M. Y. Norton

Staging of the axilla in breast cancer: accurate in vivo assessment using positron emission tomography with 2-(fluorine-18)-fluoro-2-deoxy-D-glucose.

OBJECTIVE To evaluate the ability of positron emission tomography (PET) with 18F-fluoro-2-deoxy-D-glucose (18F-FDG) to determine noninvasively axillary lymph node status in patients with breast cancer. BACKGROUND The presence of axillary lymph node metastasis is the most important prognostic factor in women with breast cancer. It signifies the presence of occult metastatic disease and indicates the need for adjuvant therapy. The only reliable way in which this important prognostic information may be obtained is by performing axillary dissection, which may be associated with significant complications and delay in discharge from the hospital. PET with 18F-FDG can visualize primary cancers in the breast and metastatic tumor deposits. METHODS Fifty patients with untreated breast cancer had clinical examination of their axilla performed (graded as positive or negative), followed by PET of the axilla and midthorax. PET data were analyzed blindly and graded as positive or negative, depending on the presence or absence of axillary nodal metastases. Cytopathologic assessment of the axillary nodes was carried out within 1 week of PET, by fine-needle aspiration cytology in 5 patients and axillary dissection in 45; the excised specimens were examined by a single pathologist. RESULTS The overall sensitivity of PET in 50 patients was 90% and the specificity was 97%. Clinical examination of the same patients had an overall sensitivity of 57% and a specificity of 90%. In the 24 patients with locally advanced breast cancer (T3, T4, TxN2), PET had a sensitivity of 93% and a specificity of 100%. In T1 tumors (seven patients), the sensitivity and specificity were 100%. PET had a high predictive value (>90%) and accuracy (94%) in staging the axilla. CONCLUSIONS PET is a sensitive and specific method of staging the axilla in patients with breast cancer. It may obviate the need for axillary surgery in women with small primary tumors, define the women likely to benefit from axillary dissection, or allow radiotherapy to be substituted for surgery, particularly in post-menopausal women.

Prevalence of hibernating myocardium in patients with severely impaired ischaemic left ventricles

Objective Severe impairment of left ventricular (LV) contraction is associated with an adverse prognosis in patients with ischaemic heart disease. Revascularisation may improve the impaired LV contraction if hibernating myocardium is present. The proportion of patients likely to benefit from this intervention is unknown. Therefore, the prevalence of hibernating myocardium in patients with ischaemic heart disease and severe impairment of LV contraction was assessed. Design From a consecutive series of patients undergoing coronary angiography for the investigation of chest pain or LV impairment, all patients with ischaemic heart disease and an LV ejection fraction (LVEF) ⩽ 30% were identified. These patients underwent positron emission tomography (PET) to detect hibernating myocardium, identified by perfusion metabolism mismatch. Setting A teaching hospital directly serving 500 000 people. Results Of a total of 301 patients, 36 had ischaemic heart disease and an LVEF ⩽ 30%. Twenty-seven patients had PET images, while nine patients were not imaged because of emergency revascularisation (three), loss to follow up (one), inability to give consent (four), and age < 50 years (one, ethics committee guidelines). Imaged and non-imaged groups were similar in LV impairment, demographic characteristics, and risk factor profile. Fourteen patients (52% of the imaged or 39% of all patients with ischaemic heart disease and LVEF ⩽ 30%) had significant areas of hibernating myocardium on PET. Conclusion It is possible that up to 50% of patients with ischaemic heart disease and severely impaired left ventricles have hibernating myocardium.

Detection of scarred and viable myocardium using a new magnetic resonance imaging technique: blood oxygen level dependent (BOLD) MRI

Background: The identification of viable myocardium in patients with impaired left ventricular contraction secondary to coronary heart disease is important clinically as such myocardium is likely to benefit from revascularisation. Blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) relies on changes in deoxyhaemoglobin concentration under stress for signal generation and could be used for the differentiation between scarred and viable myocardium. Aim: To assess the signal change on BOLD MRI in viable and scarred myocardium as identified by positron emission tomography (PET). Method: 19 patients with impaired left ventricular contraction and at least one akinetic area were enrolled. They underwent rest and dipyridamole stress MRI, using a double breath hold T2* weighted, ECG gated sequence to produce BOLD contrast images, and cine-MRI for wall thickening assessment. Dynamic perfusion and metabolic PET images followed the MRI. Signal change on BOLD MRI and the wall thickening were compared between rest and stress images in hibernating and scarred segments identified by PET on two short axis slices of mid ventricle, with eight segments each. Results: Using PET, 68 segments were identified as hibernating and 42 as scarred. The hibernating segments were found on BOLD MRI to have an average signal change between rest and stress of −9.53%, compared with −2.15% in the scarred segments (p = 0.008). The average wall thickening was 8.7 mm in the hibernating segments compared with 5.9 mm in the scarred segments (p < 0.0001). Conclusions: BOLD MRI with wall thickening may differentiate scarred and viable myocardium and help identify suitable patients for revascularisation. Further larger studies are needed to establish a threshold for detection, sensitivity, and specificity.

