Non-enhanced CT Images Research Articles

Dual-layer spectral computed tomography: Virtual non-contrast in comparison to true non-contrast images

PurposeTo evaluate virtual-non-contrast (VNC) images obtained from clinical triphasic scans with a dual-layer spectral computed tomography system regarding accuracy of iodine subtraction. Material and methodsFrom September to December 2016, 62 consecutive patients who underwent a clinical routine triphasic CT examination were included into this retrospective study. VNC images based on the arterial and portal venous phase were generated. For every patient and every contrast phase, a region-of-interest (ROI) was defined in aorta, liver, renal cortex, spongious bone, fat, muscle and fluid (i.e. gallbladder, urinary bladder), resulting in 2170 ROIs. VNC images were compared to true-non-contrast (TNC) images regarding difference in attenuation. Consistency between VNC images obtained from the arterial and portal venous phase as well as the influence of the initial attenuation on respective VNC images were evaluated. ResultsComparison of HU in VNC and TNC images showed a high accuracy of iodine elimination. Mean difference between TNC and VNC images was only 0.5 ± 8.5 HU and >90% of all comparisons showed a difference of less than 15 HU. For all tissues but spongious bone, mean absolute difference between TNC and VNC images was below 10 HU. VNC images derived from the arterial and the portal venous phase showed excellent correlation. The quality of iodine removal in VNC images was not influenced by the original contrast enhancement. However, VNC images cannot be used for evaluation of iodine removal in bone as bone and iodine can hardly be differentiated via spectral CT. ConclusionVNC imaging in DL-CT is a promising tool for daily clinical routine. As non-enhanced CT images are essential in multiple clinical situations, the permanent availability of VNC images with dual-layer spectral CT will result in a substantial reduction of radiation exposure and an increased diagnostic value of monophasic contrast-enhanced CT scans.

A CT-based radiomics analysis for clinical staging of non-small cell lung cancer

Objective To develop and validate a CT-based radiomics predictive model for preoperative predicting the stage of non-small cell lung cancer (NSCLC). Methods In this retrospective study, 657 patients with histologically confirmed was collected from October 2007 to December 2014. The primary dataset consisted of patients with histologically confirmed NSCLC from October 2007 to April 2012, while independent validation was conducted from May 2012 to December 2014. All the patients underwent non-enhanced and contrast-enhanced CT images scan with a standard protocol. The pathological stage (PTNM) of patients with NSCLC were determined by the intraoperative and postoperative pathological findings, and were divided into early stage (Ⅰ,Ⅱ stage) and advanced stage (Ⅲ,Ⅳ stage). A list of radiomics features were extracted using the software Matlab 2014a and the corresponding radiomics signature was constructed. Multivariable logistic regression analysis was performed with radiomics signature and clinical variables for developing the prediction model. The model performance was assessed with respect to discrimination using the area under the curve (AUC) of receiver operating characteristic(ROC) analysis. Results The discrimination performance of radiomics signature yielded a AUC of 0.715[95% confidence interval (CI):0.709 to 0.721] in the primary dataset and a AUC of 0.724(95%CI:0.717 to 0.731) in the validation dataset. On multivariable logistic regression, radiomics signature, tumor diameter, carcinoembryonic antigen (CEA) level, and cytokeratin 19 fragment (CYFRA21-1) level were showed independently associated with the stage (Ⅰ,Ⅱ stage vs. Ⅲ, Ⅳ stage) of NSCLC. The prediction model showed good discrimination in both primary dataset (AUC=0.787, 95%CI:0.781 to 0.793;sensitivity=73.4%, specificity=72.2%,positive predictive value=0.707,negative predictive value=0.868) and independent validation dataset (AUC=0.777, 95%CI:0.771 to 0.783,sensitivity=91.3%,specificity=67.3%,positive predictive value=0.607, negative predictive value=0.946). Conclusion The radiomics predictive model, which integrated with the radiomics signature and clinical characteristics can be used as a promising and applicable adjunct approach for preoperatively predicting the clinical stage (Ⅰ,Ⅱ stage vs. Ⅲ,Ⅳ stage) of patients with NSCLC. Key words: Lung neoplasms; Tomography,X-ray computed; Radiomics

Assessment of noise reduction potential and image quality improvement of a new generation adaptive statistical iterative reconstruction (ASIR-V) in chest CT.

