Pixels In Region Of Interest Research Articles

A Dynamic Region-of-Interest Vision Tracking System Applied to the Real-Time Wing Kinematic Analysis of TetheredDrosophila

Tracking objects that move fast with respect to their size is challenging because it necessitates large field of views often incompatible with the required spatial and temporal resolutions. Here, we present a novel computer vision system that overcomes this tradeoff by employing a camera with dynamic region-of-interest (ROI) capabilities, combined with an efficient predictive approach. We apply this method to extract the wing kinematics of tethered flying fruit flies in real time. At each frame, only the pixels immediately surrounding the wing are exposed, and the wing position is extracted. It is then fed to an extended Kalman filter that extracts four key parameters of the measurement time-course and, therefore, provides real-time feedback of wing motion. Using this approach, we are able to sample the wing position of both wings at 7 kHz in a 2500 pixel ROI. Our methods promise new applications that can be implemented in general purpose digital hardware for high performance tracking and process control in a broad range of applications in technology and science.

TU-E-BRB-06: Results from Multiple Radiations of an Anthropomorphic Spine Phantom

Purpose: To credential institutions to participate in an IMRT‐dose painting spine metastasis protocol. Method and Materials: A mailable anthropomorphic spine phantom was developed and shipped to 21 institutions interested in participating in protocols sponsored by the National Cancer Institute (NCI). The phantom was a modification of the Radiological Physics Center's lung‐thorax phantom. An insert was designed to simulate a solid water spinal cord surrounded by a high impact polystyrene bone structure. An acrylic planning target volume is adjacent to the bone structure. The insert houses radiochromic film and TLD. The phantom also contains an esophagus, a heart and two lungs. Institutions were asked to image the phantom, create an IMRT plan to deliver 6 Gy to at least 90% of the PTV, perform their normal IMRT QA, and deliver the treatment plan to the phantom. The spinal cord dose was limited to 3.75 Gy to a volume of less than 0.35 cc and 2.63 Gy to a volume of less than 1.2 cc. The following criteria were applied: PTV TLD ±7%, ≥85% of the pixels in regions of interest in the axial and sagittal planes must pass a gamma criteria of 5%, 3 mm, and the plan must comply with the protocol. Results: 21 institutions irradiated the phantom 24 times. 8 of the irradiations failed the criteria. 4 of the failing irradiations passed the TLD criterion, but did not pass the gamma criterion. 4 irradiations failed both the TLD and gamma criteria. One of these also failed the plan criteria. The 3 institutions that irradiated the phantom twice all passed on the second irradiation. Conclusion: The phantom is a useful tool in credentialing institutions to participate in protocols. The investigation was supported by PHS grants CA10953 and CA81647 awarded by the NCI, DHHS.

Diaphragm motion quantification in megavoltage cone‐beam CT projection images

To quantify diaphragm motion in megavoltage (MV) cone-beam computed tomography (CBCT) projections. User identified ipsilateral hemidiaphragm apex (IHDA) positions in two full exhale and inhale frames were used to create bounding rectangles in all other frames of a CBCT scan. The bounding rectangle was enlarged to create a region of interest (ROI). ROI pixels were associated with a cost function: The product of image gradients and a gradient direction matching function for an ideal hemidiaphragm determined from 40 training sets. A dynamic Hough transform (DHT) models a hemidiaphragm as a contour made of two parabola segments with a common vertex (the IHDA). The images within the ROIs are transformed into Hough space where a contour's Hough value is the sum of the cost function over all contour pixels. Dynamic programming finds the optimal trajectory of the common vertex in Hough space subject to motion constraints between frames, and an active contour model further refines the result. Interpolated ray tracing converts the positions to room coordinates. Root-mean-square (RMS) distances between these positions and those resulting from an expert's identification of the IHDA were determined for 21 Siemens MV CBCT scans. Computation time on a 2.66 GHz CPU was 30 s. The average craniocaudal RMS error was 1.38 +/- 0.67 mm. While much larger errors occurred in a few near-sagittal frames on one patient's scans, adjustments to algorithm constraints corrected them. The DHT based algorithm can compute IHDA trajectories immediately prior to radiation therapy on a daily basis using localization MVCBCT projection data. This has potential for calibrating external motion surrogates against diaphragm motion.

