Injection Of Contrast Medium Research Articles

The effect of contrast material on radiation dose during computed tomography pulmonary angiography

This study evaluated the impact of contrast material (CM) on radiation dose for adults undergoing computed tomography pulmonary angiography (CTPA). A previously developed physiologically based pharmacokinetic (PBPK) model and phantoms representing the average (reference) adult male and female individual were used to evaluate the iodine concentration in tissues as a function of time elapsed since the initiation of iodinated contrast medium administration. In order to estimate the radiation dose more accurately, a detailed model of pulmonary vessels was added to the phantoms. Then, the material composition of phantoms was modified to include the iodine concentration in different organs and tissues at different acquisition times after CM injection. The calculations were performed using Monte Carlo N-Particle extended code (MCNPX) version 2.6.0.The radiation dose estimates during CTPA were provided as a function of scan acquisition time after injection considering the distribution of iodinated CM within ICRP reference phantoms. It was shown that the estimated radiation dose to the lungs could be 31–40% (27–34%) larger when considering the effect of iodinated contrast administration with injection rate of 5 (3)mL/s. Moreover, the effective dose for contrast-enhanced CT (CECT) would be utmost 10–13% larger than that for non-enhanced CT (NECT). The radiation doses to the other organs in-/outside the scanned region would be decreased if the scan performed on time. In case of late scanning, absorbed dose decreases slightly for lungs (∼15–20%) whereas becomes (∼10% or more) higher than its NECT value for some organs such as heart muscle, kidneys, and spleen. To sum up, the late scanning (Δt>5s after the end of injection) is not recommended because of higher dose delivered to other organs than the lungs (particularly heart muscle).

Dual-energy CT angiography in suspected pulmonary embolism: influence of injection protocols on image quality and perfused blood volume

To compare intravenous contrast material (CM) injection protocols for dual-energy CT pulmonary angiography (CTPA) in patients with suspected acute pulmonary embolism with regard to image quality and pulmonary perfused blood volume (PBV) values. A total of 198 studies performed with four CM injection protocols varying in CM volume and iodine delivery rates (IDR) were retrospectively included: (A) 60 ml at 5 ml/s (IDR = 1.75gI/s), (B) 50 ml at 5 ml/s (IDR = 1.75gI/s), (C) 50 ml at 4 ml/s (IDR = 1.40gI/s), (D) 40 ml at 3 ml/s (IDR = 1.05gI/s). Image quality and PBV values at different resolution settings were compared. Pulmonary arterial tract attenuation was highest for protocol A (397 ± 110 HU; p vs. B = 0.13; vs. C = 0.02; vs. D < 0.001). CTPA image quality of protocol A was rated superior compared to protocols B and D by reader 1 (p = 0.01; < 0.001), and superior to protocols B, C and D by reader 2 (p < 0.001; 0.02; < 0.001). Otherwise, there were no significant differences in CTPA quality ratings. Subjective iodine map ratings did not vary significantly between protocols A, B, and C. Both readers rated protocol D inferior to all other protocols (p < 0.05). PBV values did not vary significantly between protocols A and B at resolution settings of 1, 4 and 10 (p = 0.10; 0.10; 0.09), while otherwise PBV values displayed a decreasing trend from protocol A to D (p < 0.05). Higher CM volume and IDR are associated with superior CTPA and iodine map quality and higher absolute PBV values.

