Ml Of Contrast Medium Research Articles

Low-tube-voltage (80 kVp) CT aortography using 320-row volume CT with adaptive iterative reconstruction: lower contrast medium and radiation dose

To evaluate CT aortography at reduced tube voltage and contrast medium dose while maintaining image quality through iterative reconstruction (IR). The Institutional Review Board approved a prospective study of 48 patients who underwent follow-up CT aortography. We performed intra-individual comparisons of arterial phase images using 120 kVp (standard tube voltage) and 80 kVp (low tube voltage). Low-tube-voltage imaging was performed on a 320-detector CT with IR following injection of 40 ml of contrast medium. We assessed aortic attenuation, aortic attenuation gradient, image noise, contrast-to-noise ratio (CNR), volume CT dose index (CTDIvol), and figure of merit (FOM) of image noise and CNR. Two readers assessed images for diagnostic quality, image noise, and artefacts. The low-tube-voltage protocol showed 23-31% higher mean aortic attenuation and image noise (both P < 0.01) than the standard-tube-voltage protocol, but no significant difference in the CNR and aortic attenuation gradients. The low-tube-voltage protocol showed a 48% reduction in CTDIvol and an 80% increase in FOM of CNR. Subjective diagnostic quality was similar for both protocols, but low-tube-voltage images showed greater image noise (P = 0.01). Application of IR to an 80-kVp CT aortography protocol allows radiation dose and contrast medium reduction without affecting image quality. • CT aortography at 80 kVp allows a significant reduction in radiation dose. • Addition of iterative reconstruction reduces image noise and improves image quality. • The injected contrast medium dose can be substantially reduced at 80 kVp. • Aortic enhancement is uniform despite a reduced volume of contrast medium.

A case of CTO treated with minimum use of contrast media

The retrograde approach is a novel technique for improving the success rate of guidewire passage through chronic total occlusion (CTO). In addition, this technique, especially when intravascular ultrasound-guided reverse controlled antegrade and retrograde subintimal tracking is employed, may help the operator to save on the contrast media used. In the case reported here, only 10 ml of contrast media was used in percutaneous coronary intervention for CTO.

Split-Bolus Spectral Multidetector CT of the Pancreas: Assessment of Radiation Dose and Tumor Conspicuity

To assess tumor conspicuity and radiation dose with a new multidetector computed tomography (CT) protocol for pancreatic imaging that combines spectral CT and split-bolus injection. This study was approved by the institutional review board and compliant with HIPAA. The requirement for informed consent was waived. One hundred sixty-three consecutive patients referred for possible pancreatic mass underwent CT with either a standard or split-bolus spectral CT protocol depending on scanner availability. Split-bolus spectral CT (CT unit with spectral imaging) combines pancreatic and portal venous phases in a single scan: 70 seconds before CT, 100 mL of contrast material is injected for the portal venous phase followed approximately 35 seconds later by injection of 40 mL of contrast material to boost the pancreatic phase. Bolus tracking after the second bolus initiates scanning 15 seconds after aorta enhancement reaches 280 HU. Images were reconstructed at 60 and 77 keV. The standard protocol (64-detector row unit) included unenhanced and pancreatic and portal venous phase imaging, with a single contrast material injection timed with bolus tracking 15 seconds after aortic enhancement of 300 HU for the pancreatic phase and 32 seconds later for the portal venous phase. Tumor conspicuity (difference in attenuation between tumor and pancreatic parenchyma) and contrast-to-noise ratio (CNR) were determined. Attenuation of aorta, main portal vein, and liver were measured. Patient size and per-examination radiation dose were recorded. The heteroscedastic t test, Fisher exact test, and Mann-Whitney test were used for statistical analysis. There were no significant differences in age, weight, and body mass index between patients in the standard CT (46 of 80 patients had lesions) and split-bolus spectral CT (39 of 83 patients had lesions) groups; however, there were significantly more women in the split-bolus group (P = .02). Tumor conspicuity and CNR were higher with the 60-keV split-bolus protocol (89.1 HU ± 56.6 and 8.8 ± 6.2, respectively) than with the pancreatic or portal venous phase of the standard protocol (43.5 HU ± 28.4 and 4.5 ± 3.0, and 51.5 HU ± 30.3 and 5.6 ± 4.0, respectively; P < .01 for all comparisons). Dose-length product was 1112 mGy · cm ± 437 with the standard protocol and 633 mGy · cm ± 105 with the split-bolus protocol (P < .001). Split-bolus spectral multidetector CT resulted in vascular, liver, and pancreatic attenuation and tumor conspicuity equal to or greater than that with multiphase CT, with a 43% reduction in radiation dose.

