Dynamic Computed Tomography Studies Research Articles

Innovative image-based planning in musculoskeletal surgery

For the preparation of surgical procedures in orthopedics and trauma surgery, precise knowledge of imaging and the three-dimensional imagination of the surgeon are of outstanding importance. Image-based, preoperative two-dimensional planning is the gold standard in arthroplasty today. In complex cases, further imaging such as computed tomography (CT) or magnetic resonance imaging is also performed, generating athree-dimensional model of the body region and helping the surgeon in the planning of the surgical treatment. Four-dimensional, dynamic CT studies have also been reported and are available as acomplementary tool. Furthermore, digital aids should generate an improved representation of the pathology to be treated and optimize the surgeon's imagination. The finite element method allows patient-specific and implant-specific parameters to be taken into account in preoperative surgical planning. Intraoperatively, relevant information can be provided by augmented reality without significantly influencing the surgical workflow.

Enhancement rate of venous phase to portal venous phase computed tomography and its correlation with ultrasound elastography determination of liver fibrosis

IntroductionThis study aimed to compare the correlation between the computed tomography (CT) enhancement rate of the venous to portal venous phase (VP-ER) and the extracellular volume (ECV) fraction with shear-wave ultrasound elastography (USE) findings in patients with liver fibrosis. MethodsWe included 450 patients with clinically suspected liver cirrhosis who underwent triphasic dynamic CT studies and USE. We compared the USE results with the unenhanced CT phase, with enhancement in the hepatic artery phase (HAP), portal venous phase (PVP), and venous phase (VP), and with the ECV fraction and the VP-ER. We also compared the area under the curve (AUC) of the receiver operating characteristic (ROC) curve of the ECV fraction and VP-ER with that of the values obtained with USE. ResultsThe VP-ER was the most highly correlated with the liver stiffness value determined with USE (Pearson's correlation coefficient: r = 0.37), followed by enhancement in the PVP (r = −0.25), CT number on unenhanced CT scans (r = −0.22), the ECV fraction (r = 0.19), enhancement in the VP (r = 0.059), and enhancement in the HAP (r = −0.023) (all p < 0.01). The VP-ER showed a significantly higher AUC than the ECV fraction (0.75 vs 0.62) when the liver stiffness was >15 kPa in USE studies (p = 0.04). ConclusionCompared to the ECV fraction, the VP-ER is more useful for predicting all degrees of liver fibrosis on routine triphasic dynamic CT images. Implications for practiceAlthough improvement is needed, the VP-ER has a higher diagnostic ability for liver fibrosis than the ECV fraction in clinical practice.

Computed Tomography-Measured Liver Volume Predicts the Risk of Hepatocellular Carcinoma Development in Chronic Hepatitis C Patients

In this retrospective cohort study, we evaluated the significance of liver volume in the prediction of hepatocellular carcinoma (HCC) in 277 chronic hepatitis C (CHC) patients who received dynamic computed tomography (CT) during surveillance. Liver volumes were measured on portal venous phase of CT images by using ImageJ software. Liver volume index, a ratio of the standard liver volume expected by weight and height to the measured liver volume, was calculated to adjust for normal variations. The cohort was randomly divided to derivation (n = 100) and validation sets (n = 177) for the generation of a liver volume-based Cox prediction model and validation of a liver volume-based nomogram, respectively. The liver volume index was independent of weight or height, and it predicted further development of HCC (hazard ratio [HR] 16.30, 95% CI 6.70-39.62; p < 0.001). Liver cirrhosis, gamma-glutamyl transferase, and liver volume index were independent predictors of HCC, and nomogram-based prediction score from these three parameters identified high-risk patients at the cutoff of 110 in both derivation (p < 0.001) and validation cohort (p < 0.001). Liver volume-based prediction model stratifies the risk of developing HCC in CHC patients whose initial dynamic CT study gave negative results.

Liver volume-based prediction model stratifies risks for hepatocellular carcinoma in chronic hepatitis B patients on surveillance.