Cat Brain Neuroanatomy using Cryosectioning, Magnetic Resonance and Computed Tomography Imaging Modalities

Magnetic resonance imaging (MRI) and computed tomography (CT) imaging modalities are invaluable for the diagnosis and treatment of neurological diseases. This study aimed to correlate the anatomical sectional data of the cats’ brain to the sections obtained by both MRI and CT examination. The present work was conducted on four cats, 1-4 years old, weighing about (2.5 to 3.5) kg admitted to the hospital with terminal diseases not related to the nervous system. The anatomical sections were taken at intervals of 5 mm, on different planes such as sagittal, frontal and transverse. The sections were obtained, following humane euthanasia, from frozen heads and identified according to the previous literatures. The images from both MRI and CT were compared with those of the gross anatomy sections and different structures were identified. To identify arterial distribution in the brain, one cat was injected with red latex through the common carotid artery, frozen, and sectioned. For vascular imaging, the same cat was examined by MRI after intravenous injection of contrast media. The descriptions of the brain anatomy from the MRI and CT images will act as a basis for the diagnosis and treatment of different neurological diseases in cat. This will assist veterinarians and radiologists in the identification of various nervous lesions related to the brain.

The two-segment caliber method of diagnosing iliac vein stenosis on routine computed tomography with contrast enhancement

BackgroundIliac vein stenosis is a frequent pathologic process in advanced chronic venous disease. Intravascular ultrasound (IVUS) has emerged as the “gold standard” to diagnose iliac vein stenosis and to guide stent treatment. A pre-IVUS test is often obtained. Routine venography is deficient in several respects to fill this role; absence of an internal scale is a critical deficiency. Computed tomography venography (CTV) may be superior; its measurement capabilities can be used to precisely identify stenotic iliac vein caliber. Furthermore, the calibers of common iliac vein (CIV) and external iliac vein (EIV) can be individually assessed, yielding two data points instead of single-point assessment used in venography and current CTV protocols. We compared the diagnostic accuracy of the two-segment caliber method of CTV (arm vein injection of contrast material) with IVUS. MethodsIn patients who underwent computed tomography assessment of iliac vein segments before IVUS examination during a 5-year period, 91 limbs were analyzed. This is a single-center, retrospective analysis of prospectively collected data. CTV images of CIV and EIV segments were compared individually and in combination with IVUS planimetry images. A caliber diameter of <16 mm for CIV and <14 mm for EIV was considered stenotic with either imaging technique. Bland-Altman plots and receiver operating characteristic curves were used. ResultsOn IVUS evaluation, 84% of CIVs and 78% of EIVs were stenotic and 16% and 22% were of normal caliber. These provided IVUS positive and negative controls for CTV comparison. On CTV, at least one of the two segments (CIV or EIV) was stenotic in 90% of the limbs, about 10% to 15% higher than single-segment involvement. Mean CTV caliber difference from IVUS was +2.5% for CIV and +7.3% for EIV. On Bland-Altman plot, single-segment diagnostic sensitivity of CTV was 83% and 73% for CIV and EIV, respectively, compared with IVUS. The sensitivity increased to 97% with a positive predictive value and accuracy of 93% and 91%, respectively, when a stenotic caliber in at least one of the two segments was considered diagnostic of iliac vein stenosis. Receiver operating characteristic analysis confirmed increased accuracy of the two-segment method over single-segment assessment with an area under the curve of 0.89 (P < .001). ConclusionsCaliber diameter of <16 mm for CIV or <14 mm for EIV on routine CTV imaging appears to correlate with IVUS caliber stenosis with good diagnostic metrics of low false positives and false negatives.

Diagnostic performance of coronary angiography utilizing intraprocedural 320-row computed tomography with minimal contrast medium.

Recently developed coronary angiography with intraprocedural 320-row computed tomography can be performed in a catheterization laboratory (XACT) by injecting contrast medium from a place close to the coronary arteries, thereby requiring a minimal amount of contrast medium. However, its clinical application has not yet been established. This study aimed to evaluate the diagnostic accuracy of XACT angiography with a minimal volume of contrast medium in patients with suspected coronary artery disease (CAD). A total of 167 coronary segments were analyzed in 14 patients (9 males, median age 70years) with suspected CAD by XACT angiography with 7.5ml of contrast medium and invasive coronary angiography (ICA) with standard techniques. The segmental-based diagnostic accuracy of XACT angiography in detecting stenosis of ≥50% and ≥75% and visualized by ICA was good (sensitivity: 74% and 62%, specificity: 99% and 99%, positive predictive value: 93% and 80%, and negative predictive value: 97% and 97%, respectively). These results suggest that XACT angiography with a very low amount of contrast medium may have strong clinical utility for screening coronary arteries in patients with renal dysfunction or undergoing clinical procedures such as pacemaker implantation.

