Bolus Chase Research Articles

Application of digital subtraction angiography in canine hindlimb arteriography

Research in the field of lower extremity vascular disease has increased in popularity over the years. To adequately characterize and validate the effectiveness of vascular interventions, in vivo experimentation in large animals is required. Thus, it is necessary to find a method to detect the shape and density of blood vessels in the lower extremities that can evaluate and verify the treatment measures' effectiveness and have high accuracy and repeatability. This study characterized factors that determined both the accuracy and overall value of digital subtraction angiography in lower limb arteriography using a canine animal model. Six beagle dogs were anesthetized and immobilized on the motorized table. The femoral artery was accessed using an indwelling needle. A bolus of contrast agent was injected into the access site, and digital subtraction angiography with bolus chase technology was used to collect contrast images for analysis. At the end of the procedure, the anesthetized dogs were euthanized using an overdose of potassium chloride. After confirming the euthanasia of the dogs, the cadavers were taken to the experimental animal center of Xinjiang Medical University and processed by qualified institutional personnel. The final arteriographic images of the hind limbs from all six dogs were precise, and the branches of small vessels could be distinguished without any visible artifacts. These results suggested that arteriography using digital subtraction angiography could reveal the shape and density of blood vessels in canine animal models. This method has great potential to significantly improve research related to limb ischemia due to its simple and reproducible results.

A Factor Increasing Venous Contamination on Bolus Chase Three-dimensional Magnetic Resonance Imaging: Charcot Neuroarthropathy.

Background:The study aimed to evaluate the ratio of venous contamination in diabetic cases without foot lesion, with foot lesion and with Charcot neuroarthropathy (CN).Materials and Methods:Bolus-chase three-dimensional magnetic resonance (MR) of 396 extremities of patients with diabetes mellitus was analyzed, retrospectively. Extremities were divided into three groups as follows: diabetic patients without foot ulcer or Charcot arthropathy (Group A), patients with diabetic foot ulcers (Group B) and patients with CN accompanying diabetic foot ulcers (Group C). Furthermore, amount of venous contamination classified as no venous contamination, mild venous contamination, and severe venous contamination. The relationship between venous contamination and extremity groups was investigated.Results:Severe venous contamination was seen in Group A, Group B, and Group C, 5.6%, 15.2%, and 34.1%, respectively. Statistically significant difference was seen between groups with regard to venous contamination.Conclusion:Venous contamination following bolus chase MR was higher in patients with CN.

The effect of four-phasic versus three-phasic contrast media injection protocols on extravasation rate in coronary CT angiography: a randomized controlled trial

ObjectivesContrast media (CM) extravasation is a well-known complication of CT angiography (CTA). Our prospective randomized control study aimed to assess whether a four-phasic CM administration protocol reduces the risk of extravasation compared to the routinely used three-phasic protocol in coronary CTA.MethodsPatients referred to coronary CTA due to suspected coronary artery disease were included in the study. All patients received 400 mg/ml iomeprol CM injected with dual-syringe automated injector. Patients were randomized into a three-phasic injection-protocol group, with a CM bolus of 85 ml followed by 40 ml of 75%:25% saline/CM mixture and 30 ml saline chaser bolus; and a four-phasic injection-protocol group, with a saline pacer bolus of 10 ml injected at a lower flow rate before the three-phasic protocol.Results2,445 consecutive patients were enrolled (mean age 60.6 ± 12.1 years; females 43.6%). Overall rate of extravasation was 0.9% (23/2,445): 1.4% (17/1,229) in the three-phasic group and 0.5% (6/1,216) in the four-phasic group (p = 0.034).ConclusionsFour-phasic CM administration protocol is easy to implement in the clinical routine at no extra cost. The extravasation rate is reduced by 65% with the application of the four-phasic protocol compared to the three-phasic protocol in coronary CTA.Key Points• Four-phasic CM injection-protocol reduces extravasation rate by 65% compared to three-phasic.• The saline pacer bolus substantially reduces the risk of CM extravasation.• The implementation of four-phasic injection-protocol is at no cost.

