Automatic quantification of defect size using normal templates: a comparative clinical study of three commercially available algorithms

Infarct size assessed by myocardial single-photon emission tomography (SPET) imaging is an important prognostic parameter after myocardial infarction (MI). We compared three commercially available automatic quantification algorithms that make use of normal templates for the evaluation of infarct extent and severity in a large population of patients with remote MI. We studied 100 consecutive patients (80 men, mean age 63 +/- 11 years, mean LVEF 47% +/- 15%) with a remote MI who underwent resting technetium-99m tetrofosmin gated SPET study for infarct extent and severity quantification. The quantification algorithms used for comparison were a short-axis algorithm (Cedars-Emory quantitative analysis software, CEqual), a vertical long-axis algorithm (VLAX) and a three-dimensional fitting algorithm (Perfit). Semiquantitative visual infarct extent and severity assessment using a 20-segment model with a 5-point score and the relation of infarct extent and severity with rest LVEF determined by quantitative gated SPET (QGS) were used as standards to compare the different algorithms. Mean infarct extent was similar for visual analysis (30% +/- 21%) and the VLAX algorithm (25% +/- 17%), but CEqual (15% +/- 11%) and Perfit (5% +/- 6%) mean infarct extents were significantly lower compared with visual analysis and the VLAX algorithm. Moreover, infarct extent determined by Perfit was significantly lower than infarct extent determined by CEqual. Correlations between automatic and visual infarct extent and severity evaluations were moderate (r = 0.47, P < 0.0001 to r = 0.62, P < 0.0001) but comparable for all three algorithms. Correlations between LVEF and visual evaluation of infarct extent (r = -0.80, P < 0.0001) and severity (r = -0.82, P < 0.0001) were good but correlations were significantly lower for all three algorithms (r = -0.48, P < 0.0001 to r = -0.65, P < 0.0001). Systematically lower correlations were found in non-anterior infarctions (n = 69) and obese patients (BMI > or = 30 kg/m2, n = 32) compared with anterior infarctions and non-obese patients for all three algorithms. In this large series of post-MI patients, results of infarct extent and severity determination by automatic quantification algorithms that make use of normal templates were not interchangeable and correlated only moderately with semiquantitative visual analysis and LVEF.     

Sialin, an anion transporter defective in sialic acid storage diseases, shows highly variable expression in adult mouse brain, and is developmentally regulated

Sialin is a lysosomal membrane protein encoded by the SLC17A5 gene, which is mutated in patients with sialic acid storage diseases (SASD). To further understand the role of sialin in normal CNS development and in the progressive neuronal atrophy and dysmyelination seen in SASD, we investigated its normal cellular distribution in adult and developing mice. Overall, sialin showed granular immunoreactivity, consistent with a vesicular protein. Adult mice showed widespread sialin expression, including in the brain, heart, lung, and liver. High-level immunoreactivity was seen in the neuropil of the hippocampus, striatum, and cerebral cortex, as well as in the perikarya of cerebellar Purkinje cells, globus pallidus, and certain thalamic and brainstem nuclei. In mouse embryos, the highest levels of expression were observed in the nervous system. We discuss the possible role of sialin in normal development and in SASD pathogenesis, as a framework for further investigation of its function in these contexts.     

Agreement between four available algorithms to evaluate global systolic left and right ventricular function from tomographic radionuclide ventriculography and comparison with planar imaging

