Showing papers in "Investigative Radiology in 2003"
TL;DR: The MAR algorithm led to a robust reduction of metal artifacts in Computed Tomography and may serve for an improvement in image quality in patients with metallic implants.
Abstract: Rationale and Objectives: To evaluate a newly developed algorithm for metal artifact reduction (MAR) in Computed Tomography (CT). Methods: A projection interpolation algorithm for MAR with threshold-based metal segmentation was developed. First, the algorithm was tested with a simulated hip phantom. On demand, the presence of metallic inserts was simulated, representing total hip endoprostheses. Second, CT data of 20 patient with total hip endoprosthesis were reconstructed with and without application of the MAR algorithm. Image quality was independently assessed by 2 experienced radiologists using a qualitative score. The results of the in vitro study were evaluated with the Student's t test. Results of the in vivo study were analyzed using a repeated-measure analysis of variance. Results: Applying the MAR algorithm the phantom study showed no significant difference between images with and without simulated metal contributions. The patient study revealed improved image quality using the MAR algorithm. Results were statistically significant for fat (P = 0.0097), vessels (P = 0.0091), and bone (P = 0.0005). Improvement of the image quality for muscle was not statistically significant (P = 0.0287). Conclusions: A new algorithm for metal artifact reduction was successfully introduced into clinical routine. The algorithm led to a robust reduction of metal artifacts. The MAR algorithm may serve for an improvement in image quality in patients with metallic implants.
225 citations
TL;DR: High-quality neuro-imaging of patients is possible at 3.0 T by paying appropriate attention to the discussed technical issues, and solutions have been developed or are currently under development.
Abstract: MR imaging at very high field (3.0 T) is a significant new clinical tool in the modern neuroradiological armamentarium. In this report, we summarize our 40-month experience in performing clinical neuroradiological examinations at 3.0 T and review the relevant technical issues. We report on these issues and, where appropriate, their solutions. Issues examined include: increased SNR, larger chemical shifts, additional problems associated with installation of these scanners, challenges in designing and obtaining appropriate clinical imaging coils, greater acoustic noise, increased power deposition, changes in relaxation rates and susceptibility effects, and issues surrounding the safety and compatibility of implanted devices. Some of the these technical factors are advantageous (eg, increased signal-to-noise ratio), some are detrimental (eg, installation, coil design and development, acoustic noise, power deposition, device compatibility, and safety), and a few have both benefits and disadvantages (eg, changes in relaxation, chemical shift, and susceptibility). Fortunately solutions have been developed or are currently under development, by us and by others, for nearly all of these challenges. A short series of 1.5 T and 3.0 T patient images are also presented to illustrate the potential diagnostic benefits of scanning at higher field strengths. In summary, by paying appropriate attention to the discussed technical issues, high-quality neuro-imaging of patients is possible at 3.0 T.
209 citations
TL;DR: In patients with clinical suspicion but negative tumor marker profile, too, F-18 FDG PET seems to be a reliable imaging tool for detection of tumor recurrence or metastases, compared with conventional imaging on a patient base.
Abstract: AIM To evaluate the role of F-18-fluorodeoxyglucose positron-emission tomography (F-18 FDG PET) in the follow-up of breast carcinoma in case of clinical suspicion of local recurrence or distant metastases and/or tumor marker increase in correlation to conventional imaging. MATERIAL AND METHODS Retrospective analysis of the results of F-18 FDG PET (ECAT ART(R), Siemens CTI MS) of 62 patients (age 58.5 +/- 12.8) with surgically resected breast carcinoma (time interval after surgery, 86 +/- 82 months, mean follow-up 24 +/- 12.6 months). Patient- and lesion-based comparison with conventional imaging (CI) including mammography (MG), ultrasonography (US), computerized tomography (CT), magnetic resonance imaging (MRI), radiography (XR) and bone scintigraphy (BS). Furthermore, we evaluated the influence on tumor stage and therapeutic strategy. A visual qualitative evaluation of lesions was performed. RESULTS On a patient base, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy for detecting local recurrence or distant metastases were calculated to be 97%, 82%, 87%, 96% and 90% compared with 84%, 60%, 73%, 75% and 74% with CI. On a lesion base, significantly more lymph node (84 vs. 23, P < 0.05) and fewer bone metastases (61 vs. 97, P < 0.05) could be detected by using F-18 FDG PET compared with CI. Sclerotic bone lesions were predominantly detected by BS. On the other hand, there were several patients with more FDG positive bone lesions and also mixed FDG positive/Tc-99m methylenediphosphonate (MDP) negative and FDG negative/Tc-99m MDP positive metastases. In case of normal tumor markers, sensitivity, specificity, PPV, NPV and accuracy for detecting local recurrence or distant metastases were calculated to be 100%, 85.0%, 78.6%, 100% and 90.3% for FDG PET and 80%, 50%, 50%, 80% and 61.5% for CI. An upstaging could be observed in 9.7% (6/62) and downstaging in 12.9% (8/62), leading to a change in therapeutic regimen in 13 patients (21%). CONCLUSIONS F-18 FDG PET demonstrates apparent advantages in the diagnosis of metastases in patients with breast carcinoma, compared with conventional imaging on a patient base. On a lesion base, significantly more lymph node and less bone metastases can be detected by using F-18 FDG PET compared with conventional imaging, including bone scintigraphy. In patients with clinical suspicion but negative tumor marker profile, too, F-18 FDG PET seems to be a reliable imaging tool for detection of tumor recurrence or metastases. Considering the high predictive value of F-18 FDG PET, tumor stage and therapeutic strategy will be reconsidered in several patients.