Lower-limb magnetic resonance angiography: performance of extracellular contrast agents versus blood pool contrast agent for both dynamic and high spatial resolution imaging in extended phase

To prospectively compare the performance of extracellular space contrast agents (ECSCAs) versus a blood-pool contrast agent (BPCA) for a comprehensive lower-limb magnetic resonance angiography (MRA) protocol in patients with either claudication or critical ischaemia. Thirty patients with claudication underwent lower-limb magnetic resonance angiography (MRA) (dynamic crural, three-station bolus chase, and infra-inguinal high resolution) using a triphasic injection method with both a ECSCA and BPCA to allow intra-individual comparison, and 30 patients with critical ischaemia were scanned with either a ECSCA or BPCA. The dynamic, bolus chase, and high-resolution images were scored for quality on a Likert scale (from 1-5). Signal- and contrast-to-noise ratios were analysed and statistical analysis performed. Overall, there was no statistically significant difference between the ECSCAs and BPCA for arteriographic dynamic imaging, bolus chase MRA, or the high spatial resolution imaging. Venous image quality was rated higher quality for BPCA scans than for ECSCA images for calf veins (not significantly for thigh veins). Venous imaging signal intensity measures were higher for BPCA imaging. Extended-phase imaging using an ECSCA with this protocol provides arteriographic image quality equal to imaging with a BPCA. Venous depiction is good using ECSCAs with this approach, although better with BPCA.

Size‐dependent ferrohydrodynamic relaxometry of magnetic particle imaging tracers in different environments

Magnetic particle imaging (MPI) is a recently developed imaging technique that seeks to provide ultrahigh resolution and tracer sensitivity with positive contrast directly originated from superparamagnetic iron oxide nanoparticles (NPs). MPI signals can be generated from a combination of Néel relaxation, Brownian rotational diffusion, and hysteretic reversal mechanisms of NPs in response to applied magnetic fields. When specific targeting of organs, such as carcinoma and endothelial cardiovascular cells, is needed, different behavior may be expected in immobilized NPs, due to complete or partial elimination of the Brownian motion. Here, the authors present an experimental investigation of the MPI spatial resolution and signal intensities as a function of a wide range of median core sizes of NPs under four representative conditions, including after immobilization in a tissue equivalent medium. Monodisperse hydrophobic NPs with median core diameters (d0) ranging from 7 to 22 nm were synthesized in organic media and subsequently dispersed in aqueous solution after a facile surface modification. Morphology, median size, size distribution, and magnetic properties of the NPs were investigated. Hydrophobic and hydrophilic NPs with various core sizes were immobilized in trioctyl phosphine oxide and agarose gel, respectively. Their size-dependent performance as MPI tracers for system matrix and x-space image reconstruction was evaluated using magnetic particle spectrometry (MPS) and compared with the free rotating counterparts. Immobilized NPs with core diameters smaller than ≈ 20 nm have similar spatial resolution, but lower signal intensities when compared with their free rotating counterparts. Compared to their performance in solution, spatial resolution was improved, but signal intensity was lower, when larger NPs with core size of 22 nm were immobilized in agarose. Same trends were observed in signal intensities, when considering either system matrix or x-space approaches. The harmonic and dm/dH signal intensities changed linearly and the spatial resolution did not change with decreasing NP concentration up to 15 μg/ml. The results show that the MPI signal is very sensitive to both NP size and environment. The authors' calculations show that Brownian rotational diffusion is slower than the field switching cycle and, therefore, it has minimal influence on MPS signals. dm/dH analyses show that Néel relaxation is the dominant mechanism determining MPI response in smaller NPs (d0 < ≈ 20 nm). Larger NPs show hysteretic reversal when the applied field amplitude is large enough to overcome the coercivity. Linear variation of the MPS signal intensity with iron concentration but with uniform spatial resolution enables quantitative imaging for a range of applications, from high-concentration bolus chase imaging to low-concentration molecular imaging (while the authors' instrument is noise-limited to ≈ millimolar iron concentrations, nanomolar sensitivity is expected for MPI, theoretically). These results pave the way for future application of the authors' synthesized tracers for immobilized or in vivo targeted MPI of tissues.

