Comparison of conventional and Si-photomultiplier-based PET systems for image quality and diagnostic performance.

BACKGROUND: A new generation of positron emission tomography with computed tomography (PET-CT) was recently introduced using silicon (Si) photomultiplier (PM)-based technology. Our aim was to compare the image quality and diagnostic performance of a SiPM-based PET-CT (Discovery MI; GE Healthcare, Milwaukee, WI, USA) with a time-of-flight PET-CT scanner with a conventional PM detector (Gemini TF; Philips Healthcare, Cleveland, OH, USA), including reconstruction algorithms per vendor's recommendations. METHODS: Imaging of the National Electrical Manufacturers Association IEC body phantom and 16 patients was carried out using 1.5 min/bed for the Discovery MI PET-CT and 2 min/bed for the Gemini TF PET-CT. Images were analysed for recovery coefficients for the phantom, signal-to-noise ratio in the liver, standardized uptake values (SUV) in lesions, number of lesions and metabolic TNM classifications in patients. RESULTS: In phantom, the correct (> 90%) activity level was measured for spheres ≥17 mm for Discovery MI, whereas the Gemini TF reached a correct measured activity level for the 37-mm sphere. In patient studies, metabolic TNM classification was worse using images obtained from the Discovery MI compared those obtained from the Gemini TF in 4 of 15 patients. A trend toward more malignant, inflammatory and unclear lesions was found using images acquired with the Discovery MI compared with the Gemini TF, but this was not statistically significant. Lesion-to-blood-pool SUV ratios were significantly higher in images from the Discovery MI compared with the Gemini TF for lesions smaller than 1 cm (p < 0.001), but this was not the case for larger lesions (p = 0.053). The signal-to-noise ratio in the liver was similar between platforms (p = 0.52). Also, shorter acquisition times were possible using the Discovery MI, with preserved signal-to-noise ratio in the liver. CONCLUSIONS: Image quality was better with Discovery MI compared to conventional Gemini TF. Although no gold standard was available, the results indicate that the new PET-CT generation will provide potentially better diagnostic performance.

Importance of standardized assessment of late gadolinium enhancement for quantification of infarct size by cardiac magnetic resonance: implications for comparison with electrocardiogram.

BACKGROUND: Cardiac magnetic resonance (CMR) is currently considered the reference standard for in vivo assessment of myocardial infarction (MI). There is, however, no international consensus on how MI quantification from CMR should be performed. The aim of this study was to test how previously published manual quantification of MI using CMR images compares with MI quantification using a semiautomated, validated method and how this impacts the relationship with MI size estimated by 12-lead electrocardiogram (ECG). METHODS: Twenty-five patients, from a previously published cohort, were included in the study. All patients had presented with clinical signs of acute coronary syndrome 6 to 12 months before undergoing a CMR examination. The patients had a standard 12-lead ECG recorded at the time of the CMR examination. The previously reported manually quantified MI size was compared with MI size determined using a semiautomated method validated by computer phantom data, experimental in vivo and ex vivo data, and patient data. The MI sizes from the 2 CMR approaches were then compared with the ECG-estimated MI size. RESULTS: There was a strong correlation between MI size determined with the 2 CMR methods (r(2) = 0.94, P < .001). There was, however, a systematic overestimation of MI size of approximately 50% by the previously published manually quantified MI size compared with the semiautomated method. This affected the comparison with estimated MI size by ECG, which showed a significant underestimation of MI size compared with manual CMR measurements, but no bias compared with the semiautomated CMR method. CONCLUSIONS: Manual quantification of MI size by CMR can differ significantly from semiautomated, validated methods taking partial volume effects into account and can lead to erroneous conclusions when compared with ECG.

Similarity of ST and T waveforms of 12-lead electrocardiogram acquired from different monitoring electrode positions.

BACKGROUND: It is not always feasible to use standard electrode placement for limb leads when recording the 12-lead electrocardiogram (ECG). Other electrode placements have been accepted during monitoring. Nonstandard electrode positions, however, fail to produce waveforms identical to those recorded from the distal limb positions that are standard for diagnostic interpretation. The purpose of the present study was to validate the ST-T-segment for an alternative "Lund system" of proximal limb electrode sites. METHODS: Twelve-lead ECGs (standard, Mason-Likar, and Lund lead placement) were collected from 167 patients. RESULTS: There were systematic differences between measurements from standard vs Mason-Likar, but not vs the Lund system. The 95% confidence intervals of measurement agreement were similar or less when comparing measurements from the Lund system vs the first standard recording with measurements for the 2 standard recordings. CONCLUSION: The Lund system might constitute a uniform convention for "diagnostic" ECGs as well as for monitoring ECG applications with regard to ST-T waveforms.

EASI-Derived vs standard 12-lead electrocardiogram for Selvester QRS score estimations of chronic myocardial infarct size, using cardiac magnetic resonance imaging as gold standard.