Diagnostic Accuracy of Contrast Enhanced Computed Tomography in Detection of Ovarian Cancer in Clinically Suspected Patients

Background: In the gynecologic malignancies, ovarian cancer is the 2nd most common and a big cause of the mortality. Contrast-enhanced CT is a recent imaging technique of choice in preoperative assessment of ovarian cancer. Objective: To determine the diagnostic accuracy of contrast enhanced computed tomography of abdomen and pelvis in detection of ovarian cancer in clinically suspected patients by using histopathology as gold standard. Study Design: Cross-Sectional Study. Settings: Department of Radiology Civil Hospital, Karachi Pakistan. Duration: Six months from 26th April to 25th October 2017. Methodology: All the clinically suspected patients of ovarian cancer were included. Contrast Enhanced Computed Tomography (CECT) of pelvis and abdomen was performed with injection of intravenous contrast material. The CECT, diagnostic accuracy was established in terms of sensitivity, specificity, PPV, NPV against histopathology. By taking p-value ≤ 0.05 as significant, chi square test (post stratification) was applied. Results: The mean age of patients was 31.84±7.95 years. Mean duration of symptoms was 13.37±5.99 weeks. Serum cancer antigen-125 level was 62.23±14.66 U/ml. Total 27.5% subjects were diagnosed with ovarian cancer by contrast enhanced CT and 29.6% by Histopathology. Specificity, Sensitivity, NPV, PPV, and accuracy were 86.7%, 97.4%, 93.4%, 94.5%, and 94.2% respectively. Conclusion: The contrast enhanced computer tomography is helpful diagnostic tool to detect the ovarian cancer, with accuracy rate of 94.2%, 86.7% sensitivity and 97.4% specificity.

Limb ischemic preconditioning ameliorates renal microcirculation through activation of PI3K/Akt/eNOS signaling pathway after acute kidney injury

PurposeContrast-induced acute kidney injury (CI-AKI) resulting from administration of iodinated contrast media (CM) is the third leading cause of hospital-acquired acute kidney injury and is associated with substantial morbidity and mortality. Deteriorated renal microcirculation plays an important role in CI-AKI. Limb ischemic preconditioning (LIPC), where brief and non-injurious ischemia/reperfusion is applied to a limb prior to the administration of the contrast agent, is emerging as a promising strategy for CI-AKI prevention. However, it is not known whether the renal protection of LIPC against CI-AKI is mediated by regulation of renal microcirculation and the molecular mechanisms remain largely unknown.MethodsIn this study, we examined the renal cortical and medullary blood flow in a stable CI-AKI model using 5/6-nephrectomized (NE) rat. The LIPC and sham procedures were performed prior to the injection of CM. Furthermore, we analyzed renal medulla hypoxia using in vivo labeling of hypoxyprobe. Pharmacological inhibitions and western blotting were used to determine the underlying molecular mechanisms.ResultsIn this study, we found LIPC significantly ameliorated CM-induced reduction of medullary blood flow and attenuated CM-induced hypoxia. PI3K inhibitor (wortmannin) treatment blocked the regulation of medullary blood flow and the attenuation of hypoxia of LIPC. Phosphorylation of Akt/eNOS was significantly decreased via wortmannin treatment compared with LIPC. Nitric oxide synthase-inhibitor [Nω-nitro-l-arginine methyl ester (L-NAME)] treatment abolished the above effects and decreased phosphorylation of eNOS, but not Akt.ConclusionsCollectively, the results demonstrate that LIPC ameliorates CM-induced renal vasocontraction and is mediated by activation of PI3K/Akt/eNOS signaling pathway.