185 citations
TL;DR: The injection of ≈1 g iodine/s resulted in an optimal (250–300 HU) contrast enhancement for cardiac 4-detector-row computed tomography angiography of the heart.
Abstract: Rationale and Objectives:This study was designed to determine the optimal contrast protocol for 4-detector-row computed tomography angiography of the heart.Methods:Sixty patients were randomly assigned to 1 of 4 groups with 300 and 400 mg/mL iodine concentrations and 2.5 and 3.5 mL/s flow rates. Con
184 citations
TL;DR: It is demonstrated that absolute quantification of metabolite concentration is essential in properly identifying pathologic differences of brain metabolites in depression.
Abstract: Rationale and ObjectivesThis study compared metabolic differences in the frontal brain of depressed patients versus age- and sex-matched controls using proton magnetic resonance spectroscopy and absolute quantification of metabolites (NAA, Cr, Cho, mI) at 3 Tesla.MethodsShort-echo-time stimulated ec
158 citations
TL;DR: The improved detection ability using high-field MR imaging is prominent even when sequence parameters are optimized around the midfield units, suggesting that multicenter trials using both 1.5 T and 3.0 T instruments may be affected by these sensitivity differences.
Abstract: ObjectiveTo evaluate the relative sensitivity of MR scanning for multiple sclerosis (MS) at 1.5 Tesla (T) and 3.0 T using identical acquisition conditions, as is typical of multicenter clinical trials.MethodsTwenty-five subjects with MS were scanned at 1.5 T and 3.0 T using fast spin echo, and T1-we
139 citations
TL;DR: Initial experience in patients evaluated for CAD shows that spiral MDCT studies may provide LV functional data in good correlation to cine magnetic resonance imaging (MRI).
Abstract: RATIONALE AND OBJECTIVES Electrocardiogram-gated 3D volume data from multidetector computed tomography coronary angiography (MDCT-CA) enable image reconstruction in any phase of the cardiac cycle. The objective was to determine left ventricular (LV) function parameters by MDCT in comparison to cine magnetic resonance imaging (MRI). METHOD Thirty patients with known or suspected coronary artery disease (CAD) underwent MDCT-CA. From multiplanar reformations in short axis orientation end-diastolic and end-systolic LV volumes (LVEDV, LVESV) were determined to calculate LV stroke volume and ejection fraction (LVSV, LVEF) and compared with MRI measurements. RESULTS LVEDV (147 +/- 27 mL) and LVESV (65 +/- 22 mL) determined by MDCT correlated well to the respective MRI measurements (LVEDV 133 +/- 27 mL, r = 0.80, P < 0.001; LVESV 48 +/- 19 mL, r = 0.89, P < 0.001). LVSV (MDCT 82 +/- 15 mL; MRI 85 +/- 17 mL; r = 0.77, P < 0.001) and LVEF (MDCT 56 +/- 9%; MRI 65 +/- 8%; r = 0.85, P < 0.001) showed a good correlation as well. LVEF was significantly underestimated by MDCT (-8.5 +/- 4.7%, P < 0.001). CONCLUSIONS Initial experience in patients evaluated for CAD shows that spiral MDCT studies may provide LV functional data in good correlation to Cine MRI.
114 citations
TL;DR: The additional diagnostic information on delayed imaging, combined with the possibility to use a lower overall dose to obtain similar diagnostic Information on dynamic imaging, offers a distinct clinical advantage for Gd-BOPTA for liver MRI.
Abstract: Schneider G, Maas R, Kool LS, et al. Low-dose gadobenate dimeglumine versus standard dose gadopentetate dimeglumine for contrast-enhanced magnetic resonance imaging of the liver: An intra-individual crossover comparison. Invest Radiol 2003;38:85–94.Rationale and Objectives.Gadobenate dimeglumine (Gd
110 citations
TL;DR: EBT and MSCT permit reliable coronary artery visualization and measurement of vessel diameters and for the used scan protocol, MSCT images had a lower CNR and were more frequently affected by motion.