Background and aimThe aim of this study was to determine whether dynamic computed tomography (CT)-measured liver volume predicts the risk of hepatocellular carcinoma (HCC) when the CT scans do not reveal evidence of HCC in chronic hepatitis B (CHB) patients on surveillance.MethodsThis retrospective multicentre cohort study included 1,246 patients who received entecavir and regular HCC surveillance in three tertiary referral centres in South Korea. Liver volumes were measured on portal venous phase CT images. A nomogram was developed based on Cox independent predictors and externally validated. Time-dependent receiver operating characteristic (ROC) analysis was performed for comparison with previous prediction models.ResultsPatients who received dynamic CT studies during surveillance had significantly higher risk for HCC compared to patients without CT studies (hazard ratio [HR] = 3.1; p < 0.001). Expected/measured liver volume ratio was an independent predictor of HCC (HR = 4.2; p = 0.002) in addition to age, sex and cirrhosis. The nomogram based on the four predictors discriminated risks for HCC (HR = 4.1 and 6.0 in derivation and validation cohort, respectively, for volume score > 150; p < 0.001). Time-dependent ROC analysis confirmed better performance of the volume score compared to HCC prediction models with conventional predictors (integrated area under curve = 0.758 vs. 0.661–0.712; p < 0.05).ConclusionsCT-measured liver volume is an independent predictor of future HCC, and nomogram-based liver volume score may stratify the risks of HCC in CHB patients who showed negative CT findings for HCC during surveillance.

High posterior cervical fusion rates with iliac autograft and Nanoss/bone marrow aspirate.

Background:Patients with severe cervical multilevel stenosis and an adequate lordotic curvature often undergo multilevel laminectomies with posterior instrumented fusions. Although the “gold standard” for the fusion mass remains iliac crest autograft, many require additional volume provided by bone graft expanders. Here, we studied the fusion rates for 32 patients undergoing multilevel cervical laminectomy and vertex/rod/eyelet/titanium cable fusions utilizing lamina/iliac autograft and the bone graft expander Nanoss (RTI Surgical, Alachua, FL, USA) with autogenous bone marrow aspirate (BMA).Methods:Thirty-two patients, averaging 63.0 years of age, presented with severe cervical myeloradiculopathy (average Nurick Grade 4.4). Magnetic resonance (MR) studies documented 2–3-level high intrinsic cord signals, whereas computed tomography (CT) scans confirmed marked stenosis and ossification of the posterior longitudinal ligament (OPLL)/ossification of the yellow ligament (OYL). Patients underwent multilevel lamnectomies/instrumented fusions, and were followed up for an average of 2.7 years.Results:Multilevel laminectomies (2.8 levels) and average 7.8-level vertex/rod/eyelet/cable fusions were performed utilizing lamina/iliac crest autograft and Nanoss/BMA. Fusion was confirmed on X-ray/CT studies an average of 4.7 months postoperatively in 31 of 32 patients (97%); there was just one pseudarthrosis requiring secondary surgery. The only other complication was a delayed transient C5 palsy that fully resolved in 6 postoperative months.Conclusions:Thirty-two severely myelopathic underwent 2.8-level cervical laminectomies/7.8 level fusions utilizing lamina/iliac autograft and Nanoss/BMA. Fusion was documented on both dynamic X-ray and CT studies in 31 of 32 (97%) patients an average of 4.7 months postoperatively. Nanoss/BMA appears to be a safe and effective bone graft expander that can be utilized for posterior cervical fusions.

Multidetector computed tomography-based microstructural analysis reveals reduced bone mineral content and trabecular bone changes in the lumbar spine after transarterial chemoembolization therapy for hepatocellular carcinoma.

