MR Imaging–guided Prostate Biopsy with a Closed MR Unit at 1.5 T: Initial Results

The authors evaluated a magnetic resonance (MR) imaging-compatible biopsy device comprising a needle guide that can be visualized with MR imaging and manipulated mechanically from outside the MR unit. With approval from the local ethics committee and patient consent, this device was tested in 12 patients by using a closed 1.5-T MR unit and a body phased-array coil. Patients had elevated prostate-specific antigen levels (6-60 ng/mL) and one or more areas in the prostate that were suspicious for carcinoma at prebiopsy MR imaging. Biopsy was performed with transrectal access and with the patient prone. A 16-gauge MR imaging-compatible needle was successfully positioned with the device, and between six and nine tissue cores were obtained in each patient. In one patient, two suspicious basal areas could not be reached with the device. Histologic analysis showed prostate cancer in five patients and prostatitis in six. No complications were observed. The device enabled MR imaging-guided core-needle biopsy of prostate areas suspicious for cancer on MR images.

Magnetic resonance imaging of the upper abdomen using a free-breathing T2-weighted turbo spin echo sequence with navigator triggered prospective acquisition correction

PURPOSE

To evaluate a free-breathing navigator triggered T2-weighted turbo spin-echo sequence with prospective acquisition correction (T2w-PACE-TSE) for MRI of the upper abdomen in comparison to a conventional T2-weighted TSE (T2w-CTSE), a single-shot TSE (T2w-HASTE), and a T1-weighted gradient-echo sequence (T1w-FLASH).

MATERIALS AND METHODS

A total of 40 consecutive patients were examined at 1.5 T using free-breathing T2w-PACE-TSE, free-breathing T2w-CTSE, and breath-hold T2w-HASTE and T1w-FLASH acquisition. Images were evaluated qualitatively by three radiologists regarding motion artifacts, liver-spleen contrast, depiction of intrahepatic vessels, the pancreas and the adrenal glands, and overall image quality on a four-point scale. Quantitative analysis of the liver-spleen contrast was performed.

RESULTS

Depiction and sharpness of intrahepatic vessels were rated significantly better (P < 0.01) using T2w-PACE-TSE compared to T2w-CTSE and T2w-HASTE sequences. Significantly higher contrast values were measured for T2w-PACE-TSE images compared to T2w-CTSE, T2w-HASTE, and T1w-FLASH images (P < 0.01). Mean examination time of the T2w-PACE-TSE was 7.91 minutes, acquisition time of the T2w-CTSE sequence was 4.52 minutes.

CONCLUSION

Prospective acquisition correction is an efficient method for reducing respiratory movement artifacts in T2w-TSE imaging of the upper abdomen. Compared to T2w-CTSE and T2w-HASTE sequences recognition of anatomical details and contrast can be significantly improved.

Contrast-enhanced magnetic resonance angiography of the lower extremities: Standard-dose vs. high-dose gadodiamide injection

PURPOSE

To compare the efficacy and safety of two different doses (0.1 and 0.3 mmol/kg of body weight [BW]) of gadodiamide for contrast-enhanced magnetic resonance angiography (ce-MRA) of the lower extremities with intraarterial digital subtraction angiography (IA-DSA).

MATERIALS AND METHODS

A total of 30 patients with peripheral arterial occlusive disease underwent IA-DSA and ce-MRA from the aortic bifurcation down to the ankle. Patients were randomized to receive a total dose of 0.1 or 0.3 mmol/kg of BW gadodiamide (Omniscan, Amersham Buchler), administered intravenously as a series of three automatic bolus injections. Ce-MRA was performed with a 1.5-T system using a body phased-array coil, centered stepwise over the calf, thigh, and pelvic region. A fast T1-weighted, three-dimensional gradient-echo sequence was obtained before and after injection of the allocated dose. IA-DSA was performed using the Seldinger technique and a femoral approach. The vessels under investigation were divided into 31 segments, and ce-MRA and IA-DSA image sets were evaluated in a double-blind fashion for the presence of stenosis, presence of collateral vessels, vessel delineation, and overall image quality. Both dose groups were compared with regard to contrast index (CI) and signal- and contrast-to-noise ratios (SNR, CNR). The occurrence of adverse events or side effects was also documented. Sensitivity, specificity, and accuracy were calculated in relation to the results of stenosis grading.

RESULTS

A total of 26 patients were entered in the efficacy evaluation, while all 30 patients were included in the safety assessment. The sensitivity, specificity, and accuracy for the 0.1 and 0.3 mmol/kg dose groups were 78.8%/93.0%/88.9% vs. 60.2.%/91.5%/83.2%, respectively. The detection of collaterals was similar to IA-DSA for the 0.3 mmol/kg dose group (30.2% vs. 27.4%), but was lower in the 0.1 mmol/kg dose group (27.3% vs. 12.3%). The high-dose gadodiamide injection proved to be superior to the 0.1 mmol/kg dose group with regard to vessel delineation and overall image quality (P = 0.007 and P = 0.002, respectively). The difference between the two dose groups regarding CI, SNR, and CNR was significant (P = 0.0001), in favor of the 0.3 mmol/kg dose group. No adverse events were observed in any of the patients.

CONCLUSION

Ce-MRA with gadodiamide is safe and efficacious. Comparison of two different doses with IA-DSA as the standard of reference showed that the 0.3 mmol/kg dose is superior to the standard 0.1 mmol/kg dose with respect to contrast enhancement, vessel delineation, image quality, and detection of collaterals. However, the 0.1 mmol/kg dose was superior to the high dose in the grading of stenosis.

On the heating of inductively coupled resonators (stents) during MRI examinations

Stents that have been implanted to preserve the results of vascular dilatation are frequently affected by in-stent restenosis, which ideally should be followed up by a noninvasive diagnostic modality. Active MRI stents can enable this kind of follow-up, while normal metallic stents can not. The prototype stents investigated in this study were designed as electric resonating circuits without a direct connection to the MR imager, and function as inductively coupled transmit coils. The model of a long solenoid coil is used to describe the additional power loss caused by such resonators. The theoretically estimated temperature increase is verified by measurements for different resonators and discussed for worst-case conditions. The RF power absorption of an active resonator is negligible compared to the total power absorbed during MRI. The local temperature increase observed for prototypes embedded in phantoms is in a range that excludes direct tissue damage. However, ruptures in the conducting structure of a resonator can cause hot spots, which may establish a high local temperature. This hazard can be reduced by designing resonators with a low quality (Q) factor or by setting the circuit slightly off resonance; however, this would lower the nominal amplification for which the resonator was designed.

