[German Radiological Society and the Professional Association of German Radiologists position paper on coronary computed tomography: clinical evidence and quality of patient care in chronic coronary syndrome]. / Positionspapier von DRG und BDR zur Computertomographie des Herzens: Klinische Evidenz und Versorgungsqualität beim chronischen Koronarsyndrom.

This position paper is a joint statement of the German Radiological Society (DRG) and the Professional Association of German Radiologists (BDR), which reflects the current state of knowledge about coronary computed tomography (CT). It is based on preclinical and clinical studies that have investigated the clinical relevance as well as the technical requirements and fundamentals of cardiac computed tomography.

Long term data of endovascularly treated patients with severe and complex aortoiliac occlusive disease.

AIM: This paper presents the recent data of the largest series (20 patients) of endovascularly treated patients and the first long term data of 9 patients with severe aortoiliac occlusive disease. METHODS: Between 2003 and 2012, 20 consecutive patients (14 men; 70 %) with Leriche syndrome underwent recanalization with solely endovascular means at our centre. The treatment strategy comprised the antegrade (transbrachial) recanalization of the occluded segments followed by retrograde (transfemoral) angioplasty with selective stent placement in the infrarenal aorta and primary stent placement in the iliac arteries. Before discharge, after 30 days and every year after the procedure, a clinical, as well as a duplex ultrasonographic examination including measurement of the ankle-brachial index was done. RESULTS: Bilateral success was achieved in 17 patients (85%). Unilateral success was achieved in three patients (15%). In one patient (5%) an early reocclusion of the stented segments occurred, necessitating bypass grafting. In nine patients long term data were evaluated. Here, the ankle brachial index (ABI) significantly increased (0.85 ± 0.15 vs. 0.51 ± 0.11 at baseline; P=0.002). Compared to baseline, the difference in the distribution of Rutherford category and the improvement of walking capacity were statistically significant (P=0.0006, P=0.01, respectively). CONCLUSION: This study shows the feasibility of solely endovascular management of severe aortoiliac occlusive disease with a high rate of success and low rate of complications. Significant clinical improvement of patients in long term follow up makes the endovascular approach a viable alternative to open surgery.

[Low-dose CT in neutropenic patients with fever of unknown origin]. / Niedrigdosis-CT der Lunge bei neutropenischen Patienten mit unklarem Fieber.

PURPOSE: To define the value of low-dose multislice CT in a clinical setting for early detection of pneumonia in neutropenic patients with fever of unknown origin. MATERIALS AND METHODS: Thirty-five neutropenic patients suffering from fever of unknown origin with normal chest X-ray underwent unenhanced low-dose CT of the chest (120 kV, 10 eff. mAs, collimation 4 x 1 mm) using a multislice CT scanner. Axial und frontal slices with a thickness of 5 mm were calculated. If no pneumonia was found, standard antibiotics were given and a repeated examination was performed if fever continued. In case of pneumonia, antimycotic therapy was added and a follow-up CT was performed within one week. Regression or progression of pneumonia at follow-up served as evidence of pneumonia; lowering of fever within 48 h or inconspicuous follow-up CT was regarded as absence of pneumonia. RESULTS: Ten of 35 patients had pneumonic infiltration, which decreased or increased on follow-up CT in 3 and 6 patients, respectively. One patient revealed leucemic infiltration by bronchoalveolar lavage. Twenty-five of 35 patients had no evidence of pneumonia. Twenty of these patients were free of fever within 48 h under antibiotics; one patient died due to his basic illness. Out of 4 patients with persisting fever, 3 patients had no pneumonia on repeated examination; one patient showed disseminated micronodular infiltration. Frontal reconstructions helped to differentiate infiltration from atelectasis in 4 patients. Sensitivity and specificity for the detection of pneumonia at the first examination were 90 % and 96 %, negative predictive value was 96 %. CONCLUSION: Low-dose multislice CT should be performed in neutropenic patients having a fever of unknown origin and normal chest X-ray.

[Individualized dose requirement for spiral-CT analysis of the abdomen]. / Individueller Dosisbedarf bei Spiral-CT-Untersuchungen des Abdomens.