Split-bolus dual-energy CT urography: protocol optimization and diagnostic performance for the detection of urinary stones

Prospective protocol optimization, determination of image quality and diagnostic performance of virtual non-enhanced images (VNEI) derived from split-bolus dual-energy computed tomography (DECT) urography in patients with urinary stones. IRB-approved, prospective study of 100 patients who, after written informed consent, underwent single-energy, non-enhanced CT and split-bolus, contrast-enhanced DECT (30 + 50 mL of contrast media; combined nephro-urographic acquisition). DECT was performed using setting A (80/140 kVp) in the first 20, and setting B (100/140 kVp) in the second 20 patients. Tin filtration was used in all patients. After a pre-analysis of VNEI quality, 60 additional patients were examined using setting B. Two readers qualitatively and quantitatively determined image quality of all weighted-average DECT images regarding urinary tract opacification (n = 100), and all VNEI regarding quality of iodine subtraction and urinary stone detection (n = 80). True nonenhanced (TNEI) images were the standard of reference for statistical analysis (inter-reader variability and diagnostic performance characteristics). The urinary tract was completely opacified in 94% (94/100) of patients. Iodine subtraction was improved (p < 0.01) and image noise of VNEI was lower (p < 0.05) in DECT setting B. On VNEI, 83% (86/104) of urinary stones were correctly identified and 17% (18/104) were missed. Stones missed (2.5 mm, 1-4) were significantly smaller than stones correctly identified (5 mm, 2-27; p < 0.001). Diagnostic accuracy was 98% on a per-renal-unit basis and 96% on a per-patient basis. Inter-reader agreements were excellent (κ = 0.91-1.00; ICC = 0.86-0.99). Split-bolus DECT urography was technically feasible and quality of VNEI was improved with the 100/140 kVp setting. Detection of urinary stones <4 mm on VNEI was limited.

Transverse Process and Needles of Medial Branch Block to Facet Joint as Landmarks for Ultrasound-Guided Selective Nerve Root Block

BackgroundSelective lumbar nerve root block (SNRB) is generally accepted as an effective treatment method for back pain with sciatica. However, it requires devices producing radioactive materials such as C-arm fluoroscopy. This study evaluated the usefulness of the longitudinal view of transverse process and needles for medial branch block as landmarks under ultrasonography.MethodsWe performed selective nerve root block for 96 nerve roots in 61 patients under the guidance of ultrasound. A curved probe was used to identify the facet joints and transverse processes. Identifying the lumbar nerve roots under the skin surface and ultrasound landmarks, the cephalad and caudal medial branch blocks were undertaken under the transverse view of sonogram first. A needle for nerve root block was inserted between the two transverse processes under longitudinal view, while estimating the depth with the needle for medial branch block. We then injected 1.0 mL of contrast medium and checked the distribution of the nerve root with C-arm fluoroscopy to evaluate the accuracy. The visual analog scale (VAS) was used to access the clinical results.ResultsSeven SNRBs were performed for the L2 nerve root, 15 for L3, 49 for L4, and 25 for L5, respectively. Eighty-six SNRBs (89.5%) showed successful positioning of the needles. We failed in the following cases: 1 case for the L2 nerve root; 2 for L3; 3 for L4; and 4 for L5. The failed needles were positioned at wrong leveled segments in 4 cases and inappropriate place in 6 cases. VAS was improved from 7.6 ± 0.6 to 3.5 ± 1.3 after the procedure.ConclusionsFor SNRB in lumbar spine, the transverse processes under longitudinal view as the ultrasound landmark and the needles of medial branch block to the facet joint can be a promising guidance.