BACKGROUND: The size of myocardial infarction (MI) is of significance for the prognosis. Selvester scores might be valuable for this estimation. OBJECTIVE: To compare the differences in Selvester scores for chronic MI provided from standard and EASI-derived 12-lead electrocardiograms (ECGs) and to compare these scores to the MI size measured by delayed-enhancement magnetic resonance imaging (DE-MRI). METHODS: Thirty-seven patients were studied. In connection with their DE-MRI scan follow-up after chest pain, body surface potential mapping was performed. Standard and EASI 12-lead ECGs were constructed from the maps. Two investigators manually performed the measurements required for scoring with the Selvester system using a quad-plot format of the ECGs. One of the investigators repeated this once for the standard leads. RESULTS: The differences between the 2 ECG estimations of MRI-measured MI size were not statistically significant. Neither the association nor the agreement between MRI and EASI-lead measurements or between MRI and standard-lead measurements were very strong. CONCLUSIONS: The differences between ECG and MRI measurements of MI size indicate that both methods may need improvement.

Diagnostic conclusions from the EASI-derived 12-lead electrocardiogram as compared with the standard 12-lead electrocardiogram in children.

BACKGROUND: Fewer electrodes on more easily located places would facilitate electrocardiogram (ECG) recording. To investigate the possibility of simplifying ECG recording in children, we compared the diagnostic conclusions when interpreting standard versus EASI-derived 12-lead ECGs. Our hypothesis was that the variation of the interpretation of standard versus EASI-derived 12-lead ECGs was not greater than the intrareader variation of the interpretation of standard ECGs. METHODS: The study included 221 children. The 2 lead systems were recorded simultaneously. Two experienced pediatric cardiologists interpreted the ECGs. First, the reader interpreted a set of 221 ECGs with randomly allocated standard and EASI-derived 12-lead ECGs. Next, the reader interpreted the complementary ECG set without having access to the first set. Finally, the reader reinterpreted the standard ECGs from 98 children. RESULTS: The variation of the interpretation of standard versus EASI-derived 12-lead ECGs was only slightly larger than the intrareader variation of the interpretation of standard ECGs. CONCLUSIONS: For most of the electrocardiographic diagnoses, the conclusions from EASI-derived 12-lead ECGs were similar to those from standard ECGs. These findings support the suggestion that the EASI lead system is a potential alternative to the standard ECG in children.

Comparison of signal quality between EASI and Mason-Likar 12-lead electrocardiograms during physical activity.

BACKGROUND: Myoelectric noise and baseline wander, artifacts that appear when patients move during electrocardiographic monitoring, can cause false alarms. This problem can be addressed by using a reduced lead set and placing electrodes on the anterior part of the torso only. The Mason-Likar modification of the standard 12-lead electrocardiogram and the EASI lead system are 2 alternative systems for lead placement. OBJECTIVES: To test the hypothesis that the EASI lead system is less susceptible to artifacts than is the Mason-Likar modification of the standard 12-lead electrocardiogram. METHODS: Baseline wander and myoelectric noise amplitudes of EASI and Mason-Likar 12-lead electrocardiograms were compared. Twenty healthy volunteers participated. Both lead systems were recorded simultaneously for different types of physical activities. For each lead in each subject, baseline wander and myoelectric noise were measured for both systems, at rest and during each physical activity. RESULTS: The outcome for baseline wander was mixed. For myoelectric noise content, the EASI system performed better for the limb leads in the different physical activities. In the precordial leads, the differences were minimal or mixed. However, for supine-to-right turning, EASI performed worse than the Mason-Likar system. CONCLUSIONS: The 2 systems have similar susceptibilities to baseline wander. The EASI system is, however, less susceptible to myoelectric noise than is the Mason-Likar system. EASI performed worse than Mason-Likar for turning supine to right, because only the EASI system uses an electrode in the right-midaxillary line.

Differences in QRS axis measurements, classification of inferior myocardial infarction, and noise tolerance for 12-lead electrocardiograms acquired from monitoring electrode positions compared to standard locations.

We tested whether the "Lund" (LU) electrode-placement system compared to the Mason-Likar (M-L) electrode-placement system would produce waveforms more similar to those of standard electrocardiograms (ECGs) with regard to the QRS axis in the frontal plane and QRS changes of inferior myocardial infarction (MI). We also tested whether LU was more noise immune than standard, and whether the noise immunities of the LU and M-L systems were comparable. Four 12-lead ECGs were recorded in 80 patients-2 standard ECGs, 1 LU ECG, and 1 M-L ECG. Further, 6 ECGs were recorded for 11 patients and 9 healthy volunteers-2 standard, 2 LU, and 2 M-L ECGs-while the subjects performed limb movements. Three electrocardiographic readers made blinded assessments of noise levels. QRS scores in patients with inferior MI differed significantly between standard and M-L ECGs but not between standard and LU ECGs. Few of those without QRS changes of MI received QRS scores, but not more often on LU ECGs than on standard ECGs, and never on M-L ECGs. QRS axis differences were small between standard and LU ECGs, but large between standard and M-L ECGs. The LU system was significantly more noise immune than the standard, whereas the difference in noise immunity between the M-L and LU systems was not significant. In conclusion, the results indicate that LU might constitute a uniform convention for "diagnostic" ECGs and for monitoring electrocardiographic applications.