To evaluate the image quality improvement and noise reduction in routine dose, non-enhanced chest CT imaging by using a new generation adaptive statistical iterative reconstruction (ASIR-V) in comparison with ASIR algorithm. 30 patients who underwent routine dose, non-enhanced chest CT using GE Discovery CT750HU (GE Healthcare, Waukesha, WI) were included. The scan parameters included tube voltage of 120 kVp, automatic tube current modulation to obtain a noise index of 14HU, rotation speed of 0.6 s, pitch of 1.375:1 and slice thickness of 5 mm. After scanning, all scans were reconstructed with the recommended level of 40%ASIR for comparison purpose and different percentages of ASIR-V from 10% to 100% in a 10% increment. The CT attenuation values and SD of the subcutaneous fat, back muscle and descending aorta were measured at the level of tracheal carina of all reconstructed images. The signal-to-noise ratio (SNR) was calculated with SD representing image noise. The subjective image quality was independently evaluated by two experienced radiologists. For all ASIR-V images, the objective image noise (SD) of fat, muscle and aorta decreased and SNR increased along with increasing ASIR-V percentage. The SD of 30% ASIR-V to 100% ASIR-V was significantly lower than that of 40% ASIR (p < 0.05). In terms of subjective image evaluation, all ASIR-V reconstructions had good diagnostic acceptability. However, the 50% ASIR-V to 70% ASIR-V series showed significantly superior visibility of small structures when compared with the 40% ASIR and ASIR-V of other percentages (p < 0.05), and 60% ASIR-V was the best series of all ASIR-V images, with a highest subjective image quality. The image sharpness was significantly decreased in images reconstructed by 80% ASIR-V and higher. In routine dose, non-enhanced chest CT, ASIR-V shows greater potential in reducing image noise and artefacts and maintaining image sharpness when compared to the recommended level of 40%ASIR algorithm. Combining both the objective and subjective evaluation of images, non-enhanced chest CT images reconstructed with 60% ASIR-V have the highest image quality. Advances in knowledge: This is the first clinical study to evaluate the clinical value of ASIR-V in the same patients using the same CT scanner in the non-enhanced chest CT scans. It suggests that ASIR-V provides the better image quality and higher diagnostic confidence in comparison with ASIR algorithm.

The effect of iodine uptake on radiation dose absorbed by patient tissues in contrast enhanced CT imaging: Implications for CT dosimetry.

To investigate the effect of iodine uptake on tissue/organ absorbed doses from CT exposure and its implications in CT dosimetry. The contrast-induced CT number increase of several radiosensitive tissues was retrospectively determined in 120 CT examinations involving both non-enhanced and contrast-enhanced CT imaging. CT images of a phantom containing aqueous solutions of varying iodine concentration were obtained. Plots of the CT number increase against iodine concentration were produced. The clinically occurring iodine tissue uptake was quantified by attributing recorded CT number increase to a certain concentration of aqueous iodine solution. Clinically occurring iodine uptake was represented in mathematical anthropomorphic phantoms. Standard 120kV CT exposures were simulated using Monte Carlo methods and resulting organ doses were derived for non-enhanced and iodine contrast-enhanced CT imaging. The mean iodine uptake range during contrast-enhanced CT imaging was found to be 0.02-0.46% w/w for the investigated tissues, while the maximum value recorded was 0.82% w/w. For the same CT exposure, iodinated tissues were found to receive higher radiation dose than non-iodinated tissues, with dose increase exceeding 100% for tissues with high iodine uptake. Administration of iodinated contrast medium considerably increases radiation dose to tissues from CT exposure. • Radiation absorption ability of organs/tissues is considerably affected by iodine uptake • Iodinated organ/tissues may absorb up to 100 % higher radiation dose • Compared to non-enhanced, contrast-enhanced CT may deliver higher dose to patient tissues • CT dosimetry of contrast-enhanced CT imaging should encounter tissue iodine uptake.

