Biomedical subjects

Kenya Murase

Publications and source records attributed to Kenya Murase.

At least 37 records · Page 2Linked to original sources

PubMed2005

Enlarged longitudinal dose profiles in cone-beam CT and the need for modified dosimetry.

In order to examine phantom length necessary to assess radiation dose delivered to patients in cone-beam CT with an enlarged beamwidth, we measured dose profiles in cylindrical phantoms of sufficient length using a prototype 256-slice CT-scanner developed at our institute. Dose profiles parallel to the rotation axis were measured at the central and peripheral positions in PMMA (polymethylmethacrylate) phantoms of 160 or 320 mm diameter and 900 mm length. For practical application, we joined unit cylinders (150 mm long) together to provide phantoms of 900 mm length. Dose profiles were measured with a pin photodiode sensor having a sensitive region of approximately 2.8 x 2.8 mm2 and 2.7 mm thickness. Beamwidths of the scanner were varied from 20 to 138 mm. Dose profile integrals (DPI) were calculated using the measured dose profiles for various beamwidths and integration ranges. For the body phantom (320-mm-diam phantom), 76% of the DPI was represented for a 20 mm beamwidth and 60% was represented for a 138 mm beamwidth if dose profiles were integrated over a 100 mm range, while more than 90% of the DPI was represented for beamwidths between 20 and 138 mm if integration was carried out over a 300 mm range. The phantom length and integration range for dosimetry of cone-beam CT needed to be more than 300 mm to represent more than 90% of the DPI for the body phantom with the beamwidth of more than 20 mm. Although we reached this conclusion using the prototype 256-slice CT-scanner, it may be applied to other multislice CT-scanners as well.

Head↗

PubMed2005

Clinical potentials for dynamic contrast-enhanced hepatic volumetric cine imaging with the prototype 256-MDCT scanner.

OBJECTIVE: To achieve dynamic contrast-enhanced hepatic volumetric cine imaging, we developed a prototype 256-MDCT scanner. This study examined the feasibility of the technique for human hepatic imaging in three hepatocellular carcinoma patients. CONCLUSION: Volumetric cine imaging successfully visualized dynamic contrast enhancement of the hepatocellular carcinoma. It is helpful to evaluate the phase of contrast enhancement or for functional studies of the head, renal artery, coronary artery, and liver.

Aged↗

PubMed2005

[Improvement in accuracy of quantitative assessment of the regional cerebral blood flow with 99mTc-ECD].

Mean cerebral blood flow (mCBF) in the slice including the basal ganglia (reference slice) is necessary for the quantification of regional CBF using Patlak plot and BUR methods on 99mTc-ECD cerebral perfusion SPECT. The mCBF was calculated from the mean counts of this slice. A region of interest (ROI) has been manually set on the reference slice to obtain the mean counts (manual ROI method). However, there was large variability observed in the value of rCBF in this method. We developed a 3DSRT method for improving the accuracy of the mean counts in the reference slice and evaluated the difference between the value of rCBF on manual ROI method and that on 3DSRT method in consecutive 11 patients with cerebral vascular disease. Difference in the value of mean counts of the reference slice was distributed within the 2 standard deviations (SD) with Blant-Altman analysis in 9 of 11 patients. Significant difference in the value of mean counts between two methods was observed in 2 of 11 patients. 3DSRT method is superior accuracy to the manual ROI method in the evaluation of the counts in the ROI. Lower accuracy in manual ROI method, therefore, results in the difference of the value of mean counts. 3DSRT method provides high accuracy with the various quantitative methods for the evaluation of rCBF using 99mTc-ECD.

Aged↗

PubMed2005

Measurement of radiation dose in cerebral CT perfusion study.

