Quantitative DECT of Iodine in Chronic Subdural Hematoma as Surrogate of Membrane Exudation: A Pilot Feasibility Study.

OBJECTIVE: We explore the feasibility to estimate the exudation from chronic subdural hematoma (CSDH) membranes, by using dual-energy computed tomography (DECT) quantification of iodine leak and test if the derived quantitative variables and membrane morphology correlates with hematoma volume, internal architecture (homogeneous, laminar, separated, and trabecular types), and fractional hyperdense hematoma at presentation. METHODS: In this retrospective study, consecutive CSDH patients with postcontrast DECT head images from January 2020 and June 2021 were analyzed. Predictor variables derived from DECT were correlated with outcome variables followed by mixed-effects regression analysis. RESULTS: The study included 36 patients with 50 observations (mean age, 72.6 years; standard deviation, 11.6 years); 31 were men. Dual-energy CT variables that correlated with hematoma volume were external membrane volume (ρ, 0.37; P = 0.008) and iodine concentration (ρ, -0.29; P = 0.04). Variables that correlated with separated type of hematoma were total iodine leak (median [Q 1 , Q 3 ], 68.3 mg [48.5, 88.9] vs 38.8 mg [15.5, 62.9]; P = 0.001) and iodine leak per unit membrane volume (median [Q 1 , Q 3 ], 16.47 mg/mL [10.19, 20.65] vs 8.68 mg/mL [5.72, 11.41]; P = 0.002). Membrane grade was the only variable that correlated with fractional hyperdense hematoma (ρ, 0.28; P = 0.05). Regression analysis showed total iodine leak as the strongest predictor of separated type hematoma (odds ratio [95% confidence interval], 1.06 per mg [1.01, 1.1]). CONCLUSIONS: Dual-energy CT demonstrates iodine leak from CSDH membranes. The variables derived from DECT correlated with hematoma volume, internal architecture, and fractional hyperdense hematoma.

Dual-energy CT imaging of chronic subdural hematoma membranes: technical note.

This technical note describes a novel dual-energy CT (DECT) protocol with iodine map reconstruction that will enable visualization of chronic subdural hematoma (CSDH) membranes. We describe the technique and discuss the potential implications for surgical management. The cohort included 36 patients with 50 hematomas. Enhancing external membrane was demonstrated in all the 50 hematomas, incomplete internal membrane in 13, and complete internal membrane in 23 hematomas. A spandrel sign at the transition zone that indicates partial or complete formation of internal membrane was demonstrated in 36 hematomas. KEY POINTS: • Iodine maps from 5-min delayed post-contrast DECT provide spectral contrast difference and facilitate segregation of chronic subdural hematoma membranes. • The ability to image the membranes helps in assessing the degree of organization of the hematoma by providing the information about the membrane thickness, volume, complexity of the membranes, and the proportion of the liquefied component within the hematoma before surgical procedures are undertaken. • Membrane visualization helps in the localization of the transition zone and extension of the membranes over the cerebral lobes helping in the determination of craniotomy location and size, during membranectomy.

Principles and Applications of Dual Energy Computed Tomography in Neuroradiology.

Dual-energy computed tomography (DE CT) is a promising tool with many current and evolving applications. Available DE CT scanners usually consist of one or two tubes, or use layered detectors for spectral separation. Most DE CT scanners can be used in single energy or dual-energy mode, except for the layered detector scanners that always acquire data in dual-energy mode. However, the layered detector scanners can retrospectively integrate the data from two layers to obtain conventional single energy images. DE CT mode enables generation of virtual monochromatic images, blended images, iodine quantification, improving conspicuity of iodinated contrast enhancement, and material decomposition maps or more sophisticated quantitative analysis not possible with conventional SE CT acquisition with an acceptable or even lower dose than the SE CT. This article reviews the basic principles of dual-energy CT and highlights many of its clinical applications in the evaluation of neurological conditions.