A simple method for accurate liver volume estimation by use of curve-fitting: a pilot study

In this paper, we describe the effectiveness of our curve-fitting method by comparing liver volumes estimated by our new technique to volumes obtained with the standard manual contour-tracing method. Hepatic parenchymal-phase images of 13 patients were obtained with multi-detector CT scanners after intravenous bolus administration of 120-150 mL of contrast material (300 mgI/mL). The liver contours of all sections were traced manually by an abdominal radiologist, and the liver volume was computed by summing of the volumes inside the contours. The section number between the first and last slice was then divided into 100 equal parts, and each volume was re-sampled by use of linear interpolation. We generated 13 model profile curves by averaging 12 cases, leaving out one case, and we estimated the profile curve for each patient by fitting the volume values at 4 points using a scale and translation transform. Finally, we determined the liver volume by integrating the sampling points of the profile curve. We used Bland-Altman analysis to evaluate the agreement between the volumes estimated with our curve-fitting method and the volumes measured by the manual contour-tracing method. The correlation between the volume measured by manual tracing and that estimated with our curve-fitting method was relatively high (r = 0.98; slope 0.97; p < 0.001). The mean difference between the manual tracing and our method was -22.9 cm(3) (SD of the difference, 46.2 cm(3)). Our volume-estimating technique that requires the tracing of only 4 images exhibited a relatively high linear correlation with the manual tracing technique.

Preoperative vascular mapping with multislice CT of deep inferior epigastric artery perforators in planning breast reconstruction after mastectomy

Our aim was to evaluate the usefulness of computed tomography angiography (CTA) in vascular mapping for planning breast reconstruction after mastectomy using a free flap made with the deep inferior epigastric perforators (DIEP). We retrospectively evaluated 41 patients, mean age 57 years, scheduled for mastectomy. CTA was performed with a 64-row scanner (Aquilion 64, Toshiba Medical Systems, Japan), with injection of 100 ml of contrast medium (iomeprol 350 mgI/ml, Bracco, Italy) at 4.5 ml/s. Maximum intensity projection (MIP) and three-dimensional volume-rendering (VR) reconstructions were made to mark perforator positions. Presentation frequency, anatomy and artery opacification quality were evaluated. DIEP were always depicted (n=81) and subdivided according to Taylor's classification into type I (65%), type II (28%), and type III (7%). We observed a mean of three (range, 1-5) DIEP arteries on the right and two (range, 1-5) on the left side. The superficial inferior epigastric artery (SIEA) was depicted in 6/41 patients, bilaterally in three cases. Opacification was optimal in 30/41 cases, venous contamination due to late arterial phase in eight and low opacification due to early scan in three. Studying DIEP with CTA is useful in the surgical planning of breast reconstruction, even though it requires careful optimisation owing to the critical timing of opacification typical of that vascular district.

Carotid Artery Plaque Characterization Using CT Multienergy Imaging

Carotid artery plaque types can be categorized with CT according to their HU values. The purpose of this work was to analyze carotid artery plaque characteristics by using multienergy imaging. Thirty-two consecutive patients (23 men; median age, 70 years) were retrospectively analyzed. Carotid arteries were studied with a multienergy CT scanner. All patients received a 15-mL timing bolus of contrast medium to synchronize the data acquisition followed by an injection of 60 mL of contrast medium at a 5-mL/s flow rate. Plaque analysis in 64 carotid arteries was performed, and datasets were reconstructed by using a dedicated workstation. For each plaque, the HU value was quantified with a 2-mm-square region of interest at monoenergy values of 66, 70, 77, and 86 keV. The Wilcoxon test was used to test the differences in HU values in the plaques at different kiloelectron volts. Four carotid arteries were excluded due to the absence of plaque, and another 7, because of the presence of calcified plaques. In the remaining 53 carotid arteries, Wilcoxon analysis showed a statistically significant difference in HU values among the monoenergy values of 66, 70, 77, and 86 keV (P=.0001). In particular, we found that with the increase in monochromatic kiloelectron volt values, there is a statistically significant reduction in the HU value of the plaque. Results of this study suggest that the HU values of plaque may significantly change according to the selected kiloelectron volt; therefore, the HU-based plaque type (fatty, mixed, calcified) should be classified according to the energy level applied.