Follow-up CT and CT angiography after intracranial aneurysm clipping and coiling-improved image quality by iterative metal artifact reduction.

This paper aims to evaluate a new iterative metal artifact reduction algorithm for post-interventional evaluation of brain tissue and intracranial arteries. The data of 20 patients that underwent follow-up cranial CT and cranial CT angiography after clipping or coiling of an intracranial aneurysm was retrospectively analyzed. After the images were processed using a novel iterative metal artifact reduction algorithm, images with and without metal artifact reduction were qualitatively evaluated by two readers, using a five-point Likert scale. Moreover, artifact strength was quantitatively assessed in terms of CT attenuation and standard deviation alterations. The qualitative analysis yielded a significant increase in image quality (p=0.0057) in iteratively processed images with substantial inter-observer agreement (ĸ=0.72), while the CTA image quality did not differ (p=0.864) and even showed vessel contrast reduction in six cases (30%). The mean relative attenuation difference was 27% without metal artifact reduction vs. 11% for iterative metal artifact reduction images (p=0.0003). The new iterative metal artifact reduction algorithm enhances non-enhanced CT image quality after clipping or coiling, but in CT-angiography images, the contrast of adjacent vessels can be compromised.

Textural Analysis of Liver Focal Lesions with Co-occurrence Matrix and Wavelet Transform on CT: A Feasible Study in FNH, HEM and HCC

Focal nodular hyperplasia (FNH), hepatocellular carcinoma (HCC) and cavernous hemangioma (HEM) are three types of solid focal liver lesions. Using CT images to identify these three types of lesions is the most commonly method. However, this method usually mainly depends on experiences. Whereas, more objective and quantitative image information could be explored with texture analysis method. This research aims to discuss the appreciations of texture analysis based on CT images for identifying FNH, HCC and HEM. This paper retrospectively analyzed 81 clinically or pathologically diagnosed cases, each of which contains contrast non-enhanced and contrast two-phasic enhanced CT images. The texture analysis was based on gray level co-occurrence matrix (GLCM) and wavelet transform. The results shows that the misclassification rates of texture classification were low to 2.73% between FNH and HEM (between benign lesions), 3.19% between FNH and HCC (between benign lesions and malignant lesions), and 1.67% between HEM and HCC (between benign lesions and malignant lesions) respectively. The effect of texture classification based on contrast two-phasic enhanced CT images was better than contrast non-enhanced CT images.

Traumatic Basilar Artery Dissection and Hypertrophic Olivary Degeneration

162 Canpolat et al. Basilar Artery Dissection and HOD Erciyes Med J 2015; 37(4): 162-5 163 Figure 1. a, b. Axial non-enhanced CT images at the level of the pons (a) and lateral ventricles (b) does not show any abnormality CT: computed tomography a b Figure 2. a, f. Axial T2-weighted images at the level of the cerebellum and brain stem (a-c) show hyperintense signal changes in the bilateral cerebellar hemispheres, which is predominant on the right side and in the pons, consistent with infarction. Diffusion-weighted images (b=1000) (d, e) reflect these changes as restricted diffusion. Besides, another focal area of infarction is demonstrated on the right side of the splenium of the corpus callosum (f) on diffusion-weighted image, which is not appreciated on T2-weighted images a

Hypervascular solid-appearing serous cystic neoplasms of the pancreas: Differential diagnosis with neuroendocrine tumours.