A high speed tri-vision system for automotive applications

Cameras are excellent ways of non-invasively monitoring the interior and exterior of vehicles. In particular, high speed stereovision and multivision systems are important for transport applications such as driver eye tracking or collision avoidance. This paper addresses the synchronisation problem which arises when multivision camera systems are used to capture the high speed motion common in such applications. An experimental, high-speed tri-vision camera system intended for real-time driver eye-blink and saccade measurement was designed, developed, implemented and tested using prototype, ultra-high dynamic range, automotive-grade image sensors specifically developed by E2V (formerly Atmel) Grenoble SA as part of the European FP6 project – sensation (advanced sensor development for attention stress, vigilance and sleep/wakefulness monitoring). The developed system can sustain frame rates of 59.8 Hz at the full stereovision resolution of 1280 × 480 but this can reach 750 Hz when a 10 k pixel Region of Interest (ROI) is used, with a maximum global shutter speed of 1/48000 s and a shutter efficiency of 99.7%. The data can be reliably transmitted uncompressed over standard copper Camera-Link® cables over 5 metres. The synchronisation error between the left and right stereo images is less than 100 ps and this has been verified both electrically and optically. Synchronisation is automatically established at boot-up and maintained during resolution changes. A third camera in the set can be configured independently. The dynamic range of the 10bit sensors exceeds 123 dB with a spectral sensitivity extending well into the infra-red range. The system was subjected to a comprehensive testing protocol, which confirms that the salient requirements for the driver monitoring application are adequately met and in some respects, exceeded. The synchronisation technique presented may also benefit several other automotive stereovision applications including near and far-field obstacle detection and collision avoidance, road condition monitoring and others.

확률기반 배경제거 기법의 향상을 위한 밝기 사영 및 변환에너지 기반 그림자 영역 제거 방법

The segmentation of moving object in video sequence is a core technique of intelligent image processing system such as video surveillance, traffic monitoring and human tracking. A typical method to segment a moving region from the background is the background subtraction. The steps of background subtraction involve calculating a reference image, subtracting new frame from reference image and then thresholding the subtracted result. One of famous background modeling is Gaussian mixture model (GMM). Even though the method is known efficient and exact, GMM suffers from a problem that includes false pixels in ROI (region of interest), specifically shadow pixels. These false pixels cause fail of the post-processing tasks such as tracking and object recognition. This paper presents a method for removing false pixels included in ROT. First, we subdivide a ROI by using shape characteristics of detected objects. Then, a method is proposed to classify pixels from using histogram characteristic and comparing difference of energy that converts the color value of pixel into grayscale value, in order to estimate whether the pixels belong to moving object area or shadow area. The method is applied to real video sequence and the performance is verified.

Sci-Fri AM(1): Imaging-08: Improved Diffusion Weighted MR Imaging of Liver in Normal Subjects

The aim of this study was to perform reliable measurements of the diffusion (D) and perfusion ( D * ) coefficients and perfusion fraction (f) for normal liver using IVIM model. Six volunteers considered to have normal liver underwent DW imaging at 1.5 Tesla. A respiratory triggered diffusion‐weighted single‐shot echo‐planar MRI sequence was performed. The diffusion gradients were applied in the slice select direction and the b values used in the protocol were: 0, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500, 650 and 800 s / mm 2 . Diffusion decays for all regions of interest (ROIs) were analyzed using a Levenberg‐Marquardt nonlinear least‐squares fit to the IVIM model equation and the parameters D, f, and D * were obtained. Diffusion coefficients and perfusion fraction maps were calculated on a pixel‐by‐pixel basis as well and color overlaid onto the corresponding anatomical images ( b =0 s / mm 2 ). No significant difference in results was observed between the whole‐liver ROIs and the peripherally located 100 pixel ROIs. To within experimental error, all patients had the same values of D ( 1.041±0.105 mm 2 / s ), D * ( 54.97±14.92 mm 2 / s ), and f (43.11±4.06 %). This shows that there are no gradual variations across the liver, as long as areas that contain large blood vessels are excluded. By increasing both the number and the range of b‐values used in the protocol we were able to get more consistent results than previously reported in the literature. Correct values for D, D * and f for normal liver are critically necessary when evaluating any distribution of patients, normal or abnormal.