Enhancement of anatomical structures and detection of metastatic cervical lymph nodes: comparison of two different contrast material doses

To determine if a 20 % reduction in the contrast material dose is acceptable in the CT evaluation of patients with head and neck malignancy. Sixty consecutive patients (mean age 67 years) with head and neck malignancy underwent contrast-enhanced CT according to two different protocols: protocol A (80 mL of contrast material administered at an injection rate of 1.5 mL/s) and protocol B (100 mL at 1.9 mL/s). The enhancement of anatomical structures and detectability of metastatic nodes were compared between the two protocols. Pathologic analysis of the surgical resection served as the reference standard. CT numbers of the anatomical structures were not significantly different between the two protocols. Mean sensitivity (64 and 77 % for protocols A and B, respectively), specificity (78 and 84 %), and accuracy (74 and 83 %) tended to be higher for protocol B than for A, but no significant difference was found. Reducing the contrast material dose by 20 % did not significantly impair the enhancement of anatomical structures or the detection of metastatic cervical lymph nodes. Radiologists should therefore consider reducing the contrast material dose used in head and neck CT.

CT Angiography of the Renal Arteries: Comparison of Lower-Tube-Voltage CTA With Moderate-Concentration Iodinated Contrast Material and Conventional CTA

The objective of our study was to investigate the feasibility of an 80-kVp protocol using a moderate-concentration contrast medium (CM) for CT angiography of the renal arteries by comparison with a conventional 120-kVp protocol using a high-concentration CM. Attenuation values and signal-to-noise ratios (SNRs) were determined in a phantom for the 120-kVp protocol with a high-concentration CM and the 80-kVp protocol with a moderate-concentration CM. In addition, 50 patients were prospectively enrolled in the study: 25 were scanned with 120 kVp and 200 effective mAs (mAs(eff)) after the administration of 110 mL of high-concentration CM (370 mg I/mL), and the other 25 were scanned with 80 kVp and 585 mAs(eff) after the administration of 110 mL of moderate-concentration CM (300 mg I/mL). Images of the two groups were compared in terms of arterial attenuation, SNR, contrast-to-noise ratio (CNR), and subjective degree of arterial enhancement and image quality. The mean attenuation of the main renal artery was significantly higher (p < 0.001) in the 80-kVp group who received moderate-concentration CM (mean ± SD, 370.0 ± 65.0 HU) than in the 120-kVp group who received high-concentration CM (269.9 ± 27.8 HU) without significant differences in SNR and CNR values. The 80-kVp protocol had significantly higher quality scores for arterial enhancement, sharpness of the artery, and overall diagnostic quality compared with the 120-kVp protocol. The effective dose of the 80-kVp protocol (4.5 mSv) was 8.2% lower than that of the 120-kVp protocol (4.9 mSv). The use of 80 kVp with moderate-concentration CM could improve arterial enhancement and provide superior image quality with a smaller amount of iodine and a lower radiation dose.

Incompatibility of Contrast Medium and Trisodium Citrate

To test the compatibility of trisodium citrate, a catheter lock solution, with iodinated contrast medium. Iohexol, iobitridol, iodixanol, ioxaglate, ioxithalamate, iomeprol, and iopromide were tested. In all tests, 2ml of contrast medium were mixed with 2ml of trisodium citrate solution. Iodixanol and ioxaglate provoked a highly viscous gluelike precipitation when mixed with trisodium citrate. A brief transient precipitate was observed with iohexol, iomeprol, and ioxithalamate. Permanent precipitation occurred with iobitridol and iopromide. One must be aware of the potential for precipitation when contrast medium is mixed with trisodium citrate solution. Before trisodium citrate solution is injected, the catheter should be thoroughly flushed with saline if a contrast medium has previously been injected through it.