PURPOSE: To evaluate radiation dose in cerebral perfusion studies with a multi-detector row CT (MDCT) scanner on various voltage and current settings by using a human head phantom. MATERIALS AND METHODS: Following the CT perfusion study protocol, continuous cine scans (1 sec/rotation x60 sec) consisting of four 5-mm-thick contiguous slices were performed three times at variable tube voltages of 80 kV, 100 kV, 120 kV, and 140 kV with the same tube current setting of 200 mA and on variable current settings of 50 mA, 100 mA, 150 mA, and 200 mA with the same tube voltage of 80 kV. Radiation doses were measured using a total of 41 theroluminescent dosimeters (TLDs) placed in the human head phantom. Thirty-six TLDs were inside and three were on the surface of the slice of the X-ray beam center, and two were placed on the surface 3 cm caudal assuming the lens position. RESULTS: Average radiation doses of surface, inside, and lens increased in proportion to the increases of tube voltage and tube current. The lowest inside dose was 87.6+/-15.3 mGy, and the lowest surface dose was 162.5+/-6.7 mGy at settings of 80 kV and 50 mA. The highest inside dose was 1,591.5+/-179.7 mGy, and the highest surface dose was 2,264.6+/-123.7 mGy at 140 kV-200 mA. At 80 kV-50 mA, the average radiation dose of lens was the lowest at 5.5+/-0.0 mGy. At 140 kV-200 mA the radiation dose of lens was the highest at 127.2+/-0.6 mGy. CONCLUSION: In cerebral CT perfusion study, radiation dose can vary considerably. Awareness of the patient's radiation dose is recommended.

Basal Ganglia↗

PubMed2005

A method for reducing radiation dose in cerebral CT perfusion study with variable scan schedule.

PURPOSE: To propose a method for reducing the radiation dose in cerebral CT perfusion studies by using a variable scan schedule. MATERIALS AND METHODS: Original images were obtained with a multi detector-row CT (MDCT) scanner using the following CT perfusion protocol: continuous scans of 1 sec/rotation x 60 sec, four 5-mm-thick contiguous slices. The original images were thinned-out using combinations of various numbers of former continuous images (10, 15, 20, 25, and 30), and the later skipped images with various scan intervals (2, 5, 10, 15 and 20 sec). The thinned-out images were interpolated by linear interpolation. In five patients with cerebrovascular disease, we generated functional images of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) from both original and interpolated data. The correlation coefficients (CC) for these parameters between the original and interpolated images were evaluated. RESULTS: The CC decreased with dose reduction. To keep the correlation coefficients greater than 0.9, the estimated dose was reduced to 33.3% on CBF with a set of 10 continuous images and scan interval of 5 sec, to 20.0% on CBV with a set of 10 continuous images and scan interval of 20 sec, and to 58.3% on MTT with a set of 10 continuous images and scan interval of 2 sec. CONCLUSION: The variable scan schedule method would be useful to reduce radiation dose while maintaining the accuracy of CT perfusion (CTP) parameters.

Aged↗

PubMed2005

Evaluation of optimal scan duration and end time in cerebral CT perfusion study.

PURPOSE: The purpose of this study was to evaluate the optimal end time of scanning and the influence of varying the number of source images adopted for calculation of the parameter values in computerized tomography (CT) perfusion. MATERIALS AND METHODS: Nineteen CT perfusion studies in 14 patients with cerebrovascular disease were retrospectively analyzed. CT perfusion scanning was performed using continuous scans of 1 sec/rotation x60 sec with 5-mm-thick sections. To determine the appropriate end time of scanning, the time-density curves (TDCs) of the anterior cerebral artery (ACA), superior sagittal sinus (SSS), and basal ganglia were analyzed. The functional maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were retrospectively generated from various numbers (30, 35, 40, 45, 50, 55, and 60) of source images. Defining the values calculated from the number of source images equal to the end time of the first pass as standard values, the percentage difference between the standard values and the values generated from various numbers of sources were evaluated. RESULTS: The TDCs of SSS showed the latest end time of the first pass (mean, 38.6+/-5.2 sec; range, 32 to 48 sec). Therefore, the values calculated from the number of source images equal to the end time of the first pass of SSS were defined as standard values. Increase and decrease of the number of source images for calculation resulted in increase of the percentage difference in every parameter value. The percentage differences ranged up to 49.6% for CBF, 48.0% for CBV, and 20.0% for MTT. CONCLUSIONS: Scanning until the end time of the first pass of SSS is necessary and sufficient for reliable measurement. Variable scan time based on the TDC of the SSS may be of better utility than use of fixed scan time. Further, the radiation dose could be minimized in many cases by reducing the scan time.

Aged↗

PubMed2004

Automatic motion correction for quantification of myocardial perfusion with dynamic magnetic resonance imaging.