Assessment of left ventricular volumes and function: intraindividual comparison of multi-slice spiral CT and electron beam CT in an animal model

PURPOSE

To evaluate multi-slice spiral computed tomography (MSCT) for measurements of left ventricular volumes, ejection fraction (EF), and myocardial mass in comparison with electron beam CT (EBCT) as a reference method.

MATERIAL AND METHODS

Six minipigs underwent both standardized contrast-enhanced MSCT (effective acquisition time per cardiac cycle 125.7+/-30.1 ms, reconstructed slice thickness 8 mm) and EBCT (acquisition time 50 ms, collimated slice thickness 8 mm). The contrast-to-noise ratio of the left ventricle was measured in each animal, and the contour sharpness of the myocardium was analyzed. Volumes (EDV, ESV, SV) ejection fraction (EF), and muscle mass were calculated by MSCT and by EBCT using the slice summation method.

RESULTS

MSCT had a higher contrast-to-noise ratio and delineated the myocardial contours more sharply than EBCT. There was a close linear correlation between both modalities for all parameters (EDV: rP=0.88, ESV: rP=0.91, SV: rP=0.85, EF: rP=0.93; mass: rP=0.90; P<0.05 each). MSCT slightly overestimated ESV and slightly underestimated SV and EF compared with EBCT (P<0.05 each).

CONCLUSIONS

Image quality in MSCT is superior to that of EBCT. Functional parameters correlate well between both modalities, but the accuracy of MSCT is limited by its lower temporal resolution.

Urinary Bladder Cancer: Preoperative Nodal Staging with Ferumoxtran-10–enhanced MR Imaging

PURPOSE

To prospectively evaluate ferumoxtran-10-enhanced magnetic resonance (MR) imaging for nodal staging in patients with urinary bladder cancer.

MATERIALS AND METHODS

Fifty-eight patients with proved bladder cancer were enrolled. Results of MR imaging performed before and after injection of ferumoxtran-10 were compared with histopathologic results in surgically removed lymph nodes. High-spatial-resolution three-dimensional T1-weighted magnetization-prepared rapid acquisition gradient-echo (voxel size, 1.4 x 1.4 x 1.4 mm) and T2*-weighted gradient-echo (voxel size, 0.8 x 0.8 x 3.0 mm) sequences were performed before and 24 hours after injection of ferumoxtran-10 (2.6 mg iron per kilogram of body weight). On precontrast images, lymph nodes were defined as malignant by using size and shape criteria (round node, >8 mm; oval, >10 mm axial diameter). On postcontrast images, nodes were considered benign if there was homogeneous decrease in signal intensity and malignant if decrease was absent or heterogeneous. Qualitative evaluation was performed on a node-to-node basis. Sensitivity, specificity, predictive values, and accuracy were evaluated with logistic regression analysis.

RESULTS

In 58 patients, 172 nodes imaged with use of ferumoxtran-10 were matched and correlated with results of node dissection. Of these, 122 were benign and 50 were malignant. With nodal size and shape criteria, accuracy, sensitivity, specificity, and positive and negative predictive values on precontrast images were 92%, 76%, 99%, 97%, and 91%, respectively; corresponding values on postcontrast images were 95%, 96%, 95%, 89%, and 98%. In the depiction of pelvic metastases, sensitivity and negative predictive value improved significantly at postcontrast compared with those at precontrast imaging, from 76% to 96% (P < .001) and from 91% to 98% (P < .01), respectively. At postcontrast imaging, metastases (4-9 mm) were prospectively found in 10 of 12 normal-sized nodes (<10 mm); these metastases were not detected on precontrast images. Postcontrast images also showed lymph nodes that were missed at pelvic node dissection in two patients.

CONCLUSION

Ferumoxtran-10-enhanced MR imaging significantly improves nodal staging in patients with bladder cancer by depicting metastases even in normal-sized lymph nodes.

Wertigkeit der Elektronenstrahl-Computertomographie (EBT)

Electron beam tomography (EBT) has been scientifically evaluated to a much lesser degree for non-cardiac indications than for cardiac purposes. Therefore, four groups of investigators in Berlin (2), Mannheim and Munchen, which were supported by the Deutsche Forschungsgemeinschaft (DFG), included applications outside the heart in their evaluation of EBT technology. EBT has proven useful to look for pulmonary embolism and to assess other vessels (aorta, aortic branches, and intracranial arteries). Imaging of the lung parenchyma benefits from its intrinsic high contrast and from the fast data acquisition of EBT. Limited photon efficiency, higher radiation exposure, increased noise levels and other artifacts, however, markedly reduce the value of EBT for imaging of low contrast objects compared to conventional spiral CT and multislice CT (MSCT), compromising, in particular, the morphologic depiction of parenchymal abdominal organs and the brain. Consequently, scientific studies to further evaluate EBT for scanning of the brain and parenchymal abdominal organs were not pursued. Radiation exposure for non-cardiac EBT studies is up to three times higher than that for respective spiral CT studies, and in children EBT can only be advocated in select cases. Radiation exposure for the various prospectively triggered cardiac examination protocols of EBT is lower than that for conventional coronary angiography. Radiation exposure in cardiac multislice CT exceeds severalfold that of EBT, but the dose efficiency of EBT and MSCT are similar due to higher spatial resolution and less image noise of MSCT. In addition, modifications of MSCT (ECG pulsing) can further reduce radiation exposure to the level of EBT. Technical improvements of the EBT successor scanner "e-Speed" enable faster data acquisition at higher spatial resolution. Within comparative studies, the "e-Speed" will have to prove its value and competitiveness, particularly in comparison with multislice CT. After profound scientific assessment in a multicenter evaluation supported by the Deutsche Forschungsgemeinschaft (DFG) and regardless of the specific suitability of electron beam tomography for various cardiac and some non-cardiac indications, the investigators unanimously find the electron beam tomograph Evolution C150 XP not suitable as a whole body CT scanner.

Image quality of noninvasive coronary angiography using multislice spiral computed tomography and electron-beam computed tomography: intraindividual comparison in an animal model

OBJECTIVE

Comparison of coronary artery visualization by multislice spiral CT (MSCT) and electron-beam CT (EBCT).

MATERIALS AND METHODS

Six minipigs underwent MSCT (collimation 4 x 1 mm, gantry rotation time 500 milliseconds, acquisition time per cardiac cycle 126 +/- 30 milliseconds) and EBCT (slice thickness 1.5 mm, acquisition time per scan 100 milliseconds). Visualized vessel length and contour sharpness was measured, contrast-to-noise ratios were calculated, and the frequency of motion artifacts were evaluated.

