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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Comparison of the prognostic value of SPECT after nitrate administration and metabolic imaging by PET in patients with ischaemic left ventricular dysfunction
No full textPURPOSE: We compared the prognostic value of 99mTc-tetrofosmin single-photon emission computed tomography (SPECT) after nitrate administration and positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) in patients with ischaemic left ventricular (LV) dysfunction. METHODS: Eighty-nine patients with previous myocardial infarction and LV dysfunction (LV ejection fraction 33 +/-10%) underwent 99mTc-tetrofosmin SPECT under control conditions (baseline) and
after sublingual administration of 10 mg of isosorbide dinitrate (nitrate). Within 1 week, all patients underwent PET imaging with 18F-FDG. Four patients were excluded because of inadequate FDG uptake caused by severe diabetes. Follow-up data were obtained by phone contact with patients and by review of hospital or physicians' records. Cardiac death, myocardial infarction and late
revascularisation for unstable angina were considered as events. Follow-up data were not available in three patients. Follow-up was 96% complete at a mean period of 29 +/- 19 months. RESULTS: At baseline SPECT, 59 (72%) patients had evidence of viable myocardium, while 23 did not. Of these latter patients, 12 (52%)
demonstrated viable myocardium after nitrate and 13 (56%) had preserved metabolic activity. Cardiac events (cardiac death, myocardial infarction and late revascularisation for unstable angina) occurred in 24 (29%) patients. Event-free survival was similar in patients with and patients without viable myocardium at
baseline SPECT (p = 0.8). In contrast, event-free survival was lower in patients with viable myocardium at nitrate SPECT and PET compared to those without viable myocardium (both p<0.05). CONCLUSION: In patients with ischaemic LV dysfunction, the prognostic value of SPECT imaging after nitrate is comparable to that of PET metabolic imaging
Estimation of coronary flow reserve by sestamibi imaging in type 2 diabetic patients with normal coronary arteries
No full textBACKGROUND: We assessed coronary flow reserve (CFR) by sestamibi imaging in patients with type 2 diabetes without coronary artery disease and normal coronary vessels. METHODS AND RESULTS: Dipyridamole/rest technetium 99m sestamibi imaging was performed in 33 patients with type 2 diabetes without a history of coronary artery disease and normal coronary vessels at angiography and in 12 control subjects. Myocardial blood flow (MBF) was estimated by measuring first-transit
counts in the pulmonary artery and myocardial counts from tomographic images. Estimated CFR was expressed as the ratio of stress MBF to rest MBF. Rest MBF and CFR were corrected for rate-pressure product and expressed as normalized MBF and
normalized CFR. At rest, estimated MBF and normalized MBF were not different in control subjects versus patients (0.98 +/- 0.4 counts x pixel(-1) x s(-1) vs 1.42 +/- 0.9 counts x pixel(-1) x s(-1) and 1.14 +/- 0.5 counts x pixel(-1) x s(-1) vs 1.61 +/- 0.9 counts x pixel(-1) x s(-1), respectively). Conversely, stress MBF
was higher in control subjects than in patients (2.34 +/- 0.8 counts x pixel(-1) x s(-1) vs 1.55 +/- 0.8 counts.pixel(-1) x s(-1), P < .01). Thus estimated CFR was higher in control subjects than in patients (2.40 +/- 0.3 vs 1.36 +/- 0.8, P < .0001). After correction for the rate-pressure product, normalized CFR was
still higher in control subjects than in patients (2.10 +/- 0.5 vs 1.28 +/- 0.8, P < .001). CONCLUSIONS: Sestamibi imaging may detect impaired coronary vascular function in response to dipyridamole in type 2 diabetic patients without a history of coronary artery disease and with normal coronary arteries
Tc-99m tetrofosmin tomography after nitrate administration in patients with ischemic left ventricular dysfunction: relation to metabolic imaging by PET
No full textPrognostic value of nitrate spect imaging in patients with ischemic left ventricular dysfunction.
No full textAssessment of coronary flow reserve by sestamibi imaging in patients with typical chest pain and normal coronary arteries
No full textPURPOSE: We assessed coronary flow reserve (CFR) by sestamibi imaging in patients with typical chest pain, positive exercise stress test and normal coronary vessels. METHODS: Thirty-five patients with typical chest pain and normal angiogram and 12 control subjects with atypical chest pain underwent dipyridamole/rest (99m)Tc-sestamibi imaging. Myocardial blood flow (MBF) was estimated by measuring first transit counts in the pulmonary artery and myocardial counts from SPECT images. Estimated CFR was expressed as the ratio of stress to rest MBF. Rest MBF and CFR were corrected for rate-pressure product (RPP) and expressed as normalised MBF (MBF(n)) and normalised CFR (CFR(n)). Coronary vascular resistances (CVR) were calculated as the ratio between mean arterial pressure and estimated MBF. RESULTS: At rest, estimated MBF and MBF(n) were lower in controls than in patients (0.98 +/- 0.4 vs 1.30 +/- 0.3 counts/pixel/s and 1.14 +/- 0.5 vs 1.64 +/- 0.6 counts/pixel/s, respectively, both p < 0.02). Stress MBF was not different between controls and patients (2.34 +/- 0.8 vs 2.01 +/- 0.7 counts/pixel/s, p=NS). Estimated CFR was 2.40 +/- 0.3 in controls and 1.54 +/- 0.3 in patients (p < 0.0001). After correction for the RPP, CFR(n) was still higher in controls than in patients (2.1 +/- 0.5 vs 1.29 +/-0.5, p < 0.0001). At baseline, CVR values were lower (p < 0.01) in patients than in controls. Dipyridamole-induced changes in CVR were greater (p < 0.0001) in controls (-63%) than in patients (-35%). In the overall study population, a
significant correlation between dipyridamole-induced changes in CVR and CFR was observed (r = -0.88, p < 0.0001). CONCLUSION: SPECT might represent a useful non-invasive method for assessing coronary vascular function in patients with
angina and a normal coronary angiogram
Comparison of prognostic value of baseline and nitrate Single-photon Emission computed tomography imaging in patients with ischaemic left ventricular dysfunction.
No full textTc-99m tetrofosmin tomography after nitrate administration in patients with ischemic left ventricular dysfunction: relation to metabolic imaging by PET.
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