In radiation therapy for glottic cancer, respiratory motion of larynx may change the dose variation in the target. The purpose of this study is to measure the respiratory motion of the larynx, and quantify the impact of the motion on the dose variation. This study included 10 patients treated by opposing portal irradiation for glottic cancer. We acquired fluoroscopy and respiratory waveform of the patients simultaneously and formulated the relationship between the displacement of larynx and the respiratory phase. We divided one field into 39 sub-fields on the basis of control points. Dose distributions accounting for the displacement were calculated by shifting isocenter calculated using the formula in every sub-fields. Dose variations of clinical target volume (CTV) were evaluated by subtracting dose distributions with displacement consideration and dose distributions without it. Average amplitude and the maximum amplitude of respiratory motion were 2.5 and 8.7 mm, respectively. Average of mean dose variation in CTV was 0.1% of the prescribed dose, and maximum of local dose variation was 2.0% of the prescribed dose. Hence, it is realized that dose variation in CTV by respiratory motion was slight.
In recent years, reports have been made that predict the state of aneurysm by performing computational fluid dynamics (CFD) analysis using cerebral aneurysm blood flow analysis software. However, analysis results are not constant and there are various opinions, and it is conceivable that the image quality and analysis conditions of medical images used for CFD analysis are not standardized. In this study, CFD analysis of cerebral aneurysm phantom was performed, and image quality and analysis conditions were standardized. Then, we investigated whether increase of cerebral aneurysm and prediction of rupture are possible. From this study, stable results of wall shear stress analysis were obtained under slice thickness 1.0 mm or less, CT value 400 HU or more, reconstruction function as soft part function, image SD under 10 HU. In addition, as the size of the cerebral aneurysm became larger, wall shear stress tended to be lower, and the same tendency was shown also in clinical cases. Although CFD analysis using software dedicated to blood flow analysis did not reach the prediction of rupture, it can be evaluated based on the quantitative values for the aneurysm increase at the preceding stage and plays an important role in prediction there is a possibility.
Countermeasures against respiratory movement are important for tumors of thorax and abdomen in stereotactic body radiation therapy. In the present paper, a web-camera-based-respiratory monitoring method without contact with patient’s body was proposed for respiratory study. Thoracic and abdominal motion images were taken by a web camera, and were analyzed using simple image-processing techniques for obtaining respiratory waveforms. Four motion images with different respiration rate were obtained from resusci anne simulator. Respiration waveforms were estimated from the moving images by the proposed method, and were compared with respiration waveforms obtained by the conventional respiratory monitoring device. That was found to have a strong correlation. In addition, the two waveforms were similar in Bland–Altman method comparison. The proposed method can provide non-contact, non-invasive, simple, and realistic respiratory monitoring system for radiotherapy.
The purpose of this study was to evaluate the degree of signal attenuation generated around the stent by the susceptibility artifacts and radiofrequency (RF) shielding in phase contrast-magnetic resonance angiography (PCA) images and construct optimal PCA imaging parameters for intracranial stent lumen images. The two types of PCA images of stents (Neuroform, Enterpraise II) placed in the vascular flow phantom were imaged with different the flip angle (FA) and echo time (TE). Each original image of the vascular flow phantom was reconstructed into a coronal multiplanar reconstruction (MPR) image and a profile curve along the long axis of the stent was calculated. The reduction of in-stent signal was assessed by relative in-stent signal (RIS) calculated by comparing intra-stent signal intensity to the reference tube in the original images. When the TE was 2.3 ms, the profile curve was the highest signal intensity. However, RIS had not changed by the extension of TE. When the FA was high, the RIS showed a high value, but when it exceeded 25 degrees, the signal attenuated in the distal part of the slab.
The susceptibility artifacts and RF shielding generated around the stent can be reduced by the shortest TbE (2.3 ms) and 20 degrees of FA in the PCA imaging.