Abstract: Achenbach S, Giesler T, Ropers D, et al. Comparison of image quality in contrast-enhanced coronary-artery visualization by electron beam tomography and retrospectively electrocardiogram-gated multislice spiral computed tomography. Invest Radiol 2003;38:119–128.Rationale and Objectives.To compare the
107 citations
TL;DR: Compared with the anatomic reference, CT imaging was an accurate and valid technique for measuring the femoral anteversion, and biplane radiography demonstrated significant inconsistencies in the measurement of this anatomic parameter.
Abstract: RATIONALE AND OBJECTIVES The ability of biplane radiography and standard computed tomography (CT) imaging techniques to measure accurately the human femoral anteversion was evaluated and compared with an anatomic reference: the osteometric method. METHODS Femoral anteversion of 10 normal adult cadaveric human femora were determined using a standardized anatomic measurement method (the anatomic reference) and the 2 selected common imaging techniques (biplane radiography and CT). RESULTS On average, anteversion measurements using biplane radiography were 21/2 times greater in magnitude than measurements using the anatomic reference (absolute mean difference, 13.5 degrees; P = 0.004). In contrast, the discrepancy between CT and anatomic reference measurements was notably less and not statistically significant (absolute mean difference, 2.8 degrees; P = 0.351). In addition, biplane radiography demonstrated greater inter- and intrarater variability than CT imaging for repeated measurements of the same bone specimens. CONCLUSIONS Compared with the anatomic reference, CT imaging was an accurate and valid technique for measuring the femoral anteversion. In contrast, biplane radiography demonstrated significant inconsistencies in the measurement of this anatomic parameter.
106 citations
TL;DR: Cumulative triple-dose images of both field strengths were superior to standard field strengths, however, administration of gadodiamide contrast agent produces higher contrast between tumor and normal brain on 3.0 T than on 1.5 T, resulting in better detection of brain metastases and leptomeningeal involvement.
Abstract: Purpose To compare the diagnostic efficacy of a standard and cumulative triple dose of magnetic resonance (MR) imaging contrast agent in the evaluation of brain metastases using a high-field 3.0 T MR unit versus a standard field 1.5 T MR unit. Methods Twenty-two patients with suspected brain metastases were examined at both field strengths using identical postcontrast coronal 3D gradient echo with magnetization preparation, which was adjusted separately for each field strength. In both groups initially, iv injection of 0.1 mmol/kg body weight gadolinium chelate (gadodiamide) and thereafter, 0.2 mmol/kg body weight gadodiamide were administered. Subjective assessment of the images was performed independently by 3 neuroradiologists. Objective measurement of signal-to-noise and contrast-to-noise ratios was obtained. Results The subjective assessment of cumulative triple-dose 3.0 T images obtained the best results compared with other sequences, detecting 84 metastases, followed by 1.5 T cumulative triple-dose enhanced images with 81 brain metastases. The objective assessment confirmed those results, showing significantly higher signal-to-noise and contrast-to-noise ratios with 3.0 T than with 1.5 T. Conclusions Cumulative triple-dose images of both field strengths were superior to standard field strengths. However, administration of gadodiamide contrast agent produces higher contrast between tumor and normal brain on 3.0 T than on 1.5 T, resulting in better detection of brain metastases and leptomeningeal involvement.
TL;DR: 16-slice CT using a dedicated sharp kernel for image reconstruction facilitates improved visualization of coronary artery stent lumen and detection of in-stent stenoses.
Abstract: Objective: The aim of this study was to compare the visualization of different coronary artery stents and the detectability of in-stent stenoses during 4-slice and 16-slice computed tomography (CT) angiography in a vesselphantom. Material and Methods: Ten coronary stents were introduced in a coronary artery vessel phantom (plastic tubes with an inner diameter of 3 mm, filled with iodinated contrast material diluted to 220 Hounsfiled Units [HU], surrounded by oil [60 HU]). CT scans were obtained perpendicular to the stent axes on a 4-slice scanner (detector collimation 4 × 1 mm; table feed 1.5 mm/rotation, mAs 300, kV 120, medium-smooth kernel) and a 16-slice scanner (detector collimation 12 × 0.75 mm; table feed 2.8 mm/rotation, mAs 370, kV 120, reconstruction with a standard and an optimized sharp kernel). Longitudinal multiplanar reformations were evaluated regarding visible lumen diameters and intraluminal attenuation values. Additionally, the stents were scanned with the same parameters after implantation of 60% stenoses (HU 30). Results: Using the same medium-smooth kernel reconstruction with 4-slice and 16-slice CT, there was a slight increase in the average visible lumen area (26% versus 31%) and less increase of average intraluminal attenuation values (380 HU versus 349 HU). Significant improvement of lumen visualization (54%, P < 0.01) and attenuation values (250, P < 0.01) was observed for the 16-slice scans using the sharp kernel reconstruction. In-stent stenoses could be more reliably identified (or ruled out) by 16-slice CT and sharp reconstruction kernel when compared with the other 2 methods. Conclusion: 16-slice CT using a dedicated sharp kernel for image reconstruction facilitates improved visualization of coronary artery stent lumen and detection of in-stent stenoses.
