Impact of motion artefact on the measurement of coronary calcium score

Coronary Artery Calcium Data and Reporting System (CAC-DRS): A Primer

The Coronary Artery Calcium Data and Reporting System (CAC-DRS) is a standardized reporting method for calcium scoring on computed tomography. CAC-DRS is applied on a per-patient basis and represents the total calcium score with the number of vessels involved. There are 4 risk categories ranging from CAC-DRS 0 to CAC-DRS 3. CAC-DRS also provides risk prediction and treatment recommendations for each category. The main strengths of CAC-DRS include a detailed and meaningful representation of CAC, improved communication between physicians, risk stratification, appropriate treatment recommendations, and uniform data collection, which provides a framework for education and research. The major limitations of CAC-DRS include a few missing components, an overly simple visual approach without any standard reference, and treatment recommendations lacking a basis in clinical trials. This consistent yet straightforward method has the potential to systemize CAC scoring in both gated and non-gated scans.

Radiomics of Coronary Artery Calcium in the Framingham Heart Study

PURPOSE

To extract radiomic features from coronary artery calcium (CAC) on CT images and to determine whether this approach could improve the ability to identify individuals at risk for a composite endpoint of clinical events.

MATERIALS AND METHODS

Participants from the Offspring and Third Generation cohorts of the community-based Framingham Heart Study underwent noncontrast cardiac CT (2002-2005) and were followed for more than a median of 9.1 years for composite major events. A total of 624 participants with CAC Agatston score (AS) of greater than 0 and good or excellent CT image quality were included for manual CAC segmentation and extraction of a predefined set of radiomic features reflecting intensity, shape, and texture. In a discovery cohort (n = 318), machine learning was used to select the 20 most informative and nonredundant CAC radiomic features, classify features predicting events, and define a radiomic-based score (RS). Performance of the RS was tested independently for the prediction of events in a validation cohort (n = 306).

RESULTS

The RS had a median value of 0.08 (interquartile range, 0.007-0.71) and a weak and modest correlation with Framingham risk score (FRS) (r = 0.2) and AS (r = 0.39), respectively. The continuous RS unadjusted, adjusted for age and sex, FRS, AS, and FRS plus AS were significantly associated with events (hazard ratio [HR] = 2.2, P < .001; HR = 1.8, P = .002; HR = 2.0, P < .001; HR = 1.7, P = .02; and HR = 1.8, P = .01, respectively). In participants with AS of less than 300, RS association with events remained significant when unadjusted and adjusted for age and sex, FRS, AS, and FRS plus AS (HR = 2.4, 2.8, 2.8, 2.3, and 2.6; P < .001, respectively). In the same subgroup of participants, adding the RS to AS resulted in a significant improvement in the discriminatory ability for events as compared with the AS (area under the receiver operating curve: 0.80 vs 0.68, respectively; P = .03).

CONCLUSION

A radiomic-based score, including the complex properties of CAC, may constitute an imaging biomarker to be further developed to identify individuals at risk for major adverse cardiovascular events in a community-based cohort. Supplemental material is available for this article. © RSNA, 2020.

Virtual Non-Contrast CT Using Dual-Energy Spectral CT: Feasibility of Coronary Artery Calcium Scoring

Objective

To evaluate the feasibility of coronary artery calcium scoring based on three virtual noncontrast-enhanced (VNC) images derived from single-source spectral dual-energy CT (DECT) as compared with true noncontrast-enhanced (TNC) images.

Materials and Methods

This prospective study was conducted with the approval of our Institutional Review Board. Ninety-seven patients underwent noncontrast CT followed by contrast-enhanced chest CT using single-source spectral DECT. Iodine eliminated VNC images were reconstructed using two kinds of 2-material decomposition algorithms (material density iodine-water pair [MDW], material density iodine-calcium pair [MDC]) and a material suppressed algorithm (material suppressed iodine [MSI]). Two readers independently quantified calcium on VNC and TNC images. The Spearman correlation coefficient test and Bland-Altman method were used for statistical analyses.