Valoración del flujo sanguíneo cerebral en pacientes con trastornos de la conducta alimentaria en fase aguda mediante SPECT con HMPAO-Tc99m

Objective. To assess the status of cerebral perfusion in patients with eating disorders (ED) in the acute phase of the disease. Materials and methods. Seventeen patients, with a mean age of 22 years, diagnosed with ED according to DSM-III-R (Diagnostic and Statistical Manual of Mental Disorders) criteria and under close clinical monitoring were studied in the initial acute phase of their disease. Brain SPECT with 15 mCi of Tc99m HMPAO was performed on all patients and assessed using visual and semi-quantitative analysis. The latter was carried out by obtaining left/right indices in sixteen symmetrical 5 ¥ 5 pixel regions of interest (ROI) in three transverse slices, one below the cantho-meatal line and two above, at 2 and 5 cm, respectively. Results. Visual analysis showed hypoperfusion of the anteroinferior region of the left temporal lobe in 7/17 patients, and in the homonymous region of the right temporal lobe in 1/17. Semi-quantitative analysis did not show statistically significant differences in the slices above the cantho-meatal line when the means of the asymmetry indices were compared between the anterior (frontal), middle (temporal and parietal) and posterior (occipital) regions of each slice, obtaining values ranging between 0.99 ± 0.05 and 1.02 ± 0.03. However, in the lowest slice, the anterior (temporal) region showed a mean asymmetry value of 0.89 ± 0.15, and on comparing it with the mean of the asymmetry indices of the posterior region (cerebellum), it showed a statistically significant difference (p < 0.05). Conclusion. Patients with ED frequently show hypoperfusion of the anteroinferior region of the temporal lobe, predominantly in the left hemisphere, in the acute phase of the illness.

Assessment of cerebral blood flow in patients with eating disorders in the acute clinical phase using Tc99m-HMPAO SPECT

Objective To assess the status of cerebral perfusion in patients with eating disorders (ED) in the acute phase of the disease. Materials and methods Seventeen patients, with a mean age of 22 years, diagnosed with ED according to DSM-III-R (Diagnostic and Statistical Manual of Mental Disorders) criteria and under close clinical monitoring were studied in the initial acute phase of their disease. Brain SPECT with 15 mCi of Tc99m HMPAO was performed on all patients and assessed using visual and semi-quantitative analysis. The latter was carried out by obtaining left/right indices in sixteen symmetrical 5 × 5 pixel regions of interest (ROI) in three transverse slices, one below the cantho-meatal line and two above, at 2 and 5 cm, respectively. Results Visual analysis showed hypoperfusion of the anteroinferior region of the left temporal lobe in 7/17 patients, and in the homonymous region of the right temporal lobe in 1/17. Semi-quantitative analysis did not show statistically significant differences in the slices above the cantho-meatal line when the means of the asymmetry indices were compared between the anterior (frontal), middle (temporal and parietal) and posterior (occipital) regions of each slice, obtaining values ranging between 0.99 ± 0.05 and 1.02 ± 0.03. However, in the lowest slice, the anterior (temporal) region showed a mean asymmetry value of 0.89 ± 0.15, and on comparing it with the mean of the asymmetry indices of the posterior region (cerebellum), it showed a statistically significant difference (p < 0.05). Conclusion Patients with ED frequently show hypoperfusion of the anteroinferior region of the temporal lobe, predominantly in the left hemisphere, in the acute phase of the illness.

Aggressive Statin Therapy can Halt the Progression of Aortic Sclerosis

Error condition detected Background: Aortic sclerosis (ASC) is very common and often progresses to symptomatic aortic stenosis. Conventional Doppler measurements of ASC are of limited value in assessing progression. Ultrasonic backscatter (UB) has recently been used to assess ASC. In the present randomized prospective study, we investigated whether aggressive LDL-cholesterol reduction (LDL goal <2 mmol/L) can halt the progression of ASC over a period of 12 months period. Methods: LDL was reduced to <2 mmol/L prospectively with atorvastatin in 44 patients with ASC for 12 months. Images of the aortic valve were obtained in the parasternal long-axis view and saved in raw data format. Six square-shaped 11 pixel × 11 pixel regions of interest were placed on all leaflets, and calibrated UB values were obtained by subtracting the regions of interest in the blood pool from the averaged backscatter values obtained from the leaflets. Results: Mean LDL cholesterol levels were 1.8 ± 0.4 mmol/L after 12 months. Mean UB values after 12 months were −14.3 ± 4.6 dB compared to 10.1 ± 5.1 dB at the beginning of the study (p < 0.05). This change in UB did not correlate with LDL, HDL, TG or lipoprotein(a) changes. Conclusion: Measurement of backscatter from the valve leaflets of patients with ASC may be a feasible means of following the progression and treatment response of aortic sclerosis. Statins may be able to halt the progression of ASC over a 12-month period.