TL;DR: Increased specific absorption rate can be a limiting fact; however, it is demonstrated that 3.0 T cardiac imaging shows gains in SNR while maintaining the CNR, and phased array coil technology is key for improving cardiac magnetic resonance imaging at 3.
Abstract: Rationale and Objectives A cardiac imaging pilot study was performed on 15 and 30 Tesla (T) whole body magnetic resonance units equipped with identical gradient sets and geometrically equivalent body coils The goals were to compare the signal-to-noise (SNR) and contrast-to-noise (CNR) ratios on matched studies conducted at both field strengths and demonstrate the potential for functional and morphologic cardiac evaluation at 30 T Methods Short axis cine true fast imaging with steady precession (True FISP) was compared at 15 and 30 T using the body coil in transmit-receive mode and transmit-only with single loop and phased array receiver coils SNR of the myocardium and CNR of the ventricular blood and myocardium were calculated from a quantitative region of interest analysis of these data Additionally at 30 T, long axis and 4-chamber cine as well as “dark blood” imaging are demonstrated with sequence and parameter settings comparable to current state of the art for cardiac evaluation at 15 T Results The 30 T data consistently demonstrates increases in SNR when all imaging conditions are closely matched but the increase has a large variability ranging from 20 to 85% depending on the radiofrequency coil configuration Ventricular blood–myocardium CNR greater than 30 is obtained at 30 T, which is comparable to an optimized 15 T acquisition despite the specific absorption rate limitation of flip angle to nearly one half the value The increased SNR at 30 T improves detection of fine anatomic detail, such as the chordae tendineae and mitral valve structure Conclusions Increased specific absorption rate can be a limiting fact; however, we have demonstrated that 30 T cardiac imaging shows gains in SNR while maintaining the CNR The SNR gain is advantageous, and phased array coil technology is key for improving cardiac magnetic resonance imaging at 30 T
TL;DR: Partially parallel MRI might be used for the assessment of lung perfusion and a significantly lower signal to noise ratio was observed in hypoperfused lung when compared with normally perfused lung.
Abstract: Rationale:Contrast-enhanced magnetic resonance imaging (MRI) of lung perfusion requires a high spatial and temporal resolution. Partially parallel MRI offers an improved spatial and temporal resolution.Objective:To assess the feasibility of partially parallel MRI for the assessment of lung perfusion
TL;DR: Both ASL and DSC EPI MRI yield highly comparable perfusion values in normal brain tissue, which correlated well by calculating Pearson's correlation coefficients and remained unchanged after stereotactic radiosurgery.
Abstract: Objectives:To evaluate relative cerebral blood flow (rCBF) in normal brain tissue using arterial spin-labeling (ASL) methods and first-pass dynamic susceptibility-weighted contrast-enhanced (DSC) magnetic resonance imaging (MRI).Methods:Sixty-two patients with brain metastases were examined on a 1.5
TL;DR: Gadobutrol- and Gd BOPTA-MRA exams lead to improved delineation of the pelvic arterial morphology compared with MRA exams performed with Gd-DTPA.
Abstract: Herborn CU, Lauenstein TC, Ruehm SG, et al. Intraindividual comparison of gadopentetate dimeglumine, gadobenate dimeglumine, and gadobutrol for pelvic 3D magnetic resonance angiography. Invest Radiol 2003;38:27–33.Rationale and Objectives.To compare the effect on image quality of a 1.0 mol/L gadolin
TL;DR: Use of SPGO and SPGO encapsulated in non–heat-hardened albumin microspheres (GOAM) represents a new approach and have suitable physicochemical properties to warrant further biophysical and animal studies and reevaluation of toxicity limitations.
Abstract: Rationale and objectiveTo prepare and characterize new particulate contrast media, small particulate gadolinium oxide (SPGO) and gadolinium oxide albumin microspheres (GOAM), as prototype multimodal imaging and therapeutic agents.MethodsSPGO was purchased from Alfa Aesar Inc. (Ward Hill, MA). GOAM w
TL;DR: The BPA P792 and USPIO have favorable properties that result from their intravascular retention and their lack of extravasation, allowing optimal contrast between the vessel and the adjacent tissue for several minutes postinjection.