Iodine-based Dual-Energy CT of Traumatic Hemorrhagic Contusions: Relationship to In-Hospital Mortality and Short-term Outcome.

BackgroundTraumatic hemorrhagic contusions are associated with iodine leak; however, quantification of leakage and its importance to outcome is unclear.PurposeTo identify iodine-based dual-energy CT variables that correlate with in-hospital mortality and short-term outcomes for contusions at hospital discharge.Materials and MethodsIn this retrospective study, consecutive patients with contusions from May 2016 through January 2017 were analyzed. Two radiologists evaluated CT variables from unenhanced admission head CT and follow-up head dual-energy CT scans obtained after contrast material-enhanced whole-body CT. The outcomes evaluated were in-hospital mortality, Rancho Los Amigos scale (RLAS) score, and disability rating scale (DRS) score. Logistic regression and linear regression were used to develop prediction models for categorical and continuous outcomes, respectively.ResultsThe study included 65 patients (median age, 48 years; interquartile range, 25-65.5 years); 50 were men. Dual-energy CT variables that correlated with mortality, RLAS score, and DRS score were iodine concentration, pseudohematoma volume, iodine quantity in pseudohematoma, and iodine quantity in contusion. The single-energy CT variable that correlated with mortality, RLAS score, and DRS score was hematoma volume at follow-up CT. Multiple logistic regression analysis after inclusion of clinical variables identified two predictors that enabled determination of mortality: postresuscitation Glasgow coma scale (P-GCS) (adjusted odds ratio, 0.42; 95% confidence interval [CI]: 0.2, 0.86; P = 0.01) and iodine quantity in pseudohematoma (adjusted odds ratio, 1.4 per milligram; 95% CI: 1.02 per milligram, 1.9 per milligram; P = 0.03), with a mean area under the receiver operating characteristic curve of 0.96 ± 0.05 (standard error). For RLAS, the predictors were P-GCS (mean coefficient, 0.32 ± 0.06; P < .001) and iodine quantity in contusion (mean coefficient, -0.04 per milligram ± 0.02; P = 0.01). Predictors for DRS were P-GCS (mean coefficient, -1.15 ± 0.27; P < .001), age (mean coefficient, 0.13 per year ± 0.04; P = .002), and iodine quantity in contusion (mean coefficient, 0.19 per milligram ± 0.07; P = .02).ConclusionIodine-based dual-energy CT variables correlate with in-hospital mortality and short-term outcomes for contusions at hospital discharge.© RSNA, 2019Online supplemental material is available for this article.See also the editorial by Talbott and Hess in this issue.

Dual-Energy Computed Tomography Imaging of Head: Virtual High-Energy Monochromatic (190 keV) Images Are More Reliable Than Standard 120 kV Images for Detecting Traumatic Intracranial Hemorrhages.

High-energy monochromatic (190 keV) images may be more reliable than standard 120 kV Images for detecting intracranial hemorrhages. We aimed to retrospectively compare virtual high monochromatic (190 keV) and standard 120 kV images from dual-energy computed tomography (CT; DECT) for the diagnosis of intracranial hemorrhages in traumatic brain injury (TBI). We analyzed admission CT studies in 100 trauma patients. Three radiologists independently reviewed four image sets: 120 kV and 190 keV (thin [1 mm] and thick [5 mm] section) images for the presence of various types of intracranial hemorrhages. The proportions of positive variables were compared and differences calculated by McNemar test and sensitivities determined by contingency tables. Randomly selected hemorrhagic lesions were analyzed for contrast index (CI). Thin-section 190 keV images were superior in the detection of subdural hematomas (SDH) (p < 0.0001), supratentorial contusions (p < 0.0001), and epidural hematomas (EDH) (p = 0.014), when compared with standard 120 kV images. However, 190 keV images were inferior to standard 120 kV images in diagnosis of subarachnoid hemorrhage (SAH) (thin-sections, p = 0.059; thick-sections, 0.0075). The 190 keV images yielded moderate increase in CI of contusions (Cohen's d > 0.53) and a large increase in CI of extra-axial hematomas (Cohen's d > 0.86). Our results indicate that virtual high monochromatic (190 keV, thin-section) images combined with standard 120 kV images may provide optimal diagnostic performance for evaluation of patients suspected of TBI.