Is it safe to inject contrast through the side arm of an introducer sheath? An in vitro study.

Occasionally, a patient requiring computed tomography (CT) with poor venous access or in an unstable condition may have a sheath as their only form of IV access. Many institutions prohibit contrast power injection through the side ports, for concern for rupture. We hypothesize that under conditions encountered in CT scanning, the side arm of the sheath introducer is safe for power injection of contrast material. In this in vitro study, we injected contrast at different flow rates varying from 2 to 8ml/s, through the side port of the sheath. Time-pressure graphs were obtained for each injection from the injector display. The assembly was observed for any signs of leakage or material failure. There was not a single event of leak, rupture, or displacement. Maximum pressures were within the range of conventional contrast administrations. This study suggests that iodinated contrast can safely be injected through the side port of a venous sheath.

Percutaneous access of the superior vena cava in patients with bilateral jugular-subclavian vein occlusion using wire-target access for placement of tunneled hemodialysis catheters: An important new tool for gaining upper body vascular access.

This study presents the technique of percutaneous wire-target access of the superior vena cava (SVC) in patients with bilateral jugular-subclavian vein occlusion requiring a tunneled hemodialysis catheter. A 3-year retrospective review of five patients was performed. The femoral vein is accessed percutaneously and a 5F sheath inserted. This is followed by placement of a pigtail catheter (wire-target) in the SVC with cavography. The SVC is percutaneously cannulated at the level of the pigtail under fluoroscopy, and a guidewire is passed into the vena cava with confirmation by injection of contrast material. A tunneled hemodialysis catheter is then placed. The wire-target technique of SVC access can be used safely and effectively to establish upper body catheter access when traditional techniques are not possible.

Evaluation of Coronary Artery Bypass Graft Using Multi-Detector CT Angiography: Comparative Study

Abstract Background: Recurrence of ischemic symptoms after coronary artery bypass graft surgery requires imaging assess-ment of bypass graft lumen to rule-out graft dysfunction. Aim of Study: Is to evaluate the role of 320-row multide-tector CT as a non-invasive imaging modality for assessment of coronary artery bypass grafts. Results: Twenty one patients were referred to assess the patency of coronary artery bypass grafts. All patients were subjected to history taking, clinical examination as well as CT angiography of coronary arteries and coronary artery bypass grafts using 320-row multidetector CT scanner after heart rate control and injection of non-ionic contrast material. Total number of 63 interpretable coronary artery bypass grafts were included in this study. On evaluating 23 arterial grafts, all of LIMA grafts were patent without stenosis except for LIMA to D2 graft which shows subtotal distal anastomotic site occlusion. The only RIMA graft in this study was occluded whereas radial artery graft to OM was patent. On evaluating 40 venous grafts, 11 (27.5%) grafts were considered patent, 3 (7.5%) grafts showed significant (>!50) stenosis and 26 (65%) grafts were occluded. Conclusion: Multidetector CT is considered convenient and reliable non-invasive imaging modality for assessment of suspected graft dysfunction.

Individual Optimization of Contrast Media Injection Protocol at Hepatic Dynamic Computed Tomography Using Patient-Specific Contrast Enhancement Optimizer.