Respiratory motion makes it difficult to quantify myocardial perfusion with dynamic magnetic resonance imaging (MRI). The purpose of this study was to evaluate an automatic registration method for motion correction for quantification of myocardial perfusion with dynamic MRI. The present method was based on the gradient-based method with robust estimation of displacement parameters. For comparison, we also corrected for motion with manual registration as the benchmark. The myocardial kinetic parameters, K1 (rate constant for transfer of contrast agent from blood to myocardium) and k2 (rate constant for transfer from myocardium to blood), were calculated from dynamic images with a two-compartment model. The images corrected by the present method were similar to those corrected by manual registration. The kinetic parameters obtained after motion correction with the present method were close to those obtained after motion correction with manual registration. These results suggest that the present method is useful for motion correction for quantification of myocardial perfusion with dynamic MRI.

Contrast Media↗

PubMed2004

Quantitative assessment of regional pulmonary perfusion in the entire lung using three-dimensional ultrafast dynamic contrast-enhanced magnetic resonance imaging: Preliminary experience in 40 subjects.

PURPOSE: To assess regional differences in quantitative pulmonary perfusion parameters, i.e., pulmonary blood flow (PBF), mean transit time (MTT), and pulmonary blood volume (PBV) in the entire lung on a pixel-by-pixel basis in normal volunteers and pulmonary hypertension patients. MATERIALS AND METHODS: Three-dimensional ultrafast dynamic contrast-enhanced MR imaging was performed in 15 normal volunteers and 25 patients with pulmonary hypertension. From the signal intensity-time course curves, PBF, MTT and PBV maps were generated using deconvolution analysis, indicator dilution theories, and the central volume principle, on a pixel-by-pixel basis. From pulmonary perfusion parameter maps of normal volunteers and pulmonary hypertension patients, regional PBF, MTT, and PBV were statistically evaluated. RESULTS: Regional PBF, MTT, and PBV showed significant differences in the gravitational and isogravitational directions (P < 0.05). The quantitative pulmonary perfusion parameter maps demonstrated significant differences between normal volunteers and pulmonary hypertension patients (P < 0.05). CONCLUSION: Three-dimensional ultrafast dynamic contrast-enhanced MR imaging is feasible for the assessment of regional quantitative pulmonary perfusion parameters in the entire lung on a pixel-by-pixel basis in normal volunteers and pulmonary hypertension patients.

Adult↗

PubMed2004

Efficient method for calculating kinetic parameters using T1-weighted dynamic contrast-enhanced magnetic resonance imaging.

It has become increasingly important to quantitatively estimate tissue physiological parameters such as perfusion, capillary permeability, and the volume of extravascular-extracellular space (EES) using T(1)-weighted dynamic contrast-enhanced MRI (DCE-MRI). A linear equation was derived by integrating the differential equation describing the kinetic behavior of contrast agent (CA) in tissue, from which K(1) (rate constant for the transfer of CA from plasma to EES), k(2) (rate constant for the transfer from EES to plasma), and V(p) (plasma volume) can be easily obtained by the linear least-squares (LLSQ) method. The usefulness of this method was investigated by means of computer simulations, in comparison with the nonlinear least-squares (NLSQ) method. The new method calculated the above parameters faster than the NLSQ method by a factor of approximately 6, and estimated them more accurately than the NLSQ method at a signal-to-noise ratio (SNR) of < approximately 10. This method will be useful for generating functional images of K(1), k(2), and V(p) from DCE-MRI data.

Algorithms↗

PubMed2004

A study on attenuation correction using Tc-99m external TCT source in Tc-99m GSA liver SPECT.

PURPOSE: In attenuation correction of ECT images by transmission CT (TCT) with an external 99mTc gamma-ray source, simultaneous TCT/ECT data acquisition is difficult, when the same radionuclide such as 99mTc-tetrofosmin or 99mTc-GSA is used as the tracer. In this case, TCT is usually acquired before administration of the tracer, and ECT is acquired separately after the tracer injection. However, misregistration may occur between the TCT and ECT images, and the repetition of examinations add to the mental and physical stress of the patients. In this study, to eliminate this problem, we evaluated whether attenuation correction of ECT images can be achieved by acquiring TCT and ECT simultaneously, then acquiring ECT alone, and preparing an attenuation map by subtracting the latter from the former using 99mTc-GSA liver ECT. METHOD: The ECT system used was a three-head gamma camera equipped with one cardiac fan beam collimator and two parallel beam collimators. External gamma-ray source for TCT of 99mTc was 740 MBq, and ECT of 99mTc-GSA was 185 MBq. First, pure TCT data were acquired for the original TCT-map, then, ECT/TCT data were acquired for the subtracted TCT-map, and finally, pure ECT data were acquired. The subtracted attenuation map was produced by subtracting the pure ECT image from the TCT/ECT image, and attenuation correction of the ECT image was done using both this subtracted TCT map and attenuation map from pure TCT. These two attenuation corrected images and non-corrected images were compared. Hot rods phantom, a liver phantom with a defect, and 10 patients were evaluated. RESULTS: Attenuation corrected ECT values using the subtraction attenuation map showed an error of about 5% underestimation compared with ECT values of the images corrected by original attenuation map at the defect in the liver phantom. A good correlation of y = 22.65 + 1.06x, r = 0.958 was observed also in clinical evaluation. CONCLUSION: By means of the method proposed in this study, it is possible to perform simultaneous TCT/ECT data acquisition for attenuation correction using Tc-99m external source in Tc-99m GSA liver SPECT. Moreover, it is thought that this method decreases the mental and physical stress of the patients.

