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PubMed1992

Visualization of myocardial infarction 6 h after injection of 111In-antimyosin antibodies using a blood pool subtraction technique.

111In-antimyosin antibodies are capable of visualizing myocardial infarction (MI). Because of slow blood clearance, images are usually recorded 24 or 48 h postinjection. In this pilot study, a blood pool subtraction technique, which makes it possible to visualize MI 6 h postinjection, is validated. Twenty-five patients with proven MI (16 anterior, 9 inferior) were imaged a few minutes, 6 and 24 h after an injection of 111 MBq 111In-labelled antimyosin antibodies. Three planar views are obtained each time. Using software which performs the geometric registration, the grey level normalization and the subtraction of images, the blood pool image (obtained a few minutes postinjection) is subtracted from the 6 h image. The resulting image is the blood pool corrected 6 h image. The 24 h images and the blood pool corrected 6 h images were interpreted blindly and the number of correct, incorrect and impossible MI localizations was counted. The number of correct localizations is 19/25 for the standard 24 h images and 22/25 for the blood pool corrected 6 h images. Then, with this blood pool subtraction method, it is possible to visualize MI 6 h postinjection. This has to be taken into account when discussing the role of antimyosin scintigraphy in the management of patients with MI.

Antibodies, Monoclonal↗
PubMed1985

Demonstration of pancreatic parenchyma by digital subtraction techniques during endoscopic retrograde cholangiopancreatography.

This paper reports the feasibility of using digital subtraction angiography techniques during endoscopic retrograde cholangiopancreatography to obtain greater detail of pancreatic structure. The pancreatic duct was filled in 23 of 27 cases attempted and in 17 cases parenchymal detail was obtained. Filling defects due to neoplasm were clearly defined and the changes of chronic pancreatitis visualised. The technique seems valuable for small lesions but may carry a higher risk of producing pancreatitis.

Acute Disease↗
PubMed1996

[Dacryocystography in digital subtraction technique].

The authors emphasize the usefulness of dacryography to approach patients affected by epiphora. Digital dacryocystography had improved the anatomic and functional assessment of lacrimal apparatus. The methodology allowed in all patients an accurate visualization of the lacrimal system and the identification, in twenty cases, of pathological causes of epiphora. One patient was examined after dacryocystorinostomy. Digital dacryocystography is a very valuable technique for better contrast resolution, the subtraction of images, and continuous acquisition.

Adolescent↗
PubMed1994

Visualization of myocardial infarction six hours after injection of 111 In-antimyosin antibodies using an image subtraction technique.

111 In-antimyosin antibodies are capable of visualizing acute myocardial infarction (MI). Because of slow blood clearance, images are usually recorded 24 or 48 h postinjection. This pilot study was aimed at validating a blood pool subtraction technique, which makes it possible to visualize MI 6 h postinjection. Twenty-five patients with proven MI (16 anterior, 9 inferior) were imaged 10 minutes, 6 and 24 h after an injection of 110 MBq 111 In-labelled antimyosin antibodies, with a mean delay of two weeks after infarction. Three planar views were obtained each time. Using software which performs geometric registration, grey level normalization and subtraction of images, the blood pool image (obtained 10 minutes postinjection) was subtracted from the 6 hour image. The resulting image was the blood pool corrected 6 h image. The 24 h images and the blood pool corrected 6 h images were interpreted blindly and the number of correct, incorrect and indeterminate MI localizations were tabulated. The number of correct localizations was 19/25 for the standard 24 h images and 22/25 for the blood pool corrected 6 h images. With this blood pool subtraction method it was possible to visualize MI 6 h postinjection. Theoretically, this method could be applied six hours after myocardial infarction.

Antibodies, Monoclonal↗
PubMedDate not supplied

Spectrum subtraction technique for minimizing extracranial influence on cerebral blood flow measurements by 133xenon inhalation.

Estimates of regional cerebral blood flow (rCBF) by the 133Xe inhalation method are influenced by isotope contamination from slow clearing extracerebral tissues. Subtraction of x-ray (31 kev) from gamma-ray counts (81 kev) has been suggested as a means of yielding clearance curves that are relatively free of such contamination. In the present study, rCBF measurements based on the total 133Xe spectrum (x-ray plus gamma) were compared with those derived from the subtracted spectrum (x-ray minus gamma) in 20 young controls, using a two-compartmental analysis of the clearance curves. In comparison with addition, the subtraction data gave substantially higher estimates of blood flow for the slow (second) compartment. This, along with a shift in the relative weights of the two compartments, indicated a decreased contribution of slow tissue components, consistent with a reduction in extracerebral contamination. Blood flow values obtained by subtraction were in good agreement with those reported for the intracarotid injection method. A limitation of the subtraction technique, however, is the relatively high dose of isotope required for adequate signal-to-noise ratios.

