P. Kalden

Dynamic contrast‐enhanced myocardial perfusion imaging using saturation‐prepared TrueFISP

To develop and test a saturation‐recovery TrueFISP (SR‐TrueFISP) pulse sequence for first‐pass myocardial perfusion imaging.

MRI Versus Helical CT for Endoleak Detection After Endovascular Aneurysm Repair

OBJECTIVE The objective of our study was to investigate the diagnostic accuracy of MRI and helical CT for endoleak detection. SUBJECTS AND METHODS Fifty-two patients underwent endovascular aneurysm repair with nitinol stent-grafts. Follow-up data sets included contrast-enhanced biphasic CT and MRI within 48 hr after the intervention; at 3, 6, and 12 months; and yearly thereafter. The endoleak size was categorized as < or = 3%, > 3% < or = 10%, > 10% < or = 30%, or > 30% of the maximum cross-sectional aneurysm area. A consensus interpretation of CT and MRI was defined as the standard of reference. RESULTS Of 252 data sets, 141 showed evidence for endoleaks. The incidence of types I, II, and III endoleaks and complex endoleaks was 3.2%, 40.1%, 8.7%, and 4.0%, respectively. The sensitivity for endoleak detection was 92.9%, 44.0%, 34.8%, and 38.3% for MRI, biphasic CT, uniphasic arterial CT, and uniphasic late CT, respectively. The corresponding negative predictive values were 91.7%, 58.4%, 54.7%, and 56.1%, respectively. The overall accuracy of endoleak detection and correct sizing was 95.2%, 58.3%, 55.6%, and 57.1% for MRI, biphasic CT, uniphasic arterial CT, and uniphasic late CT, respectively. CONCLUSION MRI is significantly superior to biphasic CT for endoleak detection and rating of endoleak size, followed by uniphasic late and uniphasic arterial CT scans. MRI shows a significant number of endoleaks in cases with negative CT findings and may help illuminate the phenomenon of endotension. Endoleak rates reported after endovascular aneurysm repair substantially depend on the imaging techniques used.

Quantification of shunt volumes in congenital heart diseases using a breath-hold MR phase contrast technique: comparison with oximetry

Aims: Comparison of breath-hold MR phase contrast technique in the estimation of cardiac shunt volumes with the invasive oximetric technique. Methods and Results: Seventeen patients with various cardiac shunts (10 ASD, 3 VSD, 1 PDA, 3 PFO) and five healthy volunteers were investigated using a 1.5 Tesla system. The mean flow velocity, the mean volume flow and the transverse area in the ascending aorta and the left and right pulmonary artery were measured using the MR phase contrast breath-hold technique (through plane, FLASH 2D-sequence, TR/TE 11/5 ms, phase length 106 ms, VENC 250 cm/s). The ratio of mean flow in the pulmonary (Qp: sum of mean flows in the left and right pulmonary arteries) and the systemic circulation (Qs: mean flow in the ascending aorta) was calculated and compared with invasively measured Qp:Qs ratios. Oximetry was performed within 24 h of the MR investigation. The non-invasive shunt measurement in the 17 patients showed a mean Qp:Qs ratio of 2.00 ± 0.86. Comparing the MR data with the invasively measured Qp:Qs showed a correlation coefficient of r = 0.91 (p < 0.001). Conclusion: Cardiac shunt volumes can be measured reliably using a shorter acquisition time with breath-hold MR phase contrast technique.

Magnetic resonance imaging of coronary artery occlusions in the navigator technique

Non-invasive assessment of coronary arteries is possible with magnetic resonance imaging (MRI). Respiratory gated MR coronary angiography is a new imaging technique that permits reconstruction of the coronary arteries based on a three-dimensional (3D) data set obtained from the free-breathing patient. In this study, respiratory gated MR angiography (MRA) was performed to assess coronary artery occlusions. MRI was performed in 25 patients who had been referred for conventional coronary angiography because of suspected coronary artery disease. Coronary artery occlusion was evaluated in the proximal and middle vessel segments after multiplanar coronary reconstruction of the MR images. Five patients were excluded from the study; in the remaining 20 patients 120 coronary artery segments were analyzed. Good image quality could be obtained for 85% of the segments. Eighteen of the 24 occlusions were confirmed by MRI, the overall sensitivity was 75% and the specificity was 100%. The best results were found in the proximal left anterior descending (LAD) and descending parts of the right coronary artery (RCA), where all occlusions were confirmed. These results showed that coronary artery occlusions can be detected in the proximal and middle LAD and RCA using 3D respiratory gated MRA. Further technical improvements, especially in spatial resolution, are necessary before MRA can become a reliable diagnostic tool in the non-invasive evaluation of coronary arteries.