Diagnostic accuracy of triple-contrast multi-detector computed tomography for detection of penetrating gastrointestinal injury: a prospective study.

PURPOSE: Neither the performance of CT in diagnosing penetrating gastrointestinal injury nor its ability to discriminate patients requiring either observation or surgery has been determined. MATERIALS AND METHODS: This was a prospective, single-institutional observational study of patients with penetrating injury to the torso who underwent CT. Based on CT signs, reviewers determined the presence of a gastrointestinal injury and the need for surgery or observation. The primary outcome measures were operative findings and clinical follow-up. CT results were compared with the primary outcome measures. RESULTS: Of one hundred and seventy-one patients (72 gunshot wounds, 99 stab wounds; age range, 18-57 years; median age, 28 years) with penetrating torso trauma who underwent CT, 45 % were followed by an operation and 55 % by clinical follow up. Thirty-five patients had a gastrointestinal injury at surgery. The sensitivity, specificity, and accuracy of CT for diagnosing a gastrointestinal injury for all patients were each 91 %, and for predicting the need for surgery, they were 94 %, 93 %, 93 %, respectively. Among the 3 % of patients who failed observation, 1 % had a gastrointestinal injury. CONCLUSION: CT is a useful technique to diagnose gastrointestinal injury following penetrating torso injury. CT can help discriminate patients requiring observation or surgery. KEY POINTS: • The most sensitive sign is wound tract extending up to gastrointestinal wall. • The most accurate sign is gastrointestinal wall thickening. • Triple-contrast CT is a useful technique to diagnose gastrointestinal injury. • Triple-contrast CT helps to discriminate patients requiring observation and surgery.

Vascular complications of penetrating brain injury: comparison of helical CT angiography and conventional angiography.

OBJECT: The authors conducted a study to compare the sensitivity and specificity of helical CT angiography (CTA) and digital subtraction angiography (DSA) in detecting intracranial arterial injuries after penetrating traumatic brain injury (PTBI). METHODS: In a retrospective evaluation of 48 sets of angiograms from 45 consecutive patients with PTBI, 3 readers unaware of the DSA findings reviewed the CTA images to determine the presence or absence of arterial injuries. A fourth reader reviewed all the disagreements and decided among the 3 interpretations. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of CTA were calculated on a per-injury basis and in a subpopulation of patients with traumatic intracranial aneurysms (TICAs). RESULTS: Sensitivity of CTA for detecting arterial injuries was 72.7% (95% CI 49.8%-89.3%); specificity, 93.5% (95% CI 78.6%-99.2%); PPV, 88.9% (95% CI 65.3%-98.6%); and NPV, 82.9% (95% CI 66.4%-93.4%). All 7 TICAs were correctly identified by CTA. Sensitivity, specificity, PPV, and NPV of CTA in detecting TICAs were 100%. To compare agreement with DSA, the standard of reference, confidence scores categorized as low, intermediate, and high probability yielded an overall effectiveness of 77.8% (95% CI 71.8%-82.9%). CONCLUSIONS: Computed tomography angiography had limited overall sensitivity in detecting arterial injuries in patients with PTBI. However, it was accurate in identifying TICAs, a subgroup of injuries usually managed by either surgical or endovascular approaches, and non-TICA injuries involving the first-order branches of intracranial arteries.

Optimizing trauma multidetector CT protocol for blunt splenic injury: need for arterial and portal venous phase scans.