Abstract: Rationale and objectives: The objective of this study is to determine the influence of the pharmacokinetic behaviors of different classes of blood pool agents (BPA) on a rabbit experimental model that mimics a magnetic resonance angiographic protocol. BPA were as follows: P792, a macromolecular agent (RCBPA), USPIO, an ultrasmall superparamagnetic iron oxide particle agent (SCBPA), and MS-325, a small gadolinium chelate that expresses intravascular behavior by reversible albumin binding. Methods: The 2 main phases of early distribution following contrast agent injection, that is, the bolus phase and the steady-state phase, are investigated by measuring Gd or Fe blood concentrations in the first 5 minutes postinjection. T1 relaxation times and r 1 relaxivity were calculated at each time point of blood sampling. Furthermore, in the case of MS-325, the concentrations of the free and bound forms were calculated, according to the measured concentrations and the apparent r, relaxivities. Results: Injected under similar conditions, the 3 BPA have, during the bolus phase, a comparable profile to Gd-DOTA. Signal enhancement was maximum during this short bolus phase, as were the Tl relaxation times under 30 ms for all agents. At 1 minute postinjection, P792 (r 1 = 39 seconds - 1 .mmol/L - 1 , 20 MHz) demonstrated the same pharmacokinetic behavior as USPIO (r 1 = 33 seconds - 1 .mmol/L - 1 , 20 MHz): Cl minute/C0 values were 91 ′ 6% and 92 ′ 12%, respectively. Immediately after the injection at clinical dose, 74% of MS-325 was in free form, resulting in an apparent r 1 relaxivity of only 13 seconds - 1 .mmol/L - 1 (20 MHz); 1 minute postinjection, the C1 minute/C0 value of 61 ′ 4% was the lowest as compared with P792 and USPIO and the bound form represented 75% of the MS-325 molecules. Conclusions: The BPA P792 and USPIO have favorable properties that result from their intravascular retention and their lack of extravasation, allowing optimal contrast between the vessel and the adjacent tissue for several minutes postinjection. Combining a rapid body clearance and a marked T 1 effect, P792 presents optimal blood pool characteristics for angiographic applications. During the bolus phase, MS-325 is mainly in free form, which presents the disadvantage of increasing the tissue signal background, due to extravasation of the free form.
TL;DR: Indirect CT-LG with iopamidol may have excellent potential for visualizing breast lymphatic drainage and for preoperative localization of breast sentinel lymph nodes.
Abstract: RATIONALE AND OBJECTIVES: The capability of an indirect computed tomographic lymphography (CT-LG) using a nonionic monometric contrast medium iopamidol for visualizing breast lymphatic pathways was preliminarily tested. MATERIALS AND METHODS: In 10 female dogs, a total of 0.5 and 1 mL of undiluted iopamidol was injected subcutaneously into the skin areas overlying the both caudal mammary glands. Contiguous 2-mm-thick multidetector raw helical CT images were obtained through the upper thorax and axilla before and during 60 minutes after gentle massage at the injection sites, with reconstruction into three-dimensional (3D) postcontrast CT images. The first lymph node (1st LN) directly draining from the injection sites was marked under CT guidance, followed by pre- and postmortem examinations. This CT-LG with 2-mL iopamidol was also attempted in five human female volunteers. RESULTS: Even with 0.5-mL iopamidol, the CT-LG clearly visualized the direct connection of the 1st LN and lymphatic vessels draining from the injection sites throughout the examination time in all the animals, with the maximum CT attenuation of 269 Hounsfield units (HU) +/- 137 in the 1st LN on the first postcontrast images. The topographic 3D images provided comprehensive anatomic outlines of these lymphatic pathways. Of the total of 20 opacified 1st LN and 110 distant nodes, all the 1st LN (100%) and 92 (83.6%) distant nodes could be resected at pre- or postmortem, with a good correlation with the CT images. The CT-LG also effectively localized the 1st LN with the maximum attenuation of 223 HU +/- 63 in the human volunteers, without any significant late adverse effects. CONCLUSION: Indirect CT-LG with iopamidol may have excellent potential for visualizing breast lymphatic drainage and for preoperative localization of breast sentinel lymph nodes.
TL;DR: Acquisition of CE-MRV data at 3 T enables spatial resolution to be increased within the same measurement time and with the same volume coverage compared with 1.5 T, thus providing more detailed information.
