease in N-pattern volume (P = 0.008) and a rapid decrease in VC (P = 0.002), but not pneumothorax, as significant predictors of poor survival.ConclusionPneumothorax in IPF patients is associated with lower VC and rapid deterioration of CT findings. The findings suggest that pneumothorax is a complication of advanced IPF.

Registration of temporal sequences of coronal and sagittal MR images through respiratory patterns

Abstract This work discusses the determination of the breathing patterns in time sequence of images obtained from magnetic resonance (MR) and their use in the temporal registration of coronal and sagittal images. The registration is made without the use of any triggering information and any special gas to enhance the contrast. The temporal sequences of images are acquired in free breathing. The real movement of the lung has never been seen directly, as it is totally dependent on its surrounding muscles and collapses without them. The visualization of the lung in motion is an actual topic of research in medicine. The lung movement is not periodic and it is susceptible to variations in the degree of respiration. Compared to computerized tomography (CT), MR imaging involves longer acquisition times and it is preferable because it does not involve radiation. As coronal and sagittal sequences of images are orthogonal to each other, their intersection corresponds to a segment in the three-dimensional space. The registration is based on the analysis of this intersection segment. A time sequence of this intersection segment can be stacked, defining a two-dimension spatio-temporal (2DST) image. The algorithm proposed in this work can detect asynchronous movements of the internal lung structures and lung surrounding organs. It is assumed that the diaphragmatic movement is the principal movement and all the lung structures move almost synchronously. The synchronization is performed through a pattern named respiratory function. This pattern is obtained by processing a 2DST image. An interval Hough transform algorithm searches for synchronized movements with the respiratory function. A greedy active contour algorithm adjusts small discrepancies originated by asynchronous movements in the respiratory patterns. The output is a set of respiratory patterns. Finally, the composition of coronal and sagittal image pairs that are in the same breathing phase is realized by comparing of respiratory patterns originated from diaphragmatic and upper boundary surfaces. When available, the respiratory patterns associated to lung internal structures are also used. The results of the proposed method are compared with the pixel-by-pixel comparison method. The proposed method increases the number of registered pairs representing composed images and allows an easy check of the breathing phase.

Line clustering with vanishing point and vanishing line

In conventional methods for detecting vanishing points and vanishing lines, the observed feature points are clustered into collections which represent different lines. The multiple lines are then detected and the vanishing points are detected as cross points of those lines. The vanishing line is then detected based on the cross points. However, for the purpose of optimization, these processes should be integrated and achieved simultaneously. In the present paper, we assume that the observed noise for the feature points is a two-dimensional Gaussian noise. And we define the likelihood function including obviously vanishing point and vanishing line parameters based on a Gaussian mixture density model. As a result the described simultaneous detection can be formulated as a maximum likelihood estimation problem. In addition, an iterative computation method for achieving this estimation is proposed based on the EM algorithm. The proposed method involves new techniques by which stable convergence is achieved and the computational cost is reduced. The effectiveness of the proposed method including these techniques can be confirmed by some experiments.

An algorithm for an eye tracking system with self-calibration

This paper proposes a simple and highly accurate eye tracking system. The eye image is observed by a system, such as an infrared eye tracking system, where the relative position between the head and the camera is kept invariant. Calibration where the examinee is instructed to gaze at a particular marker is avoided, and the calibration is executed automatically using only the input time sequence images. In the eye image, when the relative position to the camera is kept invariant, two queues exist to estimate the eye direction, which are the center coordinate and the flatness of the pupil. There are problems in the accuracy and the stability of the detection in the flatness data, however, although the absolute direction can be estimated. In the study, the eye direction is estimated as follows. The flatness is estimated by using multiple images. The eye parameters, such as the radius and the center of the eye rotation, are corrected, and the eye direction is estimated with stability. An evaluation experiment used actual eye images, and it was found that a more accurate measurement is realized, compared to the estimation of the eye direction based on flatness. Thus, the usefulness of the proposed method is demonstrated.