PURPOSE: To search for individualized scan protocols that provide adequate diagnostic information with minimal radiation exposure for abdominal CT in adults. MATERIAL AND METHODS: Beginning with standard settings (120 kVp, 200 mA, 0.75 s, CTDI (w = 11.7 mGy)), which are in the lowest quartile of the actual German radiation dose survey, 119 adults were examined using a single-row detector helical CT with 8 mm collimation and a pitch of 1.5. The individualized scan protocol was defined by repeating the reference scan up to 3 times with different radiation doses following a predefined iteration scheme. The image qualities with standard dose and with individualized dose were assessed independently by 3 radiologists blinded to the exposure parameters. The individualized dose was correlated with the diameter of the patients. RESULTS: The patient diameters varied from 16 to 35 cm and correlated with individualized radiation doses CTDI (w) from 6.4 to 17.6 mGy. We found an exponential correlation (y = 52.3 x e (0.05 x); r(2) = 0.48; p < 0.001) between required tube current (mA) and a. p. diameter (cm) in the epigastric region in adults. CONCLUSION: Maintaining constant exposure parameters results in unnecessary radiation exposure in patients with a diameter of less than 27 cm measured in anterior-posterior direction in the epigastric area. The radiation exposure in adult abdominal CT can be reduced up to 45 % by individualized selection of the tube current without adversely affecting diagnostic performance.

Auto-SENSE view-sharing cine cardiac imaging.

Cardiac MR cine imaging during breath hold is a compromise between spatial and temporal resolution and duration of breath hold. Especially for sick patients who have problems holding their breath, a short acquisition time is mandatory for all sequences. A combination of Auto-SENSE parallel imaging and view-sharing was implemented for fast cine imaging of the human heart and applied to healthy volunteers. Compared to conventional Fourier imaging, data acquisition could be accelerated by a factor of 3.6. Neither a pre-scan nor additional lines in k-space are required to generate the sensitivity maps in Auto-SENSE.

[Quantitative analysis of left ventricular wall motion with MRI tagging]. / Quantitative Analyse der linksventrikulären Wandbewegung mit MR-tagging.

PURPOSE: The purpose of this study was to establish a quantification of different parameters of left ventricular wall motion from tagged MR images. This evaluation method was to be applied to characterize the physiological contraction cycle and to determine pathophysiological changes. MATERIALS AND METHODS: Myocardial tagging was performed at a basal, a mid-ventricular and an apical level of the left ventricle. A suitable software was programmed for the automatic quantification of rotation, contraction and circumferential shortening. The evaluation method was used in 8 healthy volunteers, 13 patients suffering from aortic stenosis before and one year after surgery and in 10 patients with myocardial infarction before and after revascularization. RESULTS: The software allows the quantification of left ventricular wall motion by assessment of rotation, contraction and circumferential shortening. In the healthy volunteers, there was a wringing motion with opposite rotation of base and apex of the heart. Before valve replacement, patients with aortic stenosis showed significantly increased apical rotation and torsion. One year after surgery, left-ventricular torsion had normalized. In patients with myocardial infarction, circumferential shortening increased after revascularization. CONCLUSION: The quantification of left ventricular wall motion using tagged MR images allows to characterize and follow-up changes of left ventricular wall motion in various diseases of the heart.

[Direct MR arthrography of the wrist- value in detecting complete and partial defects of intrinsic ligaments and the TFCC in comparison with arthroscopy]. / Direkte MR-Arthrographie des Handgelenkes - Wertigkeit im Nachweis von Komplett- und Partialdefekten der intrinsischen Ligamente und des TFCC im Vergleich zur Arthroskopie.