RESULTS

MSCT depicted significantly longer segments of the coronary tree than EBCT (length: 248.8 vs. 222.8 mm; P < 0.05), delineated the vessel contours more sharply (slope of density curves: 219.2 vs. 160.2 DeltaHU/mm; P < 0.05), and had a higher contrast-to-noise ratio (13.4 vs. 7.3; P < 0.05). The frequency of motion artifacts did not differ between both modalities (94.7% vs. 95.7% of visualized vessel length; P > 0.05).

CONCLUSIONS

Because its higher spatial resolution and lower image noise, MSCT seems to be superior to EBCT in the visualization of the coronary arteries. Despite different temporal resolutions motion artifacts seem to be similar with both modalities.

Comparison of the Iron Oxide-Based Blood-Pool Contrast Medium VSOP-C184 With Gadopentetate Dimeglumine for First-Pass Magnetic Resonance Angiography of the Aorta and Renal Arteries in Pigs

RATIONALE AND OBJECTIVES

VSOP-C184 at a dose of 0.045 mmol Fe/kg has been shown to be an efficient blood pool contrast medium for equilibrium magnetic resonance angiography (MRA) that can be administered as a bolus. The present study was performed to determine whether VSOP-C184 is also suitable for first-pass MRA.

MATERIALS AND METHODS

Fifteen MRA examinations at 1.5 T were performed in minipigs using a fast 3D fast low-angle shot (FLASH) sequence (repetition time = 4.5 ms, echo time = 1.7 ms, excitation angle = 25 degrees, matrix 256, body phased-array coil). The citrate-stabilized iron oxide preparation VSOP-C184 was investigated (total particle diameter: 7.0 +/- 0.15 nm; core size: 4 nm) and compared with gadopentetate dimeglumine (Gd-DTPA). The following doses were tested: VSOP-C184: 0.015, 0.025, and 0.035 mmol Fe/kg; Gd-DTPA: 0.1 and 0.2 mmol Gd/kg; n = 3 examinations/dose. Data were analyzed quantitatively (signal enhancement (ENH) and vessel edge definition (VED)) and qualitatively.

RESULTS

First-pass MRA using the 3 doses of VSOP-C184 yielded the following ENH: aorta: 9.4 +/- 2.6; 12.31 +/- 1.2; 16.53 +/- 1.7; renal arteries: 7.6 +/- 2.2; 9.9 +/- 1.0; 13.2 +/- 0.5. The values for the 2 doses of Gd-DTPA were aorta: 12.9 +/- 1.0; 16.8 +/- 2.2; renal arteries: 11.2 +/- 1.23; 11.3 +/- 1.7. VED for the 3 doses of VSOP-C184 was aorta: 106.3 +/- 31.0; 135.3 +/- 58.8; 141.3 +/- 71.0; renal arteries: 102.2 +/- 24.3; 146.8 +/- 63.0; 126.9 +/- 37.6 and for the 2 doses of Gd-DTPA, aorta: 157.2 +/- 47.8; 164.2 +/- 36.8; renal arteries: 165.9 +/- 30.4; 170.3 +/- 38.2 respectively. The differences between VSOP-C184 and Gd-DTPA are clinically not relevant and statistically not significant (p > or = .05). Qualitative evaluation of image quality, contrast, and delineation of vessels showed the results obtained with VSOP-C184 at doses of 0.025 and 0.035 mmol Fe/kg to be similar to those of Gd-DTPA at 0.1 and 0.2 mmol Gd/kg.

CONCLUSION

VSOP-C184 is suitable for first-pass MRA at doses of 0.025 and 0.035 mmol Fe/kg and thus, in addition to its blood pool characteristics, allows for selective visualization of the arteries without interfering venous signal.

[Cross-section diagnosis of tumors of the kidney and prostate gland: CT and MRI]

Computed tomography (CT) and magnetic resonance imaging (MRI) underwent significant technical advances in the past ten years, especially in the diagnostic evaluation of renal tumors. Either modality can perform unenhanced and contrast enhanced imaging with high resolution display of three-dimensional data sets of the entire abdomen including the arterial and the parenchymatous perfusion phase after injection of contrast medium. Multiplanar reconstructions of these three-dimensional data allow the display in any chosen orientation. The maximum intensity projection can create CT and MR angiograms. For the diagnosis of renal tumors, both modalities offer the possibility of a detailed visualization of both the parenchyma and the arterial and venous vessels, leading to an efficient preoperative work-up. For the MRI diagnosis of the prostate cancer, the achievable accuracy depends on the applied coil technique and on the available clinical information as well as on the experience of the examiner. For the preoperative MRI staging of prostate cancer, the accuracy has been stated to be between 51 % and 97 %.

Magnetic Resonance Imaging of Myocardial Perfusion and Viability Using a Blood Pool Contrast Agent

RATIONALE AND OBJECTIVES

A comprehensive cardiac magnetic resonance (MR) examination should comprise imaging of myocardial perfusion, viability, and the coronary arteries. Blood pool contrast agents (BPCAs) improve coronary MR angiography, whereas their potential for imaging of perfusion and viability is unknown. The abilities to noninvasively image myocardial perfusion and viability using the BPCA P792 (Guerbet, France) were tested in a closed-chest model of nonreperfused myocardial infarction in 5 pigs.

MATERIALS AND METHODS

Two to 3 days after instrumentation, myocardial perfusion imaging with a saturation-recovery steady-state free precession technique and viability imaging with an inversion-recovery fast low-angle shot sequence were conducted on a 1.5-T MR scanner using the extracellular contrast agents (ECCA) Gd-DOTA (0.1 mmol Gd/kg) and blood pool contrast agent (BPCA) P792 (0.013 mmol Gd/kg).

RESULTS

Perfusion defects were visualized in all pigs with good correlation between the ECCA and the BPCA (1.77 +/- 1.16 cm2 vs. 1.80 +/- 1.19 cm2, r = 0.959, P < 0.01). Reduced myocardial perfusion was detected using the ECCA up to 80 seconds after injection. In contrast, BPCA administration enabled visualization of perfusion defects on equilibrium perfusion imaging in all cases for 10 minutes. The size of myocardial infarction detected with viability MR imaging correlated well between the standard method (ECCA) and delayed-enhancement imaging with the BPCA (5.40 +/- 3.16 versus 5.52 +/- 3.13 cm3, r = 0.994, P < 0.002).