We developed a patient-specific contrast enhancement optimizer (p-COP) that can exploratorily calculate the contrast injection protocol required to obtain optimal enhancement at target organs using a computer simulator. Appropriate contrast media dose calculated by the p-COP may minimize interpatient enhancement variability. Our study sought to investigate the clinical utility of p-COP in hepatic dynamic computed tomography (CT). One hundred thirty patients (74 men, 56 women; median age, 65 years) undergoing hepatic dynamic CT were randomly assigned to 1 of 2 contrast media injection protocols using a random number table. Group A (n = 65) was injected with a p-COP-determined iodine dose (developed by Higaki and Awai, Hiroshima University, Japan). In group B (n = 65), a standard protocol was used. The variability of measured CT number (SD) between the 2 groups of aortic and hepatic enhancement was compared using the F test. In the equivalence test, the equivalence margins for aortic and hepatic enhancement were set at 50 and 10 Hounsfield units (HU), respectively. The rate of patients with an acceptable aortic enhancement (250-350 HU) for the diagnosis of hypervascular liver tumors was compared using the χ test. The mean ± SD values of aortic and hepatic enhancement were 311.0 ± 39.9 versus 318.7 ± 56.5 and 59.0 ± 11.5 versus 58.6 ± 11.8 HU in groups A and B, respectively. Although the SD for aortic enhancement was significantly lower in group A (P = 0.006), the SD for hepatic enhancement was not significantly different (P = 0.871). The 95% confidence interval for the difference in aortic and hepatic enhancement between the 2 groups was within the range of the equivalence margins. The number of patients with acceptable aortic enhancement was significantly greater in group A than in group B (P < 0.01). The p-COP software reduced interpatient variability in aortic enhancement and obtained acceptable aortic enhancement at a significantly higher rate compared with the standard injection protocol for hepatic dynamic CT.

Relationship Between Serum Iron Profile and Liver Density in Non-Enhanced CT-Scan

It is known that liver biopsy is the gold standard of diagnosing liver iron deposition. By considering liver biopsy complication and cost, introducing a method to restrict unnecessary biopsy or even an alternative for liver biopsy can be useful. This study examined the relationship between serum iron profile and liver density on CT-Scan without contrast material injection. In this study, 76 patients were referred from different Rasoul-Akram Hospital parts in 2015-2016 (People who have undergone abdominal CT-scan for any reason, and blood tests included iron and lipid profiles). To calculate the liver mean density of a CT-scan, densities of 12 sites with an individual area of 1 cm2 on 3 different sections of the liver were obtained, and their average was recorded. Data were analyzed by SPSS V.16 using Kolmogorov-Smirnov, independent T-test, and two-sample T-tests with a significance level of P&lt;0.05. There is a significant relationship between the serum iron and serum ferritin levels with liver density. By increasing TIBC levels, the difference between liver and spleen densities increases, but no significant correlation was found between TIBC level and liver density. Moreover, there was no relationship between serum iron levels and serum ferritin with the difference between liver and spleen densities. The evaluation of liver density may be an alternative to liver biopsy in some cases or at least can be considered to restrict unnecessary biopsies. © 2019 Tehran University of Medical Sciences. All rights reserved. Acta Med Iran 2019;57(8):499-502.

CT angiography with 15 mL contrast material injection on time-resolved imaging for endovascular abdominal aortic aneurysm repair

PurposeTo assess the utility of whole-aorta CT angiography (CTA) with 15 mL contrast material (CM) on time-resolved imaging for endovascular abdominal aortic repair (EVAR). MethodsTwenty-six patients with a high-risk of post-contrast acute kidney injury (PC-AKI) underwent CTA with 15 mL CM using temporal maximum intensity projection (tMIP-CTA) generated from time-resolved imaging. The aortoiliac CT values were measured. Two observers measured the arterial diameters in unenhanced CT and tMIP-CTA images, and image quality was evaluated on a 5-point scale. The presence of the accessory renal artery, inferior mesenteric artery (IMA) occlusion, and instructions for use (IFU) of EVAR were evaluated. ResultsCT examinations were successfully performed, and no patients developed PC-AKI. The mean CT values of the whole aorta were 267.5 ± 51.4 HU, which gradually decreased according to the distal levels of the aorta. Bland-Altman analysis revealed excellent agreement for the external arterial diameter measurements between unenhanced CT and tMIP-CTA. Excellent interobserver agreement was achieved for the measurements of the external (ICCs, 0.910–0.992) and internal arterial diameters (ICCs, 0.895–0.993). Excellent or good overall image quality was achieved in 24 (92 %) patients. The presence of the accessory renal artery, IMA occlusion and the assessment of IFU were in 100 % agreement. Multivariate analysis revealed aortic volume as the most significant independent factor associated with strong aortic enhancement (p = 0.004). ConclusionsWhole-aorta tMIP-CTA on time-resolved imaging is useful for maintaining contrast enhancement and image quality for EVAR planning, and can substantially reduce the amount of CM.