PURPOSE: To assess the value of two-compartment magnetic resonance (MR) wrist arthrography in comparison with diagnostic arthroscopy for the evaluation of defects of the triangular fibrocartilage complex (TFCC) and intrinsic ligaments in patients with refractory wrist pain. The direct MR arthrographies were evaluated following arthroscopic classification with consideration of complete and partial defects. The distinction between these types of lesions has clinical implications for treatment procedures such as cast immobilization, arthroscopic debridement, surgical repair or partial intercarpal arthrodesis. MATERIALS AND METHODS: Seventy-five patients (25 female, 50 males, mean age 38.3 years) who suffered from refractory wrist pain without radiography evidence of carpal instability underwent two-compartment wrist MR arthrography. Under aseptic conditions a solution of gadopentate dimeglumine and iodinated contrast agent (concentration 2.5 mmol/l) was injected into the radiocarpal and midcarpal joints under fluoroscopy guidance. Using a scanner of 1.5 T field strength and a wrist-coil following sequences were acquired: coronary and sagittal T (1)-weighted spin-echo (SE) sequences (TR 500 ms, TE 25 ms, matrix 512 x 512.3 mm) and coronary fast low angle shot (FLASH) 3D sequences (TR 24 ms, TE 11 ms, matrix 256 x 256, 1.5 mm, flip angle 50 degrees). All patients underwent subsequent arthroscopy of the wrist. The direct MR arthrographies were evaluated retrospectively by two observers experienced in the diagnosis of wrist pathology. They were not aware of the clinicial, arthrographic and arthroscopic findings. Pathology of the scapholunate ligament was classified according to the guidelines of the German Society of Hand Surgery (DGH), lesions of the lunotriquetral ligament according to Hempfling and lesions of the TFCC according to Palmer. RESULTS: Twenty-five complete and 47 partial defects were detected arthroscopically (TFCC: 21/20, scapholunate ligament: 3/18, lunotriquetral ligament: 1/9). The TFCC showed a higher prevalence for degenerative lesions (11 type 2C-lesions and 20 type 2A/B lesions) than for traumatic lesions (5 type 1A lesions, 5 type 1D lesions). For direct MR arthrography, the obtained sensitivities and specificities in assessing complete defects were 96 % and 99.6 % (T (1)-weighted SE) and 92 % and 100 % (FLASH 3D), respectively. For all partial defects, sensitivities and specificities were 68.1 % and 93.3 % (T (1)-weighted SE) and 63 % and 96.1 % (FLASH 3D), respectively. For depicting partial defects of the scapholunate ligament the T (1)-weighted SE sequence (83.3/95.5 %) was superior to the FLASH 3D sequence (64.7/96.6 %), p < 0.05. For the evaluation of the TFCC (T (1)-weighted SE: 65/94.4 %, FLASH 3D: 70/94.6 %) and the lunotriquetral ligament (T (1)-weighted SE: 44/89.4 %, FLASH 3D: 44 /96.7 %), direct MR arthrography showed an insufficient correlation with arthroscopy. CONCLUSION: Direct MR arthrography proved to be of equal value compared with diagnostic arthroscopy in detecting complete defects of the intrinsic ligaments and the TFCC. The method has the potential of replacing diagnostic arthroscopy for the evaluation of the intrinsic ligaments and the TFCC. The T (1)-weighted SE sequence appeared to be superior to the FLASH 3D sequence in evaluating partial defects of the scapholunate ligament. Direct MR arthrography did not reliably detect partial defects of the TFCC and the lunotriquetral ligament.

Detection of myocardial viability in acute infarction using contrast-enhanced (1)H magnetic resonance imaging.

BACKGROUND: Reperfusion strategies salvage myocardium at risk in acute myocardial infarction (MI). This clinical study was performed to determine whether areas without evidence of delayed MRI contrast enhancement in MI correspond to viability by means of percent systolic wall thickening (%SWT) and enddiastolic wall thickness (EDWT) in chronic infarction. METHODS: Twenty MRI studies were performed in ten patients within 6 days of MI and 3 months post-MI. On a segmental basis the percentage of viable myocardium as defined by contrast-enhanced MRI (no delayed MRI contrast enhancement) in acute MI was measured and was compared with %SWT and EDWT in chronic MI. RESULTS: Of the 1718 segments in acute infarction in which the percentage of viable myocardium was measured 1333 were found to be completely viable by means of contrast-enhanced MRI (no delayed MRI contrast enhancement). All of these segments revealed %SWT on day 90 post-MI, and 97% of segments were viable by means of an EDWT of more than 5.5 mm. In 85 segments the proportion of viable myocardium was 50-99% (mean 56+/-8%), with 92% segments found to be viable by means of %SWT and 92% by EDWT, and of 156 segments with viable myocardium between 1-49% (36+/-8%) 79% were found to be viable by means of %SWT and 82% by EDWT. Corresponding proportions of 144 segments with transmural delayed MRI contrast enhancement in acute MI were 45% and 17%. CONCLUSIONS: In acute reperfused MI viable myocardium as delineated by contrast-enhanced MRI is correlated with clinical parameters of viability. Delayed MRI contrast enhancement resolves nontransmural MI and may become a valuable clinical tool when planning revascularization procedures.