CONCLUSIONS

The BPCA investigated in this study allows both reliable detection of perfusion defects on first pass and equilibrium perfusion imaging and characterization of viability after myocardial infarction. Thus, this contrast agent is suitable for a comprehensive cardiac MR examination.

[Ultra-low-dose CT to search for stones in kidneys and collecting system]

Unenhanced computed tomography (CT) has a sensitivity of 97.7 to 100 % for the detection of urolithiasis. Using a modified examination protocol, the radiation exposure of a CT examination can be reduced to the level of a single conventional radiographic view of the abdomen (ultra-low-dose CT), assuming the examination is performed on a modern multirow CT. Automatic postprocessing of thin-section images can delineate stones on coronal images. In 30 patients, ultra-low-dose CT could detect more stones (6 renal and 19 ureteral stones) than ultrasonography.

Phase I Clinical Evaluation of Citrate-coated Monocrystalline Very Small Superparamagnetic Iron Oxide Particles as a New Contrast Medium for Magnetic Resonance Imaging

RATIONALE AND OBJECTIVES

To evaluate the safety and pharmacokinetics of a newly developed MR contrast medium consisting of very small superparamagnetic iron oxide particles (VSOP) coated with citrate (VSOP-C184) in a clinical phase I trial.

METHODS

A total of 18 healthy subjects received either VSOP-C184 (core diameter: 4 nm; total diameter: 7 +/- 0.15 nm; relaxivities in water at 0.47 T (T1) 18.7 and (T2) 30 L/(mmol*seconds)) at doses of 0.015, 0.045, or 0.075 mmol Fe/kg (n = 5 per dose) or placebo (n = 1 per dose) as intravenous injections. Physical status and vital parameters were recorded, blood samples were collected for clinical chemistry and relaxometry (0.94 T), and urinalyses were performed before and for up to 2 weeks after administration.

RESULTS

No serious adverse events occurred. The most pronounced adverse events occurred in 2 subjects of the highest dose group 45-50 minutes after injection. These were a drop in blood pressure and a drop in oxygen saturation, which were considered to be possibly drug-related and rapidly resolved without medication. Otherwise, no relevant changes in vital and laboratory parameters were observed. The parameters of iron metabolism exhibited short-term, dose-related changes. The injection of VSOP-C184 decreased T1 relaxation time of blood below 100 milliseconds for 18 minutes after a dose of 0.045 mmol [corrected] Fe/kg and for 60 minutes after 0.075 mmol [corrected] Fe/kg.

CONCLUSIONS

The favorable data on the safety, tolerability, and efficacy of VSOP-C184 justify further clinical phase II and III trials as a contrast medium for MRI.

[Preoperative MRT of the breast in invasive lobular carcinoma in comparison with invasive ductal carcinoma]

PURPOSE

To evaluate the role of preoperative MRI of the breast in invasive lobular carcinoma (ILC) compared to invasive ductal carcinoma (IDC).

MATERIALS AND METHODS

For one year, all patients transferred by the hospital's gynecologic outpatient service for suspicious findings in routine mammography and/or ultrasound (conventional modalities = CM) underwent preoperative MRI of the breast. Retrospective analysis of the histologic findings identified 17 patients with ILC. These were compared with 30 proven IDC patients, chosen by random. The MRI findings of these 2 patient groups were compared with regard to the detection of additional lesions. The average number of additional lesions detected by MRI was compared for significant differences between both groups using the T-test for paired samples.

RESULTS

In the 17 patients with ILC, conventional modalities (CM) identified 21malignant lesions whereas MRI detected a total of 30 lesions. At least one additional lesion was detected by MRI in 7 of the 17 patients with ILC. In the 30 patients with IDC, on the other hand, MRI detected an additional lesion in three instances only. In one patient of the ILC group, MRI identified an additional lesion in the contralateral breast that had escaped detection by CM. No additional contralateral lesion was detected by MRI in any of the IDC patients. Benefit of MRI in ILC-Group: The mean numbers of detected malignant lesions differed significantly between diagnosis by MRI and CM in the ILC group (1.77 carcinomas per patient with MRI versus 1.24 with conventional modalities, T-test, p = 0.0078). Benefit of MRI in IDC-Group: although it was possible to find 1.27 carcinomas vs. 1.17 carcinomas per patient in the IDC-Group, this benefit was not statistical significant (T-test, p = 0.0831).

CONCLUSION

Preoperative MRI detects multiple additional lesions compared to the ones already known by CM. The higher incidence of multiple lesions in ILC compared to IDC and the difficult diagnosis of ILC in CM might be the reason for the fact that preoperative MRI is particularly useful in patients with ILC.

[Diagnostic value of electron-beam computed tomography (EBT). I. Cardiac applications]

Electron beam tomography (EBT) directly competes with other non-invasive imaging modalities, such as multislice computed tomography, magnetic resonance imaging, and echocardiography, in the diagnostic assessment of cardiac diseases. EBT is the gold standard for the detection and quantification of coronary calcium as a preclinical sign of coronary artery disease (CAD). Its standardized examination protocols and the broad experience with this method favor EBT. First results with multislice CT indicate that this new technology may be equivalent to EBT for coronary calcium studies. The principal value of CT-based coronary calcium measurements continues to be an issue of controversy amongst radiologists and cardiologists due to lack of prospective randomized trials. Coronary angiography with EBT is characterized by a high negative predictive value and, in addition, may be indicated in some patients with manifest CAD. It remains to be shown whether coronary angiography with multislice CT is reliable and accurate enough to be introduced into the routine work-up, to replace some of the many strictly diagnostic coronary catheterizations in Germany and elsewhere. Assessment of coronary stent patency with EBT is associated with several problems and in our opinion cannot be advocated as a routine procedure. EBT may be recommended for the evaluation of coronary bypasses to look for bypass occlusions and significant stenoses, which, however, can be equally well achieved with multislice CT. Quantification of myocardial perfusion with EBT could not replace MRI or other modalities in this field. EBT has proven to be accurate, reliable and in some instances equivalent to MRI, which is the gold standard for the quantitative and qualitative evaluation of cardiac function. Some disadvantages, not the least of which is the limited distribution of electron beam scanners, favor MRI for functional assessment of the heart.

Improved detection of focal liver lesions at MR imaging: multicenter comparison of gadoxetic acid-enhanced MR images with intraoperative findings

PURPOSE

To evaluate the safety and efficacy of gadoxetic acid disodium-enhanced magnetic resonance (MR) imaging for the detection of focal liver lesions, with results of histopathologic examination and/or intraoperative ultrasonography used as a standard of reference.