Results

Coronary artery calcium scores from all three VNC images showed excellent correlation with those from the TNC images (Spearman's correlation coefficient [ρ] = 0.94, 0.88, and 0.89 for MDW, MDC, and MSI, respectively; p < 0.001 for all pairs). Measured coronary calcium volumes from VNC images also correlated well with those from TNC images (ρ = 0.92, 0.87, and 0.91 for MDW, MDC, and MSI, respectively; p < 0.001 for all pairs). Among the three VNC images, coronary calcium from MDW correlated best with that from TNC. The coronary artery calcium scores and volumes were significantly lower from the VNC images than from the TNC images (p < 0.001 for all pairs).

Conclusion

The use of VNC images from contrast-enhanced CT using dual-energy material decomposition/suppression is feasible for coronary calcium scoring. The absolute value from VNC tends to be smaller than that from TNC.

Coronary artery calcium scoring on different 64-detector scanners using a low-tube voltage (80 kVp)

PURPOSE

The aim of this study was to compare the calcium score and reproducibility of coronary artery calcium scores obtained on the four kinds of 64-detector computed tomography (CT) scanners using standard (120 kVp) and low tube voltage (80 kVp) scan techniques.

MATERIALS AND METHODS

We scanned 80 and 120 kVp on all scanners. We calculated Agatston, volume, and mass scores for coronary artery calcium scoring on each scanner and compared the coefficients of variation of the calcium scores to evaluate reproducibility of among CT scanners.

RESULTS

The averages of the total mean Agatston score, total mean volume score, and total mean mass score at 80 kVp/120 kVp were 798.9/683.8, and 627.2/567.3, and 157.1/156.7, respectively. The total mean mass score was almost constant irrespective of the tube voltage. The total mean coefficients of variation for the four CT scanners were lower at 80 than 120 kVp (4.1% vs. 10.2% [total mean Agatston score], 3.2% vs. 9.6% [total mean volume score], and 3.2% vs. 9.4% [total mean mass score]).

CONCLUSION

Use of the low tube voltage technique can reduce variations in the coronary artery calcium scores obtained on different CT scanners.

[Quantitative evaluation of calcium (content) in the coronary artery using hybrid iterative reconstruction (iDose) algorithm on low-dose 64-detector CT: comparison of iDose and filtered back projection]

To evaluate the usefulness of hybrid iterative reconstruction (iDose) for quantification of calcium content in the coronary artery on 64-detector computed tomography (CT), an anthropomorphic cardiac CT phantom containing cylinders with known calcium content was scanned at tube current-time products of 15, 20, 25, and 50 mAs using 64-detector CT. The images obtained at 15, 20, 25, and 50 mAs were reconstructed using filtered back projection (FBP), and those at 15, 20, and 25 mAs were also reconstructed using iDose. Then the volume and mass of the calcium content in the cylinders were calculated and compared with the true values. The Agatston score was also evaluated. The Agatston score and mass of calcium obtained at 50 mAs using FBP were 656.92 and 159.91 mg, respectively. In contrast, those obtained at 25 mAs using iDose were 641.91 and 159.05 mg, respectively. No significant differences were found in the calcium measurements obtained using FBP and iDose. In addition, the Agatston score and mass of calcium obtained at 15 mAs and 20 mAs using iDose were not significantly different from those obtained at 25 mAs with iDose. By using iDose, accurate quantification of calcium in the coronary artery can be achieved at 15 mAs using 64-detector CT. The radiation dose can be significantly reduced in coronary artery calcium scoring without impairing the detection and quantification of coronary calcification.

A model for quantitative correction of coronary calcium scores on multidetector, dual source, and electron beam computed tomography for influences of linear motion, calcification density, and temporal resolution: a cardiac phantom study

PURPOSE

The objective of this study is to quantify the influence of linear motion, calcification density, and temporal resolution on coronary calcium determination using multidetector computed tomography (MDCT), dual source CT (DSCT), and electron beam tomography (EBT) and to find a quantitative method which corrects for the influences of these parameters using a linear moving cardiac phantom.