Late improvement of regional wall motion after the subacute phase of myocardial infarction treated by acute PTCA in a 6-month follow-up.

BACKGROUND The aim of this follow-up study was to investigate the late effects of acute coronary angioplasty (PTCA) on regional wall motion after the subacute phase of myocardial infarction (MI). METHODS AND RESULTS Seventeen patients were investigated initially at a median of 11 days and again at 6 months after acute PTCA for myocardial infarction (< 8 hours after onset of symptoms) by cardiac magnetic resonance imaging. Corresponding short-axis slices encompassing the left ventricle (LV) were acquired using a standard cine MR for regional wall motion analysis and using delayed contrast enhanced magnetic resonance imaging (ceMRI) for infarct size quantification. The infarct size was similar in the subacute phase and the 6 month follow-up (20.8 and 21.9%, respectively; n.s.). Regional wall motion improved significantly in the area of hyperenhancement [percentage wall thickening (PWT) 21.9% and 37.9%, p < 0.05] in contrast to remote normal myocardium (46.4% and 38.4%; n.s.). Regional wall motion was significantly poorer in transmural compared with nontransmural MI in the subacute stage, and a late improvement could only be observed in transmural MI. CONCLUSION Transmural areas of hyperenhancement displayed significant late long-term improvement of regional wall motion after acute PTCA, possibly related to prolonged stunning compared with nontransmural areas.

Diagnostic value of routine clinical parameters in acute myocardial infarction: a comparison to delayed contrast enhanced magnetic resonance imaging

Aims: Contrast enhanced magnetic resonance imaging (ceMRI) has been shown to reliably identify irreversible myocardial injury. The aim of this study was to compare the findings on ceMRI with routine clinical markers of myocardial injury in patients with acute myocardial infarction (MI). Methods and results: Twenty-four patients with acute MI were investigated at 1.5 T. The global myocardial function was analysed with a standard cine MR protocol and a stack of short axis slices encompassing the entire left ventricle. Corresponding short axis slices were acquired for delayed ceMRI 15–20 min after the administration of 0.2 mmol gadolinium–DTPA/kg body weight. Mass of hyperenhancement and peak creatine kinase release (peak CK) was determined for each patient. The presenting 12-lead ECG was analysed for ST-elevation on admission and later development of Q-waves. Mass of hyperenhancement correlated moderately well to peak CK (r = 0.65, p < 0.01) and endsystolic volume index (r = 0.55, p < 0.01). Mass of hyperenhancement was inversely correlated to ejection fraction (r = −0.50, p = 0.02). Neither the presence of ST elevation on the admission ECG nor the later development of Q-waves did relate to the transmural extent of hyperenhancement and to the mass of hyperenhancement. Conclusion: Mass of hyperenhancement significantly correlates to global myocardial function and to peak CK. However, there is no relationship between the findings in ceMRI and 12-lead ECG abnormalities on admission suggesting an advantage of ceMRI in defining transmural extent and depicting small areas of necrosis.