[Diagnostic impact of multiplanar reformations in multi-slice CT of laryngeal and hypopharyngeal carcinomas]. / Diagnostischer Nutzen multiplanarer Reformationen bei der Mehrschicht-CT von Larynx- und Hypopharynxkarzinomen.

PURPOSE: Assessment of the diagnostic value of multiplanar reformations (MPR) in multi-slice computed tomography (MSCT) by comparing relevant anatomic structures of the larynx and hypopharynx. MATERIALS AND METHODS: MSCT of the neck was performed in 69 consecutive patients (including 30 laryngeal and 12 hypopharyngeal carcinomas). From a 4 x 1.0 mm collimation data set, 3.0-mm and 1.25-mm axial slices as well as 3-mm coronal and sagittal slices were reconstructed. Using the histological examination as gold standard, sensitivity and specificity regarding tumor infiltration for all relevant anatomical structures of the larynx and the hypopharynx were determined for each reconstruction and compared with the McNemar test. Moreover, 42 patients with laryngeal and/or hypopharyngeal carcinoma were subjectively evaluated to determine whether the respective reconstructions enables a better topographical visualization of the tumor in relation to surrounding structures and, furthermore, whether this has an influence on the therapeutical strategy (operation versus radiation therapy, type of operation, surgical approach). RESULTS: Sensitivities and specificities were not significantly different between the reconstructions. However, coronal and sagittal MPR provided a better topographical visualization of the tumor in 14 of 42 (33 %) of the patients, and influenced the therapeutical strategy in 8 of 42 (19 %) of the patients. A lowered signal-to-noise ratio impeded the evaluation of the relatively thin 1.25-mm axial slices in more than 23 % of the cases. CONCLUSION: Besides the 3-mm axial slices, coronal and sagittal MPR can improve the topographical visualization of laryngopharyngeal tumors and are recommended for preoperative MSCT of laryngeal and/or hypopharyngeal carcinomas. Additionally reconstructed 1.25-mm axial slices can be discarded since they do not hold a higher value compared to 3-mm axial reconstructions.

[Primary diagnosis of coronary artery disease by MRI and CT]. / Primärdiagnostik der koronaren Herzerkrankung mit MRT und CT.

Invasive coronary angiography is the gold standard for the primary diagnosis of coronary artery disease (CAD). At most, only every other examination leads to revascularization therapy. The other coronary angiographies could be replaced by non-invasive examinations. Diagnosing CAD by cardiac MRI and CT can utilize three different strategies: detection of coronary calcifications; imaging of coronary artery stenoses; and detection of restricted myocardial perfusion reserve. Applications are coronary calcification scoring by CT, coronary angiography by MRI or CT, stress cine MRI, and stress perfusion MRI. All these methods are currently used clinically because of their high negative predictive value, i.e., a normal result mostly rules out a hemodynamically significant CAD. For a reasonable implication in clinical practice, however, the pre-test probability must be considered to avoid needless examinations. High pre-test probability invariably demands invasive coronary angiography for planning or performing revascularization therapy. Intermediate pre-test probability, on the contrary, justifies to defer further imaging studies if MRI or CT is normal. Thus, adequate selection of patients for cardiac MRI and CT may reduce the number of invasive coronary angiographies in the future.

[Interindividual-variability of the analysis of regional myocardial wall function after myocardial infarction and revascularization]. / Interindividuelle-Variabilität der regionalen myokardialen Wandfunktionsanalyse nach Herzinfarkt und Revaskularisierung.