METHODS

On a robotic arm with artificial arteries with four calcifications of increasing density, a linear movement was applied between 0 and 120 mm/s (step of 10 mm/s). The phantom was scanned five times on 64-slice MDCT, DSCT, and EBT using a standard acquisition protocol. The average Agatston, volume, and mass scores were determined for each velocity, calcification, and scanner. Susceptibility to motion was quantified using a cardiac motion susceptibility (CMS) index. Resemblance to EBT and physical volume and mass was quantified using a Delta index.

RESULTS

Increasing motion artifacts were observed at increasing velocities on all scanners, with increasing severity from EBT to DSCT to 64-slice MDCT. The calcium score showed a linear dependency on motion from which a correction factor could be derived. This correction factor showed a linear dependency on the mean calcification density with a good fit for all three scoring methods and all three scanners (0.73 < or = R2 < or = 0.95). The slope and offset of this correction factor showed a linear dependency on temporal resolution with a good fit for all three scoring methods and all three scanners (0.83 < or = R2 < or = 0.98). CMS was minimal for EBT and increasing values were observed for DSCT and highest values for 64-slice MDCT. CMS was minimal for mass score and increasing values were observed for volume score and highest values for Agatston score. For all densities and scoring methods DSCT showed on average the closest resemblance to EBT calcium scores. When using the correction factor, CMS index decreased on average by 15% and Delta index decreased by 35%.

CONCLUSIONS

Calcium scores determined on DSCT and 64-slice MDCT are highly susceptible to motion as compared to EBT. The mass score is less susceptible to motion compared to volume and Agatston score. Calcium scores determined on DSCT bear a closer resemblance to EBT obtained calcium scores than 64-slice MDCT. In addition, the calcium score is highly dependent on the average density of individual calcifications and the dependency of the calcium score on motion showed a linear behavior on calcification density. From these relations, a quantitative method could be derived which corrects the measured calcium score for the influence of linear motion, mean calcification density, and temporal resolution.

Coronary calcium screening using low-dose lung cancer screening: effectiveness of MDCT with retrospective reconstruction

OBJECTIVE

The purpose of our study was to show the usefulness of nongated low-dose chest CT for coronary screening by comparing the results of coronary artery calcium measurement with that of dedicated calcium-scoring CT.

MATERIALS AND METHODS

One hundred twenty-eight consecutive participants (all men; mean age, 52 +/- 7 years) underwent low-dose chest CT and calcium-scoring CT with prospective ECG gating using 40-MDCT. Low-dose chest CT volume data were reconstructed as 25-cm field of view and three slice thicknesses: 1, 2.5, and 5 mm. For each examination, the lesion area, Agatston calcium score, and calcium mass were measured at 90- and 130-H thresholds. All measurements (130-H threshold) from the calcium-scoring CT were used as reference standards. Spearman's correlation test was used to compare the results.

RESULTS

Among the low-dose chest CT examinations, sensitivity was best determined with a 1-mm slice thickness at 130 H and 2.5-mm slice thickness at 90 H. Specificity was best determined with a 5-mm slice thickness at 130 H. Accuracy (90%) was best determined with a 2.5-mm slice thickness at 130 H. Of all protocols, calcium area, score, and mass from a 2.5-mm slice thickness at 130 H correlated best with the reference results (r = 0.89 for all three criteria).

CONCLUSION

Using a low radiation dose and nongated MDCT, we can detect coronary artery calcium and obtain results comparable to those obtained with dedicated calcium-scoring CT that uses a higher dose and ECG gating.