Evaluation of computed tomography arterial portography scan timing using different bolus tracking methods.

Computed tomography arterial portography (CTAP) is widely used with a fixed scan timing and contrast medium quantity; however, these parameters are not necessarily optimal. In this study, CTAP scan timing was analyzed by different bolus tracking methods to monitor the inflow of the contrast medium in real-time. A total of 249 patients who underwent CTAP were assessed. In 30 patients, the CTAP scanning began 33s after contrast medium injection started (fixed method). In 74 patients, the regions of interest (ROIs) were established at two places in the inferior vena cava above the hepatic vein (inferior vena cava-ROI method). In 145 patients, the ROI was established at two places in the liver parenchyma (liver parenchyma-ROI method). Scan timing was considered appropriate when the difference in the CT value between the hepatic and portal veins approached 0; this was observed significantly more with the liver parenchyma-ROI method than with the other methods. CTAP scan timing with the liver parenchyma-ROI method was better than that with the fixed and inferior vena cava-ROI methods.

Diagnosis of Ventriculoperitoneal Shunt Malfunction: A Practical Algorithm

This study aims to present a practical method to accurately diagnose ventriculoperitoneal shunt (VPS) malfunction and to detect the exact level at which the system has failed to tailor VPS revision at that level only. A tertiary referral single-center algorithm for diagnosis of VPS malfunction is proposed. Based on clinical symptoms and confirmed ventricular dilatation on computed tomography, the VPS reservoir is punctured; if no cerebrospinal fluid is obtained, ventricular catheter replacement is recommended. Conversely, if cerebrospinal fluid is obtained, a sample is sent for cultural examination and the macroscopic integrity of the whole system is checked via plain radiography in the angiographic suite. Then, through the injection of iodate contrast medium into the reservoir and selective exclusion of the proximal and distal catheters, the patency and correct VPS functioning are investigated. A total of 102 (56 males) patients (mean age, 41.5 years; range, 1-86 years) underwent a VPS function test from 2012 to 2018: 59 cases of VPS malfunction (57.8%) were diagnosed. Ventricular catheter obstruction/damage/displacement occurred in 12/59 patients (20.3%), valve damage in 11/59 patients (18.6%), distal catheter obstruction/damage/displacement in 17/59 patients (28.8%) and 2-level (valve/proximal catheter or valve/distal catheter) obstruction/damage/displacement in 16/59 patients (27.1%). Subclinical infection was diagnosed in 3 patients (5.1%). VPS revision was performed selectively at the level of failure. The proposed algorithm is a practical, simple and minimally invasive technique to accurately diagnose VPS malfunction, identifying the exact level of system failure and allowing surgical VPS revision to be tailored, avoiding unnecessary complete system replacement.

Novel Technique for Detection of Actual Position of Clot During Endovascular Clot Retrieval: Assessment of Microcatheter Withdrawing Angiography

When endovascular clot retrievals are performed using a stent retriever and/or an aspiration catheter, identifying the accurate position of a clot is extremely important for a successful immediate recanalization. Herein, we report a new technique called microcatheter withdrawing angiography, which facilitates the identification of the precise position of a clot. Thenegative shadow appearance of the clot on angiography was referred to as the actual crab claw sign. When a 0.027-inch microcatheter penetrated the clot after inserting a 0.014-inch microwire, selective angiography was conducted using the microcatheter. Simultaneously, the microcatheter was slowly withdrawn with continuous contrast media injection, while the microwire was kept in the distal vessel. The precise position of the clot was found, which was referred to as the actual crab claw sign. Next, we conducted invitro and invivo analyses. The actual crab claw sign could be identified in the vascular model and in actual clinical settings. Therefore the sweet spot of the stent retriever could be set over the clot, and an accurate contact aspiration could be performed using an aspirator. Microcatheter withdrawing angiography can help identify the actual crab claw sign. This technique has a higher success rate and faster recanalization than conventional strategy, particularly in challenging cases of unsuccessful recanalization during the first attempt.