Adult↗
PubMed2001

Effect of power Doppler and digital subtraction techniques on the comparison of myocardial contrast echocardiography with SPECT.

OBJECTIVE: To compare the accuracy and feasibility of harmonic power Doppler and digitally subtracted colour coded grey scale imaging for the assessment of perfusion defect severity by single photon emission computed tomography (SPECT) in an unselected group of patients. DESIGN: Cohort study. SETTING: Regional cardiothoracic unit. PATIENTS: 49 patients (mean (SD) age 61 (11) years; 27 women, 22 men) with known or suspected coronary artery disease were studied with simultaneous myocardial contrast echo (MCE) and SPECT after standard dipyridamole stress. MAIN OUTCOME MEASURES: Regional myocardial perfusion by SPECT, performed with (99m)Tc tetrafosmin, scored qualitatively and also quantitated as per cent maximum activity. RESULTS: Normal perfusion was identified by SPECT in 225 of 270 segments (83%). Contrast echo images were interpretable in 92% of patients. The proportion of normal MCE by grey scale, subtracted, and power Doppler techniques were respectively 76%, 74%, and 88% (p < 0.05) at > 80% of maximum counts, compared with 65%, 69%, and 61% at < 60% of maximum counts. For each technique, specificity was lowest in the lateral wall, although power Doppler was the least affected. Grey scale and subtraction techniques were least accurate in the septal wall, but power Doppler showed particular problems in the apex. On a per patient analysis, the sensitivity was 67%, 75%, and 83% for detection of coronary artery disease using grey scale, colour coded, and power Doppler, respectively, with a significant difference between power Doppler and grey scale only (p < 0.05). Specificity was also the highest for power Doppler, at 55%, but not significantly different from subtracted colour coded images. CONCLUSIONS: Myocardial contrast echo using harmonic power Doppler has greater accuracy than with grey scale imaging and digital subtraction. However, power Doppler appears to be less sensitive for mild perfusion defects.

Aged↗
PubMed1983

Digital intraarterial subtraction technique of the extracerebral vascular system.

We report the results from intraarterial digital subtraction angiography (IA DSA) of the extracerebral vessels with aortic arch injection of contrast medium via femoro-arterial puncture, instead of the more widely used intravenous digital subtraction angiography (IV DSA). Intraarterial DSA is performed using a lower contrast dose and rate, making this study less invasive and costly than the conventional arteriographic study of the aortic arch. Intraarterial DSA provides better resolution than IV DSA. The diagnostic accuracy is almost equivalent to conventional angiography and is largely superior to photographic subtraction angiography with intravenous injection of contrast media.

Angiography↗
PubMed1996

Quantitative renography with the organ volume method and interporative background subtraction technique.

When quantification of renal activity is performed by planar imaging, many correction factors must be considered. To obtain quantitative renal images and renogram, we have examined our proposed method by using the organ volume for scatter, attenuation, and background activity, and the interporative background subtraction (IBS) technique in phantom and clinical studies. A renal phantom study was performed by varying the renal depth from 3 to 11 cm and the kidney-to-background activity concentration ratio from 5 to 80. Planar images were properly corrected for scatter, attenuation and background activity by our method and the corrected images were compared with the images obtained by the conventional method for the estimation of true renal activity. Clinical Tc-99m DTPA dynamic data for both a good and a poor renal function were also corrected by our method and volume-corrected renograms were obtained. For the phantom study, depth-independent images were obtained and these images gave a good estimation of the true count rate. In the clinical study, the conventional renogram was especially modified to allow for oversubtraction of background counts in the early phase (0-4 min). In conclusion, our proposed correction method can assess renal function qualitatively and quantitatively in both static and dynamic planar renal imaging.

Evaluation Studies as Topic↗
PubMed1990

Limitations of the digital image subtraction technique in assessing alveolar bone crest changes due to misalignment errors during image capture.