Buildup of image quality in view‐shared time‐resolved 3D CE‐MRA

Time-resolved three-dimensional contrast-enhanced MR angiography often relies on view sharing of peripheral k-space data to enable acquisition of angiograms with both high spatial resolution and a rapid frame rate. It is typically assumed that k-space will be fully sampled during passage of the contrast bolus arterial phase. However, this is not the case when view sharing is incomplete, for example, at the leading edge of an enhancing vessel or if acquisition time is limited as in fluoroscopic tracking for multistation bolus chase MR angiography. Incomplete view sharing will degrade image quality, for example, by reducing vessel signal and sharpness and increasing undersampling artifacts. In this work, the evolution of angiogram quality with view sharing is quantitatively assessed in phantom experiments and in vivo contrast-enhanced MR angiography calf studies. It is demonstrated that there are multiple sets of sequence parameters that can yield a target image update time, but the choice of parameters can profoundly affect how image quality evolves with view sharing. A fundamental tradeoff between vessel signal and sharpness and its relationship to the sequence temporal footprint is investigated and discussed.

Comprehensive MRA of the lower limbs including high-resolution extended-phase infra-inguinal imaging with gadobenate dimeglumine: Initial experience with inter-individual comparison to the blood-pool contrast agent gadofosveset trisodium

To compare extended-phase imaging using an extracellular space contrast agent, gadobenate dimeglumine, to imaging with a blood-pool contrast agent, gadofosveset, for magnetic resonance angiography. A lower-limb magnetic resonance angiography (MRA) protocol (dynamic crural, three-station bolus chase, and infra-inguinal high resolution) designed for blood-pool agent imaging was adapted for use with the extracellular agent, gadobenate dimeglumine, primarily by using a triphasic injection protocol. Ten patients scanned with gadofosveset were compared to 10 patients scanned with gadobenate. The dynamic, bolus chase, and high-resolution images were scored for quality on a Likert scale (from 1-5). Signal- and contrast-to-noise ratios were analysed, and Mann-Whitney U statistical analysis performed. There was no significant difference for the dynamic imaging or the aorto-iliac station of the bolus chase. Infra-inguinal bolus chase images were higher quality (p < 0.05 Mann-Whitney U test) with gadobenate. Signal analysis confirmed lower signal and contrast for venous imaging on the high spatial resolution acquisitions with gadobenate; however, this allowed improved arterial conspicuity. Extended-phase imaging using an extracellular space contrast agent is feasible and provides image quality to equal imaging with a blood-pool contrast agent.

Time‐resolved dual‐station calf–foot three‐dimensional bolus chase MR angiography with fluoroscopic tracking

To refine, adapt, and evaluate the technical aspects of fluoroscopic tracking for generating dual-station high-spatial-resolution MR angiograms of the calves and feet using a single injection of contrast material. Nine subjects (seven healthy volunteers followed by two patients) were imaged using a two-station calf-foot three-dimensional time-resolved bolus chase MR angiography protocol which provided <1.0 mm(3) spatial resolution throughout and 2.5- and 6.6-s frame times at the calf and foot stations, respectively. Real-time reconstruction of calf station time frames allowed visually guided triggering of table advance to the foot station. The studies were independently read and scored by two radiologists in six image quality categories. On average, overall diagnostic quality at the calf and foot stations was good-to-excellent, the calf arteries and all but the smallest foot arteries had good-to-excellent signal and sharpness, artifact and venous contamination were minor, and signal continuity across the inter-station interface was good. The feasibility of fluoroscopic tracking has been demonstrated as an efficient approach for high spatiotemporal imaging of the arteries of the calves and feet with good-to-excellent diagnostic quality and low degrading venous contamination.