To describe imaging findings of arterial hypervascular solid-appearing serous cystic neoplasms (SCNs) of the pancreas on CT and MR and determine imaging features differentiating them from neuroendocrine tumours (NETs). We retrospectively identified 15 arterial hypervascular solid-appearing SCNs and randomly chose 30 size-matched pancreatic NETs. On CT, two radiologists in consensus assessed the size, morphology, and CT attenuation. On MR, predominant signal intensity and the amount of the cystic component on T2-weighted images and ADC maps were evaluated and compared using Fisher's exact and Student's t-test. The mean SCN size was 2.6 cm (range, 0.8-8.3). The CT findings were similar between the two tumours: location, shape, margin, and enhancement pattern. SCNs were significantly more hypodense on non-enhanced CT images than NETs (P = .03). They differed significantly on MR: bright signal intensity (P = .01) and more than a 10% cystic component on T2-weighted images (P = .01) were more common in SCNs than in NETs. All SCNs showed a non-restrictive pattern on the ADC map, while NETs showed diffusion restriction (P < .01). Arterial hypervascular solid-appearing SCNs and NETs share similar imaging features. Non-enhanced CT and MR images with T2-weighted images and ADC maps can facilitate the differentiation. • Frequency of hypervascular solid-appearing SCNs was 7.3% among surgically confirmed SCNs. • Hypervascular solid-appearing SCN of the pancreas can mimic pancreatic NETs. • Unenhanced CT and MR features help to differentiate the two tumours.

Different Imaging Strategies in Patients With Possible Basilar Artery Occlusion: Cost-Effectiveness Analysis.

This study evaluated the cost-effectiveness of different noninvasive imaging strategies in patients with possible basilar artery occlusion. A Markov decision analytic model was used to evaluate long-term outcomes resulting from strategies using computed tomographic angiography (CTA), magnetic resonance imaging, nonenhanced CT, or duplex ultrasound with intravenous (IV) thrombolysis being administered after positive findings. The analysis was performed from the societal perspective based on US recommendations. Input parameters were derived from the literature. Costs were obtained from United States costing sources and published literature. Outcomes were lifetime costs, quality-adjusted life-years (QALYs), incremental cost-effectiveness ratios, and net monetary benefits, with a willingness-to-pay threshold of $80,000 per QALY. The strategy with the highest net monetary benefit was considered the most cost-effective. Extensive deterministic and probabilistic sensitivity analyses were performed to explore the effect of varying parameter values. In the reference case analysis, CTA dominated all other imaging strategies. CTA yielded 0.02 QALYs more than magnetic resonance imaging and 0.04 QALYs more than duplex ultrasound followed by CTA. At a willingness-to-pay threshold of $80,000 per QALY, CTA yielded the highest net monetary benefits. The probability that CTA is cost-effective was 96% at a willingness-to-pay threshold of $80,000/QALY. Sensitivity analyses showed that duplex ultrasound was cost-effective only for a prior probability of ≤0.02 and that these results were only minimally influenced by duplex ultrasound sensitivity and specificity. Nonenhanced CT and magnetic resonance imaging never became the most cost-effective strategy. Our results suggest that CTA in patients with possible basilar artery occlusion is cost-effective.

Dual-source dual-energy CT angiography with virtual non-enhanced images and iodine map for active gastrointestinal bleeding: Image quality, radiation dose and diagnostic performance

ObjectivesTo evaluate the clinical feasibility of dual-source dual-energy CT angiography (DSDECTA) with virtual non-enhanced images and iodine map for active gastrointestinal bleeding (GIB). MethodsFrom June 2010 to December 2012, 112 consecutive patients with clinical signs of active GIB underwent DSDECTA with true non-enhanced (TNE), arterial phase with single-source mode, and portal-venous phase with dual-energy mode (100kVp/230mAs and Sn 140kVp/178mAs). Virtual non-enhanced CT (VNE) image sets and iodine map were reformatted from ‘Liver VNC’ software. The mean CT number, noise, signal to noise ratio (SNR), image quality and radiation dose were compared between TNE and VNE image sets. Two radiologists, blinded to clinical data, interpreted images from DSDECTA with TNE (protocol 1), and DSDECTA with VNE and iodine map (protocol 2) respectively, with discordant interpretation resolved by consensus. The standards of reference included digital subtraction angiography, endoscopy, surgery, or final pathology reports. Receiver–operating characteristic (ROC) analysis was undertaken and the area under the curve (AUC) calculated for CT protocols 1 and 2, respectively. ResultsThere was no significant difference in mean CT numbers of all organs (including liver, pancreas, spleen, kidney, abdominal aorta, and psoas muscle) (P>0.05). Lower noise and higher SNR were found on VNE images than TNE images (P<0.05). Image quality of VNE was lower than that of TNE without significant difference (P>0.05). The active GIB source was identified in 84 patients, 83 (83/84, 98.8%) of which were confirmed by one or more reference standard. The AUC was 0.935±0.027 and 0.947±0.026 for protocols 1 and 2, respectively. There was no significant difference between protocols 1 and 2 for diagnostic performance (Z=1.672, P>0.05). The radiation dose reduction achieved by omitting the TNE acquisition was (30.11±6.32)%. ConclusionDSDECTA with arterial phase with single-source mode, portal-venous phase with dual-energy mode and post-processing VNE image sets and iodine map could act as an accurate screening method for detection and localization of active GIB with lower radiation dose.