PURPOSE: To retrospectively compare the diagnostic performance of arterial, portal venous, and dual-phase computed tomography (CT) for blunt traumatic splenic injury. MATERIALS AND METHODS: Informed consent was waived for this institutional review board-approved, HIPAA-compliant study. Retrospective record review identified 120 blunt trauma patients (87 male [72.5%] 33 female [27.5%]; age range, 18-94 years) who had undergone dual-phase abdominal CT within 5 years, including 30 without splenic injury, 30 with parenchymal injury only, 30 with splenic active bleeding, and 30 with intrasplenic pseudoaneurysm. Six radiologists each performed blinded review of 20 different cases, and scored the presence of pseudoaneurysm, active bleeding, parenchymal injury, and hematoma; 20 cases were interpreted by all radiologists. Data analysis included calculation of diagnostic performance measures with confidence intervals, areas under receiver operating characteristic curves, and interobserver agreement/variability. RESULTS: For intrasplenic pseudoaneurysm, arterial phase imaging was more sensitive (70% [21 of 30] vs 17% [five of 30]; P < .0002) and more accurate (87% [78 of 90] vs 72% [65 of 90]; P = .0165) than portal venous phase imaging. For active bleeding, arterial phase imaging was less sensitive (70% [21 of 30] vs 93% [28 of 30]; P = .0195) and less accurate (89% [80 of 90] vs 98% [88 of 90]; P = .0168) than portal venous phase imaging. For parenchymal injury, arterial phase CT was less sensitive (76% [68 of 90] vs 93% [84 of 90]; P = .001) and less accurate (81% [nine of 120] vs 95% [114 of 120]; P = .0008) than portal venous phase CT. For all injuries, dual-phase review was equivalent to or better than single-phase review. CONCLUSION: For CT evaluation of blunt splenic injury, arterial phase is superior to portal venous phase imaging for pseudoaneurysm but inferior for active bleeding and parenchymal disruption; dual-phase CT provides optimal overall performance.

Focal cystic high-attenuation lesions: characterization in renal phantom by using photon-counting spectral CT--improved differentiation of lesion composition.

PURPOSE: To evaluate the capability of spectral computed tomography (CT) to improve the characterization of cystic high-attenuation lesions in a renal phantom and to test the hypothesis that spectral CT will improve the differentiation of cystic renal lesions with high protein content and those that have undergone hemorrhage or malignant contrast-enhancing transformation. MATERIALS AND METHODS: A renal phantom that contained cystic lesions grouped in nonenhancing cyst and hemorrhage series and an iodine-enhancing series was developed. Spectral CT is based on new detector designs that may possess energy-sensitive photon-counting abilities, thereby facilitating the assessment of quantitative information about the elemental and molecular composition of tissue or contrast materials. Imaging of the renal phantom was performed with a prototype scanner at 20 mAs and 70 keV, allowing characterization of x-ray photons at 25-34, 34-39, 39-44, 44-49, 49-55, and more than 55 keV. Region of interest analysis was used to determine lesion attenuation values at various x-ray energies. Statistical analysis was performed to assess attenuation patterns and identify distinct levels of attenuation on the basis of curve regression analysis with analysis of variance tables. RESULTS: Spectral CT depicted linear clusters for the cyst (P < .001, R(2) > 0.940) and hemorrhage (P < .001, R(2) > 0.962) series without spectral overlap. A distinct linear attenuation profile without spectral overlap was also detected for the iodine-enhancing series (P < .001, R(2) > 0.964), with attenuation values attained in the 34-39-keV energy bin statistically identified as outliers (mean slope variation, >37%), corresponding with iodine k-edge effects at 33.2 keV. CONCLUSION: Spectral CT has the potential to enable distinct characterization of hyperattenuating fluids in a renal phantom by helping identify proteinaceous and hemorrhagic lesions through assessment of their distinct levels of attenuation as well as by revealing iodine-containing lesions through analysis of their specific k-edge discontinuities.

