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Biomedical subjects

Knut Kröger

Publications and source records attributed to Knut Kröger.

25 records · Page 2Linked to original sources
PubMed2003

Using a 1 M Gd-chelate (gadobutrol) for total-body three-dimensional MR angiography: preliminary experience.

PURPOSE: To determine whether higher concentrated gadolinium chelates are advantageous for the recently introduced concept of total-body magnetic resonance angiography (MRA), allowing whole-body coverage, extending from the carotid arteries to the runoff vessels, in merely 72 seconds. MATERIALS AND METHODS: Total-body three-dimensional (3D) MRA using a 1 M Gd-chelate (gadobutrol, Gadovist, Schering, Berlin, Germany) at a dosage of 0.2 mmol/kg body-weight (biphasic injection protocol: 1.3 mL/second and 0.7 mL/second) was performed on three healthy volunteers and ten consecutive patients with DSA-documented peripheral vascular disease. Separated by at least 72 hours, the three healthy volunteers also underwent the same MRA-protocol, using gadopentetate dimeglumine in equimolar dosages. RESULTS: Compared to equimolar dosages, mean signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) values in the three volunteers were significantly higher (up to 32.5% for the arteries of the thighs and calves) using gadobutrol. In the ten patients, gadobutrol-based total-body MRA accurately assessed significant stenoses (luminal narrowing > 50%) with sensitivities and specificities of 96.2% (95% CI 0.83-0.97) and 95.7% (95% CI 0.84-0.96), respectively, compared to digital subtraction angiography. CONCLUSION: The MRA image quality for total-body MRA provided by the administration of gadobutrol is superior to that obtained following administration of an identical dose of gadopentetate dimeglumine, and therefore shows promise for use as a comprehensive single exam assessing the entire arterial system for the presence of atherosclerotic disease manifestations.

Adult↗
PubMed2003

Toe pressure measurements compared to ankle artery pressure measurements.

The Trans-Atlantic Inter-Society Consensus (TASC)-recommended absolute toe pressure is < 30-50 mm Hg for definition of chronic critical limb ischemia (CLI). Toe pressures can be measured by different techniques. The authors analyzed the clinical use of the Doppler technique and an automatic device with optical sensors and estimated their value in documentation of chronic critical limb ischemia compared to ankle artery pressures. Three different investigations were performed: (1) In 16 healthy subjects the digital artery pressures were measured by using 3 different optical sensors (transmission, reflection, and microcirculation sensor) and compared to the systolic brachial pressure. (2) In 50 patients with and without peripheral arterial occlusive disease the toe pressures at digits 1 and 2 of both feet were determined by Doppler technique (8 MHz) and by optical sensors (cuff width constant 1.5 cm) and were compared to the ankle artery pressure determined by Doppler technique. (3) In 175 patients the toe pressures were measured at 1 toe and the ankle artery pressures were determined. In this group they estimated the clinical use of the toe pressure in regard to the definition of CLI (toe pressure < 50 mm Hg) compared to the ankle pressure < 70 mm Hg. The digital artery pressures measured with the different optical sensors, and the systolic brachial pressures were not significantly different and the correlation coefficients were around 0.7. In 21 of 50 patients the toe pressure at D1 and D2 could not be measured by Doppler technique because with the applied cuff no Doppler signal could be detected at the tip of the toe, but in 24 of these 29 patients the optical measurement was possible. Mean toe pressures at D1 were 108 +/- 45 mm Hg and D2 102 +/- 45 mm Hg, which were statistically not different. The correlation coefficient for the highest ankle artery pressure and the highest toe pressure determined by the Doppler technique was 0.389; for the highest ankle artery pressure and the toe pressure measured by the optical sensors it was 0.369, and for the toe pressures measured by Doppler technique and the optical sensors it was 0.506. Defining systolic ankle artery pressure < or = 50 to 70 mm Hg as the golden standard for CLI, the sensitivity of optical toe pressure measurement for the detection of CLI was 8%, the specificity was 96%, the positive predictive value 12%, and the negative predictive value was 94%. Independent of technique the absolute systolic toe pressures did not correlate with the absolute systolic ankle pressures. The optical measurement was more suitable for toe pressure measurement because it could be used in 90% of all patients. All in all, toe pressure measurements are more useful to exclude CLI than to prove it.

Adult↗
PubMed2003

Comprehensive time-resolved MRI of peripheral vascular malformations.