Dynamic Contrast Enhanced Magnetic Resonance Perfusion Imaging in High-Risk Smokers and Smoking-Related COPD: Correlations with Pulmonary Function Tests and Quantitative Computed Tomography

The study aimed to prospectively evaluate correlations between dynamic contrast-enhanced (DCE) MR perfusion imaging, pulmonary function tests (PFT) and volume quantitative CT in smokers with or without chronic obstructive pulmonary disease (COPD) and to determine the value of DCE-MR perfusion imaging and CT volumetric imaging on the assessment of smokers. According to the ATS/ERS guidelines, 51 male smokers were categorized into five groups: At risk for COPD (n = 8), mild COPD (n = 9), moderate COPD (n = 12), severe COPD (n = 10), and very severe COPD (n = 12). Maximum slope of increase (MSI), positive enhancement integral (PEI), etc. were obtained from MR perfusion data. The signal intensity ratio (RSI) of the PDs and normal lung was calculated (RSI = SIPD/SInormal). Total lung volume (TLV), total emphysema volume (TEV) and emphysema index (EI) were obtained from volumetric CT data. For “at risk for COPD,” the positive rate of PDs on MR perfusion images was higher than that of abnormal changes on non-enhanced CT images (p < 0.05). Moderate-to-strong positive correlations were found between all the PFT parameters and SIPD, or RSI (r range 0.445∼0.683, p ≤ 0.001). TEV and EI were negatively correlated better with FEV1/FVC than other PFT parameters (r range −0.48 –−0.63, p < 0.001). There were significant differences in RSI and SIPD between “at risk for COPD” and “very severe COPD,” and between “mild COPD” and “very severe COPD”. Thus, MR perfusion imaging may be a good approach to identify early evidence of COPD and may have potential to assist in classification of COPD.

Can virtual non-enhanced CT be used to replace true non-enhanced CT for the detection of palpable cervical lymph nodes? A preliminary study

To investigate the potential of virtual non-contrast CT (VNCT) from dual-energy CT to replace true nonenhanced CT (TNCT) for the detection of enlarged cervical lymph nodes. Thirty-nine patients with 94 histopathologically proven cervical lymph nodes were imaged with the dual-energy CT technique. VNCT images from the arterial [VNCT-A] and venous phases [VNCT-V] were obtained with the liver VNC application. The mean CT number and signal-to-noise ratio (SNR) were compared. Image quality was evaluated with a score scale of 1-5. Effective dose (ED) was calculated and compared. Mean CT numbers of cervical lymph nodes were higher on VNCT than on TNCT (P = 0.034). There was no difference in the SNR among three sets of non-enhanced CT images, but the CNR of VNCT images was higher than that of TNCT images (P < 0.001). Image quality of VNCT from two phases was comparable to that of TNCT (P = 0.070). There was no difference in image quality of three sets of non-enhanced CT images (P > 0.05). ED from dual-phase dual-energy CT was lower than that from tri-phase CT scans (P < 0.001). VNCT images from dual-energy CT of the neck had diagnostic image quality; they have the potential to replace TNCT, thus reducing the radiation dose.

E-046 THERAPY: A Prospective, Randomised, Concurrent Controlled Trial to Assess the Role of Mechanical Thrombectomy As Adjunctive Treatment to IV rtPA

Introduction/PurposeLiterature indicates that recanalisation with IV rtPA therapy is more likely when clot length is <8mm. Thin-sliced non-enhanced CT (NCCT) images (2.5 mm or less) may be used to evaluate...