Can the surface electrocardiogram be used to predict myocardial viability

OBJECTIVE To investigate whether QRS morphology on the surface ECG can be used to predict myocardial viability. DESIGN ECGs of 58 patients with left ventricular impairment undergoing positron emission tomography (PET) were studied. 13N-Ammonia (NH3) and 18F-fluorodeoxyglucose (FDG) were the perfusion and the metabolic markers, respectively. The myocardium is scarred when the uptake of both markers is reduced (matched defect). Reduced NH3 uptake with persistent FDG uptake (mismatched defect) represents hibernating myocardium. First, the relation between pathological Q waves and myocardial scarring was investigated. Second, the significance of QR and QS complexes in predicting hibernating myocardium was determined. RESULTS As a marker of matched PET defects, Q waves were specific (79%) but not sensitive (41%), with a 77% positive predictive accuracy and a poor (43%) negative predictive accuracy. The mean size of the matched PET defect associated with Q waves was 20% of the left ventricle. This was not significantly different from the size of the matched PET defects associated with no Q waves (18%). Among the regions associated with Q waves on the ECG, there were 16 regions with QR pattern (group A) and 23 regions with QS pattern (group B). The incidence of mismatched PET defects was 19% of group A and 30% of group B (NS). CONCLUSIONS Q waves are specific but not sensitive markers of matched defects representing scarred myocardium. Q waves followed by R waves are not more likely to be associated with hibernating myocardium than QS complexes.

Assessment of left ventricular regional wall motion with blood pool tomography: comparison of 11CO PET with 99Tcm SPECT

Left ventricular contraction is routinely assessed by radionuclide ventriculography. Although a planar image is conventionally used, tomography has been shown to improve the detection of wall motion abnormalities. A blood pool image is often used in positron emission tomography on which to superimpose metabolic tracers. Can this image also be used to assess left ventricular contraction? Nine healthy controls, mean (S.D.) age 55 (5) years, and 12 patients, mean (S.D.) age 61 (8) years, with normal, proven or suspected left ventricular damage underwent blood pool tomography with 11CO positron emission tomography (PET) and 99Tcm single photon emission computed tomography (SPECT). A normal value of ejection fraction and range of phase were defined. The normal left ventricular ejection fraction was ≥37% for PET and ≥40% for SPECT. The ejection fractions obtained by the two methods in the patient group were positively correlated (r = 0.89, P < 0.001). Abnormalities of left ventricular contraction were detected in nine patients by PET and 10 patients by SPECT imaging. The discrepancy was in a patient with a previous inferior myocardial infarction. Blood pool imaging with 11CO PET can be used to assess left ventricular ejection fraction and regional wall motion.

Polar map or novel three-dimensional display technique for the improved detection of inferior wall myocardial infarction using tomographic radionuclide ventriculography.

Tomographic radionuclide ventriculography has the potential to be a significant improvement over conventional planar imaging. Although tomographic imaging can now be performed with relative ease, it is little used. This is most probably due to a perceived imbalance between potential clinical benefit and the extra complications of imaging. We investigated this matter by examining a series of 30 patients with isolated inferior or anterior myocardial infarction, identified by cardiac catheterization. Using either radionuclide imaging method, a significant wall motion abnormality was defined as matching (and appropriately located) phase and amplitude values outwith of two standard deviations from control values. These values were obtained from a series of 25 controls and represent construction values used to create a conventional polar map display. Overall detection rates for anterior myocardial infarction were 93 and 100% for planar and tomographic imaging, respectively (ns). For inferior myocardial infarction the rates were 7 and 93%, respectively (p < 0.001). Identical results were found using a novel three-dimensional method of displaying wall motion abnormalities. Tomography is therefore superior to planar imaging for the detection of inferior myocardial infarction but similar to planar imaging for the detection of anterior myocardial infarction.