Abstract WMP34: Multimodal Evaluation of Unruptured Intracranial Aneurysm Wall

Background and Purpose: Recent studies have suggested that MR-vessel wall imaging (VWI) or computational fluid dynamics (CFD) could evaluate aneurysm wall features in unruptured intracranial aneurysms (UIAs). The combination of these modalities might be comprehensive and help better understanding of the pathophysiology of aneurysm wall. This study was performed to disclose the relationship between VWI and hemodynamic characteristics evaluated by CFD. Methods: From April 2017 through May 2019, a total of 36 microsurgically-treated UIAs preoperatively underwent VWI and CFD were reviewed. Three-dimensional T1-weighted fast spin-echo sequences were obtained before and after injection of contrast medium, and aneurysm wall enhancement (AWE) was evaluated. CFD was carried out using patient specific geometry models from three-dimensional CT angiography. Morphological variables, intraoperative inspection and hemodynamic parameters were statistically analyzed between enhanced and nonenhanced wall of UIAs. Fourteen UIAs were available for histopathological examination. Results: In morphological variables, maximum diameter and irregularity were associated with AWE (p=0.02, respectively). AWE lesions corresponded to intraoperatively inspected atherosclerotic lesions of UIAs (sensitivity, 0.90; specificity, 0.79). Among hemodynamic parameters, oscillatory velocity index that suggests the directional changes of the flow velocity was significantly higher in UIAs with AWE (p=0.02). Histopathologic studies revealed that wall thickening accompanied by atherosclerosis, neovascularization, and macrophage infiltration corresponded to AWE lesions, while UIAs without AWE demonstrated various histopathological findings such as myointimal hyperplasia or thinning wall with loss of mural cells and wall degeneration. Conclusions: Pathophysiology of AWE could be explained as atherosclerotic changes with inflammation presumably associated with aberrant flow conditions in irregular UIAs. VWI and CFD are complementarily valuable imaging techniques to understand an aneurysm wall pathophysiology.

Abstract TP86: Clinical Significance of Gadolinium Enhancement in Non-Hemorrhagic Intracranial Artery Dissection

Background and Purpose: The mechanisms involved in progression of non-hemorrhagic intracranial artery dissection (IAD) are poorly understood. Contrast enhancement of intracranial saccular aneurysms on magnetic resonance vessel wall imaging (VWI) is thought to predict instability. We investigated the relationship between contrast enhancement of dissecting lesions and progression of IADs based on the hypothesis that this finding might predict instability. Methods: A total of 39 IADs in 36 patients (17 women and 19 men; mean age: 49 years) were investigated retrospectively. Three-dimensional T1-weighted fast spin-echo sequences were obtained before and after injection of contrast medium, and the vessel wall/pituitary stalk contrast enhancement ratio (CRstalk) was calculated. Progression of IADs was defined as morphological deterioration; progressive dilatation or stenosis. The relations between IAD progression and potential risk factors, including patient demographic data, IAD morphology, and VWI findings, were investigated by statistical analysis. Results: The mean follow-up period was 9.7 months (range: 1-24 months). Progression was detected in 6 of 39 IADs (15%). Five IADs demonstrated aneurysmal dilatation and the other showed stenosis/occlusion. There were no significant differences of demographic factors between the patients with or without IADs progression. IADs with aneurysmal dilation demonstrated significant morphological deterioration (p=0.01). All IADs without contrast enhancement (n=7) improved within one month. Contrast enhancement corresponded to the pseudo-lumen of dissecting lesions. The CRstalk value was significantly higher in IADs with progression than in stable lesions (1.10 ± 0.09 vs. 0.80 ± 0.05, p =0.01). Conclusions: The pseudo-lumen of dissecting lesions may be identified by contrast enhancement. Quantitative analysis of contrast enhancement could be useful for predicting instability of IADs during follow-up.