Hepatocellular carcinoma associated with budd-chiari syndrome: imaging features and transcatheter arterial chemoembolization

BackgroundBudd–Chiari syndrome (BCS) often leads to hepatocellular carcinoma (HCC). Transcatheter arterial chemoembolization (TACE) has been increasingly used to treat BCS patients with HCC. The purposes of this study were to illustrate imaging features in BCS patients with HCC, and to analyze the effects of TACE on BCS patients with HCC.Methods246 consecutive patients with primary BCS were retrospectively studied. 14 BCS patients with HCC were included in this study. BCS were treated with angioplasty and/or stenting, and HCC were managed with TACE. Imaging features on ultrasonography, CT, MRI, and angiography and the serum AFP level were analyzed.ResultsInferior vena cava block and stricture of hepatic venous outflow tract more frequently occurred. Portal vein invasion was found in only 2 patients (14.2%). Imaging studies showed that most nodules of HCC were near the edge of liver, irregular, more than 3 cm in diameter, heterogeneous mass and solitary (≤3 nodules). HCC in patients associated with BCS was isointense or hypointense in nonenhanced CT images, and exhibited heterogeneous enhancement during the arterial phase and washout during the portal venous phase on enhanced CT and MRI. The serum AFP level significantly declined after TACE treatment.ConclusionsBCS patients with inferior vena cava block and stricture of hepatic venous outflow tract seems to be associated with HCC. A single, large, irregular nodule with a peripheral location appears to be HCC. TACE can effectively treat HCC in BCS patients.

Abstract 193: Preliminary Clot Length Analysis of Anterior Circulation Large Vessel Occlusions:

Purpose: Thin-section (≤ 2.5 mm) non-enhanced CT images may be used to reliably measure clot lengths in acute MCA occlusions, with clots ≥ 8mm long having a low probability of recanalization with IV rtPA alone. However, it is unclear what proportion of large vessel anterior circulation strokes have clot lengths ≥ 8mm and may potentially benefit from a bridging interventional approach. Methods: A multicenter imaging case review (target enrollment= 200 patients at 5 U.S. centers) was initiated to determine the proportion of patients meeting the below study criteria who have clot lengths ≥ 8mm. Study criteria include presentation within 8 hours of onset; imaging evidence of ICA-T, MCA M1, or M2 occlusion; and thin slice (≤ 2.5 mm) admission non-contrast CT images. Results are reported from an interim analysis of the data. Results: At 2 comprehensive stroke centers, all consecutive stroke admissions between August 2011 and July 2012 were reviewed for eligibility. Of these patients, 64 met study criteria (mean age= 72.3 years; 60% female; mean baseline NIHSS= 18). Mean times from symptom onset to presentation and to CT scan were 3.6 and 4.4 hours, respectively. Primary occlusions were located in the ICA-T (26.6%), M1 (64.1%), and M2 MCA (9.4%). Thrombus was visible in 92% (59/64) of cases, with lengths ranging from 3.0 to 64.8mm (mean = 18.6mm). Of these, 83% were ≥ 8mm in length. Clot length was statistically significantly longer in ICA-T occlusions and for those who did not receive IV rtPA prior to CT scan. Conclusion: This interim analysis suggests that the vast majority of anterior circulation large vessel occlusions have extensive (≥ 8mm length) clot burden, and may benefit from an IV-IA bridging approach. This idea will be tested in the ongoing THERAPY randomized controlled trial.

Thin-Slice Reconstructions of Nonenhanced CT Images Allow for Detection of Thrombus in Acute Stroke