MATERIALS AND METHODS

One hundred sixty-nine patients who were known to have or suspected of having focal liver lesions and were scheduled for liver surgery were included in this study. Results in 131 patients could be included in the efficacy analysis. MR imaging was performed before and immediately and 20 minutes after bolus injection of 0.025 mmol/kg of the liver-specific hepatobiliary contrast agent gadoxetic acid. T1-weighted gradient-echo (with and without fat saturation and including dynamic data sets) and T2-weighted fast spin-echo/turbo spin-echo sequences were performed. All images were evaluated on site and by three independent and blinded off-site reviewers. Lesion matching based on the standard-of-reference results was performed. Differences in lesion detection with precontrast and with postcontrast MR images were assessed with the two-sided Wilcoxon signed rank test.

RESULTS

Gadoxetic acid was well tolerated. In the on-site review, the number of patients in whom all lesions were correctly matched increased from 89 of 129 patients at precontrast MR imaging to 103 of 129 patients at postcontrast MR imaging. In the off-site evaluation, the number of patients in whom all lesions were correctly matched and the corresponding sensitivity values increased from 72 (55.8%), 68 (52.7%), and 66 (51.2%) with the precontrast images to 88 (68.2%), 69 (53.5%), and 76 (58.9%) with the postcontrast images for readers 1, 2, and 3, respectively. Two of the three blinded readers showed a statistically significant difference in lesion detection between precontrast and postcontrast MR imaging (P <.001 and P =.008). A large number of additionally correctly detected and localized lesions were smaller than 1 cm.

CONCLUSION

MR imaging with gadoxetic acid is safe and improves lesion detection and localization.

Assessment of myocardial infarction in pigs using a rapid clearance blood pool contrast medium

Delayed enhancement MRI using extracellular contrast media allows reliable detection of myocardial infarction. If blood pool contrast media like P792 (Vistarem, Guerbet, France), in addition to improving coronary MR angiography, can be shown to also produce delayed enhancement in myocardial infarction they could improve the prerequisites for a comprehensive cardiac MR examination. In this study reperfused myocardial infarction in five minipigs was imaged with an inversion-recovery fast low-angle shot sequence using P792 (0.013 mmol Gd/kg) and the extracellular contrast medium Gd-DOTA (Dotarem, 0.1 mmol Gd/kg, Guerbet). The infarction size determined on MRI using P792 (7.55 +/- 2.31 cm(2)) highly correlated both with histomorphometry (7.81 +/- 2.18 cm(2), r = 0.991, P < 0.002) and with MRI using Gd-DOTA (7.85 +/- 2.35 cm(2), r = 0.978, P < 0.005). Bland-Altman analysis showed that the limit of agreement of MRI using P792 compared to histomorphometry was 3.3 +/- 7.6% of the infarction size. The contrast-to-noise ratio between infarcted and remote myocardium was not significantly different between Gd-DOTA (5.9 +/- 2.4) and P792 (4.4 +/- 1.1, P = 0.5). The blood pool contrast medium P792 allows reliable assessment of viability with good contrast and accuracy.

Coronary artery disease: new insights and their implications for radiology

Coronary artery disease (CAD) diminishes local, regional, or global blood supply to the heart and is most commonly caused by coronary atherosclerosis. New insights into the etiology of atherosclerosis suggest that CAD is an inflammatory disorder that responds well to modulation rather than an unchangeable chronic process. Since 75% of all acute coronary syndromes result from rupture of atherosclerotic plaques, factors causing rupture have a crucial role. Magnetic resonance imaging and CT have the potential to visualize the composition of coronary artery plaques and thus to identify plaques at risk. Considering the new insights into stunning and hibernation, myocardial late enhancement on MRI might provide pivotal information for therapeutic decision making among lysis therapy, catheter intervention, and bypass surgery. Exercise electrocardiography without or with right precordial leads, stress echocardiography, and stress scintigraphy are simple clinical procedures to identify CAD with high sensitivities of 67, 92, 76, and 88%, respectively. The MRI and CT have to be compared with these good results. Nevertheless, we are expecting that MRI and CT will replace the conventional diagnostic modalities, gain a central role in diagnosing patients with suspected CAD, and prove to be cost-effective in this regard.

Gadobutrol-enhanced moving-table magnetic resonance angiography in patients with peripheral vascular disease: a prospective, multi-centre blinded comparison with digital subtraction angiography

The purpose of this study was to compare moving-table three-dimensional contrast-enhanced magnetic resonance angiography (CE MRA), using 1.0-mol gadobutrol, with intra-arterial digital subtraction angiography (i.a. DSA) for evaluation of pelvic and peripheral arteries in patients with peripheral arterial occlusive disease. A total of 203 patients were examined in a prospective, multi-centre study at 1.0/1.5 T. Ten vessel segments of one leg were evaluated on-site and by three independent blinded reviewers off-site. One hundred eighty-two patients were evaluable in blinded reading. For pelvis and thigh, there was statistically significant diagnostic agreement between CE MRA and i.a. DSA on-site (94%) and off-site (86-88%). Overall, for detection of clinically significant stenoses, 93% sensitivity and 90% specificity were achieved in on-site evaluation, with 71-76 and 87-93% off-site; for detection of occlusion, sensitivity and specificity on-site were 91 and 97%, with 75-82 and 94-98% off-site. Evaluation was more sensitive on-site than off-site for detection of stenoses and occlusion, whereas specificity was similar. The CE MRA with 1.0-mol gadobutrol gave results comparable to those of i.a. DSA for the larger arteries of pelvis and thigh. Results for calf arteries were compromised by spatial resolution and technical limitations.

Gadolinium-enhanced three-dimensional magnetic resonance angiography versus conventional digital subtraction angiography: which modality is superior in evaluating living kidney donors?1

This study evaluates the correlation of magnetic resonance angiography (MRA) and digital subtraction angiography (DSA) with the operative vessel findings in living kidney donors. The intraoperative vessel findings of 52 living renal donors were compared with the preoperative diagnoses of each imaging technique. Sixty-seven arteries were found during explantation. Forty kidneys showed a single arterial blood supply, and 12 kidneys showed a multiple arterial blood supply. No advantage of either imaging method was found for arterial imaging. There were 55 veins identified during organ harvesting. MRA could not determine the venous system in one donor (1.9%) and failed to detect one small pole vein in another. DSA did not yield a venous diagnosis in seven patients (13.5%) and yielded misdiagnoses in four patients. The correct diagnosis of renal donor veins differed significantly in favor of MRA (kappa 0.79 vs. 0.45; P=0.008). MRA is superior to DSA in assessing the renal vasculature in living kidney donors.