Algorithms↗

PubMed2004

Spectral analysis of 99mTc-HMPAO for estimating cerebral blood flow: a comparison with H2(15)O PET.

Cerebral blood flow (CBF) can be quantified non-invasively using the brain perfusion index (BPI), which is determined using radionuclide angiographic data obtained through the use of technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO). The BPI is generally calculated using graphical analysis (GA). In this study, BPI was measured using spectral analysis (SA), and the usefulness of SA was compared with that of GA. Thirteen patients with various brain diseases and four healthy male volunteers were examined using radionuclide angiography with 99mTc-HMPAO. The BPI was measured for each subject using both SA and GA. In the four healthy volunteers, the BPI was examined at rest and after the intravenous administration of 1 g of acetazolamide (ACZ). An H2(15)O PET examination was also performed in the 13 patients; the BPIS and BPIG values were compared with the CBF measurements obtained using H2(15)O PET (CBFPET). The BPI values obtained by SA (BPIS) (x) and by GA (BPIG) (y) were correlated (y = 0.568x + 0.055, r = 0.901) in the 13 patients and four healthy volunteers at rest, although the BPIG values were underestimated by 36.1 +/- 7.5% (mean +/- SD) compared with the BPIS values. The degree of underestimation tended to increase with increasing BPIS values. The increase in the BPIS was 32.1 +/- 8.0% after the intravenous administration of ACZ, while the increase in BPIG was only 8.1 +/- 2.8%. This discrepancy was considered to be the result of the BPIG values being affected by the first-pass extraction fraction of the tracer. Although both BPIS and BPIG values were significantly correlated with the CBFPET values, the correlation coefficient for BPIS was higher than that for BPIG (BPIS: r = 0.881; BPIG: r = 0.832). These results suggest that SA produces a more reliable BPI for quantifying CBF using 99mTc-HMPAO than the conventional method using GA. The SA method should be especially useful for activation studies involving pharmacological intervention and/or clinical cases with an increased CBF.

Adult↗

PubMed2004

Segmented attenuation correction for myocardial SPECT.

PURPOSE: One of the main factors contributing to the accuracy of attenuation correction for SPECT imaging using transmission computed tomography (TCT) with an external gamma-ray source is the radionuclide count. To reduce deterioration of TCT images due to inadequate radionuclide counts, a correction method, segmented attenuation correction (SAC), in which TCT data are transformed into several components (segments) such as water, lungs and spine, providing a satisfactory attenuation correction map with less counts, has been developed. The purpose of this study was to examine the usefulness of SAC for myocardial SPECT with attenuation correction. METHODS: A myocardial phantom filled with Tc-99m was scanned with a triple headed SPECT system, equipped with one cardiac fan beam collimator for TCT and two parallel hole collimators for ECT. As an external gamma-ray source for TCT, 740 MBq of Tc-99m was also used. Since Tc-99m was also used for ECT, the TCT and ECT data were acquired separately. To make radionuclide counts, the TCT data were acquired in the sequential repetition mode, in which a 3-min-rotation was repeated 7 times followed by a 10-min-rotation 4 times (a total of 61 minutes). The TCT data were reconstructed by adding some of these rotations to make TCT maps with various radionuclide counts. Three types of SAC were used: (a) 1-segment SAC in which the body structure was regarded as water, (b) 2-segment SAC, in which the body structure was regarded as water and lungs, and (c) 3-segment SAC, in which the body structure was regarded as water, lungs and spine. We compared corrected images obtained with non-segmentation methods, and with 1- to 3-segment SACs. We also investigated the influence of radionuclide counts of TCT (3, 6, 9, 12, 15, 18, 21, 31, 41, 51, 61 min acquisition) on the accuracy of the attenuation correction. RESULTS: Either 1-segment or 2-segment SAC was sufficient to correct the attenuation. When non-segmentation TCT attenuation methods were used, rotations of at least 31 minutes were required to obtain sufficiently large counts for TCT. When the 3-segment SAC was used, the minimal acquisition time for a satisfactory TCT map was 7 min. CONCLUSION: The 3-segment SAC was effective for attenuation correction, requiring fewer counts (about 1/5 of the value for non-segmentation TCT), or less radiation for TCT.