Time-resolved MR angiography of the calf arteries using a phased array cardiac coil: comparison of visibility with standard three-step bolus chase MR angiography

Standard bolus chase MR angiography (MRA) is increasingly replacing digital subtraction angiography (DSA) in the diagnostic evaluation of peripheral vascular disease. However, a major limitation of bolus chase MRA is the relatively poor visibility of the calf arteries. To evaluate the feasibility of visualizing the calf arteries and the visibility quality of an 8-channel cardiac phased array coil using time-resolved imaging of contrast kinetics (TRICKS) MRA compared with standard bolus chase MRA on a 1.5 Tesla MRI scanner. MRA findings of 59 sequential patients (mean age 57.8 years, range 14-83 years; 41 men) were retrospectively evaluated. All examinations included preliminary TRICKS for the lower leg using a surface 8-channel cardiac coil, followed by a 3-step MRA of the abdominal aorta, thigh, and lower leg using a body coil. Images yielded by both methods were separately evaluated by consensus of two radiologists unaware of the patients' clinical data. Visibility of the calf arteries (popliteal, tibialis anterior, tibialis posterior, tibioperoneal trunk, and peroneal) for both sides was subjectively classified as 'diagnostic' or 'non-diagnostic'. Descriptive statistics for image diagnostic quality were assessed. A total of 575 calf arterial segments were evaluated. Visibility of all calf arteries was significantly better with TRICKS than with the standard bolus chase MRA (P < 0.001). The improvement of calf artery visibility with TRICKS was more pronounced in patients with peripheral vascular disease compared to those with arteritis, vascular malformation and popliteal entrapment syndrome. Using a cardiac coil for MRA of the lower extremities resulted in visibility comparable to that of a dedicated leg coil, with diagnostic superiority for the TRICKS method compared to the standard bolus chase method.

Triphasic contrast injection improves evaluation of dual energy lung perfusion in pulmonary CT angiography

Lung perfusion analysis at dual energy CT (DECT) is sensitive to beam hardening artifacts from dense contrast material (CM). We compared two scan and four CM injection protocols in terms of severity of artifacts and attenuation levels in the thoracic vessels. Data of 120 patients who had undergone dual source dual energy CT pulmonary angiography for suspected acute pulmonary embolism were evaluated. Group 1 (n=30) was scanned in craniocaudal direction using 64×0.6 mm collimation; groups 2-4 (n=30 each) were scanned in caudocranial direction using 14×1.2 mm collimation. In groups 1-3 biphasic injection protocols with different amounts of CM and NaCl were investigated. In group 4 a split-bolus protocol with an initial CM bolus of 50 ml followed by 30 ml of a 70%:30% NaCl/CM mixture and a 50 ml NaCl chaser bolus was used. CT density values in the subclavian vein (SV), superior vena cava (SVC), pulmonary artery tree (PA), and the descending aorta (DA) were measured. Artifacts arising from the SV and SVC on DE pulmonary iodine distribution map were rated on a scale from 1 to 5 (1=fully diagnostic; 5=non-diagnostic) by two blinded readers. In protocol 4 mean attenuation in the SV (645±158 HU) and SVC (389±114 HU) were significantly lower compared to groups 1-3 (p<0.002). Artifacts in group 4 (1.1±0.4 and 1.5±0.7 for the SV and SVC, respectively) were rated significantly less severe compared to group 1 (3.2±1.0 and 3.0±1.1), 2 (2.6±1.1 and 2.3±1.0) and 3 (1.9±0.9 and 1.9±0.7) (p<0.01 for all), whereas no significant difference was found between groups 1 and 2 for the subclavian vein (p=0.07). Attenuation in the PA was also significantly lower in group 4 (282±116 HU) compared to group 1 (397±137 HU), group 2 (376±115 HU) and group 3 (311±104 HU), but still on a diagnostic level. Split-bolus injection provides sufficient attenuation for pulmonary DECT angiography while beam hardening artifacts arising from high density contrast material in the thoracic vessels can be reduced significantly.