The digital image subtraction method depends critically on the very precise registration of sequential radiographs. A method of using a single radiograph to form two identical digital images was created, eliminating any potential effects from irradiation or processing variation, to investigate the effects of misregistration between images. These images were displaced by 0.1-0.42 mm in the X, Y and XY directions before subtraction. A total of 35 alveolar crest margins from five bitewing radiographs were investigated for the extent of false bone loss or gain produced in the subtracted images. The mean grey level gradient across the interdental space/crestal margin interface was 3.1 (SD 1.4) grey levels per 0.05 mm pixel. Small displacements between subtracted images of 0.1-0.14 mm in the Y or XY directions caused 20-25% of crestal pixels to vary by greater than or equal to +/- 2.5% of the grey range. Larger displacements of 0.3-0.42 mm caused 65% of crestal pixels to vary by greater than or equal to +/- 2.5% of the grey range. A higher threshold of greater than or equal to +/- 4.1% of the grey range still showed up to 48% of crestal pixels were in this higher deviation band. A high noise threshold of +/- 8% of the grey range should be used to discriminate against false grey values. A visual method for estimating the direction of displacement error between images is discussed together with a method for setting noise thresholds for individual alveolar crest grey level gradients. In any radiograph, a range of alveolar crest gradients will be found and those with the higher gradients will produce the largest subtraction errors for any given displacement between images.

Alveolar Bone Loss↗
PubMed2001

Value of subtraction technique in Gd-DTPA-enhanced magnetic resonance angiography of the thoracic aorta.

AIM: To assess routine image subtraction in 3D gadopentate dimeglumine (Gd-DTPA)-enhanced magnetic resonance (MR) angiography of the thoracic aorta. MATERIALS AND METHODS: This was a prospective study of 22 consecutive patients referred for magnetic resonance imaging (MRI) of the thoracic aorta. All patients had 3D MR aortography (TR/TE/FA; 5/2 ms/25 degrees ) performed before and after bolus intravenous injection of Gd-DTPA. The Gd-DTPA enhanced and unenhanced data sets were subtracted and maximum intensity projections (MIP) projections of the thoracic aorta were performed. The standard unsubtracted MIP images were initially evaluated. These were then reviewed together with the subtracted images to assess for additional diagnostic information. Signal to noise ratios (SNR) and contrast to noise ratios (CNR) were measured. RESULTS: In four cases there was mild image degradation due to patient movement. In no case did subtraction alter the diagnosis. The mean SNR in the unsubtracted MIP images was 10.8 +/- 4.0 (median 11.1) and on the subtracted images was 21.2 +/- 9.9 (median 20.7;P < 0.0001). The mean aorta-to-mediastinal fat CNR was 3.9 +/- 2.8 (median 3.9) on the unsubtracted images and 15.0 +/- 10.6 (median 13) on the subtracted images (P < 0.0001). The mean aorta-to-vertebral body CNR was 5.2 +/- 3.1 (median 4.4) on the unsubtracted images and 15.1 +/- 9.3 on the subtracted images (P < 0.0001). CONCLUSION: Image subtraction significantly improved both the SNR and CNR, but did not alter the final diagnosis, and does not appear warranted in routine practice.

Adolescent↗
PubMed2003

Angiography for acute lower gastrointestinal hemorrhage: efficacy of cut film compared with digital subtraction techniques.

PURPOSE: To find out if digital subtraction angiography (DSA) has a different diagnostic power than conventional cut-film angiography in investigating acute lower gastrointestinal (GI) hemorrhage. MATERIALS AND METHODS: Retrospective analysis of two cohorts of patients investigated by angiography for acute lower GI hemorrhage was performed. One group of patients treated at one center ("hospital H") underwent conventional angiography. The other patients, treated at another center ("hospital G"), were investigated exclusively by DSA. The groups were compared for demographic characteristics, etiology, and bleeding parameters. The diagnostic power of both angiographic modalities was compared and statistically analyzed. RESULTS: Fifty-five lower GI hemorrhages investigated by conventional cut-film angiography and 53 cases studied by DSA were included. Both study groups had statistically similar demographic and bleeding characteristics. Overall sensitivity, specificity, and positive and negative predictive values of cut-film angiography for localizing the lower GI bleeding were 62%, 73%, 86%, and 42%, whereas, for DSA, the respective values were 60%, 100%, 100%, and 24% (Z-test P values were.78,.02,.03, and.16). CONCLUSIONS: DSA is as sensitive as conventional cut-film angiography for localizing acute lower GI bleeding. If a lesion is found, the chance that it will be the bleeding source is higher with DSA than with conventional angiography.

Acute Disease↗