A comprehensive approach to CT radiation dose reduction: one institution's experience.

OBJECTIVE: The purpose of this article is to review the process of creating and implementing a comprehensive plan to reduce diagnostic radiation exposure at our institution. CONCLUSION: This process, which was initiated by forming a radiation dose reduction committee, addressed several different issues to improve patient safety. These include avoidance of unnecessary CT examinations, adjusting individual scanning parameters, revising protocols, use of shielding and dose monitoring, and implementing computer-based dose modulation software as well as educating referring physicians and radiologic technologists.

Contrast volume reduction with superior vena cava catheter-directed coronary CT angiography: comparison with peripheral i.v. contrast enhancement in a swine model.

OBJECTIVE: Conventional MDCT angiography uses a traditional peripheral i.v. approach for contrast injection; however, we describe our experience with a superior vena cava (SVC) catheter approach for coronary artery MDCT angiography as a potential means of decreasing iodinated contrast volume. CONCLUSION: Central SVC contrast injection can decrease the contrast volume by 50% while maintaining coronary attenuation similar to that of peripheral i.v. injection. This approach has potential in reducing the contrast volume on coronary MDCT angiography studies and therefore the risk of contrast-induced nephropathy in certain high-risk patients. Further studies with higher injection rates and faster scan acquisition are needed for defining a lower contrast volume threshold.

Normal and variant coronary arterial and venous anatomy on high-resolution CT angiography.

OBJECTIVE: This article displays the normal and variant anatomy of the coronary arteries and subjacent cardiac veins using a high-resolution 64-MDCT scanner. CONCLUSION: Knowledge of the anatomy of the coronary arteries and subjacent cardiac veins as displayed with maximum intensity and volume-rendered projections is important for correct image interpretation of coronary CT angiography examinations.

Aortic root catheter-directed coronary CT angiography in swine: coronary enhancement with minimum volume of iodinated contrast material.

OBJECTIVE: The purpose of this study was to evaluate the minimum amount of contrast material for coronary imaging with aortic root catheter-directed enhancement and 64-MDCT angiography (MDCTA). MATERIALS AND METHODS: A 64-MDCT scanner was used after animal institutional review board approval to study four swine (40-60 kg). Heart rate reduction to 65 beats per minute was achieved with atenolol by mouth and i.v. Cardizem. Common femoral artery access was obtained with a 5-French micropuncture kit and sonographic guidance. A diffusiontip (640 side holes), 5-French pigtail catheter was positioned in the aortic root on the CT table with a retrofitted C-arm fluoroscopy unit and connected to an arterial power injector. Aortic root MDCTA (retrospective ECG gating; collimation, 0.6 mm; tube rotation time, 0.33 second; scanning time, 10-12 seconds; tube voltage, 120 kVp; effective mAs, 850 mAs; pitch, 0.2; field of view, 109-123 mm; slice thickness and increment, 0.6 and 0.3 mm) was begun 1 second after the injection of 100 mL of various Visipaque (iodixanol) concentrations (10%, 20%, 30%, 40%) at 10 mL/s. Coronary mean and peak densities, 3D maximum intensity projections, and 4D projections were obtained. RESULTS: The mean pooled coronary attenuation values (H +/- SD) for the right (RCA), left anterior descending (LAD), and left circumflex (LCx) coronary arteries at various concentrations (10%, 20%, 30%, 40%) were as follows: 10% (RCA [232.6 +/- 64.0], LAD [180.4 +/- 45.1], and LCx [176.6 +/- 56.2]); 20% (RCA [383.0 +/- 98.7], LAD [324.3 +/- 60.1], and LCx [331.8 +/- 105.5]); 30% (RCA [441.8 +/- 137.6], LAD [401.3 +/- 125.8], and LCx [418.5 +/- 173.0]); and 40% (RCA [717.3 +/- 377.7], LAD [573.3 +/- 233.3], and LCx [584.8 +/- 189.0]). Coronary imaging with aortic root MDCTA was feasible at all concentrations, and the attenuation values were statistically significantly greater than 250 H at 20%, 30%, and 40% (p < 0.05). The attenuation values with aortic root MDCTA using one fifth of the volume of contrast material are comparable to those currently achieved both clinically and experimentally with peripheral i.v. MDCTA. CONCLUSION: Aortic root MDCTA can depict the coronary arteries with as little as 20 mL of contrast material. This may provide an alternative means of coronary evaluation in patients with renal insufficiency.

Complications of renal transplantation.

Continued improvements in graft survival have led to widespread acceptance of renal transplantation as the preferred treatment for the majority of patients with end-stage renal disease. The long-term care of these patients is often provided away from transplantation centers. This article presents both the clinical and imaging features of renal transplantation complications and their interventional management. Urologic and vascular complications may occur. Vascular complications include renal artery stenosis and renal artery and renal vein thrombosis. Ultrasound can accurately depict and characterize many of the potential complications of renal transplantation and increasingly magnetic resonance imaging also facilitates this role. In addition, interventional radiologic techniques allow nonsurgical treatment.