PurposeIt is well recognized that therapeutic irradiation can result in bone damage. However, long-term bone toxicity associated with computed tomography (CT) performed during interventional angiography has received little attention. The purpose of this study was to determine the prevalence of osteoporosis and trabecular microstructural changes in patients after transarterial chemoembolization (TACE) for hepatocellular carcinoma therapy using an interventional-CT system.Materials and MethodsSpinal microarchitecture was examined by 64-detector CT in 81 patients who underwent TACE, 35 patients with chronic hepatitis, and 79 controls. For each patient, the volumetric CT dose index (CTDIv) during TACE (CTDIv (TACE)), the dose-length product (DLP) during TACE (DLP (TACE)), and CTDIv and DLP of routine dynamic CT scans (CTDIv (CT) and DLP (CT), respectively), were calculated as the sum since 2008. Using a three dimensional (3D) image analysis system, the tissue bone mineral density (tBMD) and trabecular parameters of the 12th thoracic vertebra were calculated. Using tBMD at a reported cutoff value of 68 mg/cm3, the prevalence of osteoporosis was assessed.ResultsThe prevalence of osteoporosis was significantly greater in the TACE vs. the control group (39.6% vs. 18.2% for males, P<0.05 and 60.6% vs. 34.8% for females, P<0.01). Multivariate regression analysis demonstrated that sex, age, and CTDIv (CT) significantly affected the risk of osteoporosis. Of these indices, CTDIv (CT) had the highest area under the curve (AUC) (0.735). Correlation analyses of tBMD with cumulative radiation dose revealed weak correlations between tBMD and CTDIv (CT) (r 2 = 0.194, P<0.001).ConclusionThe prevalence of osteoporosis was significantly higher in post TACE patients than in control subjects. The cumulative radiation dose related to routine dynamic CT studies was a significant contributor to the prevalence of osteoporosis.

Vascular Communications Between Donor and Recipient Tissues After Successful Full Face Transplantation

The vascular reorganization after facial transplantation has important implications on future surgical planning. The purpose of this study was to evaluate blood flow (BF) after full face transplantation using wide area-detector computed tomography (CT) techniques. Three subjects with severe craniofacial injury who underwent full face transplantation were included. All subjects underwent a single anastomosis bilaterally of the artery and vein, and the recipient tongue was preserved. Before and after surgery, dynamic volume CT studies were analyzed for vascular anatomy and blood perfusion. Postsurgical CT showed extensive vascular reorganization for external carotid artery (ECA) angiosome; collateral flows from vertebral, ascending pharyngeal or maxillary arteries supplied the branches from the recipient ECAs distal to the ligation. While allograft tissue was slightly less perfused when the facial artery was the only donor artery when compared to an ECA-ECA anastomosis (4.4 ± 0.4% vs. 5.7 ± 0.7%), allograft perfusion was higher than the recipient normal neck tissue. BF for the recipient tongue was maintained from contralateral/donor arteries when the lingual artery was sacrificed. Venous drainage was adequate for all subjects, even when the recipient internal jugular vein was anastomosed in end-to-end fashion on one side. In conclusion, dynamic CT identified adequate BF for facial allografts via extensive vascular reorganization.

Condylus tertius with atlanto-axial rotatory fixation: an unreported association

The "condylus tertius" or the "third occipital condyle" is an embryological remnant of the proatlas sclerotome. Anatomically, it is attached to the basion and often articulates with the anterior arch of the atlas and the odontoid apex; hence, it is also called the "median occipital condyle". It is a rare anomaly of the cranio-vertebral junction (CVJ) that can lead to instability and compression of important surrounding neurovascular structures. We report a case of a 16-year-old boy who presented with suboccipital neck pain, torticollis and right sided hemiparesis. Plain radiographs revealed an increased atlanto-dental interspace (ADI) with a retroflexed odontoid. Open mouth view showed asymmetry of the articular processes of the atlas with respect to the dens. Computed tomography (CT) of the CVJ delineated the third occipital condyle. Furthermore, on dynamic CT study, a type 3 atlanto-axial rotatory fixation (AARF) was clearly demonstrated. Magnetic resonance imaging (MRI) of the CVJ revealed severe right-sided spinal cord compression by the retroflexed and rightward deviated dens. It also revealed disruption of the left alar and transverse ligaments. The patient was treated with 8 weeks of cranial traction and reasonable alignment was obtained. This was followed by C1-C2 lateral mass screw fixation and C1-C2 interlaminar wiring to maintain the alignment. A review of the literature did not reveal any cases of condylus tertius associated with non-traumatic AARF. An accurate knowledge of the embryology and imaging features of this rare CVJ anomaly is useful in the prompt diagnosis and management of such patients.