Inverse-direction scanning improves the image quality of whole carotid CT angiography with 64-MDCT

The purpose of this prospective study was to clarify whether reducing the incidence of perivenous artifacts through craniocaudal scanning improves the quality of 64-multidetecter computed tomography (MDCT) angiography images of the whole carotid artery. Forty patients underwent MDCT angiography in the caudocranial (n=20) or craniocaudal (n=20) direction in 2007. All patients were injected with 75 ml of contrast media followed by a 35-ml saline chaser bolus at 4.0 ml/s in the right antecubital vein. Maximum intensity projection (MIP) images were scored according to image quality on a scale of 1-5. Bilateral arterial and venous attenuation was measured on 10 separated slices. We compared the mean image quality score of the two groups (i.e. those scanned caudocranially and those scanned craniocaudally). We analyzed the correlation between vascular attenuation and mean image quality. Compared with the caudocranial group, the craniocaudal group had higher image quality scores (median, 3.70 vs. 3.40; 95% CI, 3.50-3.96 vs. 3.06-3.60; p<0.05), higher arterial attenuation (median, 550 HU vs. 489 HU; range, 270-686 vs. 302-574; p<0.05), and lower maximum venous attenuation (median, 436 vs. 1452 HU; range, 250-617 vs. 377-2044; p<0.01). Multiple regression analysis revealed that the most significant correlation factor with image quality was minimum arterial attenuation (R2=0.42, p<0.001) measured near the brachiocephalic artery. In the caudocranial group only, there was a negative correlation between right brachiocephalic venous attenuation and minimum arterial attenuation. Compared with conventional caudocranial scanning, craniocaudal scanning improves the image quality of 64-MDCT angiography images of the whole carotid artery.

Arterial imaging in patients with lower extremity ischemia and diabetes mellitus

Precise, comprehensive imaging of the arterial circulation is the cornerstone of successful revascularization of the ischemic extremity in patients with diabetes mellitus. Arterial imaging is challenging in these patients because the disease is often multisegmental with a predilection for the distal tibial and peroneal arteries. Occlusive lesions and the arterial wall itself are often calcified and patients presenting with ischemic complications frequently have underlying renal insufficiency. Intra-arterial digital subtraction angiography (DSA), contrast enhanced magnetic resonance angiography (MRA), and more recently, computerized tomographic angiography (CTA) have been used as imaging modalities in lower extremity ischemia. Each has specific advantages and shortcomings in this patient population, which will be summarized and contrasted in this review. DSA is an invasive technique most often performed from a femoral arterial puncture and requires the injection of arterial contrast, which can occasionally cause allergic reactions. In patients with pre-existing renal insufficiency, contrast infusion can result in worsening renal failure; although usually self-limited, it may occasionally require hemodialysis, especially in patients with diabetes. However, DSA provides the highest degree of spatial resolution and image quality. It is also the only modality in which the diagnosis and treatment of arterial disease can be performed simultaneously. MRA is noninvasive, and when enhanced with gadolinium contrast injection provides arterial images of comparable quality to DSA and in some circumstances may uncover distal arterial targets not visualized on DSA. However, spatial resolution is inferior to DSA and erroneous interpretations due to acquisition artifacts are common. Specialized equipment and imaging techniques are necessary to minimize their occurrence in the distal lower extremity. In addition, due to the risk of inducing nephrogenic systemic fibrosis, gadolinium-enhanced MRA cannot be used in patients with renal insufficiency. CTA is noninvasive and rapidly performed, with better spatial resolution than MRA, but requires the largest volume of contrast infusion, exposes patients to high-doses of radiation, and is subject to interpretive error due to reconstruction artifacts especially in heavily calcified arteries, limiting its usefulness in many patients with diabetes. For patients in whom the planned intervention is a surgical bypass, DSA and MRA will provide high quality images of the lower extremity arterial anatomy. For patients in whom a catheter-based intervention is the likely treatment, a diagnostic DSA immediately followed by a catheter-based treatment in the same procedure is the preferred approach. In patients with pre-existing renal dysfunction, in which gadolinium-enhanced MRA is contraindicated, DSA or CTA can be performed. However, patients should have an infusion of intravenous normal saline solution or sodium bicarbonate before the procedure to reduce the incidence of contrast-induced nephropathy.