Evaluating functional MRI procedures for assessing hemispheric language dominance in neurosurgical patients

Two methods of quantifying hemispheric language dominance (HLD) in neurosurgical patients are compared: (1) an average magnitudes (AM) method, which is a calculation of the average signal intensity variation in regions of interest for each patient that were predefined in a group analysis for each task, and (2) a lateralization indices (LI) method, which is based on the number of activated pixels in regions of interest predefined in each individual patient. Four language tasks [a living/nonliving (LNL) judgment, word stem completion (WSC), semantic associate (SA) and a phonological associate (PA) task] were compared with "gold standard" measures such as the Wada test or electrocortical stimulation. Results showed that the LI method was more accurate (73% agreement with gold standard methods) than the AM method (only 40% agreement) across tasks and subjects. Furthermore, by varying the threshold used for determining laterality, the ability of functional magnetic resonance imaging (fMRI) to predict HLD was influenced for the AM method, whereas the LI method was relatively unaffected by changing the threshold. Using the LI method, the SA task was the most accurate for quantifying HLD (100% agreement with gold standard methods) with respect to the other three language tasks (80% accuracy for WSC, 65% for the LNL and 63% for phonological task). Depending on the method and the task, fMRI may be a promising tool for assessing HLD in neurosurgical patients.

Effects of ROI definition and reconstruction method on quantitative outcome and applicability in a response monitoring trial

Quantitative measurement of tracer uptake in a tumour can be influenced by a number of factors, including the method of defining regions of interest (ROIs) and the reconstruction parameters used. The main purpose of this study was to determine the effects of different ROI methods on quantitative outcome, using two reconstruction methods and the standard uptake value (SUV) as a simple quantitative measure of FDG uptake. Four commonly used methods of ROI definition (manual placement, fixed dimensions, threshold based and maximum pixel value) were used to calculate SUV (SUV([MAN]), SUV15 mm, SUV50, SUV75 and SUVmax, respectively) and to generate "metabolic" tumour volumes. Test-retest reproducibility of SUVs and of "metabolic" tumour volumes and the applicability of ROI methods during chemotherapy were assessed. In addition, SUVs calculated on ordered subsets expectation maximisation (OSEM) and filtered back-projection (FBP) images were compared. ROI definition had a direct effect on quantitative outcome. On average, SUV[MAN), SUV15 mm, SUV50 and SUV75, were respectively 48%, 27%, 34% and 15% lower than SUVmax when calculated on OSEM images. No statistically significant differences were found between SUVs calculated on OSEM and FBP reconstructed images. Highest reproducibility was found for SUV15 mm and SUV[MAN] (ICC 0.95 and 0.94, respectively) and for "metabolic" volumes measured with the manual and 50% threshold ROIs (ICC 0.99 for both). Manual, 75% threshold and maximum pixel ROIs could be used throughout therapy, regardless of changes in tumour uptake or geometry. SUVs showed the same trend in relative change in FDG uptake after chemotherapy, irrespective of the ROI method used. The method of ROI definition has a direct influence on quantitative outcome. In terms of simplicity, user-independence, reproducibility and general applicability the threshold-based and fixed dimension methods are the best ROI methods. Threshold methods are in addition relatively independent of changes in size and geometry, however, and may therefore be more suitable for response monitoring purposes.

Reproducibility of electrical impedance tomographic spectroscopy (EITS) parametric images of neonatal lungs

The reproducibility of electrical impedance tomographic spectroscopy (EITS) images of neonatal lungs have been investigated in 11 clinically stable babies. We have used the Sheffield Mark IIIa EITS system. An average inspiration frame was generated from the data frames associated with maximum inspiration. Frequency images were reconstructed from these frames. The frequency images were analysed to locate the pixel with the maximum change in the right lung field. The change was defined as the 614 kHz measurement relative to 9.6 kHz. A pixel region of interest was centred at this point. The changes in impedance with frequency for this region of interest show good overall reproducibility between electrode applications for eight frequencies (95% limits of agreement ). This reproducibility is improved (95% limits of agreement ) by omitting the highest frequency (1.2 MHz) which is most subject to system noise. The parameters for the Cole model derived from data with the highest frequency omitted are less reproducible between electrode applications (95% limits of agreement, ). We suspect that the parametric model used may have an effect on this. The signals recorded at the highest frequency (1.2 MHz) are a major source of variability. The reproducibility results are improved by omitting this frequency from the analysis.

Is image subtraction necessary in the clinical interpretation of single-day split-dose stress cerebral perfusion single-photon emission tomography using technetium-99m compounds?