Abstract: Rationale and Objectives: To evaluate the clinical potential of high-resolution 3D contrast-enhanced blood oxygenation level-dependent MR-Venography (CE-MRV) for primary brain tumors and metastases at 3 Tesla (T) in comparison to 1.5 T. Methods: Eighteen patients with brain tumors were examined using CE-MRV after application of a standard dose of MRI contrast agent (0.1 mmol/kg gadodiamide). CE-MRV is based on a high-resolution 3D flow-compensated gradient-echo sequence with long echo times that uses the contrast-enhanced blood oxygenation level-dependent effect. This technique was performed using the same volume coverage and acquisition time at both field strengths after performing standard imaging sequences. Results: The higher spatial resolution of CE-MRV at 3 T showed more details within and around tumors than at 1.5 T. Visibility was enhanced by stronger susceptibility weighting and higher intrinsic signal-to-noise at 3 T. Compared with standard imaging protocols, additional information characterized as tubular and nontubular hypointense structures were found within or around lesions on CEMRV images. Conclusions: Acquisition of CE-MRV data at 3 T enables spatial resolution to be increased within the same measurement time and with the same volume coverage compared with 1.5 T, thus providing more detailed information. The method may also show the potential to estimate oxygen supply of tumors, especially at high field
TL;DR: MRE is able to measure a dependence of tissue elasticity on the menstrual cycle and is a promising diagnostic method that produces images with a contrast proportional to the elasticity of the tissue.
Abstract: RATIONALE AND OBJECTIVES. Magnetic resonance elastography (MRE) is a promising diagnostic method that produces images with a contrast proportional to the elasticity of the tissue. This study investigated using MRE the dependence of breast tissue elasticity from the menstrual cycle of healthy volunteers. METHODS. Five volunteers (age 26-36) without breast disease and contraceptive medication were examined once weekly over 2 menstrual cycles. Examinations were performed with a 1.5 T magnet (ACS-NT, Philips Medical Systems, Best, The Netherlands). Low-frequency mechanical waves (65 Hz) were transmitted into the tissue by an oscillator. By means of a motion-sensitive spin-echo sequence, mechanical waves were displayed within the phase of the MR image and phase images were used to reconstruct the local distribution of elasticity. The elasticity of fibroglandular tissue and adipose breast tissue was analyzed individually, and the median and mean values of elasticity over the menstrual cycle were determined. RESULTS. All volunteers presented a repeating pattern concerning the elasticity over the 2 cycles. After 5 days of the onset of menses, the median value of elasticity for fibroglandular adipose tissue declined significantly by -29% (P = 0.010). After the second week of the cycle, fibroglandular tissue showed again an increase in elasticity (P = 0.028). The highest median values of elasticity were obtained during days 11 to 23 with an increase of up to 35%. For adipose tissue, only a slight and not significant variation of elasticity during the menstrual cycle was determined. CONCLUSION. MRE is able to measure a dependence of tissue elasticity on the menstrual cycle.
TL;DR: This PPI agent resulted in significant contrast signal enhancement and may also provide a valuable contrast agent backbone, as well as test the adequacy and viability of a new family of dendrimers for use as MRI contrast agents in vitro and in vivo.
Abstract: Rationale and objectives: Dendrimer-based magnetic resonance imaging (MRI) contrast agents offer many advantages including high levels of amplification. The objective of this research was to test the adequacy and viability of a new family of dendrimers for use as MRI contrast agents in vitro and in vivo. Methods: Dendrimers based on 1,4-diaminobutane core polypropyleneimine (PPI) generation 2 and ammonia core polyamidoamine dendrimers had the free surface amines conjugated to a diethylenetriaminepentaacetic acid derivative followed by complex formation with gadolinium. Relaxivity measurements were made on an IBM Field Cycling Relaxometer. Biodistribution and pharmacokinetic studies were examined with the radiotracer 1 5 3 Gd in rats and a counting window of 95 to 105 keV. MR1 images were conducted at 4.7 T. Results: The relaxivity of the PP1 agent exceeded that of the corresponding generation polyamidoamine (PAMAM) agent. Uptake occurred in the liver, spleen, and kidney. Pharmacokinetic studies showed a biexponential decay with excretion half-lives of 3 hours and 33.6 days respectively. The agent increased the contrast enhancement, I hour after injection, of T1-weighted images by 52%. Conclusions: This PPI agent resulted in significant contrast signal enhancement. This family of agent may also provide a valuable contrast agent backbone.
TL;DR: Dynamic MRI and contrast enhanced ultrasound are supplementing methods for examining perfusion and vascularity of experimental tumors.