Adult↗

PubMed2004

Heterogeneity of cerebral blood flow in frontotemporal lobar degeneration and Alzheimer's disease.

This study was designed to quantify the heterogeneity on cerebral blood flow single-photon emission tomography (SPET) images in frontotemporal lobar degeneration (FTLD) and Alzheimer's disease (AD) using a three-dimensional fractal analysis. Twenty-one FTLD patients, 21 AD patients and 11 healthy controls underwent technetium-99m hexamethylpropylene amine oxime SPET scanning. Patients with FTLD and AD matched for sex, age and the severity of dementia as estimated with the Clinical Dementia Rating and were determined to be in the early stage of illness. We delineated the SPET images using a 35% cut-off and a 50% cut-off of the maximal voxel radioactivity and measured the number of voxels included in the contours of two different cut-offs. The fractal dimension (FD) was calculated by relating the logarithms of the cut-offs and the numbers of voxels, and it was defined as the heterogeneity of the cerebral perfusion. We divided the SPET images into two sets, anterior and posterior, with equal numbers of coronal SPET slices. We calculated total FD, anterior FD and posterior FD for total, anterior and posterior SPET images. Anterior FDs for FTLD and AD were 1.55 +/- 0.34 and 1.24 +/- 0.19 (P = 0.0002). The ratios of anterior to posterior FD for FTLD and AD were 1.81 +/- 0.41 and 1.32 +/- 0.14 (P < 0.0001). Use of the anterior FD and the ratio of anterior to posterior FD separated FTLD patients from AD patients and controls with a sensitivity of 85.7% and a specificity of 93.8%. Anterior FD and the ratio of anterior to posterior FD may be useful in distinguishing FTLD from AD.

Aged↗

PubMed2004

Assessment of coronary artery and cardiac function using multidetector CT.

Multidetector CT is able to reconstruct artifact-less cardiac images due to improved temporal resolution. In this article, we review the potential benefits of the cardiac application of multidetector CT in the assessment of coronary artery and cardiac function, such as wall motion and systolic thickening. By applying retrospective ECG-gating, 10 phases throughout 1 cardiac cycle are extracted for functional analysis. Animated movies are generated by paging through these 2D and 3D images in cardiac phase order. Left ventricular end-diastolic volume, end-systolic volume, and ejection fraction can also be generated. Using the data acquired during a single breath hold, coronary artery and cardiac function can be assessed by multidetector CT.

Contrast Media↗

PubMed2004

Extraction of arterial input function for measurement of brain perfusion index with 99mTc compounds using fuzzy clustering.

Cerebral blood flow (CBF) can be quantified non-invasively using the brain perfusion index (BPI) determined from radionuclide angiographic data generated with 99mTc-hexamethylpropylene amine oxime (99mTc-HMPAO). When measuring the BPI, manual drawing of regions of interest (ROIs) (manual ROI method) for the extraction of the arterial input function (AIF) can lead to serious individual differences. The purpose of this study was to apply the fuzzy c-means (FCM) clustering method to determine AIF, and to investigate its usefulness in comparison with the manual ROI method. Radionuclide angiography was performed using a bolus injection of about 555 MBq of 99mTc-HMPAO, followed by sequential imaging (1 sec/frame x 120 s) using a solid-state gamma camera, and the BPI values were calculated using spectral analysis. To investigate the dependence of BPI on the ROI size, we drew five ROIs with different sizes over the aortic arch, and calculated the BPI using the manual ROI method [BPI(manual)] and the FCM clustering method [BPI(FCM)]. Furthermore, we asked 10 individuals to draw ROIs to investigate the inter-operator variability of the two methods. The mean and standard deviation (SD) of BPI(manual) increased with increasing ROI size, whereas the mean of BPI(FCM) was almost constant regardless of the ROI size; the SD of BPI(FCM) was smaller than that of BPI(manual). The inter-operator variability of the FCM clustering method was smaller than that of the manual ROI method. These results suggest that the FCM clustering method appears to be useful for the measurement of BPI, because it allows a reliable and objective determination of AIF.