The aim of this study was to validate a simplified semiquantitative method of evaluating a single-day stress cerebral perfusion test to obtain cerebrovascular reserve capacity (CVRC) for routine clinical uses. A split-dose protocol was tested in 36 pairs of technetium-99m hexamethylpropylene amino oxime baseline (low dose) and acetazolamide (high dose) stress brain single-photon emission tomographic (SPET) studies from 16 patients with cerebrovascular disease. The images were displayed on a semiquantitative color scale with (corrected) and without (uncorrected) image subtraction, dose adjustment, and decay correction. The representative CVRC was determined by placing 3x3 pixel regions of interest on midthalamic and midcerebellar slices. The corrected and uncorrected relative changes in CVRC were correlated using linear regression. The relative changes of corrected (x) and uncorrected (y) CVRC by quantitative analysis were highly correlated in a linear fashion (y=0.67x+0.002, r=0.998, P<0.0005). As predicted by theory, the slope was related to the ratio of split dose and independent of ROI sampling. Single-day split-dose stress brain SPET can be accurately performed without image subtraction and complicated dose adjustment or decay correction for clinical studies.

Stimulus parameters influence characteristics of optical intrinsic signal responses in somatosensory cortex.

Optical imaging of intrinsic signals was performed in the barrel cortex of the rat during whisker deflections of varying frequencies (1 to 20 Hz) and durations (0.1 to 5 s). A dose-response relationship was shown between these stimuli and the characteristics of the optically recorded intrinsic signal response. At constant frequencies, longer stimulus durations increased response magnitude, as defined by mean pixel value in statistically determined regions of interest. At constant durations, higher stimulus frequencies increased response magnitude. Response magnitude was also increased by greater numbers of deflections. When stimulus number was constant, there were no differences in response magnitude, regardless of stimulus frequency and duration. Spatial extent of responses, as defined by number of pixels in regions of interest, did not differ between stimulus frequencies, durations, or numbers. Comparison of the time to reach peak intrinsic signal response after stimulus onset ("time-to-peak") suggested that higher frequencies were associated with faster time-to-peak. Registration of intrinsic signal responses with cytochrome oxidase-stained whisker barrels demonstrated that responses were located over the barrel corresponding to the stimulated whisker. In summary, we have shown that the absolute number of stimuli delivered to the system is, at least for short stimulus periods (< or = 5 s), a determining factor for the magnitude of these responses, whereas stimulus frequency appears to influence time-to-peak response.

The effects of hyperthyroidism on MIBG uptakes in the human heart--preliminary report.

Twelve cases of hyperthyroidism with cardiac manifestations (4 males, 8 females, ages: 20 to 70 years) and 12 normal controls of euthyroidism (6 males, 6 females, ages: 27 to 70 years) were included in our study. Each case accepted an I.V. injection of I-131 MIBG (I.R.E., Belgium) with 0.5mCi/1.7m2 of body surface area. The 24 and 48 hr imagings of the anterior chest, including total heart and lungs, were used to estimate cardiac sympathetic nerve innervation by the following formula: H/L = (the mean counts of pixels in the regions of interest (ROI) over the heart)/(the mean counts of pixels in the ROI over the lungs). The results showed that the 24 and 48 hr H/L values in euthyroidism were a little higher than those in hyperthyroidism, but the differences were not significant by a Wilcoxon rank sum test. The correlation between H/L and 24 hr I-131 thyroid uptake in patients with hyperthyroidism were also evaluated and the results showed no significant correlation between the H/L and uptake. In conclusion, we consider that the clinical manifestations concerning the heart in hyperthyroidism may not totally depend on the effects of increased cardiac sympathetic nerve innervation.

Regional lung microvascular permeability using dual isotope scintigraphy

We have extended the dual isotope probe technique of Basran et al. for the measurement of pulmonary microvascular permeability (PMVP) to include gamma camera data acquisition and functional imaging of the plasma protein accumulation index (PPA) throughout the lung fields. The study group consisted of 11 patients with possible increased PMVP following the drainage of a pleural effusion or the evacuation of air from a pneumothorax, and 11 control patients. The PPA was calculated (1) for probe data, (2) on a pixel by pixel basis for the camera data, the results being stored in a functional image and (3) for four pixel x four pixel regions of interest positioned over the lung fields using the functional image and raw data as a guide. Functional images of the control group showed uniformly low PPAs throughout the lung fields. Nine of the eleven patients in the effusion/pneumothorax group showed discrete areas of increased PPA on the functional images. In the effusion/pneumothorax group, the re-expanded lung four pixel x four pixel ROI PPA values were significantly higher than the nonexpanded lung ROI values (p less than 0.001). The re-expanded lung ROI values were also significantly higher than the mean of the left and right lung ROIs in the control group (p less than 0.01). Five of the eleven patients in the effusion/pneumothorax group had probe PPAs that differed significantly from zero. We believe that probe positioning problems in the absence of sufficient clinical guidelines were largely responsible for there being no overall significant difference in the probe PPAs between the two study groups.