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PubMed1988

Modified histogram subtraction technique for analysis of flow cytometry data.

Analysis of flow cytometry histogram data by the subjective selection of an integration window can be a tedious and time-consuming task and is often inaccurate. A new method for automated calculation of the percent positive from immunofluorescence histograms is presented. This new method is a modification of the currently used method of channel-by-channel histogram subtraction. Its accuracy is compared to that of the channel-by-channel histogram subtraction method and to another currently used automated method, which selects an integration window by finding the channels that contain the most fluorescent 2% of a control histogram. The new histogram subtraction method is objective, easy to use, and is more accurate than other currently used automated analysis methods. PASCAL source code is given for each method of analysis.

Cell Separation↗
PubMed1995

[Clinical application prospect of digital subtraction technique for periapical radiographs].

The composition and functions of digital subtraction system for conventional radiographs were introduced. Based on the experimental test for this system, it has been found that digital subtraction system for conventional radiographs is very valuable for the diagnoses of minute bone lesions in the bifurcation, root side and apical part of the teeth as well as in the alveolar crest. In addition, the reproducibility of the projection geometry, the principle of digital subtraction and its clinical application prospect are also discussed in the present paper.

Humans↗
PubMed1988

[Evaluation of coronary blood flow using digital subtraction technique and cine coronary angiography: a preliminary report].

To evaluate coronary circulation in ischemic heart disease, digital image processing with cine coronary angiography was performed. Using time-density curves obtained from individual pixels, images showing the distribution of contrast density and transit time were obtained. To record angiograms, contrast medium was injected into the coronary artery in a steady manner during right atrial pacing. Frames in the end-diastolic phase immediately before the P wave were selected, and digitized into a 512 x 512 x 8 bit matrix using a system composed of a video camera, an analog-to-digital converter, and a computer. These digitized images were then stored in a disk memory. A mask image was prepared before the injection of contrast medium. Subtraction was performed using the mask image and a series of images following contrast injection. The subtracted images were of sufficient quality to permit clear observation of the individual coronary arterial branches. Time-density curves were then determined from these subtracted images. From these curves, time from the onset of contrast injection to its peak density (Tp), time from the peak density to the half peak density (T 1/2) and the attenuation factor of the curves (tau) were derived. Their distributions were expressed as color images. Examples of a normal control and a case of inferior infarction were demonstrated. Blood flow function images with good spatial resolution were thus obtained. This method is useful for evaluating coronary blood flow.

Angioplasty, Balloon↗
PubMed1989

The effect of in-vivo-occurring errors in the reproducibility of radiographs on the use of the subtraction technique.

A device for serial radiography in maxillary and mandibular premolar and molar regions was developed. Radiographs of 9 patients were made during a period of 1 year. When testing the device, the influence of the time interval between the radiographs and the influence of the construction of the device on the reproducibility of the X-ray images were determined. An increase of the time interval between radiographs reduced the reproducibility. The use of bilateral bite blocks improved the reproducibility of the X-ray images in comparison with the images obtained with a device with a one-sided bite block. Errors in the reproducibility caused differences in the image geometry of radiographs. The in-vivo-found differences were studied for their effect on the detection threshold of observers using photographic subtraction radiography. An increase of the differences in image geometry between the radiographs resulted in a higher detection threshold and a higher % of false positive decisions. It appeared that very small differences between clinical radiographs, corresponding with an angulation error of 0.7 degrees, can be tolerated in order to prevent the occurrence of high numbers of type-I errors. The % of radiographs, which met this requirement and could be used for photographic subtraction radiography, was 55%, when taken at time intervals of 1 year.

Adult↗
PubMed1985

99mTc particle perfusion/99mTc aerosol ventilation imaging using a subtraction technique in suspected pulmonary embolism.

It is generally acknowledged that ventilation-perfusion mismatch is diagnostic of pulmonary embolism. Lung ventilation imaging with radioactive gases is a good method for the detection of pulmonary embolism, but it is not in widespread use because of the limited availability of 81mKr gas and the poor physical properties of 133Xe. Aerosols have been proposed, instead of gases for use in lung ventilation imaging. As perfusion and ventilation distributions may change very rapidly, the two imaging procedures should be done in rapid succession. The cheapest way to perform the combined perfusion-ventilation (Q/V) imaging is to use 99mTc-labelled macroaggregates and aerosols. In our method the perfusion imaging was done first, immediately followed by the ventilation imaging with 99mTc-labelled aerosols. A computer program was used to subtract the contribution of the perfusion from the combined Q/V image so that the pure ventilation image alone was obtained. The method was tested in 41 patients with suspected pulmonary embolism.

Aerosols↗
PubMed1994

MR characterization of suspicious breast lesions with a gadolinium-enhanced TurboFLASH subtraction technique.

PURPOSE: To assess the utility of gadolinium-enhanced dynamic magnetic resonance (MR) imaging with turbo fast low-angle shot (TurboFLASH) technique in the differentiation of benign from malignant lesions of the breast. MATERIALS AND METHODS: Contrast material-enhanced MR images were obtained at intervals of 2.3 seconds for 2 minutes. After the first four images were obtained, contrast medium was intravenously injected within 10 seconds. Lesions that enhanced within 11.5 seconds after the aorta opacified were regarded as malignant. Lesions that enhanced more than 11.5 seconds after the aorta were regarded as benign. A centrifugal pattern of enhancement was regarded as a sign that a lesion was benign. RESULTS: Eighty-seven lesions were evaluated. Histologic examination showed 65 lesions were malignant and 22 were benign. Gadolinium-enhanced TurboFLASH imaging had a sensitivity of 95%, a specificity of 86%, and an overall accuracy of 93% in differentiating benign from malignant lesions. CONCLUSION: Gadolinium-enhanced TurboFLASH imaging is a valuable method in the examination of breast lesions suspected of being malignant.