A variable threshold edge-detector for improved quantitation of gated tomographic imaging of the left ventricular blood pool

SummaryThe accurate measurement of left ventricular volume from tomographic MUGA studies is difficult due to the limited resolving power of the gamma camera, which causes errors in the detection of the correct ventricular boundaries. Therefore, the use of fixed threshold or second-derivative edge-detectors results in overestimates at small volumes. A variable threshold edge-detection technique was developed to overcome this. Computer-simulated short-axis slices through the heart over a range of left ventricular dimensions were convolved by the Point Spread Response Function of the system to model the acquired image. The maximum pixel value and the threshold value required to detect the true ventricular edge from each simulation were then combined into a look-up table for the calculation of the required threshold value. As the dimension of the ventricle decreased, the threshold value chosen to detect the ventricular edge increased. Left ventricular volumes and ejection fraction measurements were calculated for seven patients using cine-MRI as the gold-standard technique for validation of the proposed method. The single photon emission tomographic studies were analysed using both the standard second-derivative edge-detection software and the proposed variable threshold technique. The variable threshold technique was shown to increase significantly the accuracy of ventricular volume measurements and ejection fraction calculations. The average error in the measurement of volumes was reduced from 41.4 ± 45.1% to 18.5 ± 14.6% and the accuracy of ejection fraction measurement was increased from 29.7 ± 4.6% to 11.3 ± 6.9%.

Gated metabolic myocardial imaging, a surrogate for dual perfusion-metabolism imaging by positron emission tomography

Objective Perfusion-metabolism mismatch pattern on positron emission tomography (PET) predicts hibernating myocardium. We assess the ECG-gated metabolic PET as a surrogate for the perfusion-metabolism mismatch pattern on PET imaging. Methods 13N-Ammonia (NH3) and 18F-fluorodeoxyglucose (FDG) are respectively perfusion and metabolism PET tracers. We used ECG gating to acquire FDG-PET to collect wall thickening (mechanical) data. These allow detection of metabolic activity in regions with reduced contraction (metabolism-mechanical mismatch pattern). We had two data sets on each patient: perfusion-metabolism and metabolism-mechanical data sets. We tested the hypothesis that metabolism-mechanical pattern on PET could predict perfusion-metabolism mismatch pattern. Results We studied 55 patients (48 males), mean age 62 years. All were in sinus rhythm, and had impaired left ventricular contraction. Perfusion-metabolism mismatch pattern was found in 26 patients. Metabolism-mechanical mismatch pattern was found in 25 patients. The results were concordant in 52 patients (95%). As a surrogate for perfusion-metabolism mismatch pattern, demonstration of metabolism-mechanical mismatch pattern is highly sensitive (92%) and specific (97%). In this cohort, the positive and negative predictive accuracy of the new method are 96% and 93%, respectively. Conclusion Metabolism-mechanical mismatch pattern could predict perfusion-metabolism mismatch pattern in patients with myocardial viability criteria on PET. Prospective validation against the gold standard of improved myocardial contraction after revascularisation is needed.

Characterization of viability, scarring and hibernation of the myocardium supplied by epicardial coronary arteries with low flow grades

Objective The aim of this study was to analyse the relationship between reduced coronary artery flow and myocardial viability, scarring and hibernation. Patients and methods Coronary flow grades and collateral vessels were scored using the thrombolysis in myocardial infarction trial (TIMI) and the Rentrop and Cohen scoring systems, respectively. 13N-ammonia and fluorine-18-fluorodeoxyglucose (18F-FDG) are the perfusion and metabolic markers on PET, respectively. The left ventricle was divided into three coronary territories. The area with the highest 13N-ammonia uptake was considered the reference region. Myocardial regions with 18F-FDG uptake of at least 50% of the reference region were considered viable and those with 18F-FDG uptake less than 50% of the reference region were considered scarred. Hibernation was considered present if the viable myocardium had significant wall motion abnormality. Results There were 80 (71 males) patients with 240 myocardial territories. TIMI 2–3 arteries supplied 151 regions (group A), and 89 regions were supplied by TIMI 0–1 arteries (group B). Viable myocardium was present in 140 (93%) regions of group A and in 76 (85%) regions of group B (P=0.068). Scarring was present in 40 (26%) regions in group A and in 49 (55%) regions in group B (P<0.0001). Wall motion data were available in 215 regions: 133 regions in group A and 82 regions in group B. Hibernating myocardium was predicted in 36 (28%) regions in group A and in 34 (41%) regions in group B (P<0.05). Conclusion Myocardial regions supplied by arteries with TIMI 0–1 are characterized by significantly increased incidence of hibernation and scarring. Video abstract: http://links.lww.com/NMC/A115