CT features of renal infarction.

PURPOSE: To demonstrate the different patterns of renal infarction to avoid pitfalls. To present 'flip-flop enhancement' pattern in renal infarction. MATERIALS AND METHODS: Retrospective review of a total of 41 renal infarction in 37 patients were done. These patients underwent initial CT and the diagnosis of renal infarction was confirmed with either follow up CT or at surgery. RESULTS: Twenty-three patients had wedge-shaped focal infarcts, nine patients had global and five patients had multifocal infarcts of the kidneys. Cortical rim sign was seen predominantly with global infarcts. In five patients, a 'flip-flop enhancement' pattern was observed. In two patients, planned renal biopsies due to tumefactive renal lesions were cancelled because of 'flip-flop enhancement' pattern on follow up CTs. CONCLUSION: Although most of our cases were straightforward for the diagnosis of renal infarction, cases with tumefactive lesions and global infarctions without the well-known cortical rim sign were particularly challenging. We describe a new sign, flip-flop enhancement pattern, which we believe solidified the diagnosis of renal infarction in five of our cases. The authors recommend further investigations for association of flip-flop enhancement and renal infarction.

Atypical chest pain: coronary, aortic, and pulmonary vasculature enhancement at biphasic single-injection 64-section CT angiography.

PURPOSE: To prospectively evaluate the enhancement of coronary, pulmonary, and thoracic aortic vasculature by using biphasic single-acquisition 64-section computed tomographic (CT) angiography and to prospectively evaluate if differences in right side of the heart and coronary venous enhancement interfere with interpretation of coronary arteries. MATERIALS AND METHODS: With internal review board approval and HIPAA compliance, 50 patients (16 men, 34 women; mean age, 51.5 years; range, 30-75 years) with atypical chest pain were referred from the emergency department and were imaged with a 64-section CT scanner after premedication with oral atenolol and/or intravenous metoprolol. Thoracic CT angiography with retrospective gating was subsequently performed with a single biphasic injection of 130 mL of iso-osmolar contrast material (100 mL at 5 mL/sec and 30 mL at 3 mL/sec) in caudal-to-cranial acquisition. Coronary, aortic, and pulmonary arterial attenuation values were obtained. Coronary venous and right atrial enhancement were evaluated to assess whether there was interference with coronary artery evaluation. A two-tailed Friedman test was used to evaluate differences among segments within each artery. RESULTS: Mean coronary arterial, pulmonary arterial, and aortic attenuation values were significantly higher than the 250-HU threshold (P < .05). Mean pooled coronary arterial (288.9 HU +/- 64.8), pulmonary arterial (316.4 HU +/- 79.9), and aortic (329.9 HU +/- 63.3) attenuation values were significantly higher than the 250-HU threshold (P < .0001). Coronary venous enhancement did not affect depiction or interpretation of coronary arteries. Right atrial streak artifact focally traversed the right coronary artery in only one study. CONCLUSION: The aforementioned thoracic CT angiographic protocol provides enhancement of coronary, aortic, and pulmonary vasculature in a single breath hold without interference from right side of the heart streak artifact or coronary venous enhancement.

Coronary 64-slice computed tomographic angiography models employing aortic root and selective catheter directed contrast enhancement in swine: technical feasibility and preliminary results using 3D and 4D reconstructions.

PURPOSE: The technical feasibility of combining catheter directed coronary enhancement and multidetector computed tomographic angiography (MD-CTA) is presented in a swine model at various cardiac and injection rates. MATERIALS/METHODS: A 64-slice CT scanner was used under animal IRB approval in four sedated swine. Common femoral venous/arterial access with a 5 Fr micropuncture kit was ultrasound guided. Investigational 5 Fr diffusion-tip pigtail [aortic root (AR)-MD-CTA] and conventional 5 Fr coronary [selective (S)-MD-CTA] catheters were positioned on the CT table with c-arm fluoroscopy. AR-MD-CTA commenced 1-2 s after injection of 50 cc Visipaque mixed with 50 cc NS at 6 cc/s (n=3), 8 cc/s (n=5) or 10 cc/s (n=7) (HR=120, 100, 90, 80 or 65 bpm). S-MD-CTA (right and left, n=4) (HR= 90, 80, or 65 bpm) commenced 1-2 s after injection of 5 cc Visipaque mixed with 5 cc NS (1 cc/s). IV-MD-CTA (n=4) (HR=80 bpm) commenced 5 or 10 s after aortic peak density with 100 cc Visipaque (5 cc/s) and 50 or 75 cc NS (5 cc/s) flush. Conventional angiography (n=2) used standard protocol. MD-CTA was performed with the following parameters: collimation 0.6 mm, tube rotation time 0.3 s, table feed/rotation 3.8 mm, scan time 10-12 s, tube voltage 120 kVp, effective mAs 850, pitch 0.2, FOV 109-123 mm, slice thickness/increment 0.6 mm/0.3 mm, kernel B25 f smooth. Ex vivo imaging (64-slice CT, n=3) was also performed. Post-processing consisted of coronary peak densities, 3D-MIP's and 4D projections. RESULTS: Catheter directed MD-CTA was feasible at all injection rates at and below 100 bpm and yielded higher peak coronary attenuation values than IV-enhanced studies. Definition and clarity of the tributary and distal anatomy was also higher than IV-enhanced CTA. CONCLUSIONS: Catheter directed MD-CTA can be performed by retrofitting the current CT scanner with a portable c-arm fluoroscopy unit. S and AR MD-CTA provide high coronary anatomy definition and luminal attenuation without obscuring cardiac chamber signal and with the least iodinated contrast volume.