[MRI of prostate cancer using three different coil systems: image quality, tumor detection, and staging]

PURPOSE

To compare three MRI coil systems in terms of image quality, delineation of prostate cancer, and tumor staging.

MATERIALS AND METHODS

49 patients with prostate cancer underwent MRI at 1.5 Tesla using a combination of an endorectal coil with a phased-array body coil (combination coil) prior to radical prostatectomy. Images were reconstructed from the data sets acquired with the endorectal coil alone and from those acquired with the combined coil. In addition, 19 patients of the study patients were examined with the body phased-array coil alone without the endorectal coil. The prostate was imaged at a slice thickness of 3 mm using axial and coronal T 2 -weighted sequences and an axial T 1 -weighted sequence. Preoperative analysis of all images acquired was done to determine the accuracy of MRI in local staging of prostate cancer. An additional retrospective analysis served to compare the different coil systems in terms of overall image quality, delineation and localization of the tumor, and criteria for local staging of prostate cancer.

RESULTS

Preoperative analysis showed MRI to have an accuracy of 59 % in local tumor staging. Retrospective coil-by-coil analysis demonstrated image quality and tumor delineation to be best for the combination coil and the endorectal coil. Regarding the staging criteria for transcapsular tumor extension and infiltration of adjacent organs, a significant advantage of the combination coil compared to the endorectal coil was identified only for the criterion of smooth bulging. In addition, the endorectal coil and the combination coil were found to be superior to the body phased-array coil in assessing 15 of 17 criteria for local tumor staging but the differences were not significant.

CONCLUSION

In view of the achieved superior image quality, the combination coil or the endorectal coil is the preferred method for staging prostate cancer.

[Superparamagnetic iron oxide particles: current state and future development]

A wide range of applications for superparamagnetic iron oxide (SPIO) particles as contrast media for MRI has emerged over the last 15 years. SPIO particles can be manufactured with different particle sizes and surface coatings. Large SPIO particles (50-150 nm) predominantly produce a signal decrease or T2 -shortening and are used as contrast media for MRI of the liver and spleen. They have a high accuracy, especially in detecting liver metastases (approved for clinical use: AMI-25 (Endorem or Ferridex), SHU-555A (Resovist)). Smaller particles (about 20 nm in diameter) show a different organ distribution and have a potential for improving noninvasive lymph node assessment or characterizing vulnerable atherosclerotic plaques (in clinical trials: AMI-227 [Sinerem or Combidex]). Particles with an optimized T1-relaxivity and prolonged intravascular circulation time can be used as blood pool contrast media for MR angiography. The currently investigated indications are MR angiography of the trunk, peripheral vessels, and coronary arteries (e.g., SHU-555 C (Supravist), VSOP-C 184). Other applications of small SPIO particles include MRI of the bone marrow and the determination of perfusion parameters in tumors or other tissues like the myocardium. SPIO particles with a modified coat can be used in so-called molecular imaging, such as receptor-directed imaging, cell labeling for in-vivo monitoring of cell migration, e.g., stem cell labeling, and labeling of gene constructs for localization in genetic therapy. In tumor therapy SPIO particles can serve as mediators for hyperthermia. SPIO is a powerful MR contrast medium with manifold applications ranging from diagnostic imaging to molecular medicine.

[MR angiography of the coronary arteries: comparison of the blood pool contrast medium Gadomer and Gd-DTPA in pigs]

AIM

To investigate the signal-enhancing effects of the macromolecular contrast medium Gadomer in MR angiography of the coronary arteries compared to Gd-DTPA.

MATERIAL AND METHODS

A total of 15 MRI examinations of the heart were performed in pigs at 1.5 T using a pulse-triggered, segmented 3D FLASH sequence with data acquisition during breathhold before and up to 30 min after contrast medium injection. Gadomer was investigated at two doses (0.05 and 0.1 mmol Gd/kg), Gd-DTPA at one (0.3 mmol Gd/kg) (n = 5 examinations per dose). Standard sequences without magnetization preparation were supplemented by sequences with magnetization saturation applied before data acquisition before and immediately after contrast medium injection. Analysis comprised quantitative determination of blood and myocardium signal to noise (S/N) and contrast to noise (C/N) and qualitative assessment of several parameters of image quality and coronary artery visualization.

RESULTS

Gadomer leads to a significant C/N increase between blood and myocardium compared to the unenhanced examination and the increase is longer-lasting than that produced by Gd-DTPA (Gd-DTPA: only directly after injection; Gadomer: up to 5 min post injection at 0.05 mmol Gd/kg, up to 10 min at 0.1 mmol Gd/kg). The qualitative evaluation shows that visualization of the coronary arteries and branch vessels is significantly better with Gadomer at both doses than with Gd-DTPA. Magnetization saturation increases the C/N in combination with Gd-DTPA and at the higher dose of Gadomer with the latter producing a higher increase in C/N values.

CONCLUSION

Gadomer is a suitable contrast medium for MR angiography of the coronary arteries with the dose of 0.1 mmol Gd/kg being superior to 0.05 mmol Gd/kg due to a longer imaging window.

Effect of partial left ventriculectomy on left and right ventricular volumes and function as assessed with electron beam tomography: preliminary results

Our objective was to determine if left ventricular reduction surgery affects left and right ventricular volumes and function. Twenty-three patients with end-stage heart failure underwent contrast-enhanced electron beam tomographic function studies before and twice after partial left ventriculectomy (PLV). The PLV was combined with other cardiosurgical procedures in 20 of 23 patients. Left and right ventricular enddiastolic volume (LVEDV, RVEDV), stroke volume (LVSV, RVSV), ejection fraction (LVEF, RVEF), and enddiastolic diameter (LVEDD, RVEDD) were determined by manual tracing of endo- and epicardial borders at enddiastole and endsystole. Patients were scanned 31 days (+/-34) before and 18 days (+/-13) and 8 months (+/-4) after PLV. Mean pre- and early and late postoperative values for LVEDV, LVSV, LVEF, and LVEDD were 387.9 ml (+/-125.5 ml), 255.6 ml (+/-79.3 ml; p<0.01), and 253.7 ml (+/-97.8 ml; p<0.05), 79.7 ml (+/-25.2 ml), 74.8 ml (+/-17.9; n.s.), and 79.1 ml (+/-26.5 ml; n.s.), 21.6% (+/-7.3%), 31.9% (+/-13.4%; p<0.05), and 34.1% (+/-14.1%; p<0.05), and 72.0 mm (+/-10.6 mm), 64.3 mm (+/-8.5 mm; p<0.05), and 63.5 mm (+/-9.4 mm; p<0.05), respectively. Mean pre- and postoperative values for RVEDV, RVSV, RVEF, and RVEDD were 177.7 ml (+/-72.8 ml), 172.4 ml (+/-59.2 ml; n.s.), and 178.9 ml (+/-60.8 ml; n.s.), 60.3 ml (+/-21.6 ml), 68.8 ml (+/-19.9 ml; n.s.), and 78.3 ml (+/-25.3 ml; n.s.), 38.1% (+/-15.4%), 43.7% (+/-16.3%; p<0.05), and 45.1% (+/-11.2%; n.s.), and 50.4 mm (+/-10.9 mm), 48.1 mm (+/-8.7 mm; n.s.), and 48.5 mm (+/-9.8 mm; n.s.), respectively. The PLV may induce a significant early reduction of left ventricular volumes and improvement of biventricular function; however, our results must be judged carefully as the majority of patients in this study underwent additional cardiosurgical procedures, the contributory effect of which on the overall outcome remains unclear.