PURPOSE: The gold standard for diagnosis myocardial viability is the functional recovery after revascularization. Aim of the study was to compare (1) qualitative analysis and (2) quantitative wall thickening by cine MRI and (3) circumferential shortening by tagged MRI the analysis of regional wall function of an infarcted area before and after revascularization. MATERIAL AND METHODS: Ten patients (age 60 +/- 11 years) with infarct-associated regional left ventricular wall motion abnormalities were examined by cine and tagged MRI on average two weeks after the myocardial infarction and re-examined three months after revascularization. Eight healthy volunteers served as a control for tagged MRI. Interobserver-variabilities of two observers were calculated using the kappa-statistics for grading of wall motion abnormalities as well as for detection of functional recovery by qualitative analysis, measurement of wall thickening of cine MRI, and measurement of circumferential shortening by tagged MRI, respectively. RESULTS: Grading of wall motion abnormalities revealed interobserver-variabilities of the study and control group of kappa = 0.8 and kappa = 0.84, kappa = 0.02 and kappa = 0.5, and kappa = 0.1 and kappa = 0.17 for qualitative analysis, wall thickening analysis and measurement of circumferential shortening, respectively. The interobserver-variability for the definition of wall motion recovery was kappa = 0.8 for all three methods. CONCLUSION: Qualitative analysis of wall motion abnormalities has the lowest interobserver-variability for the grading of wall motion abnormalities. The interobserver-variabilities of qualitative and quantitative analysis are comparable for the diagnosis of regional wall motion recovery. Thus, qualitative analysis of cine MRI can be used for grading regional wall motion in clinical studies.

Metallic stents and plastic endoprostheses in percutaneous treatment of biliary obstruction.

BACKGROUND: In the light of the clinical controversy whether metallic stents or plastic endoprostheses should be used in the percutaneous treatment of biliary obstruction we retrospectively evaluated our experience with both drainage-systems. METHODS: 71 patients (mean age 68 +/- 12 years) underwent a total of 81 interventions and received either plastic endoprostheses (11.5 or 12 French diameter; N = 57/81) or metallic stents (N = 24/81). RESULTS: Drainage insertion was technically successful in all of the 71 patients. There was no procedure-related mortality, but a 30-day mortality of 15 % (N = 11). Overall, 27 complications occurred in 81 interventions with a statistically significant higher complication-rate in plastic endoprostheses (39 %; N = 21/54) compared to metallic stents (22 %; N = 6/27). The average patency of the drainage-systems was 166 +/- 341 days (range 1-2,705 days) and did not differ significantly between the drainage-subtypes. Incidence of complications and a further increase in serum bilirubin following intervention was associated with a higher drainage occlusion-rate and reduced survival, irrespective of the drainage-system used. CONCLUSIONS: Percutaneous transhepatic treatment of biliary obstructions with internal drainages is a reliable therapy. The overall complication-rate of metallic stents was lower compared to plastic endoprostheses; however, no significant differences were found with respect to drainage patency or success-rate.

Quantitative analysis of energy metabolism in human muscle using SLOOP 31P-MR-spectroscopy.

OBJECTIVE: Energy metabolism is vital for regular muscle function. In humans, in-vivo analysis using (31)P-MR-spectroscopy (MRS) is mostly restricted to semiquantitative parameters due to technical demands. We applied Spatial Localization with Optimal Pointspread Function (SLOOP) for quantification in human skeletal and cardiac muscle. SUBJECTS/METHODS: 10 healthy volunteers and 4 patients with myotonic dystrophy type 1 were examined using a 1.5 T system (Magnetom VISION) and chemical shift imaging (CSI) for data collection. Concentrations of PCr, ATP and Pi as well as PCr/ATP ratios were calculated by SLOOP. RESULTS: Concentrations of PCr, ATP and Pi were 29.9 +/- 3.4, 7.1 +/- 0.9 and 5.7 +/- 1.2 [mmol/kg] in normal skeletal muscle, corresponding to previously published studies. Two of the patients with a duration of disease longer than 10 years and a pronounced muscle weakness showed a significant decrease of PCr and ATP in skeletal muscle below 10 and 5 mmol/kg. One of these patients had an additional reduction of PCr in cardiac muscle. CONCLUSIONS: With MRS and SLOOP, a more accurate quantitative assessment of metabolism is now available in skeletal and cardiac muscle. Longitudinal studies of larger patient groups will allow to better describe the metabolic disorder in muscle disease over time. Moreover, these techniques offer a new way to quantify treatment effects in future trials.