BACKGROUND AND AIM: Left and right ventricular ejection fractions (LVEF and RVEF) and end-diastolic and end-systolic volumes (LVEDV, RVEDV, LVESV and RVESV) can be calculated from tomographic radionuclide ventriculography (TRV). The aim of this study was to validate and compare these parameters obtained using four different TRV software programs (QBS, QUBE, 4D-MSPECT and BP-SPECT). METHODS: LVEF obtained from planar radionuclide ventriculography (PRV) was compared with LVEF obtained from TRV using the four different software programs in 166 patients. Furthermore, ventricular volumes obtained using TRV (QBS, QUBE and 4D-MSPECT) were compared with those obtained using BP-SPECT, the latter being the only method with the validation of ventricular volumes in the literature. RESULTS: The correlation of LVEF between PRV and TRV was good for all methods: 0.81 for QBS, 0.79 for QUBE, 0.71 for 4D-MSPECT and 0.79 for BP-SPECT. The mean differences+/-standard deviation (SD) were 3.16+/-9.88, 10.72+/-10.92, 3.43+/-11.79 and 2.91+/-10.39, respectively. The correlation of RVEF between BP-SPECT and QUBE and QBS was poor: 0.33 and 0.38, respectively. LV volumes calculated using QBS, QUBE and 4D-MSPECT correlated well with those obtained using BP-SPECT (0.98, 0.90 and 0.98, respectively), with mean differences+/-SD of 7.31+/-42.94, -22.09+/-36.07 and -40.55+/-39.36, respectively. RV volumes showed poorer correlation between QBS and BP-SPECT and between QUBE and BP-SPECT (0.82 and 0.57, respectively). CONCLUSION: LVEF calculated using TRV correlates well with that calculated using PRV, but is not interchangeable with the value obtained using PRV. Volume calculations (for left and right ventricle) and RVEF require further validation before they can be used in clinical practice.     

Accuracy of commercially available processing algorithms for planar radionuclide ventriculography using data for a dynamic left ventricular phantom

BACKGROUND: Automatic and semi-automatic algorithms to calculate ejection fraction (EF) from planar radionuclide ventriculography (PRV) have been used for many years in nuclear medicine. Validation of these algorithms is scarce and often performed on outdated versions of the software. Nevertheless, clinical trials where PRV is being used as the 'gold standard' for EF are numerous. Because of the importance attributed to the EF calculated by these programs, the accuracy of the resulting EF was assessed with a dynamic left ventricular physical phantom. METHODS: A dynamic left ventricular phantom was used to simulate 21 combinations of various ejection fractions (7-66%) and end diastolic volumes (27-290 ml). For each combination, a planar radionuclide ventriculograph was acquired, converted to an interfile format and transferred into processing stations with 10 different contemporaneously available commercial algorithms. The gold standard was the 'real' EF of the phantom, derived from the exact volume of the ventricle in end diastolic and end systolic position. Correlation and Bland-Altman analysis was performed between the real EF and the calculated EF. RESULTS: The correlation for all data was excellent (r=0.98), the mean difference was very acceptable (0.98%). Nevertheless, Bland-Altman analysis showed a significant trend in the difference between real and calculated EF, with a growing underestimation for higher ranges of EF, due to an overestimation of background in larger volumes compared to smaller ones. CONCLUSION: The determination of EF from PRV, calculated with commercially available algorithms, correlates closely to the real EF of a dynamic left ventricular phantom. This phantom can be used in the development and validation of algorithms for PRV studies, in software audits and in quality assurance procedures.     

Protection of children born to hepatitis-B-infected mothers

The vaccination schedule implemented on 1 March 2003 for the approximately 1000 Dutch children per year born to hepatitis-B-virus-infected mothers is under discussion. The Health Council of The Netherlands and TNO have both published reports which reveal that the current schedule does not fulfil its objectives, as too many children are completely missed and many of the vaccinated children do not receive their scheduled vaccinations on time. Furthermore, doubts have been expressed about the effectiveness of the present vaccination schedule. In line with one of the schedules proposed by the Health Council we suggest the introduction of a 4-dose vaccination, in which the first vaccination is given immediately after the birth of the child. The subsequent vaccinations can then take place after 2, 4 and 11 months. These are the ages at which other children are also vaccinated against hepatitis B in accordance with the Dutch national vaccination programme. Furthermore, we advise an improved surveillance to ensure compliance with the individual vaccination schedules for these children. If data from the hepatitis-B screening of pregnant women, the regional vaccination registers, and the vaccinations actually administered are linked, then it will be possible to take swift action if a child is late for a hepatitis-B vaccination. In our opinion, this can best be achieved if a single national organisation is made responsible for the entire process, starting from the collection of the hepatitis-B data of pregnant women up to concluding the scheme, whether or not the serologic response is checked.     