Calcium scoring using 64-slice MDCT, dual source CT and EBT: a comparative phantom study

Purpose Assessment of calcium scoring (Ca-scoring) on a 64-slice multi-detector computed tomography (MDCT) scanner, a dual-source computed tomography (DSCT) scanner and an electron beam tomography (EBT) scanner with a moving cardiac phantom as a function of heart rate, slice thickness and calcium density. Methods and materials Three artificial arteries with inserted calcifications of different sizes and densities were scanned at rest (0 beats per minute) and at 50–110 beats per minute (bpm) with an interval of 10 bpm using 64-slice MDCT, DSCT and EBT. Images were reconstructed with a slice thickness of 0.6 and 3.0 mm. Agatston score, volume score and equivalent mass score were determined for each artery. A cardiac motion susceptibility (CMS) index was introduced to assess the susceptibility of Ca-scoring to heart rate. In addition, a difference (Δ) index was introduced to assess the difference of absolute Ca-scoring on MDCT and DSCT with EBT. Results Ca-score is relatively constant up to 60 bpm and starts to decrease or increase above 70 bpm, depending on scoring method, calcification density and slice thickness. EBT showed the least susceptibility to cardiac motion with the smallest average CMS-index (2.5). The average CMS-index of 64-slice MDCT (9.0) is approximately 2.5 times the average CMS-index of DSCT (3.6). The use of a smaller slice thickness decreases the CMS-index for both CT-modalities. The Δ-index for DSCT at 0.6 mm (53.2) is approximately 30% lower than the Δ-index for 64-slice MDCT at 0.6 mm (72.0). The Δ-indexes at 3.0 mm are approximately equal for both modalities (96.9 and 102.0 for 64-slice MDCT and DSCT respectively). Conclusion Ca-scoring is influenced by heart rate, slice thickness and modality used. Ca-scoring on DSCT is approximately 50% less susceptible to cardiac motion as 64-slice MDCT. DSCT offers a better approximation of absolute calcium score on EBT than 64-slice MDCT when using a smaller slice thickness. A smaller slice thickness reduces the susceptibility to cardiac motion and reduces the difference between CT-data and EBT-data. The best approximation of EBT on CT is found for DSCT with a slice thickness of 0.6 mm.

The accuracy of 1- and 3-mm slices in coronary calcium scoring using multi-slice CT in vitro and in vivo

The accuracy of coronary calcium scoring using 16-row MSCT comparing 1- and 3-mm slices was assessed. A thorax phantom with calcium cylinder inserts was scanned applying a non-enhanced retrospectively ECG-gated examination protocol: collimation 12 x 0.75 mm; 120 kV; 133 mAs(eff). Thirty-eight patients were examined using the same scan protocol. Image reconstruction was performed with an effective slice thickness of 3 and 1 mm. The volume score, calcium mass and Agatston score were determined. Image noise was measured in both studies. The volume score and calcium mass varied less than the Agatston score. The overall measured calcium mass compared to the actual calcium mass revealed a relative difference of +2.0% for 1-mm slices and -1.2% for 3-mm slices. Due to increased image noise in thinner slices in the patient study (26.1 HU), overall calcium scoring with a scoring threshold of 130 HU was not feasible. Interlesion comparison showed significantly higher scoring results for thinner slices (all P<0.001). A similar accuracy comparing calcium scoring results of 1- and 3-mm slices was shown in the phantom study; therefore, the potentially necessary increase of the patient's dose in order to achieve assessable 1-mm slices with an acceptable image-to-noise-ratio appears not to be justified.

Effect of Varying Slice Thickness on Coronary Calcium Scoring With Multislice Computed Tomography in Vitro and in Vivo

OBJECTIVES

To compare coronary calcium scoring results (calcium volume, calcium mass, Agatston score, and number of lesions) of different slice thicknesses using a 16-slice CT (MSCT) scanner.

MATERIALS AND METHODS

A nonmoving anthropomorphic thorax phantom with calcium cylinders of different sizes and densities was scanned 30 times with repositioning applying a standardized retrospectively ECG-gated MSCT (SOMATOM Sensation 16; Siemens, Forchheim, Germany) scan protocol: collimation 12 x 0.75 mm, tube voltage 120 kV, effective tube current time-product 133 mAs(eff). Fifty patients (29 male; age 57.2 +/- 8.4 years) underwent a nonenhanced scan applying the same scan protocol. Two image sets (effective slice thicknesses 3 mm and 1 mm) were reconstructed at 60% of the RR interval. Image noise was measured in both studies. Calcium volume, calcium mass and Agatston score were calculated using a commercially available software tool.