MDCT diagnosis of penetrating diaphragm injury.

The purpose of the study was to determine the diagnostic sensitivity and specificity of multidetector CT (MDCT) in detection of diaphragmatic injury following penetrating trauma. Chest and abdominal CT examinations performed preoperatively in 136 patients after penetrating trauma to the torso with injury trajectory in close proximity to the diaphragm were reviewed by radiologists unaware of surgical findings. Signs associated with diaphragmatic injuries in penetrating trauma were noted. These signs were correlated with surgical diagnoses, and their sensitivity and specificity in assisting the diagnosis were calculated. CT confirmed diaphragmatic injury in 41 of 47 injuries (sensitivity, 87.2%), and an intact diaphragm in 71 of 98 patients (specificity, 72.4%). The overall accuracy of MDCT was 77%. The most accurate sign helping the diagnosis was contiguous injury on either side of the diaphragm in single-entry penetrating trauma (sensitivity, 88%; specificity, 82%). Thus MDCT has high sensitivity and good specificity in detecting penetrating diaphragmatic injuries.

Calcified vascular plaque specimens: assessment with cardiac dual-energy multidetector CT in anthropomorphically moving heart phantom.

PURPOSE: To evaluate whether dual-energy multidetector computed tomography (CT) with image postprocessing techniques enhances accuracy of calcified plaque quantification beyond the scope of single-energy multidetector CT, by using optical coherence tomography (OCT) as the reference standard. MATERIALS AND METHODS: Four atherosclerotic specimens were examined with 64-section dual-energy multidetector CT by using a novel dual-detector "double-decker" design, with stacked high- and low-energy detector arrays with 32 x 0.625-mm collimation, at 140 kVp and 400 mAs, acquiring simultaneous and isopedic low- and high-energy data sets. Additionally, combined-energy data sets were calculated, and an enhancement algorithm was proposed. Cardiac motion was simulated by an anthropomorphically moving phantom, and OCT was used as a reference standard for plaque quantification. Univariate general linear model (GLM) analysis was used to compare sizes of plaque calcifications determined with OCT with those determined with dual-energy multidetector CT, and the significance of factors such as cardiac motion was assessed. RESULTS: GLM analysis revealed that plaque quantification based on low-, high-, and combined-energy data sets differed significantly from that based on OCT (P < .001). Greater data variation occurred in smaller (<8 mm(2)) and larger (>12 mm(2)) calcifications. Comparison of calcified plaque sizes determined with OCT with those determined with the dual-energy multidetector CT enhancement algorithm revealed no significant difference (P = .550). Cardiac activity led to a slight increase in data variation in regard to OCT for corresponding static (mean, 10.2% +/- 3.2 [standard deviation]) and dynamic (13.8% +/- 4.9) dual-energy multidetector CT data sets. CONCLUSION: Dual-energy multidetector CT with novel postprocessing techniques enhanced accuracy of calcified plaque quantification by reducing effects of tissue blooming and beam hardening beyond single-energy multidetector CT.

Coronary stent patency: dual-energy multidetector CT assessment in a pilot study with anthropomorphic phantom.