MR-Angiographie und Flussmessung in Koronararterien und koronaren Bypassgefäßen

Better MR image quality of coronary arteries and coronary grafts is the product of increased spatial and temporal resolution. Breathing artifacts could be reduced by implementing breath-holding and navigator techniques. With these developments normal coronary arteries can often be imaged reliably. Several trials have been performed in order to test the reliability of MR angiography to detect coronary artery stenosis. But up to now, sensitivity and specificity have proven to be too low to introduce these techniques in clinical routine. The patency of coronary grafts can be detected reliably using different MR techniques. Coronary flow reserve can be measured using the MR phase contrast technique. This noninvasive approach was tested in diseased coronary arteries and in graft stenoses. A reduced MR coronary flow reserve corresponded to reduced flow reserve measured invasively. Measurement of MR flow reserve in normal and diseased coronary grafts revealed significant differences (3.3±0.4 vs. 1.3±0.2). Die neuen Techniken der Magnetresonanztomographie ermöglichen eine verbesserte örtliche und zeitliche Auflösung und eine deutliche Reduktion der Störung der Bildgebung durch die Atembewegung. Dadurch ist die Bildgebung der nativen Koronaraterien und der koronaren Bypassgefäße erheblich verbessert worden, und normale Koronararterien können häufig gut dargestellt werden. Bei der Diagnose von Koronarstenosen haben die bisherigen klinischen Studien keine ausreichende Zuverlässigkeit gezeigt. Die Offenheitsbestimmung von Bypassgefäßen ist jedoch zuverlässig möglich. Die MR-Phasenkontrastmethode ist geeignet, die koronare Flussreserve in nativen Koronararterien und in koronaren Bypassgefäßen zu messen. Die Ergebnisse der MR-Messung der koronaren Flussreserve in normalen und stenosierten Koronararterien korrespondieren mit den Ergebnissen der invasiven Dopplermessung. Angiographisch normale und stenosierte koronare Bypassgefäße unterscheiden sich signifikant hinsichtlich der MR-Flussresreve (3,3±0,4 vs. 1,3±0,2).

Möglichkeiten und Perspektiven der nichtinvasiven Bypassdiagnostik: Vergleich verschiedener kernspintomographischer Methoden mit der konventionellen Koronarangiographie

ZusammenfassungZiel: Das Studienziel war die kernspintomographische Evaluierung koronarer Bypassgefäße mit der Hast-, Fisp-3-D- und Navigatorsequenz unter besonderer Berücksichtigung der distalen Bypassanastomose. Patienten: Eingeschlossen wurden 25 Patienten mit 63 Bypassgefäßen und insgesamt 78 distalen Anastomosen. Ergebnisse: Mit der Haste- und der Fisp-3-D-Sequenz konnten 44 der 47 offenen und 14 der 16 verschlossenen Bypasses korrekt beurteilt werden, die Sensitivität und Spezifität betrugen 94% und 88%. Überlegen war die Haste-Sequenz (43/54) der Fisp-3-D-Sequenz (38/54) in der Beurteilung der distalen Anastomosen. Die Navigatorsequenz wies aufgrund der eingeschränkten Bildqualität lediglich eine Sensitivität von 74% und eine Spezifität von 63% auf. Schlussfolgerung: Mit der Kernspintomographie ist eine nichtinvasive Evaluierung koronarer Bypassgefäße möglich, wobei die Haste-Sequenz in der Beurteilung distaler Bypassanteile überlegen ist. Eine Verbesserung der Aussagekraft der Methode ist durch den Einsatz gefäßständiger Kontrastmittel sowie durch eine Verbesserung der räumlichen Auflösung zu erwarten.AbstractObjective: The aim of the study was to evaluate the patency of coronary artery bypass grafts (CABGs) with different MR imaging techniques. Patients: 25 patients with 63 bypass grafts and a total of 78 distal anastomoses were studied at a 1.5-Tesla scanner. A 2-D T2-weighted breath-hold turbo spin echo sequence (Haste), a 3-D breath-hold contrast-enhanced MR angiography sequence (Fisp-3-D), and 3-D angiography sequence in navigator techniques were used. Results: With the Haste and Fisp-3-D sequences, 44 of the 47 patent and 14 of the 16 occluded grafts were recognized, the sensitivity and specificity were 94% and 88%, respectively. With the Haste sequence, 80% (43/54) of the distal anastomoses were seen in good image quality, and with the Fish-3-D sequence 70% (38/54). The navigator sequence showed less sensitivity and specificity (74% and 63%, respectively). Conclusion: The patency of CABGs can be evaluated noninvasively with the Haste and the Fisp-3-D angiography sequences. Better results can be expected with the development of a blood-pool contrast medium and an improvement of the spatial resolution.