Contrast media volume optimization in high-pitch dual-source CT coronary angiography: feasibility study

To investigate the feasibility of contrast media (CM) volume reduction in dual-source coronary computed tomography angiography high-pitch mode without affecting coronary artery enhancement. Eighty patients were involved in a preliminary experiment with a default injection protocol (60ml of CM). The age, BMI, test bolus (TB) enhancement peak and the CT values of coronary artery for each patient were recorded and the key factors for determining coronary artery enhancement were investigated. Based on the results of the preliminary experiment, 120 patients were involved in the main experiment with a new injection protocol. For each patient, the CT values and noise of left coronary sinus (LCS), and the distal segment of right coronary artery were measured. In the preliminary experiment, the peak enhancement of TB correlated most strongly with the HU values of coronary artery. Consequently, the new injection protocol was devised to catalog patients into four groups (30, 40, 50 and 60ml) of CM based on their TB peak enhancement. In the main experiment, the 30ml CM injection group whose peak attenuation of TB were the highest (30 vs. 40,50,60ml: 323.0±27.5 vs. 264.2±11.9, 242.1±8.8, 206.2±18.2 HU, p<0.05), obtained the highest attenuation of LCS (30 vs. 40,50,60ml: 365.0±41.2 vs. 341.8±40.0, 326.9±34.7, 312.5±38.2 HU p<0.05). Contrast optimization is feasible in high-pitch DSCT coronary angiography. Certain patients may receive 30ml of CM without affecting vessel enhancement.

Clinical expert consensus statement on best practices in the cardiac catheterization laboratory: Society for cardiovascular angiography and interventions

The cardiac catheterization laboratory (CCL) is a setting in which elective, urgent, and emergent percutaneous procedures are performed. This poses challenges to maintaining and prioritizing high quality care and patient safety. Nonetheless, process expectations of a high-quality CCL include appropriate periprocedural communication, clinical management, documentation, and universal protocol. Regulations primarily targeted at open surgical operating rooms have the potential to negatively impact care because they may mandate focus on performance measures that are not necessarily relevant to the cardiac catheterization laboratory. For example, routine site marking for percutaneous access is irrelevant for most patients since failure to obtain access on one side (e.g., right femoral artery) simply leads to attempting access on the other side (e.g., left femoral artery). Instead, directives should be tailored to the percutaneous procedure setting to assure quality and optimal patient safety. This document will therefore provide expert consensus opinion on a number of issues pertaining to ‘‘best practices’’ within the CCL, focusing on quality and safety during each step of the process. The writing committee acknowledges a dearth in high-quality published studies in this area, making many of the enclosed recommendations based primarily on expert consensus. Although references are provided when available, further research specifically in catheterization laboratory processes and quality improvement is needed. The document is divided into ‘‘best practices’’ that should be performed during the preprocedure, intraprocedure, and postprocedure settings for diagnostic cardiac catheterization and coronary intervention, to be consistent with the typical patient flow into and out of the CCL. Despite the long history of cardiac catheterization that dates back several decades, a document describing these ‘‘best practices’’ has not yet been written. The purpose of this document is not to represent all acceptable practices, but to provide consensus opinion on what would currently be considered ‘‘best practices’’ as future goals for catheterization laboratories.