RESULTS

Due to increased image noise in thinner slices, calcium scoring in all scans was performed applying a scoring threshold of 350 HU. In the phantom study, 1-mm slices showed significantly higher scoring results in respect to calcium volume (+8.2%), calcium mass (+12.5%), and Agatston score (+5.3%) (all P < 0.0001). In the patient study, 27 patients had coronary calcifications in 3-mm slices, and 31 patients had coronary calcifications in 1-mm slices. Thinner slices showed significantly higher scoring results in respect to volume (+47.1%), mass (+47.2%), and Agatston score (+29.7%) (all P < 0.0001).

CONCLUSIONS

When comparing 3-mm and 1-mm slices in coronary calcium scoring in MSCT, thinner slices lead to significantly increased scoring results.

Study on motion artifacts in coronary arteries with an anthropomorphic moving heart phantom on an ECG-gated multidetector computed tomography unit

Acquisition time plays a key role in the quality of cardiac multidetector computed tomography (MDCT) and is directly related to the rotation time of the scanner. The purpose of this study is to examine the influence of heart rate and a multisector reconstruction algorithm on the image quality of coronary arteries of an anthropomorphic adjustable moving heart phantom on an ECG-gated MDCT unit. The heart phantom and a coronary artery phantom were used on a MDCT unit with a rotation time of 500 ms. The movement of the heart was determined by analysis of the images taken at different phases. The results indicate that the movement of the coronary arteries on the heart phantom is comparable to that in a clinical setting. The influence of the heart rate on image quality and artifacts was determined by analysis of several heart rates between 40 and 80 bpm where the movement of the heart was synchronized using a retrospective ECG-gated acquisition protocol. The resulting reformatted volume rendering images of the moving heart and the coronary arteries were qualitatively compared as a result of the heart rate. The evaluation was performed on three independent series by two independent radiologists for the image quality of the coronary arteries and the presence of artifacts. The evaluation shows that at heart rates above 50 bpm the influence of motion artifacts in the coronary arteries becomes apparent. In addition the influence of a dedicated multisector reconstruction technique on image quality was determined. The results show that the image quality of the coronary arteries is not only related to the heart rate and that the influence of the multisector reconstruction technique becomes significant above 70 bpm. Therefore, this study proves that from the actual acquisition time per heart cycle one cannot determine an actual acquisition time, but only a mathematical acquisition time.

Coronary Calcification at Electron-Beam CT: Effect of Section Thickness on Calcium Scoring in Vitro and in Vivo

PURPOSE

To compare the accuracy of electron-beam computed tomography (CT) with 3.0- and 1.5-mm section thickness for calcium quantification and the prevalence of coronary calcifications with each.

MATERIALS AND METHODS

Electron-beam CT images were acquired with nonoverlapping 1.5- and 3.0-mm section thickness. Scans were obtained in an anthropomorphic thorax phantom with calcium cylinders of different sizes and densities, as well as in 1,302 study participants. A calcified lesion was defined as a minimum of 2 pixels (area, 0.52 mm2) with a minimum attenuation of 130 HU. The calcified lesions were quantified by means of a volumetric method with isotropic interpolation. From the phantom scans, mean volume scores, SDs, and measurement variations were calculated. From the participant scans, median volume scores and interquartile ranges were calculated. Participants were classified in categories based on cutoff levels for volume score quartiles for the 1.5-mm scans. An intraclass correlation coefficient (kappa value) was calculated as a measure of correlation between categories.