NGF Promotes Hemodynamic Recovery in a Rabbit Hindlimb Ischemic Model Through trkA- and VEGFR2-dependent Pathways

Nerve growth factor (NGF) has been reported to play an important role in physiological and pathological angiogenesis. Based on these observations, we hypothesized that NGF may induce the formation of functional blood vessels in a hindlimb ischemic rabbit model. Hindlimb ischemia was induced in 34 rabbits bilaterally by endovascular embolization of femoral arteries. On the 7th, 14th, and 20th postembolization days, NGF was injected intramuscularly, in 1 ischemic limb, and vehicle was injected in the contralateral control limb. On the 40th day, newly developed collateral vessels (diameter >500 μm) were quantified by transauricular intraarterial subtraction angiography. Perfusion analysis of an in vivo dynamic computed tomography study was performed to the limbs to investigate the hemodynamic recovery of the distal ischemic tissues. Functional estimation of limb perfusion showed a statistically significant increase of blood flow and blood volume for NGF. However, the increase of the collateral vessels was not detectable angiographically, providing evidence for the existence of a NGF-stimulated capillary angiogenic network but not increase of arteriogenesis. The combination of NGF with either tropomyosin-related kinase type A or vascular endothelial growth factor receptor 2 antagonists abolished the NGF-induced hemodynamic recovery. These findings provide new insights into understanding the involvement of NGF in vascular formation and its applications in therapeutic angiogenesis.

Computed Tomography and Magnetic Resonance Imaging Features of Posterior Mediastinal Ganglioneuroma

To evaluate computed tomography (CT) and magnetic resonance (MR) imaging findings of posterior mediastinal ganglioneuromas. Of 14 pathologically confirmed ganglioneuromas seen in 13 patients, 13 were evaluated by CT images with and without contrast, 11 were evaluated with conventional spin-echo MR images, and 5 were evaluated with contrast-enhanced MR examination. The morphologic features, attenuation, signal intensity, and dynamic enhancement pattern of the neoplasms were evaluated. All lesions were identified as a well-demarcated oval and/or lobular mass. CT attenuation was predominantly low. Calcification on CT scan was seen in 38% of the cases. Whorled appearance (42%) and tailed-shaped edge (14%) were seen on both CT and MR images. Fat components (29%) observed histologically were also detected in tumors on CT and MR images. MR signal intensity in the lesions was mainly low on T1-weighted images and high on T2-weighted images. Contrast enhancement of the tumors was poor in 46% on dynamic CT study. In all 5 contrast-enhanced MR examinations, all lesions were enhanced. The characteristic findings of posterior mediastinal ganglioneuromas are a craniocaudally oblong-shaped mass, calcification, whorled appearance, tail-like extension, and fat component. Poor enhancement on dynamic CT studies is commonly observed.

Thrombin promotes arteriogenesis and hemodynamic recovery in a rabbit hindlimb ischemia model