The purpose of this study was to investigate whether thin-slice image reconstructions of cranial nonenhanced CT scans could be used to significantly increase sensitivity for detecting intraluminal thrombus in patients with acute ischemic stroke due to proximal occlusion of the middle cerebral artery. In a prospective case series, the raw data of nonenhanced CT scans from 54 patients presenting with acute ischemic stroke and proven vascular obliteration of the middle cerebral artery were collected along with the same data from patients not having a stroke but the same sex and age. All raw data were reconstructed with a slice thickness of 5 mm and as thin slices with a thickness of 0.625 mm. Three observers independently evaluated the 5-mm nonenhanced CT reconstructions and 5-mm maximum intensity projections of the thin slices and rated the likelihood of a clot obliterating the middle cerebral artery trunk or first-order branches using a 5-point scale. The results were evaluated in comparison with base data using receiver operating curve analysis. Interobserver agreement was measured using Cohen κ for every pair of observers. The area under the curve for the receiver operating curve analysis for the thick slices ranged from 0.63 to 0.67, whereas for the maximum intensity projection images of the thin slice reconstructions, receiver operating curve analysis revealed areas under the curve between 0.94 and 0.97. Interobserver agreement was higher for thin-slice (κ, 0.69-0.83) versus thick-slice nonenhanced CT reconstructions (κ, 0.38-0.45). Thin-slice reconstructions of standard cranial nonenhanced CT raw data allow for more sensitive and reliable detection of clots occluding the proximal middle cerebral artery.

Abstract 2433: Outcomes Of Thrombolysis In The 0-4.5 Hour Time Window In Acute Stroke Patients Selected Using Ct Perfusion Imaging

Background: Thrombolytic treatment within 4.5 hours of symptom onset is effective in preventing death or significant disability in 1 out of 7 stroke patients, but with a 5% risk of symptomatic intracerebral haemorrhage (sICH). We hypothesised that patient selection using CT perfusion (CTP) imaging can increase the benefit of thrombolysis and reduce the risk of sICH. Methods: We extracted data from a prospective thrombolysis database of 533 consecutive stroke patients of all ages thrombolysed with 4.5 hours of symptom onset. Thrombolysis decisions were made on the basis of a non-enhanced CT (NECT) scan but CTP was undertaken in a proportion of patients, depending upon physician decisions. In the analysis, patients with an Alberta Stroke Program Early CT Score (ASPECTS) of ≥7 on NECT and an estimated volumetric perfusion mismatch of ≥100% on PCT were defined as optimal candidates for thrombolysis. Imaging was reviewed by 2 raters masked to outcomes. Nine patients were excluded from analysis because of poor PCT quality. Findings: Of the 524 patients included, 97 patients had CTP mismatch that met the defined criteria for mismatch guided thrombolysis. Their age (72 v 70 years), sex (50% v 54% male), pre-morbid modified Rankin Scale (mRS) score, baseline National Institute of Health Stroke Scale (NIHSS) score (13.6 v 12.6,p=0.20), blood glucose (6.8 v 6.6 mmols) and blood pressure (149/84 v 148/79 mm Hg) were comparable with those thrombolysed on the basis of NECT imaging. At 3 months, the proportion of patients with modified Rankin Score of 0-1 and 0-2 was higher in those with mismatch (36% v 29%, p=0.003 and 51% v 42%, p=0.007 respectively) and there was a non-statistical trend towards reductions in any ICH (13% v 16%), sICH (1.1% v 2.8%) and mortality (23% v 18%). CTP mismatch was an independent determinant of a favourable outcome at 3 months in regression analyses to adjust for covariates. Conclusions: Patient selection based on estimation of salvageable brain tissue using CTP mismatch may improve functional outcomes at 3 months. The value of CT perfusion in increasing the effectiveness and safety of thrombolysis within established therapeutic time windows merits investigation.

The Importance of Size

We hypothesize that in acute middle cerebral artery stroke, thrombus lengths measured in thin-slice nonenhanced CT images define a limit beyond which systemic thrombolysis will fail to recanalize occluded arteries. In 138 patients who presented with acute middle cerebral artery stroke and who were treated with intravenous thrombolysis (IVT), we measured lengths of thrombotic clots depicted as arterial hyperdensities in admission nonenhanced CT images with 2.5-mm slice width. Vascular recanalization was investigated after thrombolysis and recanalization results were related to thrombus lengths by logistic regression. In 62 patients, IVT resulted in recanalization; among these patients, no thrombus length exceeded 8 mm. The median modified Rankin scale score at hospital discharge was 2. In the remaining 76 patients, thrombus lengths mostly exceeded 8 mm and IVT failed in recanalization. These patients were discharged with a median modified Rankin scale score of 5. This study shows that in acute middle cerebral artery stroke, IVT has nearly no potential to recanalize occluded vessels if thrombus length exceeds 8 mm.