We performed a basic evaluation for measuring the input function using a fan-beam collimator. Furthermore, we examined the validity of the brain blood flow quantitative measurement from the input function. Using the fanbeam collimator, we imaged syringes of various diameters containing 99 mTc as well as a virtual aorta inside a thoracic phantom. We changed the collimator distance and angle in relation to the sources, and the syringe was placed in vertical and horizontal positions as well. For evaluation, we used region of interest (ROI) of various sizes and positions. Furthermore, we conducted clinical evaluation for 19 subjects and calculated whole-brain mean cerebral blood flow using improved brain uptake ratio method by examination of 99 mTc-ECD cerebral blood flow. For ROIs smaller in size than diameter of the syringes and virtual ascending aorta, amount of change in the ROI counts by fan-beam collimator became smaller as distance to the source became closer, with less than 5% at 175 mm. Also, change with respect to angle of the collimator was less than 5% at 20°. In a clinical study, aortas could be imaged without truncation and input-functions could be measured in all 19 patients. By using ROIs smaller than the aorta diameter and placing the collimator close to the source, it was suggested that fan-beam collimator can be used to determine the input function.
The shape of the kinetic curve for gadobutrol is reportedly different compared with that for other conventional contrast agents. We speculate that the shape of gadobutrol kinetic curve may be influenced by different magnetic resonance imaging (MRI) protocols and evaluation methods. The purpose of our study was to assess the influence between gadobutrol and other conventional contrast agent (gadodiamide hydrate) on the kinetic curve in invasive ductal carcinoma (IDC). We assessed 139 women of IDC in this study. Gadodiamide hydrate (2 ml/s) was administered to 69 women, and gadobutrol (1 ml/s) was administrated to 70 women, both contrast agents at 0.1 mmol/kg BW. When the kinetic curves of contrast agents were evaluated between by Breast Imaging Reporting and Data System (BI-RADS) 4th edition and BI-RADS 5th edition, suggested that the analysis method of BI-RADS may affect. Patient group who were administered gadobutrol demonstrated a lower washout rate when compared with patient group who were administered gadodiamide hydrate administration (P<0.01). These results suggest that the kinetic curve characteristics of gadobutrol are an important consideration in diagnosis. Therefore, it is necessary to perform image diagnosis by considering the influence of the contrast agent and the analysis method, when image diagnostic doctor perform image diagnosis.
Purpose: Generally, non-contrast, lower-extremity, magnetic resonance angiography (MRA) uses electrocardiography; thus, examination is difficult in patients who exhibit arrhythmia. However, the use of electrocardiography can be avoided by using the selective excitation technique in non-electrocardiogram-gated three-dimensional time-of-flight (TOF) (pNon-Gate) MRA. Therefore, patients who exhibit arrhythmia can be examined with pNon-Gate MRA. The purpose of this study was to assess the usefulness of pNon-Gate MRA by using a whole-body coil. Methods: Images acquired using pNon-Gate MRA were compared with images acquired using electrocardiogram-gated two-dimensional TOF (Gate) MRA. Comparisons comprised visual evaluation, as well as comparisons of contrast-to-noise ratio and imaging time. Results: In visual evaluation of the pelvic region, Gate MRA showed better results than pNon-Gate MRA. In terms of contrast-to-noise ratio, there were no significant differences in either region. Imaging time showed no significant differences between the two methods. However, it exceeded 30 minutes frequently for Gate MRA, but rarely for pNon-Gate MRA. Conclusions: pNon-Gate MRA is useful in patients with frequent arrhythmia and in those with difficulty in maintaining long-term postures. By using a whole-body coil, pNon-Gate MRA enables easier patient positioning and setting. Therefore, pNon-Gate MRA can be used in routine examinations.
The purpose of this study was to analyze the native T1 value of myocardium and the relationship between myocardial native T1 value and gender, age and myocardial areas in Japanese. The subject of this study was 145 Japanese healthy subjects who underwent cardiac magnetic resonance imaging (MRI) at medical examination. MRI scanner was Ingenia 1.5T (Philips Healthcare, Best, The Netherlands). T1 mapping was acquired with modified look-locker inversion recovery method using IR pulse. The native T1 value of all subjects was 983.5±34.8 ms, and we were able to acquire the reference value of the native T1 value at our hospital. The native T1 value was significantly higher in females than in males. There was variation in native T1 value among the myocardial areas, and the native T1 value was significantly higher in the septum than in the lateral region. In the future, collaborative research in multicenter is necessary to obtain the reference value of Japanese.