RESULTS

In the phantom, deviations of calculated volumes from the true cylinder volumes and measurement variations were generally higher for the 3.0-mm protocol than for the 1.5-mm protocol. In the participants, the median volume score was 100 mm3 (interquartile range, 11-409 mm3) for the 3.0-mm protocol and 144 mm3 (interquartile range, 35-513 mm3) for the 1.5-mm protocol. Agreement between classifications of volume scores for the 1.5- and 3.0-mm scans was good (kappa = 0.62, P <.001). Compared with the quartile classification for the 1.5-mm scan, however, classifications for 370 (28%) participants were put in a different category with the 3.0-mm protocol.

CONCLUSION

In a phantom, electron-beam CT scans with 3.0-mm section thickness yield less accurate estimates of calcified volume than do 1.5-mm scans. Electron-beam CT protocols with thinner sections considerably affect classification of individuals on the basis of the amount of coronary calcification depicted.

Does electron beam computer tomography provide added value in the diagnosis of coronary artery disease?

PURPOSE OF REVIEW

Electron beam computer tomography (EBCT) is increasingly being used to diagnose coronary artery disease (CAD) in the asymptomatic patient. The aim of this review is to assess the current findings concerning EBCT in the diagnosis and prognostication of CAD.

RECENT FINDINGS

Review of the English language peer-reviewed medical literature for EBCT was done with emphasis on the diagnosis and prognosis of CAD.

SUMMARY

The goal of risk stratification is to limit aggressive and costly care to group of high-risk patients. EBCT has been used to track the progression of coronary atherosclerosis periodically. Studies have shown that the calcium score will increase from 18 to 22% per year and depends on the age, sex and renal function. Patients with end-stage renal disease have much higher counts. Because it is cheap and noninvasive, EBCT has been used to assess the effects of medications on velocity of increase in the calcium scores. There is concern about radiation for its use long term to assess the calcium score increase over a long period of time.

Quantification of coronary artery calcium with multi-detector row CT: assessing interscan variability with different tube currents pilot study

PURPOSE

To assess the interscan variability of coronary artery calcium as measured with different tube currents and quantification methods in prospective electrocardiography (ECG)-gated multi-detector row CT.

MATERIALS AND METHODS

Thirty-three subjects who were asymptomatic for coronary heart disease underwent prospective ECG-gated, subsecond multi-detector row CT of the heart. Each subject underwent two consecutive CT examinations, the first with a dose of either 40 mAs (n = 18) or 80 mAs (n = 15) and the second with a dose of 150 mAs. Calcium volume and calcium score were calculated. Pearson correlation coefficient was computed between the calcium scores of high- and low-dose examinations. Interscan variability in these measurements (ie, the absolute percentage difference) was compared between the examinations with 40-150 mAs and those with 80-150 mAs by using an independent sample t test. In addition, the interscan variabilities of calcium scores between vessels were evaluated with repeated measures of analysis of variance. The interscan variabilities between calcium score and volume measurement were also compared with paired t tests.

RESULTS

Twenty-seven of 33 subjects had coronary artery calcium deposits on both CT scans. Five subjects had no calcium deposit on either scan. One subject had calcium deposits on only one scan. The total calcium score between the high- and low-dose scans was highly correlated (r = 0.98) and was not significantly different (P =.58). The interscan variability of calcium score showed no significant difference with respect to subject (P =.25) or vessel (P =.84). The interscan variability of the calcium volume measurement was significantly lower than that of the calcium score with respect to both the subject (P <.01) and the vessel (P <.01).

CONCLUSION

A dose of 40 mAs appears adequate for quantifying coronary artery calcium at multi-detector row CT. Interscan variability of multi-detector row CT is substantially reduced by using the calcium volume method.