PURPOSE: To prospectively evaluate, by optimizing image acquisition and introducing alternative image postprocessing techniques, dual-energy multidetector computed tomography (CT) for depiction of the lumens of coronary artery stents placed in a moving anthropomorphic heart phantom. MATERIALS AND METHODS: Four coronary stents (2, 3, 4, and 5 mm) were examined at 64-section dual-energy multidetector CT by using a dual-detector "double-decker" imager with stacked high- and low-energy detector arrays, 0.67-mm section thickness, and 32 x 0.625-mm collimation. Simultaneous high- and low-energy data sets were acquired at 80 and 140 kVp and at 400 mAs. Cardiac motion was simulated in a moving anthropomorphic heart phantom. Stents were imaged longitudinally and axially with the phantom at rest and with it in motion. Use of an enhancement algorithm based on high- and low-energy absorption profiles was proposed. Stent lumen depiction and stent mesh delineation were quantified in terms of contrast-to-noise ratio (CNR) and kurtosis (kappa), respectively. Image quality was analyzed at univariate general linear model analysis in which peak voltage and data enhancement algorithm were dependent factors and stent orientation and cardiac motion were independent factors. RESULTS: Analysis of CNR and kappa revealed an interdependency between CNR and kappa and stent diameter: The CNR and kappa of smaller stents increased significantly when these stents were imaged at lower peak voltages in the axial plane and with the enhancement algorithm applied to the 80-kVp data sets (P < .001). The CNR and kappa of larger stents increased significantly when these stents were imaged at higher peak voltages in the longitudinal plane, and imaging of these stents benefited from the enhancement algorithm being applied to the 140-kVp data sets (P < .001). CONCLUSION: Dual-energy multidetector CT performed with optimized acquisition parameters and alternative image postprocessing led to enhanced coronary stent lumen depiction to an extent beyond that achieved with single-energy multidetector CT.

The role of 3D-CTA in the assessment of peripheral vascular lesions in trauma patients.

PURPOSE: The goal of any imaging in the setting of a level 1 trauma center is to assess the injuries of a patient as fast as possible with the least amount of time spend to move the patients between rooms or scanners in order to reduce the time till final diagnosis. CT-angiography (CTA) has become increasingly used to analyze peripheral vascular lesions in blunt and penetrating trauma. METHODS: Diagnostic angiography and CTA are competing methods for the display of peripheral vascular lesions. The specific advantages and shortcomings of both techniques for the routine use in a trauma center are discussed. RESULTS: The inherent limitations of the spatial and temporal resolution of a CTA are compensated by the availability of the procedure and reduced time needed for the final diagnosis. CONCLUSION: 3D-CTA with multislice CT (MSCT) can be used to replace the diagnostic angiography in patients with blunt or penetrating extremity injuries.

Spectral coronary multidetector computed tomography angiography: dual benefit by facilitating plaque characterization and enhancing lumen depiction.

OBJECTIVE: To assess ex vivo specimens of atherosclerotic coronary arteries by dual energy (DE) multidetector computed tomography (MDCT) imaging, and to correlate depicted vessel lumen morphology and detected tissue characteristics with histopathologic analysis. METHODS: Coronary arteries were imaged on a 16-slice MDCT using a DE protocol consisting of a 90- and 140-kV scan. Coronary arteries were perfused with iodine- and gadolinium-based contrast agents. The DE K-edge subtractions were performed. Regions-of-interest were placed on histopathologically/radiographically-matched vascular lumen and wall, fibromuscular and calcified plaque, and fat tissues. Vascular/tissue contrast-to-noise ratios (CNR) were calculated, and their dependence on tissue type and contrast agent type was statistically evaluated. RESULTS: Tissue CNR analysis confirmed that all tissue types were successfully distinguished. Vascular wall and fibromuscular plaque achieved a significant increase in CNR ratios when DE techniques were used compared with 140 kV protocols. CONCLUSIONS: Spectral DE MDCT imaging of ex vivo atherosclerotic coronary arteries allows successful tissue characterization and enhances depiction of coronary lumen.

CT colonography: comparison of a colon dissection display versus 3D endoluminal view for the detection of polyps.