Breast↗
PubMed2005

Sclerotherapy for venous malformations using a "negative subtraction" technique.

We describe a technique of injecting alcohol into venous malformations (VM) under slow digital subtraction angiography (DSA) which eliminates the need to pre-mix the alcohol with a contrast agent. The technique presented here is especially helpful when Metrizamide is not available or not permitted for use. It offers an elegant way to visualize, in real time, the alcohol injected into the VM, while preserving its high concentration and potency as a sclerosing agent.

Angiography, Digital Subtraction↗
PubMed1992

99Tcm HMPAO-labelled leucocyte imaging in Crohn's disease: a subtraction technique for the quantification of disease activity.

A new technique for the quantitative analysis of labelled leucocyte images from patients with inflammatory bowel disease is described. The method involves the computer generation of a 'background' image which, after appropriate registration, is subtracted from the patient's image to leave a residue which represents abnormal uptake in the bowel. Quantification of the residual activity yields a scan score which can be related to the level of disease activity in patients with Crohn's disease. In 54 investigations on 33 patients the scan scores correctly agreed with a clinical assessment of disease activity in 16 of 20 cases with inactive disease and 32 out of 34 cases with active disease. Most of the discrepancies reflected inaccuracies in the clinical assessment of activity rather than shortcomings of the imaging technique.

Crohn Disease↗
PubMed1997

Dynamic TurboFLASH subtraction technique for contrast-enhanced MR imaging of the prostate: correlation with histopathologic results.

PURPOSE: To assess whether a TurboFLASH (fast low-angle shot) magnetic resonance (MR) sequence can improve the accuracy of fast spin-echo (SE) endorectal coil MR imaging in the staging and localization of prostate cancer. MATERIALS AND METHODS: In 57 patients with prostate cancer, MR imaging was performed with the following sequences: T1-weighted SE, T2-weighted fast SE, single-section gadolinium-enhanced dynamic subtracted TurboFLASH (one image every 1.25 or 2.5 seconds), and late-phase gadolinium-enhanced T1-weighted SE. Retrospectively, two blinded independent readers graded onset and steepest slope of enhancement and assessed tumor involvement and capsular penetration. MR findings were correlated with histopathologic results. RESULTS: On TurboFLASH images, prostate cancer was characterized by early and rapidly accelerating enhancement compared with that of surrounding tissues. Average sensitivity, specificity, and accuracy for detection of tumor involvement for the two readers with TurboFLASH images were 73.5%, 81.0%, and 77.5%. These values with fast SE images were 57.5%, 80.5%, and 72.0%. Depiction of capsular penetration and delineation and staging of tumor were better when TurboFLASH images were included with fast SE images. Differences between the two sequences, however, were not statistically significant. CONCLUSION: Because the TurboFLASH sequence did not statistically significantly improve tumor localization and staging results, routine use is not recommended. The technique may be useful for selected patients with equivocal evidence of capsular penetration.

Aged↗
PubMed1987

Autoradiographic study of regional protein synthesis in focal cerebral ischemia with TCA wash and image subtraction techniques.

The standard biochemical method of trichloracetic acid (TCA) wash and the image processing technique were combined to differentiate and visualize the distributions of polypeptide-incorporated and unincorporated tracers in an autoradiographic study of regional protein synthesis. The validity of applying TCA wash procedures to cryostat sections was considered by histologic and chemical evaluations. For the autoradiographic study of in vivo protein synthesis, a tracer dose of L-[14C]valine was administered 30 min after occlusion of the posterior communicating artery in gerbils. Images of total (polypeptide-incorporated and unincorporated) radioactivity and of polypeptide-incorporated radioactivity were obtained from an identical cryostat section before and after TCA wash. The polypeptide-unincorporated radioactivity image was produced with an image processing system by subtracting pixel by pixel the polypeptide-incorporated radioactivity from the total radioactivity. The present study clearly demonstrated that in spite of the sufficient delivery of tracer amino acids, the polypeptide synthesis was completely lost in the ischemic focus. Free tracer was markedly accumulated in the brain adjacent to the ischemic focus. This kind of autoradiographic technique seems to be indispensible in studying the topographical complexity of the altered protein metabolism in the pathologic brain.

Animals↗
PubMed1994

Computerized detection of masses in digital mammograms: automated alignment of breast images and its effect on bilateral-subtraction technique.

An automated technique for the alignment of right and left breast images has been developed for use in the computerized analysis of bilateral breast images. In this technique, the breast region is first identified in each digital mammogram by use of histogram analysis and morphological filtering operations. The anterior portions of the tracked breast border and computer-identified nipple positions are selected as landmarks for use in image registration. The paired right and left breast images, either from mediolateral oblique or craniocaudal views, are then registered relative to each other by use of a least-squares matching method. This automated alignment technique has been applied to our computerized detection scheme that employs a nonlinear bilateral-subtraction method for the initial identification of possible masses. The effectiveness of using bilateral subtraction in identifying asymmetries between corresponding right and left breast images is examined by comparing detection performances obtained with various computer-simulated misalignments of 40 pairs of clinical mammograms. Based on free-response receiver operating characteristic and regression analyses, the detection performance obtained with the automated alignment technique was found to be higher than that obtained with simulated misalignments. Detection performance decreased gradually as the amount of simulated misalignment increased. These results indicate that automatic alignment of breast images is possible and that mass-detection performance appears to improve with the inclusion of asymmetric anatomic information but is not sensitive to slight misalignment.

Breast Neoplasms↗