Time‐resolved lower extremity MRA with temporal interpolation and stochastic spiral trajectories: Preliminary clinical experience

To assess added value of a new time-resolved technique with temporal interpolation and stochastic spiral trajectory through k-space and parallel imaging (TR-MRA) to conventional bolus chase MRA (BC-MRA) for infragenual peripheral artery evaluation. An institutional review board-approved retrospective review of peripheral arterial disease patients was performed. Infragenual TR-MRA and BC-MRA were performed in 26 patients over four months. Two readers individually assessed image quality, diagnostic confidence, and stenosis severity and length in 13 defined below knee segments, first with BC-MRA alone, and then with a combined BC-MRA and TR-MRA reading (BC+TR-MRA). Perceived contribution of TR-MRA was rated by each reader. The reference standard was a consensus reading of both sequences. Catheter angiographic (CA) correlation was available in 6 patients. A total of 646 infragenual segments in 51 extremities were evaluated. Image quality and diagnostic confidence were superior for BC+TR-MRA compared with BC-MRA alone (P < 0.001). Adding TR-MRA improved sensitivity (85.7% versus 80.7%; P < 0.05) and diagnostic accuracy (88.1% versus 85.4%; P < 0.05) for hemodynamically significant stenosis. Venous contamination (0% versus 13.1% segments) and motion (0.9% versus 8.0%) were decreased for BC+TR-MRA versus BC-MRA alone, P < 0.01. For BC+TR-MRA, TR-MRA was rated more useful than BC-MRA in 30/51 legs (58.8%). TR-MRA identified retrograde flow in 5 segments. Where available, there was high concordance between CA and BC+TR-MRA (91.6%) for stenosis. Adding TR-MRA with temporal interpolation and stochastic spiral trajectories to bolus chase MRA improves image quality, diagnostic confidence and accuracy. It provides hemodynamic information and minimizes venous contamination and patient motion.

Abgrenzbarkeit des interventrikulären Septums mit einem 20 % Kontrastmittelspülbolus in der CT-Koronarangiografie: Ein Vergleich von 64-Schicht- und Dual-Source-CT

Due to the technical advance of multislice cardiac CT and the recently introduced dual source CT, the acquisition times for cardiac CT exams are < 10 sec. At the same time the assessment of left ventricular function is possible. However, in many patients a complete right ventricular outwash is noted, leading to insufficient septal delineation. Studies were able to demonstrate that contrast media (CM) mixed in the saline chaser bolus is sufficient for significantly better visualization of septal structures. The aim of this study was to investigate whether this dual flow concept works as well for 64-slice and dual source CT angiography using only 20 % CM in the saline chaser bolus. 97 patients were included in this prospective study. 47 patients underwent 64-slice CT coronary angiography. 80 cc were administered at 5 cc/sec as the main bolus followed by a 50 cc saline chaser bolus containing 20 % contrast media. The other 50 patients were examined using dual source CT. They received a CM protocol adapted for the scan time with the identical saline/CM chaser bolus. The datasets were quantitatively examined in defined ROIs along the septum and in the right ventricle with respect to the density. The septal delineation was qualitatively analyzed and both groups were compared. In a final step the density was measured in the proximal and distal RCA as well as in the LAD and also compared. Using the protocol adapted for the scan time, significantly less CM was used. No significant difference was able to be found regarding the septal delineation or coronary enhancement. The study shows that the dual flow concept allows for robust septal delineation regardless of the CM injection protocol used as long as a 20 % saline chaser bolus is used. A CM protocol adapted for the scan time also leads to significant CM reduction at equal image quality.