Disintegration and stepwise expulsion of a large uterine leiomyoma with restoration of the uterine architecture after successful uterine fibroid embolization: case report

Uterine fibroid embolization (UFE) is a new minimally-invasive treatment option for leiomyomata of the uterus leading to symptomatic improvement and shrinkage of the fibroids. We present a case of restoration of the uterine architecture after disintegration and stepwise expulsion of infarcted leiomyoma tissue 7 months after UFE for leiomyoma-related menorrhagia.

A vascular stent as an active component for locally enhanced magnetic resonance imaging: initial in vivo imaging results after catheter-guided placement in rabbits

RATIONALE AND OBJECTIVE

A vascular stent constructed as a high frequency resonator improves the local signal-to-noise ratio at magnetic resonance (MR) imaging. After catheter placement and intravascular expansion, the stent can be used as an inductively coupled coil for MRI. The imaging properties of this balloon-expandable active MRI stent (AMRIS) were evaluated after x-ray fluoroscopy guided placement in the abdominal aorta of five rabbits using MR angiography (MRA) and flow measurements.

METHODS

The AMRIS was implanted in the abdominal aorta of five rabbits using a balloon catheter inserted through the common carotid artery. The rabbits were examined by MRA (3D fast low-angle shot) at 1.5 tesla before and after intravenous injection of an iron-oxide-based blood pool contrast medium (dose 50 micro mol Fe/kg) and flow measurements (ECG-triggered phase contrast cine gradient-echo sequence). Signal-to-noise ratios (SNR) were calculated and flow volume curves were generated. The in-stent increase in temperature was measured in vitro using a fiberoptic thermometry system.

RESULTS

The SNR was 5.0 +/- 0.6 outside the stent and 23.2 +/- 14.1 within the stent ( < 0.0 5) in plain MRA, 19.5 +/- 5.0 outside and 30.7 +/- 8.2 within the stent ( < 0.05) in contrast enhanced MRA, and 5.8 +/- 1.6 and 13.9 +/- 5.9, respectively ( < 0.05) in the magnitude images of the flow measurements. Flow volume curves within and distal to the stent were comparable.

CONCLUSIONS

The expandable active MRI stent produces local signal enhancement in MRA and MR flow measurements after catheter placement and thus may improve assessment of the stented vessel segment by MR imaging.

Visualization of the pulmonary valve using cine MR imaging

PURPOSE

To evaluate the capability of bright-blood cine MR to directly visualize the leaflets of the valve replacement in pulmonary position following Ross operation.

MATERIAL AND METHODS

Long and short axis views of the pulmonary valve were obtained in 10 normal subjects and 14 patients after Ross operation. Valve morphology and function were analyzed and signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were calculated. Flow measurements were performed in the pulmonary trunk to assess pulmonary regurgitation.

RESULTS

In all subjects, tricuspid morphology of the pulmonary valve was visualized. SNR of the leaflets in normal subjects (9.8 +/- 3.0) and in patients after Ross operation (7.5 +/- 2.2) differed significantly from blood (12.6 +/- 3.2 and 11.3 +/- 2.5, respectively, p < 0.05). Valvular regurgitation was seen in 5 patients as an insufficient closure of the valve which was confirmed by flow measurements.

CONCLUSION

Cine MR enables in-plane visualization of the pulmonary valve and allows for functional and morphological evaluation in patients after pulmonary valve surgery.

Use of iodine-based contrast media in digital full-field mammography--initial experience

AIM

To investigate the use of iodine-based contrast media in digital full-field mammography.

METHODS

After performing initial phantom studies, seven patients underwent digital mammography (Senographe 2000D, GE Medical Systems, Milwaukee, USA) using a specially filtered beam before as well as 60, 120, and 180 seconds after injection of 80 ml of iodine contrast medium (Ultravist 370, Schering AG, Germany). The precontrast mammograms were then subtracted from the postcontrast mammograms and the resulting images compared with a contrast-enhanced dynamic MRI study, performed on all women.

RESULTS

Contrast medium accumulation within the tumors was visualized with a good quality in all cases. The conditions under which successful contrast-enhanced digital mammography can be performed were determined in phantom studies.

CONCLUSIONS

Contrast-enhanced digital mammography has a potential for improving the visualization of breast tumors in mammography using special beam filtering, adjusted x-ray parameters, proper timing, and suitable subtraction software.

Visualization of the pulmonary valve using cine MR imaging

PURPOSE

To evaluate the capability of bright-blood cine MR to directly visualize the leaflets of the valve replacement in pulmonary position following Ross operation.

MATERIAL AND METHODS

Long and short axis views of the pulmonary valve were obtained in 10 normal subjects and 14 patients after Ross operation. Valve morphology and function were analyzed and signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were calculated. Flow measurements were performed in the pulmonary trunk to assess pulmonary regurgitation.

RESULTS

In all subjects, tricuspid morphology of the pulmonary valve was visualized. SNR of the leaflets in normal subjects (9.8 +/- 3.0) and in patients after Ross operation (7.5 +/- 2.2) differed significantly from blood (12.6 +/- 3.2 and 11.3 +/- 2.5, respectively, p < 0.05). Valvular regurgitation was seen in 5 patients as an insufficient closure of the valve which was confirmed by flow measurements.

CONCLUSION

Cine MR enables in-plane visualization of the pulmonary valve and allows for functional and morphological evaluation in patients after pulmonary valve surgery.