Aged↗

PubMed2004

Truncation correction of fan beam transmission data for attenuation correction using parallel beam emission data on a 3-detector SPECT system.

BACKGROUND: When the simultaneous transmission computed tomography (TCT)/single photon emission CT (SPECT) acquisition protocol is applied to myocardial studies using a 3-detector SPECT, the narrow effective field of view of a fan beam collimator used for TCT acquisition may cause truncation artifacts on TCT images. In this paper, we propose a new method of correcting for the truncation of TCT. METHODS: The truncated parts of the TCT projection data are corrected using quadratic functions, based on the properties that the integral of non-truncated TCT projection data is constant at any projection angle and the position of the centre of gravity is focused on a fixed point. The usefulness of our method was investigated in phantom and human studies using a 3-detector SPECT equipped with one cardiac fan beam collimator for TCT and two parallel beam collimators for SPECT. We used Tl as a tracer for SPECT and Tc as an external source for TCT. RESULTS: The phantom and human studies showed that our method can adequately correct for the truncation of TCT data acquired using a fan beam collimator in a 3-detector SPECT, as long as there is no truncation in SPECT data. CONCLUSION: Our method appears to be useful for improving the SPECT images obtained using simultaneous TCT/SPECT acquisition in a 3-detector SPECT. However, further studies will be necessary to establish the clinical usefulness of this method.

Algorithms↗

PubMed2004

Deconvolution analysis of dynamic contrast-enhanced data based on singular value decomposition optimized by generalized cross validation.

PURPOSE: To present an implementation of generalized cross validation (GCV) for automatically determining the regularization parameter--i.e., the threshold value in deconvolution analysis based on truncated singular value decomposition (TSVD) of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) data--and to investigate the usefulness of this approach in comparison with TSVD with a fixed threshold value (TSVD-F). METHODS: Using computer simulations, we generated a time-dependent concentration of the contrast agent in the volume of interest (VOI) from the arterial input function (AIF) modeled as a gamma-variate function under various cerebral blood flows (CBFs), cerebral blood volumes (CBVs), and signal-to-noise ratios (SNRs) for three different types of residue functions (exponential, triangular, and box-shaped). We also considered the effects of delay and dispersion in AIF. The TSVD with GCV (TSVD-G) and TSVD-F with a fixed threshold value of 0.2 were used to estimate CBF values from the simulated concentration-time curves in the VOI and AIF, and the estimated values were compared with the assumed values. Additionally, the optimal threshold value was determined from the threshold value in TSVD-F giving the mean CBF value closest to the assumed value and was compared with the threshold value determined with TSVD-G. RESULTS: With TSVD-G, the CBF estimation was substantially improved over a wide range of CBFs for all types of residue functions at the cost of more noise than was seen with TSVD-F. The dependency of the threshold value determined with TSVD-G on the CBF, CBV, and SNR was similar to that of the optimal threshold value, with some discrepancy being observed for the box-shaped residue function, although they did not always agree in terms of absolute value. CONCLUSION: Given an improved SNR, TSVD-G is useful for quantification of CBF with deconvolution analysis of DCE-MRI data.

Algorithms↗

PubMed2004

Quantitative analysis of resolving power for computed radiographic portal images.

This study presents a quantitative analysis method of resolution for computed radiography (CR) portal images using three different types of cassettes. A copper wire chart (test piece, Shimadzu Medical Corp.) for fluoroscopy was selected as the test tool for analysis. Images of the test chart were obtained on a linear accelerator operating at nominal beam energies of 4 MV. The CR portal imaging data were transmitted to a personal computer via a DICOM network system. The imaging data were imported into NIH Image, which is public domain software. The extent of analysis was established on the chart image (160 x 540 pixels). A density profile plot was generated based on the current rectangular selection and this plot was used was used for quantitative analysis of the resolution. This quantitative analysis method using NIH Image is expected to prove useful for digital portal images.

Diagnostic Imaging↗