Abstract: Rationale: Angiogenesis is essential for spread and growth of malignant tumors. Because noninvasive methods for observing tumor vascularization are limited, most of previous results were based on histologic findings alone. In this study, dynamic parameters obtained using intermittent contrast-enhanced Doppler sonography and dynamic MRI were compared and correlated with microvessel density. Methods: Eleven tumor-bearing nude mice were examined with dynamic T 1 -weighted sequences using Gd-DTPA in a 1.5 T magnetic resonance (MR) scanner and with intermittent power Doppler sonography after a single bolus of galactose based contrast agent. After examination 6 tumors were harvested for immtmofluorescence microscopy using a CD31 stain. Using a 2-compartment model, the MR parameters amplitude (reflecting plasma volume) and k e p (influenced by the vessel permeability) were calculated and compared with maximal enhancement (max) and perfusion P measured with ultrasound. Results: The MR amplitude correlated with the ultrasound parameter max significantly (r = 0.61; P = 0.01). Max (r = 0.67; P = 0.01), amplitude (r = 0.72; P = 0.01), and perfusion (r = 0.62; P = 0.05) correlated with the microvessel density. k e p moderately correlated with max, but not with perfusion and microvessel density. Conclusions: Dynamic MRI and contrast enhanced ultrasound are supplementing methods for examining perfusion and vascularity of experimental tumors.
TL;DR: Preliminary findings suggest that submicron or near-micron-diameter bubbles may be suitable for lymphatic imaging applications, and Contrast-enhanced interstitial US lymphography could serve as an alternative to current sentinel node detection methods.
Abstract: Rationale and objectives: To establish the feasibility of using contrast-enhanced interstitial ultrasound (US) lymphography as an alternative to current sentinel node detection methods. Methods: Aqueous US contrast microbubble suspensions of varying diameter were evaluated in vitro to characterize response to insonation. Contrast media were then injected subcutaneously into the distal extremities of 11 normal dogs to target the cervical and popliteal lymph nodes (nodes, n = 40). First-order (sentinel) lymph nodes and second-order sublumbar nodes were imaged intennittently from 0 to at least 120 minutes following contrast injection using continuous power Doppler mode. Lymphoscintigraphy studies were performed on 4 dogs to verify lymphatic drainage patterns and sentinel lymph nodes. Results: Contrast enhancement occurred in 34/40 (85%) sentinel nodes overall and in 30/32 (94%) nodes when submicron or near-micron diameter bubble formulations were used. In many instances, enhancement persisted throughout the imaging period. Contrast response was most pronounced using a high mechanical index and tissue artifact was reduced or eliminated when using a high pulse repetition frequency. Conclusions: Contrast-enhanced interstitial US lymphography could serve as an alternative to current sentinel node detection methods. Preliminary findings suggest that submicron or near-micron-diameter bubbles may be suitable for lymphatic imaging applications.
TL;DR: Navigator-gated free-breathing T2-prepared SSFP cMRA is a promising new imaging approach for high signal and high contrast imaging of the coronary arteries with improved vessel border definition.
Abstract: Rationale and Objectives. Recent developments of magnetic resonance imaging enabled free-breathing coronary MRA (cMRA) using steady-state-free-precession (SSFP) for endogenous contrast. The purpose of this study was a systematic comparison of SSFP cMRA with standard T2-prepared gradient-echo and spiral cMRA. Methods. Navigator-gated free-breathing T2-prepared SSFP-, T2-prepared gradient-echo- and T2-prepared spiral cMRA was performed in 18 healthy swine (45-68 kg body-weight). Image quality was investigated subjectively and signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and vessel sharpness were compared. Results. SSFP cMRA allowed for high quality cMRA during free breathing with substantial improvements in SNR. CNR and vessel sharpness when compared with standard T2-prepared gradient-echo imaging. Spiral imaging demonstrated the highest SNR while image quality score and vessel definition was best for SSFP imaging. Conclusion. Navigator-gated free-breathing T2-prepared SSFP cMRA is a promising new imaging approach for high signal and high contrast imaging of the coronary arteries with improved vessel border definition.
TL;DR: Using a flow-sensitive calibration, an accurate arterial input function can be measured from the blood MR signal and used in a realistic model to assess the RP and validates absolute RP quantification by MRI and contrast media injection and justifies further clinical studies.
Abstract: Objective:The aim of this study was to validate the quantification of absolute renal perfusion (RP) determined by dynamic magnetic resonance imaging (MRI) and contrast media using an experimental model in the rabbit and a transit-timed ultrasound flow probe around the left renal artery as comparison
TL;DR: An overestimation of the tracer activity concentration is to be expected in the presence of oral contrast agents, if PET attenuation correction is attained CT-based.