[Modern imaging modalities in renal disease: CT and MRI]

Considerable technical advances have been made in computed tomography (CT) and magnetic resonance imaging (MRI) over the last 10 years. Both modalities allow for high-resolution imaging of the entire abdomen before as well as during the arterial and parenchymal perfusion phase after intravenous contrast medium administration. Multiplanar reconstructions of the three-dimensional source data sets yield views in any spatial orientation. Maximum intensity projections enable the generation of CT or MR angiographies as well as CT or MR urographies from delayed images. Thus, both modalities today allow for comprehensive diagnostic evaluation of renal disease by a single examination comprising detailed visualization of the parenchyma as well as of arterial and venous vessels and assessment of excretion. CT and MRI thus enable efficient preoperative diagnostic assessment in particular in patients with renal masses.

Gadobenate dimeglumine-enhanced MR angiography of the abdominal aorta and renal arteries

OBJECTIVE

This study was conducted to determine the efficacy and safety of four different doses of gadobenate dimeglumine for contrast-enhanced three-dimensional MR angiography of the abdominal aorta and renal arteries.

SUBJECTS AND METHODS

Ninety-four patients with suspected abnormality of the abdominal aorta or renal arteries underwent unenhanced three-dimensional gradient-recalled echo time-of-flight MR angiography and contrast-enhanced MR angiography after the IV injection of one of four doses of gadobenate dimeglumine (0.025, 0.05, 0.1, and 0.2 mmol/kg of body weight). Efficacy was assessed on-site and by two blinded off-site reviewers in terms of change in total diagnostic quality score and diagnostic quality score per vessel segment from baseline unenhanced time-of-flight MR angiography to contrast-enhanced MR angiography. Secondary efficacy end points included lesion count and level of confidence in lesion characterization. Safety assessments comprised adverse event monitoring, physical evaluation, vital signs, ECG, and laboratory investigations.

RESULTS

A significant change in the total diagnostic quality score from unenhanced to contrast-enhanced MR angiography was observed at all doses. The change increased with increased dose, plateauing at the 0.1 mmol/kg dose level. More patients with lesions detected and increased reviewer confidence for lesion characterization were noted on contrast-enhanced MR angiography compared with unenhanced MR angiography, although no dose-related trends were observed. All doses were well tolerated, and no significant changes in safety parameters were observed.

CONCLUSION

Gadobenate dimeglumine is an effective and safe agent for contrast-enhanced MR angiography of the abdominal aorta and renal arteries. A dose of 0.1 mmol/kg of body weight appears to be the most suitable.

Use of contrast enhanced magnetic resonance imaging to detect spinal inflammation in patients with spondyloarthritides

Inflammation of spinal structures is a characteristic feature of the spondyloarthritides (SpA). The term SpA covers patients with inflammatory back pain and/or peripheral arthritis who can be further categorized. Ankylosing spondylitis (AS), the prototype of the SpA, the most frequent inflammatory spinal disease in adults, usually starts in the sacroiliac joints. Pathologic spinal changes occurring in AS are spondylitis, spondylodiscitis and inflammation and ankylosis also at other sites in the axial skeleton. In the later stages of AS such changes can be well recognized by spinal x-rays. In the early disease stages it has been more difficult to analyze the exact anatomic localization of spinal inflammation to date, because conventional imaging systems have only a limited capacity to demonstrate such changes early. There is some evidence that magnetic resonance imaging (MRI) with fat saturation and contrast enhanced MRI are useful to visualize early and late inflammatory changes in the sacroiliac joints. In this paper we report that MRI is also useful to localize the site of inflammation to distinct regions of the spine in AS and other SpA.

[Image quality and detection of pathology by ultrasound: comparison of B-mode ultrasound with photopic imaging and tissue harmonic imaging alone and in combination]

PURPOSE

To determine the accuracy of photopic imaging (PI) in detecting pathology by ultrasound (US) and to assess the image quality in direct comparison with conventional B-mode ultrasound and tissue harmonic imaging (THI).

MATERIAL AND METHODS

Fifty-two patients underwent US examination, among them 29 patients for abdominal assessment and 23 for otolaryngological assessment. A total of 208 freeze frames, 52 B-mode scans each with and without THI and 52 B-mode scans each with and without PI, were assessed by three readers, who determined the presence of pathology on a scale of 1 (definitely abnormal) to 5 (definitely normal). All 52 patients underwent US follow-up within six weeks. The results were confirmed by CT in 30 patients and by histology in five cases. Image quality and different color encodings of each technique were rated on a ranking scale of 1 (optimal) to 4 (poor). The different US techniques were compared in terms of image quality, diagnostic accuracy, and color encoding using McNemar's test and ROC analysis.

RESULTS

The results for image quality were as follows: B-scan 3.9; THI 1.9; PI 2.8; and THI plus PI 1.5 (each p < 0.05). The following AUCs (Area under Curve, presence of pathology) were calculated: 0.925, 0.990, and 0.990 for B-mode US, THI, and PI, respectively (not significant), and 0.994 for THI plus PI (significant compared to B-mode scan). The different color encodings were rated as follows: reddish brown 1.6, gray 1.9, blue 3.1, and green 3.6 (each p < 0.05).

CONCLUSION

For ultrasound examinations, PI in combination with THI improves the image quality and conspicuity of pathology.

In vitro characterization of two different ultrasmall iron oxide particles for magnetic resonance cell tracking

RATIONALE AND OBJECTIVES

Comparison of two different ultrasmall superparamagnetic iron oxide (USPIO) particles in terms of their intracellular cell-labeling properties of macrophages and subsequent visualization by MR imaging.

MATERIALS AND METHODS

Cultures containing the macrophage cell line P-388D1 were incubated with a neutral carboxydextran-coated USPIO preparation (DDM 43/34/103) or an acidic citrate-coated USPIO (VSOP-C125). Experiments were performed in which incubation concentration and duration were varied and phagocytosis and pinocytosis suppressed by specific inhibitors. In cell culture specimens iron content was measured quantitatively and signal intensities determined by in vitro MR imaging.

RESULTS

VSOP-C125 is incorporated by cells much faster than DDM 43/34/103 and produces significantly higher final intracellular iron concentrations per cell (3420 vs. 727 ng/million cells). Both preparations show similar signal-reducing effects at MR imaging relative to the Fe content per cell. Intracellular USPIO has a much lower detection threshold at MR imaging (50/80 micromol/L) than extracellular USPIO in free solution (300 micromol/L).

CONCLUSIONS

Citrate-coated USPIO particles VSOP-C125 appear to have more favorable properties for magnetic labeling of macrophages than the carboxydextran-coated USPIO preparation DDM 43/34/103.