Reduced iodinated contrast media dose and injection speed for CT: how much does this decrease the risk of a hypersensitivity reactions?

Adverse reactions developing after administration of iodinated contrast media (ICM) can either constitute hypersensitivity reactions, toxic reactions, or even events unrelated to ICM exposure, such as acute spontaneous or infection-induced urticaria (1). Toxicity-related reactions (also called “physiologic” or “chemotoxic” reactions) are more common than hypersensitivity reactions and often manifest with mild unspecific symptoms, such as pruritus, heat sensation, transient erythema, dizziness, nausea, sneezing, chest tightness, arrhythmia, hypertension, and vasovagal signs (i.e., hypotension and bradycardia). Immediate hypersensitivity reactions (IHR) (acute hypersensitivity reactions) occur within 1 hour after ICM administration and either present with full anaphylaxis, involving skin, gastrointestinal, respiratory and/or cardiovascular organ systems simultaneously, sometimes with bronchospasm and/or hypotension, but may also manifest as fractions of anaphylaxis, such as urticaria, or angioedema only (2,3). Fatalities do occur (4). Among IHR, there is growing evidence that particularly severe reactions may be immunoglobulin E (IgE)-mediated and skin test- positive, whereas mild to moderate hypersensitivity reactions are mostly non-allergic (5-7). IHR have been reported in a frequency of about 0.3–3% of ICM injections (1).

Reliability of CT myelography versus MRI in the assessment of spinal epidural disease

The spine is the third most common site of metastatic disease after the lungs and liver [1–2]. Several imaging modalities exist for the evaluation of epidural disease, namely computed tomography (CT) and magnetic resonance imaging (MRI). CT myelography (CTM) involves the injection of contrast material into the cerebrospinal fluid prior to imaging and requires ionizing radiation. Though previously widely used, CTM has steadily fallen out of favor to MRI at many institutions and in some cases, is used alone in radiation therapy planning. MRI is notable for its non-invasive nature, excellent visualization of soft tissues, and lack of exposure to ionizing radiation. CTM, however, can provide improved visualization of bony structures and is more resistant than MRI to geometric distortion and patient motion due to the rapid acquisition of images [3]. Additionally, CTM can be used in patients with contraindications to MRI and can also provide a direct correlation of electron density to doses used for radiation therapy planning [4]. With recent advances in radiation therapy, including intensity-modulated and image-guided radiation therapy, which aim to improve tumor targeting thereby sparing normal tissue, precise tumor localization for treatment planning often requires the use of CT integrated with MRI [5–7]. A previous study comparing CTM and MRI in the evaluation of degenerative disease in the cervical spine found that MRI was superior in its reliability for assessing the degree of nerve root compression while CTM provided greater reliability in the assessment of bony lesions and foraminal stenosis [8]. Other studies focusing on the lumbar spine also found that CTM provided greater reliability and reproducibility in the assessment of the extent of lumbar stenosis than did MRI [9] and that MRI underestimated the degree of spinal root compression in the lumbar spine [10]. While both imaging modalities have complementary advantages, studies to date have not investigated a composite evaluation of spinal epidural disease. Furthermore, given the limitations of MRI, it has not been studied whether there is merit in continuing to use CTM to complement MRI for radiation therapy planning. This study is the first to investigate whether axial and sagittal projections of the spinal epidural space using both T1 and T2-weighted MRI compared to CTM produce compatible levels of inter- and intra-rater reliability in measuring the extent of epidural disease by neuroradiologists trained in both imaging modalities. The results of this study will be useful in determining whether CTM should continue to be used in conjunction with MRI when evaluating spinal metastases and planning radiation therapy.