Microvascular obstruction and myocardial function after acute myocardial infarction: assessment by using contrast-enhanced cine MR imaging.

UNLABELLED: This study was approved by the Human Investigation Committee of William Beaumont Hospital, and all patients gave informed consent. The purpose of this study was to prospectively compare contrast material-enhanced cine magnetic resonance (MR) imaging with more-standard MR imaging for the evaluation of microvascular obstruction and myocardial function in 80 patients (56 men, 24 women; mean age, 57 years; range, 29-80 years) with acute myocardial infarction after reperfusion therapy. Findings at contrast-enhanced cine MR imaging agreed with the global and transmural extent of microvascular obstruction at first-pass perfusion (intraclass correlation coefficient [IC] of 0.96 [P < .001] and 0.88 [P < .001], respectively) and inversion-recovery gradient-echo (IC of 0.90 [P < .001] and 0.93 [P < .001], respectively) MR imaging. There was no significant difference between myocardial function parameters before and after contrast material enhancement. Contrast-enhanced cine MR imaging reduced imaging time by 34% (11 of 32 minutes) and improved spatial resolution. SUPPLEMENTAL MATERIAL: radiology.rsnajnls.org/cgi/content/full/240/2/529/DC1

Catheter contrast-enhanced coronary CT-angiography using an aortic root injection--preliminary technical development in four patients.

The feasibility of performing coronary computed tomographic angiography (CTA) with an intra-aortic injection of iodinated contrast was tested in four patients immediately following diagnostic cardiac catheterization and placement of a 6-french pigtail catheter into the aortic root. A diluted contrast mixture [75 cc Omnipaque 350 mixed with 125 cc normal saline (4-slice scanner) vs. 40 cc Omnipaque 350 mixed with 60 cc normal saline (16-slice scanner)] was injected at a rate of 6 to 7.7 cc/sec at the onset of breath-hold and helical (4 slice, n=3, and 16-slice, n=1) retrospective ECG-triggered acquisition. The proximal and distal coronary vasculature including small tributaries were depicted with high signal-to-noise (S/N) and free from underlying blood pool enhancement. The right coronary artery was sub optimally enhanced in two patients. No significant disease was found on CTA or XRA in two patients; however, severe multivessel disease was demonstrated on both modalities in two patients. Catheter contrast-enhanced coronary CTA is feasible utilizing low injection rates and low iodinated contrast volumes, however, catheter modifications are required for consistent and homogeneous opacification of the aortic root.

Lower extremity MR angiography: universal retrofitting of high-field-strength systems with stepping kinematic imaging platforms initial experience.

In 15 volunteers and 84 patients with clinically suspected peripheral vascular disease, a stepping kinematic imaging platform, a manual retrofit stepping magnetic resonance (MR) imaging table, was used with three high-field-strength MR imaging systems to perform multistation peripheral contrast material-enhanced MR angiography in the lower extremity with the existing system phased-array coil. Each examination was performed in less than 45 minutes. Mounting of the stepping kinematic imaging platform was quick and simple and allowed rapid repositioning of a patient relative to the phased-array coil and acquisition of high-spatial-resolution MR angiograms of the peripheral vasculature with use of one injection of MR imaging contrast agent.

Contrast-enhanced three-dimensional MR angiography of the pulmonary vascular tree.

Contrast-enhanced three-dimensional MR angiography has evolved into a promising technique in the study of the pulmonary vasculature. Both congenital and acquired entities can be now morphologically demonstrated in a non-invasive manner obviating the need for conventional pulmonary angiography. Due to spatial resolution limitations, however, it is still premature to routinely apply the method in the detection of small subsegmental emboli, in cases of suspected pulmonary embolism, and further technical developments will be required. In this paper we present a spectrum of congenital and acquired disorders affecting the pulmonary vascular tree as demonstrated with contrast-enhanced three-dimensional MR angiography.