The purpose of this study was to compare sensitivity, specificity, and postprocessing time of a colon dissection approach to regular 3D-endoluminal workup of computed tomography (CT) colonography for the detection of polypoid lesions. Twenty-one patients who had received conventional colonoscopy after CT colonography were selected; 18 patients had either colon polyps or colon cancer and three had no findings. CT colonography was performed using a 4-channel multi-detector-row (MDR) CT in ten cases and a 16-channel MDR-CT in 11 cases. A blinded reader retrospectively evaluated all colonographies using both viewing methods in a randomized order. Thirty-seven polyps were identified by optical colonoscopy. An overall per-lesion sensitivity of 47.1% for lesions smaller than 5 mm, 56.3% for lesions between 5 mm and 10 mm, and 75.0% for lesion larger than 10 mm was calculated using the colon dissection approach. This compared to an overall per-lesion sensitivity of 35.3% (<5 mm), 81.5% (5-10 mm), and 100.0% (>10 mm) using the endoluminal view. The average time consumption for CT colonography evaluation with the colon dissection software was 10 min versus 38 min using the endoluminal view. A colon dissection approach may provide a significant time advantage for evaluation of CT colonography while obtaining a high sensitivity. It is especially superior in the detection of lesions smaller than 5 mm.

Multi-detector row CT: is prospective electrocardiographic triggering improving the detection of small pulmonary tumors?

RATIONALE AND OBJECTIVES: To compare prospectively ECG-triggered multi-detector row computed tomography (ECG-MDR-CT) and multi-detector row computed tomography (MDR-CT) without triggering for the detection of pulmonary tumors. MATERIALS AND METHODS: 100 patients with proven or suspected tumors were referred for CT of the lung for staging of lung metastases. First, a non-enhanced scan was performed using prospective ECG-triggering on a four-row multidetector helical CT scanner, followed by a contrast-enhanced scan without triggering. The diagnostic assessibility in detecting intrapulmonary nodules and mediastinal structures was graded using a 5-point scale (rated 1 = bad to 5 = very good image quality). RESULTS: ECG-MDR-CT images detected a total of 26% more pulmonary nodules than MDR-CT. For tumors <5 mm, the detection rate was 62% higher using ECG-triggered scans (P = .024). Subjective assessment found median demarcation ratings for all pulmonary findings of 4 (ECG-MDR-CT) versus 3 (MDR-CT). Mediastinal structures were delineated better using ECG triggering. The median ranking for demarcation of pulmonary findings <10 mm was 4 on ECG-MDR-CT and 3 on MDR-CT, respectively. For vessels and the left bronchus, the median of demarcation was 4 on triggered images and 2 on MDR-CT, respectively. The median values referring to the demarcation of mediastinal structures were not significantly different between ECG-MDR-CT and MDR-CT. CONCLUSION: Our data indicate the superiority of prospectively triggered ECG-MDR-CT over MDR-CT for the diagnosis of small pulmonary tumors using a 4-row multidetector CT.

Functional cardiac CT and MR: effects of heart rate and software applications on measurement validity.

This study sought to validate different software applications for cardiac function analysis using ECG-gated CT and MR datasets in correlation with underlying heart rate. Ten patients and a set of ventricular phantoms underwent concurrent multislice-CT and cine-MR imaging for evaluation of cardiac function. Datasets from both imaging modalities were evaluated utilizing 2 volumetric analysis tools to determine left ventricular volume and mass. Initially, intraobserver measurement variability was assessed. Detected measurement variability was correlated with underlying absolute magnitude of cardiac volumes and masses. Subsequently, results were statistically evaluated by determining significant data variability depending on imaging modality and choice of evaluation software. Finally, the data variability was correlated with underlying heart rates. This study showed that all analyzed datasets uniformly presented intraobserver variations below 2%, and variability was not related to the magnitude of measurement. Significant measurement accuracy was proven in all calculated parameters obtained from the cardiac phantoms. Acquired patient datasets and calculated functional parameters showed significant data homogeneity, with measurement variability coefficients ranging from 0.935-0.955. CT datasets showed maximal data variability at heart rates below 60 BpM. MR datasets showed maximal data variability at heart rates above 90 BpM. In conclusion, CT and MR datasets allowed an interchangeable utilization of volumetric analysis tools. However, reliable volumetric analysis was limited to an optimal range of cardiac rates for each modality, thus emphasizing the necessity of reporting volumetric measurement results in combination with heart rate to allow for consideration of this possible cause for measurement variation.