Compared with angiogenesis, arteriogenesis is a distinct process based on the remodeling and maturation of pre-existing arterioles into large conductance arteries. Therapeutic angiogenesis has been proposed as a potential treatment for ischemic atherosclerotic diseases. Since a variety of angiogenic factors have been tested with inconsistent so far clinical results, the challenge remains in identifying the factor(s) that will stimulate functional neovascularization. Thrombin has been reported to play a pivotal role in the initiation of angiogenesis by regulating and organizing a network of angiogenic mediators. Also, it was recently demonstrated that thrombin is a potent anti-apoptotic factor for endothelial cells, providing evidence on a potential role of thrombin in vascular protection and maintenance of vessel integrity. Based on these observations, we hypothesized that thrombin may promote the development of mature functional blood vessels. Seventy-four (n=74) rabbits underwent bilateral femoral artery surgical excision. On the 20th postsurgical day increasing doses of VEGF or bFGF or thrombin were injected in one ischemic limb per rabbit and an equal volume of normal saline to the contralateral control limbs. Quantification of newly developed collateral vessels (diameter >500 mum) was performed by transauricular intra-arterial subtraction angiography. Computerized quantitative analysis of collateral vessels in angiography images was based on the concept of multiscale structural tensor. Perfusion analysis of an in vivo dynamic computed tomography study was performed to investigate hemodynamic recovery of the distal ischemic limbs. Tissue perfusion analysis was performed with the semiquantitative slope methodology, which focuses on the first-pass arterial phase. A single administration of thrombin exhibited a dose-dependent increase of arteriogenic outcome. Thrombin at 5000 IU induced a 30.2 +/- 7.4% (P < 0.05) increase of total collateral area and length. Both VEGF and bFGF were without any significant effect at the concentrations used. Functional estimation of limb perfusion showed a statistically significant increase of blood flow recovery only for thrombin. The semiquantitative slope method perfusion score differed significantly in the 5000 IU thrombin treated limbs (5.7 +/- 0.3 vs 5.0 +/- 0.3 in control ischemic limbs; P < .05), and was not significantly inferior from the score of normal nonoperated limbs (6.5 +/- 0.3) suggesting a trend towards hemodynamic recovery of distal limb perfusion. In a rabbit hindlimb ischemia model, thrombin promoted the formation of large collateral vessels and improved the perfusion of distal ischemic tissue. These results provide new insights in understanding the involvement of thrombin in vascular formation and point to a novel role of thrombin in arteriogenesis.

Dose reduction in dynamic perfusion CT of the brain: effects of the scan frequency on measurements of cerebral blood flow, cerebral blood volume, and mean transit time

The influence of the frequency of computed tomography (CT) image acquisition on the diagnostic quality of dynamic perfusion CT (PCT) studies of the brain was investigated. Eight patients with clinically suspected acute ischemia of one hemisphere underwent PCT, performed on average 3.4 h after the onset of symptoms. Sixty consecutive images per slice were obtained with individual CT images obtained at a temporal resolution of two images per second. Eight additional data sets were reconstructed with temporal resolutions ranging from one image per second to one image per 5 s. Cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) measurements were performed in identical regions of interest. Two neuroradiologists evaluated the PCT images visually to identify areas of abnormal perfusion. Perfusion images created up to a temporal resolution of one image per 3 s were rated to be diagnostically equal to the original data. Even at one image per 4 s, all areas of infarction were identified. Quantitative differences of CBF, CBV and MTT measurements were < or = 10% up to one image per 3 s. For PCT of the brain, temporal resolution can be reduced to one image per 3 s without significant compromise in image quality. This significantly reduces the radiation dose of the patient.

Gadolinium as a CT Contrast Agent: An Experimental Study for the Effects of Injection Parameters in the Rabbit Brain Model

Purpose: We wanted to investigate the use of gadolinium based contrast agent (Gd- DTPA) for computed tomography (CT), and we also wanted to assess the effects of valuable injection parameters on enhancement in an experimental rabbit brain model. Materials and Methods: In vitro, attenuation measurements of serial dilutions of Gd- DTPA and iopromide were compared. In five rabbits, single level dynamic gadoliniumenhanced brain CT studies were obtained using different injection parameters. A comparison CT scan after iopromide administration was performed. The time-attenuation curves of the brain vessel and parenchyma were obtained and the magnitude of enhancement (Hmax) and the time to peak enhancement (Tmax) were analyzed. Results: In vitro, the attenuation coefficient of undiluted Gd-DTPA (2,578 HU) was higher than that of iopromide (1,761 HU) at equimolar concentrations. In 5 rabbits, the time-attenuation curve demonstrated a distinct pattern with peak enhancement only in the brain vessel, but not in the brain parenchyma. There was increasing linear relationship between the injection rate of Gd-DTPA and Hmax, and a declining linear relationship with Tmax. The higher the concentration of Gd-DTPA, the higher Hmax was, but no significant difference was found for the Tmax. Higher volumes of Gd-DTPA revealed a higher Hmax and a delayed Tmax. Conclusion: Enhancement of the brain parenchyma on gadolinium-enhanced CT is minimal, while enhancement of the brain vessels is distinctive. The most important factor affecting Hmax of the vessel is the concentration of the contrast medium and the most important factor affecting Tmax of the vessel is volume of the contrast medium. The gadolinium-based contrast agent may be an reasonable alternative contrast agent for brain CT, and especially in cerebral vessels, and it may also be advantageous for brain parenchyma of those patients with BBB dysfunction.