OBJECTIVE: The purpose of this study was to evaluate the usefulness of MRI and MR angiography for the assessment of peripheral vascular malformations compared with the usefulness of conventional duplex sonography, venography, and arteriography. SUBJECTS AND METHODS. Nineteen patients (age range, 8-64 years; 11 males and eight females) with clinically diagnosed or suspected angiodyplastic abnormalities of the extremities were examined on a 1.5-T whole-body MR scanner. Using parameters based on a fast localizer sequence, we acquired transverse or coronal T1-, T2-, short tau inversion recovery (STIR), and contrast-enhanced T1-weighted images. Dynamic contrast-enhanced three-dimensional (3D) gradient-echo MRIs were acquired to determine the extent and type of the arteriovenous malformation for each patient. MR data sets were evaluated for lesion depiction, determination of the extent of the malformation, involvement of neighboring structures, vascular detail, and treatment planning. Results were compared with findings from duplex sonography, venography, and intraarterial digital subtraction angiography. RESULTS: All MRIs were of diagnostic quality and revealed 12 venous vascular malformations, four arteriovenous malformations, and three hemangiomas. The STIR sequence was helpful for determining the extent of the vascular malformation, which was often underestimated using contrast-enhanced 3D MR angiography alone, whereas dynamic contrast-enhanced 3D MR angiography was required for classifying the type of the lesion. MR angiography was inferior to conventional angiography for revealing vascular detail and for planning intervention. CONCLUSION: MRI and MR angiography appear to be valuable for the assessment of vascular malformations of the extremities. The protocol for imaging such malformations should combine dynamic contrast-enhanced 3D gradient-echo MRI with STIR sequences. However, digital subtraction angiography and venography are still required for definitive treatment decisions.

Adolescent↗
PubMed2002

Diameter of occluded superficial femoral arteries limits percutaneous recanalization: preliminary results.

PURPOSE: To explore if the diameter of an occluded superficial femoral artery (SFA) can predict the technical success of percutaneous recanalization. METHODS: Two hundred patients (151 men; mean age 57 +/- 16 years) suffering from peripheral arterial occlusive disease were evaluated with duplex ultrasonography to measure arterial diameters and percent diameter reduction. Seventy-nine (39.5%) patients had segmental or complete SFA occlusions that ranged in age from 2 to 26 months (median 11). The majority of occlusions (45, 57.0%) were < or =10 cm long (range 10-35). Percutaneous recanalization was performed in 71 patients using either conventional angioplasty or local low-dose thrombolysis with rtPA. RESULTS: Diameters of 79 unilaterally occluded SFAs at the level of occlusion were 4.5 +/- 1.4 mm versus 5.7 +/- 1.3 mm for the patent contralateral artery (p=0.055). None of the 121 patent SFAs had diameters < or =3.5 mm, but 12 (15%) of the 79 occluded SFAs did, and none of these could be recanalized. The sensitivity of the 3.5-mm cut point to predict recanalization failure was 44% (specificity 100%). CONCLUSIONS; Our data suggest that occluded SFAs with a diameter reduction to < or =3.5 mm are not suitable for percutaneous recanalization, as the original arterial lumen cannot be reconstructed.

Angioplasty, Balloon↗
PubMedDate not supplied

Sonographic correlate of stationary waves.

Stationary waves are a rare and inconsistent angiographic finding that has been attributed to various causes, including angiographic artifact. We present 2 cases of patients with arterial occlusion in whom sonographic examination revealed a correlate of stationary waves that was present on angiography. This report is, to our knowledge, the first to document the phenomenon of stationary waves using an imaging modality other than angiography. If the sonographic findings presented here are accepted as a correlate of stationary waves, the phenomenon of stationary waves can no longer be considered a specific angiographic finding, and theories attributing the phenomenon to an angiographic artifact must be rejected.

Adult↗
PubMedDate not supplied

Dyslipoproteinemia and peripheral arterial occlusive disease.

Peripheral arterial occlusive disease (PAOD) is common in older age. PAOD is associated with an increased risk of vascular events (eg, myocardial infarction or stroke). Therefore, the prevention and treatment of PAOD is important, especially at a time when the elderly population is increasing. There is an association between lipid abnormalities and the risk of developing PAOD. However, it is not yet definitively established that early intervention with lipid-lowering drugs prevents the development of PAOD. There is evidence that vascular events in patients with PAOD can be significantly reduced by statins and that the symptoms associated with PAOD are improved by this treatment. There is an urgent need for appropriately designed lipid-lowering trials in patients with PAOD.

Arterial Occlusive Diseases↗