Noninvasive monitoring of local drug release using X-ray computed tomography: optimization and in vitro/in vivo validation

In vivo release profiles of drug-loaded biodegradable implants were noninvasively monitored and characterized using X-ray computed tomography (CT). The imaging method was adapted and optimized to quantitatively examine the release of an active agent from a model cylindrical PLGA device (the millirod) into rabbit livers over 48 h. Iohexol, a CT contrast agent, served as a model drug; optimization of CT acquisition parameters yielded a sensitivity of 0.21 mg/mL (or 95 microg iodine/mL) for this agent. In vitro validation of the method was carried out by tracking release of iohexol in gelatin gel phantoms. In vivo release in rabbit livers was characterized through quantitative analysis of CT images and compared with UV-Vis analysis of the explanted devices at three implantation times. After correction for respiratory motion, CT analysis correlates well with the extracted iohexol data at all time points. The percent error between the actual and experimental image data was below 10%. This study demonstrates the potential of using computed tomography to noninvasively quantify the rate of agent release from controlled delivery devices in vivo.

Evaluation of reconstruction windows for multislice computed tomography in quantification of coronary calcium

RATIONALE AND OBJECTIVES

To search for an optimum reconstruction window in retrospectively gated multislice computed tomography (MSCT) for quantification of coronary calcium.

MATERIALS AND METHODS

Coronary calcium quantified was examined as Agatston and volume scores by two experienced observers at 10 time points across the R-R interval of the electrocardiogram in 42 patients. A combination of statistical approaches was used to evaluate the distributions of minimum and maximum scores and of interobserver variability for both scoring methods across the cardiac cycle.

RESULTS

Based on the combination of evaluation approaches, 60% to 70% of the R-R interval appeared to be the optimum time point for obtaining maximum calcium scores with minimum interobserver variability. The optimum time point was more clearly defined for the Agatston score than for the volume score.

CONCLUSION

A reconstruction window beginning at 60% to 70% of the R-R interval seems to be most advantageous for retrospective gating of MSCT studies performed to quantify coronary calcium.

Multislice computed tomography cardiac imaging: current status

Non-invasive CT coronary artery imaging has previously had little relevance to most UK radiologists due to the limited availability of electron beam CT scanners. Major advances in CT technology have promoted new applications for helical CT, which include cardiac imaging. Widespread installation of 'multislice' helical CT scanners will make CT coronary artery imaging available for the first time in many UK hospitals. The technical advances and early clinical trial data are reviewed and multislice helical CT cardiac imaging in general is discussed.

Variation of the coronary calcium score depending on image reconstruction interval and scoring algorithm

RATIONALE AND OBJECTIVES

To evaluate the reconstruction interval dependent bandwidth of the coronary calcium score, considering different methods of image reconstruction and quantification of coronary calcifications.

MATERIALS AND METHODS

Seventy-five patients underwent coronary calcium scoring by use of retrospectively ECG-gated multislice spiral CT. In all patients overlapping and nonoverlapping image reconstruction was performed every 10% of the RR-interval. Coronary calcium score was calculated for every reconstructed image series using the Agatston score and a volumetric scoring method. In 25 patients the analysis was performed twice to determine the reconstruction interval dependent intraobserver variability.

RESULTS

For nonoverlapping image reconstruction the median of the calcium score determined by the Agatston method ranged from 125.8 to 216.2 and from 166.9 to 211.7 for the volumetric scoring method. For overlapping image reconstruction the corresponding values ranged from 91.6 to 160.5 for the Agatston score and 128.3 to 175.3 for the volumetric calcium score. Reconstruction interval dependent median (mean) variation of the coronary calcium score ranged from 24.1 (45.5)% for nonoverlapping image reconstruction using the Agatston score to 17.5 (25.2)% utilizing a volumetric calcium score with overlapping image reconstruction. There was no statistical significant (P< 0.05) difference between the different methods. Intraobserver variability for the different image reconstruction intervals ranged from 0.78% to 21.51%. The least intraobserver variability was found for overlapping image reconstruction during the diastole using the volumetric scoring method.

CONCLUSIONS

Diastolic image reconstruction at 50% or 60% of the RR-interval is recommendable for retrospectively ECG-gated multislice spiral CT. Volumetric calcium scoring and overlapping image reconstruction are beneficial to reduce the variation of the coronary calcium score.