Abstract: Rationale and objectives To evaluate the effect of iodine- and barium-based contrast agents on the computed tomography (CT)-based positron emission tomography (PET) attenuation correction in dual-modality PET/CT. Methods Experiments were conducted on a Society of Nuclear Medicine/National Electrical Manufacturers Association-PET phantom equipped with cylinders containing [18F]-2-fluoro-2-desoxy-D-glucose. The main compartment was filled with iodine (0.5-10%), barium (0.5-50%), or water (negative control). The error in attenuation correction was determined by comparison of measured tracer quantities in the presence of contrast agents with expected quantities. Contrast agent attenuation was demonstrated to be comparable to in vivo conditions. Results The presence of contrast agents resulted in an overestimation of the intracylindrical activity concentration on PET images and overestimation directly related to contrast concentrations (iodine 5-38%; barium 15-580%). Iodine and barium concentrations in clinical use resulted in an activity overestimation of 20 +/- 1.8% for iodine and 21 +/- 2.9% for barium. Conclusion An overestimation of the tracer activity concentration is to be expected in the presence of oral contrast agents, if PET attenuation correction is attained CT-based.
TL;DR: Iomeprol, which has a different physico-chemical properties, proved to be less proapoptotic compared with other contrast compounds, and all types of cells similarly respond by apoptosis to contrast media induced injury.
Abstract: Rationale and Objective. Nephrotoxicity of contrast media, resulting in apoptosis and acute necrosis of tubular cells, is well documented. No studies concerning mesangial cells apoptosis have been published yet. Aim Apoptosis of cultured mesangial, tubular, and hepatic cell lines was investigated following exposure to different contrast media. Methods. Apoptosis was assessed by TUNEL assay and verified by Mayer Hematoxylin staining. Results. Iopromide, Ioxaglate, and Ioxatalamate induced apoptosis in all cell cultures at final concentrations ranged from 0.1% to 10.0%. However, only 1% to 10% Iomeprol elicited a significant apoptosis. Moreover, at 10% concentration, Iomeprol induced significantly less apoptosis than Iopromide, Ioxaglate, or Ioxatalamate. Conclusions. First, Iomeprol, which has a different physico-chemical properties, proved to be less proapoptotic compared with other contrast compounds. Second, all types of cells similarly respond by apoptosis to contrast media induced injury. However, apoptosis of mesangial cells might generate additional deleterious effects in vivo.
TL;DR: Morphologic measures extracted from HR-MRI considering local 3D-scaling properties can be used to predict biomechanical properties of bone in vitro and are superior to 2-dimensional standard linear morphometric measures and more reliably predict bone strength as measured by MCS than does BMD.
Abstract: RATIONALE AND OBJECTIVES A novel, nonlinear morphologic measure [DeltaP(alpha)] based on local 3D scaling properties was applied to high-resolution magnetic resonance images (HR-MRI) of human trabecular bone to predict biomechanical strength in vitro. METHODS We extracted DeltaP(alpha) and traditional morphologic parameters (apparent trabecular volume fraction, apparent trabecular separation) from HR-MR images of 32 femoral and 13 spinal bone specimens. Furthermore, bone mineral density (BMD) and maximum compressive strength (MCS) were determined. The morphologic measures were compared with BMD in predicting the biomechanical strength. RESULTS In the vertebral (femoral) specimens, R2 for MCS versus DeltaP(alpha) was 0.87 (0.61) (P < 0.001). Correlation between BMD and MCS was 0.53 (P = 0.05) (0.79 [P < 0.001]) for the vertebral (femoral) specimens. For the femoral specimens, prediction of MCS could be improved further by combining BMD and morphologic parameters by multiple regression (R2 = 0.88). CONCLUSIONS Morphologic measures extracted from HR-MRI considering local 3D-scaling properties can be used to predict biomechanical properties of bone in vitro. They are superior to 2-dimensional standard linear morphometric measures and, depending on the anatomic location, more reliably predict bone strength as measured by MCS than does BMD.
TL;DR: In a preliminary comparison the signal-to-noise ratio is improved in phantoms and humans when compared with a 1.5 T receive-only pelvic phased array coil, and high quality spectral resolution is demonstrated through the delineation of the citrate quadruplet in localized 1H prostate spectra.
Abstract: Magnetic resonance (MR) systems operating at 3 Telsa (T) and above have demonstrated considerable potential in human studies, offering improved signal-to-noise ratio and spectral resolution. However, because of radiofrequency limitations and concerns, and the lack of large volume body coils, most studies have been limited to the head. In this study we describe the design and construction of a transceive pelvic phased array coil with which MR images and spectra of the human prostate at 3 T have been obtained. Comparison with 1.5 T instruments with different hardware configurations is difficult; however, in a preliminary comparison the signal-to-noise ratio is improved in phantoms and humans when compared with a 1.5 T receive-only pelvic phased array coil, and high quality spectral resolution is demonstrated through the delineation of the citrate quadruplet in localized 1 H prostate spectra. Higher fields offer the potential for MR prostate studies without the use of an endorectal coil.