Kernspintomographische Flussquantifizierung in Koronargefäßen zur Evaluierung hochgradiger Koronarstenosen

Zusammenfassung.Ziel: Zweck der Studie war die Bestimmung des intrakoronaren Blutflusses im Verhältnis zum Aortenfluss bei Patienten mit hochgradigen Koronarstenosen. Die MR-Flussmessung wurde bei 15 Patienten in 18 Koronargefäßen durchgeführt. Zur Flussmessung eine segmentierte 2-D-Flash-Sequenz mit einer zeitlichen Auflösung von 110 bzw. 125 ms verwendet. Der mittlere Koronarfluss im Verhältnis zum aortalen Fluss war bei Patienten mit hochgradigen Koronarstenosen signifikant (p < 0,001) erniedrigt. Die MR-Phasenkontrastmethode ermöglicht eine genaue Bestimmung des Blutflusses in Koronargefässen und in Korrelation zum Aortenfluss eine Aussage über hochgradige Koronarstenosen. Weiterentwicklungen der Methode müssen eine Verbesserung der räumlichen und zeitlichen Auflösung zum Ziel haben.Abstract.Aim: The purpose of the study was to evaluate the accuracy of velocity encoded cine MR imaging for the determination of blood flow in patients with coronary artery stenoses. Flow measurements were performed in 18 coronary arteries in 15 patients. We used velocity-encoded k-space segmented gradient echo sequences with a temporal resolution of 110–125 ms. The mean coronary flow in correlation to aortic flow was significantly reduced in patients with severely stenosed arteries. Velocity-encoded MR imaging enables determination of flow in coronary arteries and in correlation of the aortic flow the detection of coronary artery stenoses. Future developments should aim at the improvement of spatial and temporal resolution of the method.

Intraoperative Flußmessung koronarer Bypassgefäße mit der Ultraschall-Transit-Zeit-Methode

The aim of the study was to compare the mean and maximum flow and the flow pattern of coronary vein grafts (SVG) supplying target vessels of the inferior and lateral wall with internal mammary (IMA) grafts to the left anterior descending artery (LAD). In 21 patients 25 bypass grafts (13/25 SVG, 12/25 IMA) were investigated. Using the transit time ultrasound method, flow was measured every 5 ms and the flow data of 60 s were acquired. The flow pattern showed significant differences between both graft types during their cycle. IMA grafts showed only one peak occurring after 22.1±12.3% and the second after 63.4±15.5% of their cycle. The mean flow was not different in both graft types (IMA: 45.3±27.0 ml/min and SVG: 41.8±26.7 ml/min, p = n. s.) as it was the case for the maximum flow (IMS: 98.4±45.2 ml/min and SVG: 75.7±55.4 ml/min, p = n. s.). In conclusion, there is a different flow pattern for both graft types concerning the number and the occurrence of flow-peaks in the bypass cycle. The mean and peak flow showed no significant difference. Ziel der Studie war es zu untersuchen, ob typische Flußcharakteristika für A.-mammaria-Bypassgefäße zum Ramus interventricularis (IMA) und venöse Bypassgefäße zu Zielgefäßen der Lateral- und Hinterwand des Herzens bestehen (ACVB). Bei 21 Patienten wurden insgesamt 25 Bypassgefäße untersucht (12/25 IMA, 13/25 ACVB). Mit der Ultraschall-Transit-Zeit-Methode wurden für 60 s Flußdaten mit einer zeitlichen Auflösung von 5 ms akquiriert. Signifikante Unterschiede zeigten sich bei den Flußmustern der beiden Bypasstypen. Die A.-mammaria-Bypassgefäße wiesen nur eine Flußspitze nach im Mittel 45,5±18,6& ihres systolisch-diastolischen Zyklus auf. Bei den venösen Bypassgefäßen traten zwei Flußspitzen auf, eine nach 22,1±12,3% und eine nach 63,4±15,5% des systolisch-diastolischen Zyklus. Der Vergleich der beiden Bypasstypen zeigte keinen Unterschied hinsichtlich des mittleren Flusses (IMA-Bypassgefäße: 41,8±26,7 ml/min vs. ACVB: 45,3±27,0 ml/min, p = n. s.) und des maximalen Fllusses (IMA-Bypassgefäße: 75,7±55,4 ml/min vs. ACVB: 98,4±45,2 ml/min, p = n. s.). A.-mammaria-Bypassgefäße zum RIVA zeigten nur eine Flußspitze nach 45% ihres Zyklus. Venöse Bypassgefäße zu Zielgefäßen der Lateral- und Hinterwand des Herzens hatten zwei Flußspitzen, eine nach 22% und eine nach 63% ihres Zyklus. Der mittlere und maximale Fluß war in beiden Bypasstypen nicht unterschiedlich.