Atherosclerotic Peripheral Vascular Disease Symposium II

The Atherosclerotic Peripheral Vascular Disease Interdisciplinary Working Group was commissioned by the American Heart Association (AHA) to provide a forum to address important and emerging issues in this multidisciplinary area of clinical science. The working group was a primary outgrowth of the AHA Atherosclerotic Vascular Disease Conference held in Boston, Mass, in July 2002. It was created in recognition of the fact that atherosclerosis is a systemic disease with important sequelae in many regional circulations in addition to the heart, including the brain, kidneys, mesentery, and limbs. Its mission is to provide a forum for the multiple disciplines engaged in research, evaluation, and management of patients with noncoronary atherosclerosis. The goals of the Atherosclerotic Peripheral Vascular Disease Interdisciplinary Working Group are to develop a strategy to increase awareness of atherosclerotic vascular disease, identify important gap areas in knowledge that require further clinical investigation, and develop programs that will facilitate prevention and treatment of peripheral atherosclerotic diseases. Developments in research and technology that are relevant to atherosclerotic vascular disease are emerging rapidly. As a result, greater opportunities to translate science to clinical practice are available. The American College of Cardiology/AHA practice guidelines for the management of patients with peripheral arterial disease (lower extremity, renal, mesenteric, and abdominal aortic) provide many evidenced-based recommendations for diagnosing and treating patients with atherosclerotic vascular diseases.1 Nevertheless, in some areas, the evidence has not matured sufficiently for definitive guidelines. Some of these areas have engendered considerable controversy among practitioners. Among these are the efficacy and outcome of screening programs for vascular disease and the appropriate and timely use of endovascular interventions. Accordingly, the Atherosclerotic Peripheral Vascular Disease Interdisciplinary Working Group convened the second AHA conference on Atherosclerotic Vascular Disease, which took place in Boston, Mass, in July 2006. The conference was also sponsored by the …

Microbiologic Contamination of Automatic Injectors at MDCT: Experimental and Clinical Investigations

It is mandatory to teach antiseptic skills to staff who use contrast agent injectors. The purpose of this study was to evaluate in an experimental setting and in clinical routine the risk of microbiologic contamination of the syringes of injectors used to administer contrast agent and saline solution for MDCT. Microbiologic contamination of CT injector syringes over multiple uses for several injections was investigated in an experimental setup simulating the clinical setting. Each refill and injection operation was performed by the same technician, who processed a contrast agent for administration in a neighboring room as in clinical CT routine. Multiple administrations of nutritive medium and a chaser bolus were performed with the injection syringes. Simultaneously with each syringe replacement and filling operation, the filling and injection operation was simulated with a separate injection system under normal clinical conditions. Hygienic conditions in the CT department also were evaluated. For microbiologic analysis of devices and of palms of staff, imprints were obtained during clinical routine at the beginning of the study and at follow-up. Throughout the study, the staff participated in continuing education on hygienic behavior, such as hand disinfection and wearing of sterile gloves. In addition, clinical injector syringes were checked for microbiologic contamination. In the experimental setup, the first four samples of each simulation experiment were sterile, and the subsequent probes were found to be contaminated with typical dermal bacteria, such as staphylococci. In the CT department, contamination with skin and oral flora was found on surfaces of devices and on palms. No imprint of surfaces or palms was contaminated with nosocomial or fecal pathogens. Because even optimization of environments does not prevent contamination of syringes, multiple uses of syringes for more than one patient should be prohibited owing to the risk of septic complications.