Volumetric assessment of pulmonary nodules with ECG-gated MDCT.

OBJECTIVE: The objective of our study was to assess physiologic lung deformation and compression originating from cardiovascular motion and their subsequent impact on determining the volume of small pulmonary nodules throughout the cardiac cycle on ECG-gated MDCT. SUBJECTS AND METHODS: Seventy-three small noncalcified pulmonary nodules were identified in 30 patients who underwent ECG-gated MDCT. The volume of each nodule was assessed throughout the cardiac cycle using computer-aided automatic segmentation algorithms, and the assessment was repeated three times. To ensure the validity of the subtle changes in volume that were detected, we determined the volume and signal attenuation in phantom data sets and patient nodules without temporal or spatial differentiation. Subsequently, nodules were assigned to pulmonary segments, and volume changes were correlated to cardiac phases, nodular location, and mean nodular size. Statistical multivariate tests were performed to evaluate significant patterns. RESULTS: The validity of significant measurements was proven in evaluated phantom data sets with a general tendency toward overestimating nodular volume (p = 0.492). Statistical evaluation of nodular signal attenuation confirmed true deformation and compression of nodules rather than partial volume effects as the reason for volume variations (p = 0.874). Differentiating pulmonary nodules in cardiac phases, pulmonary locations, and mean nodular volumes, we found that one single effect did not determine the amount of cardiovascular motion conveyed to pulmonary parenchyma and subsequently led to nodule deformation. Multivariate testing revealed statistically significant measures identifying patterns correlating variation in nodular volume with cardiac phase (p < 0.001), nodular location (p = 0.007), and mean nodular size (p < 0.001). CONCLUSION: Cardiovascular motion was disproportionately conveyed to various pulmonary segments and led to changes in the volume of pulmonary nodules, especially in small pulmonary nodules. A precise volumetric assessment was therefore possible only by identifying the underlying cardiac phase.

Multidetector CT angiography of arterial inflow and runoff in the lower extremities: a challenge in data acquisition and evaluation.

PURPOSE: To show the feasibility of acquiring homogenous 3-dimensional datasets with high temporal and spatial resolution from computed tomographic angiographic (CTA) scans of the lower extremities and to assess automated vessel-tracking techniques for vascular evaluation. METHODS: Eighteen men (mean age 67.0 years, range 43-83) with aneurysmal or occlusive vascular diseases underwent contrast-enhanced CTA of the lower limb arteries utilizing a 16-row CT imager. Curved multiplanar reformations were generated by manual selection of vessel centerlines in the infrarenal aorta and the arterial vasculature in the pelvis, thigh, and calf based on volume-rendering techniques. For each vessel, opacification and depiction were quantitatively evaluated. The manually segmented images were compared to datasets processed with automated vessel-tracking strategies by 5 radiologists, who evaluated diagnostic reliability and image quality. A Differential Receiver Operating Characteristic (DROC) analysis was performed. RESULTS: An increase in the temporal and spatial resolution led to acquisition of high quality CTA datasets. Significant homogeneity of the vascular contrast-to-noise ratios was achieved in the pelvic (coefficient of variance 1.5% to 10.1%), thigh (0.1% to 9.4%), and calf (3.3% to 19.2%) vessels. The assessment of vascular delineation revealed full-width-at-half-maximum contrast values of 96.4%, 95.5%, and 111.3% in the pelvis, thigh, and calf, respectively. Observers were not able to distinguish between manual and automated vascular segmentation, as represented by a 0.56 value for the area under the DROC curve. CONCLUSIONS: High-resolution CTA lower extremity datasets were acquired successfully, presenting vascular signal intensities of high homogeneity suitable for automated vessel-tracking techniques. Automated 3D visualization tools produced reliable, reproducible, and time-efficient centerline extractions that were comparable to manually defined centerlines.