Computed Tomography Features of Portal Hypertensive Gastropathy

The aim of this study was to detect the computed tomography features in portal hypertensive gastropathy (PHG). This study included 32 patients with portal hypertension. Ten of 32 patients were diagnosed with (PHG), and the other 22 patients were not diagnosed with PHG on the basis of upper endoscopic examination. Dynamic computed tomography studies were performed in all 32 patients. Each computed tomography scan was evaluated with regard to whether the gastric inner layer was enhanced or not. Nine patients with PHG had delayed enhancement on the inner layers of gastric walls, but in 17 of 22 patients without PHG, delayed enhancement was not observed. Enhancement on the inner layer of gastric walls may reflect gastric congestion. Portal hypertensive gastropathy should be suspected when this finding is detected on computed tomography scans in patients with portal hypertension.

Portal thrombosis complicating appendicitis: Ultrasound detection and hepatic computed tomography lobar attenuation alteration

Lobar attentuation difference of liver on computed tomography was seen in a case of portal pyemia complicating perforated appendicitis. Left portal vein thrombus was detected first by ultrasound and subsequently confirmed by computed tomography. The left lobe of the liver showed greater contrast enhancement during the dynamic computed tomography study. The possible cause of this lobar attenuation difference is discussed.

DYNAMIC COMPUTED TOMOGRAPHY STUDY OF THE BRAIN

The dynamic computed tomography study of the brain consists of the rapid intravenous injection of 49 ml of radiographic contrast material in 7 sec followed by serial 5-sec CT scans with interscan times of only 1 sec. The data from these scans can be reprocessed to create 12 segmented images in 35 sec. When small samples of four or six pixels of cortex are examined by the cursor, sharp rises of 20 to 25 CT units (500 scale) are seen on the time-density curves. Samples of white matter are usually no more than two CT units. When larger cursor samples of 220 to 255 pixels including cortex and white matter are examined, the time-density curves represent a combination of these two patterns. Comparison between symmetrical areas in the two hemispheres generally shows parallel curves in controls. The studies provide high-resolution cerebral perfusion images. In ischemia secondary to ipsilateral carotid stenosis, there is depression of the up-slope and a depressed late peak. Infarctions show a flat perfusion curve. Several patterns in brain tumors have been illustrated. The study, simple to perform, adds significant perfusion information to the previously static CT examination of the brain.

Diagnosis of internal carotid artery occlusion by dynamic computed tomography.

To evaluate internal carotid artery occlusion noninvasively by means of computed tomography (CT), dynamic CT studies with intravenous bolus injection of contrast medium were performed in 13 patients with hemispheric cerebral infarction and one patient with vascular headache. The slice level of dynamic CT was fixed at the atlas. The initial CT scan was taken after the start of infection of 20 or 40 ml of 60% meglumine amidotrizoate (this scan was used as a precontrast density reference), and 10 additional scans were made during 51.6 sec from the start of injection. The occluded internal carotid arteries were not visualized in patients with ICA occlusion, while all nonoccluded internal carotid arteries proven by angiography were enhanced clearly. It is concluded that this simple and noninvasive diagnostic examination should be added to the routine test procedures for evaluation and follow-up study of extracranial cerebral vascular disease.