Detection of Renal Lesion Enhancement with Dual-Energy Multidetector CT

To determine whether dual-energy multidetector CT enables detection of renal lesion enhancement by using calculated nonenhanced images with spectral-based extraction in a non-body weight-restricted patient population. Between January 2008 and December 2009, 139 patients were enrolled in this prospective HIPAA-compliant, institutional review board-approved study. Written informed consent was obtained from all patients. After single-energy nonenhanced 120-kVp CT images were acquired, contrast material-enhanced dual-energy multidetector CT images were acquired at 80 and 140 kVp. Calculated nonenhanced images were generated by using spectral-based iodine extraction. Lesion attenuation was measured on the acquired nonenhanced, calculated nonenhanced, and 140-kVp contrast-enhanced nephrographic images. Enhancement, defined as a 15-HU or greater increase in attenuation on the nephrographic images, was assessed by using the baseline attenuation on the acquired and calculated nonenhanced images. Acquired nonenhanced versus calculated nonenhanced image attenuation, as well as enhancement values, were compared by using paired Student t tests and Bland-Altman plots. Hypoattenuating (n = 66) and hyperattenuating (n = 28) cysts, angiomyolipomas (n = 18), and solid enhancing lesions (n = 27) were detected. Mean attenuation values for hypoattenuating cysts on the acquired and calculated nonenhanced CT images were 6.5 HU ± 5.8 (standard deviation) and 8.1 HU ± 3.1 (P = .13), respectively, with corresponding enhancement values of 1.1 HU ± 5.2 and -0.5 HU ± 6.2 (P = .12), respectively. Mean values for hyperattenuating cysts were 29.4 HU ± 5.6 on acquired images and 31.7 HU ± 5.1 on calculated images (P = .39) (corresponding enhancement, 4.7 HU ± 3.3 and 2.3 HU ± 4.1, respectively; P = .09). Mean values for fat-containing enhancing lesions were -90.6 HU ± 24.7 on acquired images and -85.9 HU ± 23.7 on calculated images (P = .57) (corresponding enhancement, 18.2 HU ± 10.1 and 13.6 HU ± 10.7, respectively; P = .19). Mean attenuation values for solid enhancing lesions were 26.0 HU ± 15.0 on acquired images and 27.7 HU ± 14.9 on calculated images (P = .45) (corresponding enhancement, 60.3 HU ± 13.1 and 58.3 HU ± 15.5, respectively; P = .38). Dual-energy CT acquisitions with spectral-based postprocessing enabled accurate detection of renal lesion enhancement across the attenuation spectrum of frequently encountered renal lesions in a non-body habitus-restricted patient population.

Effectiveness of temporal and dynamic subtraction images of the liver for detection of small HCC on abdominal CT images: comparison of 3D nonlinear image-warping and 3D global-matching techniques

Misregistration errors occur at the periphery of the hepatic region due to respiratory- and interval-related changes in hepatic shape. To reduce these misregistration errors, we developed a temporal and dynamic subtraction technique to enhance small hepatocellular carcinoma (HCC) by using a 3D nonlinear image-warping technique. The study population consisted of 21 patients with HCC. We registered the present and previous arterial-phase CT images or the present nonenhanced and arterial-phase CT images obtained in the same position by 3D global-matching plus 3D nonlinear image-warping. Temporal subtraction images were obtained by subtraction of the previous arterial-phase CT image from the warped present arterial-phase CT image. Dynamic subtraction images were obtained by subtraction of the present nonenhanced CT image from the warped present arterial-phase CT image. When we used this new technique, the number of good or excellent cases increased from 14.2% (3/21 cases) to 71.4% (15/21 cases) on temporal subtraction images. With this technique, subjective rating scores for image quality improved in 57.1% of cases (12/21 cases) on temporal subtraction images and 81.0% of cases (17/21 cases) on dynamic subtraction images. The results indicated that the new subtraction images were greatly improved by use of the 3D nonlinear image-warping technique.