Functional cardiac CT imaging: A new contrast application strategy for a better visualization of the cardiac chambers

Purpose Evaluation of a new protocol for Dual-source CT contrast-enhanced cardiac imaging for better visualization of right ventricle structures. Methods A total of 106 patients were included in this prospective, controlled study. The control group ( n = 53) underwent our clinic's standard procedure for contrast-enhanced imaging of coronary arteries. The study group ( n = 53) was imaged using a protocol with the dual flow injection protocol in which the saline chaser bolus contained 20% contrast media. The images were analyzed for mean density values using defined ROIs in the septum and both ventricles. In addition the data sets were semi-quantitatively evaluated for visual delineation between right ventricle and septum. To investigate whether this new protocol influenced the visualization of coronary arteries, mean density was also measured in the right and left coronary artery. Results The dual flow concept allows for a statistically significant better delineation of the septum in Dual-source cardiac computed tomography for both the quantitative and semi-quantitative analyses. Also, the dual flow concept allows for statistically relevant higher coronary attenuation. Conclusion Using a saline chaser containing 20% contrast medium improves septal delineation for functional ventricular analysis as well as unimpaired coronary visualization.

An Adaptive Optimal Control Design for a Bolus Chasing Computed Tomography Angiography

To improve imaging quality and to reduce contrast dose and radiation exposure, an optimal adaptive bolus chasing controller is proposed and tested based on actual patient data. The controller estimates and predicts the unknown 2D bolus density online and then determines the optimal control actions. Tracking errors are mathematically quantified in terms of estimation errors. The test results not only support the analytical analysis and exhibit its superior performance over the current constant-speed controller, but also demonstrate the clinical feasibility.

Whole-body imaging of oncologic patients using 16-channel PET-CT

This study evaluated a MDCT protocol for contrast-enhanced 16-channel PET-CT with regard to scan range and duration of a whole-body (18)F-FDG PET-CT examination, the occurrence of contrast-material induced artefacts and quantitative assessment of CT attenuation. 205 patients (51.9+/-12.4 years) with different malignant tumours underwent whole-body PET-CT; the study protocol had been approved by the institutional review board. Contrast-enhanced MDCT (16 x 1.5 mm; 120 ml Iomeprol 3 ml/s, 50 ml saline chaser bolus, scan delay 70 s; oral contrast) was also used for attenuation correction. From MDCT data mean scan range and duration, occurrence of contrast media-induced artefacts, and mean CT densities of jugular (jv) and subclavian (scv), superior (vcs) and inferior (vci) caval, portal (pv), and bilateral external iliac veins, pulmonary (ap) and iliac arteries, descending thoracic and abdominal aorta, all cardiac chambers, as well as both liver lobes, spleen, adrenal glands and kidneys were determined. Attenuation corrected PET images were free of contrast media-related image artefacts. Homogeneous contrast enhancement was found in the mediastinal veins (right/left jv 171+/-34/171+/-35, scv 127+/-50/127+/-40, vcs 153+/-36 HU) and arteries (e.g. ap 145+/-26/151+/-26). Cardiac chambers, abdominal vessels (e.g. vci 138+/-24, pv 159+/-25 HU), and parenchymal organs revealed sufficient and homogenous contrast-enhancement in all cases. No beam-hardening artefacts occurred in the neighbourhood of the subclavian veins. The chosen whole-body (18)F-FDG 16-slice PET-CT protocol allowed for craniocaudal CT scanning with high vessel and parenchymal contrast revealing no IV contrast-media induced artefacts in attenuation-corrected PET data sets.

Adaptive Bolus Chasing Computed Tomography Angiography

Synchronization of the contrast bolus peak and CT imaging aperture is a crucial issue for CTA. It effects the CTA imaging quality and the necessary amount of contrast dose. In this paper, we propose an optimal adaptive bolus chasing controller. The controller estimates and predicts the unknown two dimensional bolus density on line and then determines the optimal control actions. Tracking errors are mathematically quantified in terms of estimation errors. Simulation results on the actual patient data exhibit its superior performance to the current constant-speed method. Also, the preliminary experiments demonstrate the clinical feasibility.