Follow-up assessment of vestibular schwannomas: volume quantification versus two-dimensional measurements

Introduction  A conservative treatment strategy is often proposed as a primary treatment option in the management of vestibular schwannomas (VS). In this “wait and scan” policy, audiovestibular symptoms are monitored regularly, and VS growth is measured on consecutive magnetic resonance images (MRI). The aim of this study is validation of two-dimensional versus volume MRI assessment in the longitudinal follow-up of VS and to define tumor growth beyond measurement error. Methods  MRI scans of 68 consecutive patients with VS were analyzed retrospectively. Two-dimensional and volume measurements on contrast enhanced (CE) T1- and T2-weighted images were performed independently by two readers. Smallest detectable differences (SDD) were calculated, and intraclass correlation coefficients (ICCs) were determined for both assessment methods. Results  Two-dimensional and volume measurements both showed best reproducibility on CE T1-weighted images. SDD for differences relative to baseline MRI [SDD (%)] for two-dimensional measurements had a higher interobserver error compared to volume measurements (40% versus 19.7%), which decreases when tumor size increases. The ICC for two-dimensional measurements in three directions was 0.947, 0.974, and 0.978 and for volume measurements 0.999. Conclusion  Volume measurements are more accurate compared to two-dimensional measurements for the evaluation of VS growth. These measurements are assessed preferably on CE T1-weighted images. SDD (%) strongly depends on VS size. SDD between consecutive scans exceeds the common clinical applied criterion of 1 or 2 mm growth to define growth.     

Persistent trigeminal artery associated with trigeminal neuralgia: hypothesis of neurovascular compression

Introduction The aim of this study was to determine the prevalence of persistent trigeminal artery (PTA) associated with trigeminal neuralgia (TN). Methods From January 1998 to January 2004, 288 MRI scans of patients examined for trigeminal deficits were retrospectively evaluated. MRI was performed at 1.5 T. Scan protocols included cerebral TSE T2-weighted imaging, contrast enhanced SE T1-weighted imaging and thin-section 3D T2-weighted imaging of the temporal bones, 3D TOF pre- and postcontrast MR angiography. TN was defined as episodes of intense stabbing, electric shock-like pain in areas of the face supplied by the trigeminal branches. Neurovascular compression (NVC) was assumed to be present if the patient showed clinical features of TN, if there was contact between an artery and the trigeminal nerve on the affected side, and if other pathology had been excluded. The prevalence and confidence intervals were calculated (95% CI of the prevalence was based on the exact binomial distribution). Results Of 288 patients, 136 matched the criteria for TN. In this series a PTA was detected in three patients, which in all patients was on the same side as the TN. The prevalence of a PTA in patients presenting with TN was 2.2% (CI 0.005–0.06). Conclusion Previous studies have shown PTA as an incidental finding in 0.1–0.6% of cerebral angiograms. The prevalence of a PTA in patients with TN was 2.2%. With respect to the clinical significance, a PTA has to be considered in TN and the diagnosis of a PTA can easily be made using MR imaging/angiography.     

Normal limits of gated blood pool SPECT count-based regional cardiac function parameters

Purpose Computations of left and right ventricular (LV and RV) gated blood pool SPECT (GBPS) ejection fraction (EF) have been well validated against other imaging modalities. As GBPS images depict the entire extent of both blood pools, it is possible to compute not only global but also regional biventricular function parameters, which have the prospect of being clinically useful for planning cardiac resynchronization therapy. This investigation sought to establish LV and RV count-based GBPS regional functional normal limits and to quantify their reproducibility. Methods and materials Count-versus-time curves were fit to third-order Fourier series for each of 17 LV and RV sub-volumes to compute global and regional EF, timing, phase and dyssynchrony parameters. Algorithms were applied to data for 40 normal controls (NLs) and 15 patients with CHF. To assess reproducibility, data were reprocessed a second time, blinded to initial calculations. Results There were no statistically significant differences between any initial and reprocessed LV or RV parameters for NLs or patients with CHF. Percent of subjects categorized as abnormal were the same for initial and reprocessed parameters (McNemar's differences = 0-7%, P > 0.05 for each parameter). Most parameters were significantly different for patients with CHF versus NLs. Normal limits for the new technique agreed well with the literature for other imaging methods, and RV normal limits closely paralleled LV limits. Conclusion GBPS global and regional LV and RV normal limits are reproducible, and application of these normal limits to patients with CHF results in reproducible detection of functional abnormalities.