Contrast-Enhanced Magnetic Resonance Angiography

To evaluate the effect of the contrast medium (CM) concentration and the saline chaser volume and injection rate on first-pass aortic enhancement characteristics in contrast-enhanced magnetic resonance angiography using a physiologic flow phantom. Imaging was performed on a 3.0-T magnetic resonance system (MAGNETOM Trio, Siemens Healthcare Solutions, Inc, Erlangen, Germany) using a 2-dimensional fast low angle shot T1-weighted sequence (repetition time, 500 milliseconds; echo time, 1.23 milliseconds; flip angle, 8 degrees; 1 frame/s × 60 seconds). The following CM concentrations injected at 2 mL/s were used with 3 different contrast agents (gadolinium [Gd]-BOPTA, Gd-HP-DO3A, Gd-DTPA): 20 mL of undiluted CM (100%) and 80%, 40%, 20%, 10%, 5%, and 2.5% of the full amount, all diluted in saline to a volume of 20 mL to ensure equal bolus volume. The CM was followed by saline chasers of 20 to 60 mL injected at 2 mL/s and 6 mL/s. Aortic signal intensity (SI) was measured, and normalized SI versus time (SI/Tn) curves were generated. The maximal SI (SI(max)), bolus length, and areas under the SI/Tn curve were calculated. Decreasing the CM concentration from 100% to 40% resulted in a decrease of SI(max) to 86.1% (mean). Further decreasing the CM concentration to 2.5% decreased SI(max) to 5.1% (mean). Altering the saline chaser volume had no significant effect on SI(max). Increasing the saline chaser injection rate had little effect (mean increase, 2.2%) on SI(max) when using ≥40% of CM. There was a larger effect (mean increase, 19.6%) when ≤20% of CM were used. Bolus time length was significantly shorter (P < 0.001), and area under the SI/T(n) curve was significantly smaller (P < 0.01) for the CM protocols followed by a saline chaser injected at 6 mL/s compared with a saline chaser injected at 2 mL/s. With 40% of CM and a fast saline chaser, SImax close to that with undiluted CM can be achieved. An increased saline chaser injection rate has a more pronounced effect on aortic enhancement characteristics at lower CM concentrations than at higher CM concentrations.

Correlation between dynamic CT findings and pathological prognostic factors of small lung adenocarcinoma

Purpose: To compare pathological prognostic factors of small lung adenocarcinomas with findings of contrast-enhanced dynamic computed tomography (CT) scans. Materials and methods: We evaluated 108 patients with lung adenocarcinomas ≤ 30 mm in diameter who underwent dynamic CT scans (80–96 ml of contrast material, 2.5–3 ml/s injection) and tumor resections. Attenuation values of both the early phase (20–36 s after injection) and delayed phase (91–95 s) of enhanced CT minus baseline plain CT attenuation were defined as ΔEarly and ΔDelay. The early enhancement ratio was defined as ΔEarly/ΔDelay×100 (%). We statistically compared the early enhancement ratios between the presence and absence of each pathological finding (lymph node metastasis, lymphatic permeation, vascular invasion, and pleural involvement). Patients were divided into 2 groups based on early enhancement ratios: ratio ≥50% (n = 41) and ratio <50% (n = 67) and we statistically compared these 2 groups. Results: The early enhancement ratios in the group with lymph node metastasis, lymphatic permeation, and vascular invasion were significantly lower than in the group without these findings (24.9% vs 48.6%; P < 0.001, 30.0% vs 47.5%; P = 0.002, and 26.5% vs 47.0%; P = 0.002, respectively). Lymph node metastasis, lymphatic permeation, and vascular invasion were significantly more frequent in tumors with a ratio <50% than in tumors with ratio ≥50% (P < 0.001, P = 0.008, and P = 0.005, respectively). Conclusions: There was a significant correlation between the early enhancement ratio of enhanced dynamic CT and the pathological prognostic factors in small lung adenocarcinomas.

Catheter-Based Reperfusion Treatment of Pulmonary Embolism

Case Presentation: A 76-year-old man with a history of hemicolectomy for colon cancer 10 days previously was admitted because of syncope and severe shortness of breath. On physical examination, the patient was hemodynamically unstable, with a systolic arterial pressure of 80 mm Hg, a heart rate of 124 beats per minute, and distended jugular veins. He was agitated and unable to speak full sentences. His respiratory rate was 28 breaths per minute, and oxygen saturation was 80% on room air. Contrast-enhanced computed tomography showed a filling defect of the left main pulmonary artery, complete occlusion of the left lower lobe pulmonary artery, nonobstructive filling defects of the right lower lobe pulmonary artery, and right ventricular enlargement (right-to-left ventricular dimension ratio of 1.4) (Figure 1). The hemodynamic situation remained unchanged after initiation of treatment with oxygen, intravenous unfractionated heparin, and normal saline. Figure 1. Contrast-enhanced chest computed tomogram from the first case. Left, Complete occlusion of the left lower lobe pulmonary artery (large arrow) and nonobstructive filling defect in the right lower lobe pulmonary artery (small arrow). Right, The subannular right-to-left ventricular dimension ratio was obtained from the reconstructed 4-chamber view.1 Right (47.3 mm) and left (33.9 mm) ventricular dimensions were measured perpendicular to the interventricular septum and 1 cm above the atrioventricular annulus plane. The right-to-left ventricular dimension ratio was calculated as 1.4. Case Presentation: A 55-year-old woman suddenly developed acute shortness of breath 3 weeks after resection of a meningioma. On physical examination, the patient appeared hemodynamically stable, with a systolic arterial pressure of 100 mm Hg, a heart rate of 96 beats per minute, a respiratory rate of 18 breaths per minute, and an oxygen saturation of 89% while receiving 3 L of oxygen via face mask. A contrast-enhanced computed tomography confirmed subtotal filling defects in both main pulmonary …

Diagnostic Accuracy of Pulmonary CT Angiography at Low Tube Voltage: Intraindividual Comparison of a Normal-Dose Protocol at 120 kVp and a Low-Dose Protocol at 80 kVp Using Reduced Amount of Contrast Medium in a Simulation Study

The purpose of this study was to simulate pulmonary emboli (PE) and image quality at low tube energy and reduced contrast material volume in normal-dose pulmonary CT angiography (CTA) images and to analyze the diagnostic accuracy with normal- and low-dose pulmonary CTA. Normal-dose pulmonary CTA examinations using 120 kVp and 100 mL of contrast material in 10 patients with no PE were retrospectively selected. The image characteristics of an 80-kVp low-dose pulmonary CTA protocol (patient exposure reduction, 57%) with 75 mL of contrast material were simulated. Four different sets of filling defects were computer simulated in identical locations in each normal-dose and corresponding low-dose examination, equaling 783 PE in 40 normal-dose and 40 low-dose datasets. Ten normal-dose and 10 low-dose examinations contained no emboli and were used as controls. The 100 pulmonary CTA studies were randomly assessed by three readers blinded to PE location and image quality. The results were assessed by nonparametric tests and Student t tests. No difference was found between the CT protocols in terms of sensitivity, specificity, and positive and negative diagnostic likelihood ratios at all ramification levels of the pulmonary arteries (p = 0.343-1). The overall sensitivity and specificity with the normal and simulated low-dose protocols were 79.9% versus 81.3% and 98.0% versus 98.2% (p = 0.444 and 0.702), respectively. The diagnostic confidence (2.81 ± 0.39 vs 2.77 ± 0.47; p = 0.297) and overall image quality (3.92 ± 0.52 vs 3.83 ± 0.54; p = 0.216) were similar at 120 kV and 80 kV. The intraindividual comparison of diagnostic accuracy with normal-dose and simulated low-dose pulmonary CTA protocols revealed no difference under experimental conditions.

Intravenous contrast material administration at high-pitch dual-source CT pulmonary angiography: Test bolus versus bolus-tracking technique

PurposeTo compare test bolus and bolus tracking for the determination of scan delay of high-pitch dual-source CT pulmonary angiography in patients with suspected pulmonary embolism using 50ml of contrast material. Materials and methodsData of 80 consecutive patients referred for CT pulmonary angiography were evaluated. All scans were performed on a 128-channel dual-source CT scanner with a high-pitch protocol (pitch 3.0, 100kV, 180mAs). Contrast enhancement was achieved by injecting 50ml of iomeprol followed by a saline chaser of 50ml injected at a rate of 4ml/s. The scan delay was determined using either the test bolus (n=40) or bolus tracking (n=40) technique. Test bolus required another 15ml CM to determine time to peak enhancement of the contrast bolus within the pulmonary trunk. Attenuation profiles in the pulmonary trunk and on segmental level as well as in the ascending aorta were measured to evaluate the timing techniques. Additionally, overall image quality was evaluated. ResultsIn all patients an adequate and homogeneous contrast enhancement of more than 250HU was achieved in the pulmonary arteries. No statistically significant difference between test bolus and bolus tracking was found regarding attenuation of the pulmonary arteries or overall image quality. However, using bolus tracking 15ml CM less was injected. ConclusionA homogeneous opacification of the pulmonary arteries and sufficient image quality can be achieved with both the bolus tracking and test bolus techniques with significant lower contrast doses compared to conventional contrast material injection protocols.

Coronary Enhancement for Prospective ECG-Gated Single R-R Axial 320-MDCT Angiography: Comparison of 60- and 80-mL Iopamidol 370 Injection

The objective of our study was to evaluate the difference in coronary enhancement provided by 60 versus 80 mL of contrast medium (370 mg I/mL) for prospectively ECG-gated single-heartbeat axial 320-MDCT. We retrospectively evaluated 108 consecutive 320-MDCT angiography studies. Group 1 (n = 36) received 60 mL of an iodinated contrast medium and group 2 (n = 72), 80 mL. All patients were imaged with a standardized protocol: iopamidol 370 followed by 40 mL of saline, both administered at a rate of 6 mL/s. Two imagers subjectively assessed image quality throughout the coronary arteries. Region-of-interest attenuation (HU) measurements were performed in the aorta plus the proximal and distal coronary arteries. Subjective analysis of all coronary segments showed slightly better image quality for group 2. Patients in group 1 had significantly (p < 0.05) lower mean attenuation values for the individual coronary vessels. Nevertheless, 96.7% of all coronary segments in the group 1 patients had an attenuation of greater than 300 HU; when analysis was limited to group 1 patients with a body mass index of greater than 30, 92.8% of the segments were more than 300 HU, and all segments measured more than 250 HU. An injection protocol based on 60 mL of iopamidol (370 mg I/mL) for prospectively ECG-gated wide-area detector single-heartbeat coronary CT angiography (CTA) has less coronary enhancement than a protocol based on 80 mL. However, using 60 mL, more than 96% of coronary segments had sufficient enhancement (i.e., > 300 HU), supporting the general use of 60-mL protocols for clinical wide-area detector coronary CTA.

Indirect Computed Tomography Venography With a Low-Tube-Voltage Technique

The objective of the study was to investigate the effects of low-tube-voltage computed tomography (CT) venography on qualitative and quantitative image parameters and the radiation dose. Eighty-eight studies on 84 patients underwent pelvic and lower-extremity CT venography under protocol A (standard 120 kV with 150 mL of contrast material, n = 44) or protocol B (80 kV with 100 mL of contrast material, n = 44) on a 64-detector CT scanner. We compared the dose length product in the 2 protocols. Two blinded observers measured CT attenuation in the veins, the image noise, contrast-to-noise ratio, and figure of merit. The mean dose length product was significantly lower under protocol B than A (603.2 [SD, 67.2] vs 1131.7 [SD, 67.0] mGy × cm) (P < 0.01). Mean CT attenuation of the veins was significantly greater with protocol B (125.3 [SD, 16.2] vs 106.1 [SD, 16.0] Hounsfield units) (P < 0.01), and the mean image noise was also significantly higher under protocol B (6.6 [SD, 0.8] vs 4.9 [SD, 0.7] Hounsfield units) (P < 0.01). There was no difference in contrast-to-noise ratio (P = 0.46). Figure of merit was significantly higher under protocol B (P < 0.01). Computed tomography venography with a low-tube-voltage technique allows reducing the radiation dose and the amount of contrast material without image quality degradation.