Time course of contrast enhancement patterns after Gd-BOPTA in correlation to myocardial infarction and viability: a feasibility study.

Our objective was to analyze contrast enhancement patterns (CEP) and their time course after myocardial infarction (MI) following injection of Gd-BOPTA in correlation with recovery of regional function. Seven patients with subacute MI (18 +/- nine days) were examined before, as well as three and six (n = six) months after, revascularization of the infarct-related artery. Regional wall motion abnormalities were assessed by cine-MRI, and repetitive images of one representative slice were acquired up to 45 minutes after 0.05 mmol/kg Gd-BOPTA using a T1-w TSE-sequence. Two patients showed mid-wall/subendocardial, one patient subendocardial enhancement of MI associated with mechanical improvement after revascularization. Three patients without improvement revealed a mid-wall hypoenhanced zone within the first five minutes after injection, which was unchanged at follow-up. One patient with partial functional improvement showed transmural enhancement and a mid-wall hypoenhanced zone in adjacent areas. With this feasibility study, we concluded that mid-wall and/or subendocardial enhancement after Gd-BOPTA was associated with viable myocardium, whereas detection of microvascular obstruction correlating with scar formation is suggested by mid-wall hypoenhancement within the first five minutes after injection.

[31P-MR spectroscopy of all regions of the human heart at 1.5 T with acquisition-weighted chemical shift imaging]. / 31P-MR-Spektroskopie aller Wandabschnitte des menschlichen Herzens bei 1,5 T mit akquisitionsgewichteter Chemical-shift- Bildgebung *

AIM: Aim of this study was to show whether or not acquisition-weighted chemical shift imaging (AW-CSI) allows the determination of PCr and ATP in the lateral and posterior wall of the human heart at 1.5 T. METHODS: 12 healthy volunteers were examined using a conventional chemical shift imaging (CSI) and an AW-CSI. The sequences differed only in the number of repetitions for each point in k space. A hanning function was used as filter function leading to 7 repetitions in the center of the k space and 0 in the corners. Thus, AW-CSI had the same resolution as the CSI sequence. The results for both sequences were analyzed using identically positioned voxels in the septal, anterior, lateral and posterior wall. RESULTS: The determined averaged AW-CSI signal to noise ratios were higher for PCr by a factor of 1.3 and for ATP by 1.4 than those of CSI. The PCr/ATP ratios were higher by a factor of 1.2 - 1.3 and showed a smaller standard deviation in all locations for AW-CSI. The mean PCr/ATP ratios determined by AW-CSI of septal, lateral and posterior wall were almost identical (1.72 - 1.76), while it was higher in the anterior wall (1.9). CONCLUSIONS: The reduced contamination in AW-CSI improves the signal to noise ratio and the determination of the PCr/ATP ratio in cardiac (31)P spectroscopy compared to CSI with the same resolution. The results in volunteers indicate that AW-CSI renders (31)P spectroscopy of the lateral and posterior wall of the human heart feasible for patient studies at 1.5 T.

Assessment of myocardial infarction in humans with (23)Na MR imaging: comparison with cine MR imaging and delayed contrast enhancement.

PURPOSE: To demonstrate the feasibility of sodium 23 ((23)Na) magnetic resonance (MR) imaging for assessment of subacute and chronic myocardial infarction and compare with cine, late enhancement, and T2-weighted imaging. MATERIALS AND METHODS: Thirty patients underwent MR imaging 8 days +/- 4 (subacute, n = 15) or more than 6 months (chronic, n = 15) after myocardial infarction by using a (23)Na surface coil with a double angulated electrocardiogram-triggered three-dimensional gradient-echo sequence at 1.5 T. In addition, cine, inversion-recovery gradient-echo, and, in the subacute group, T2-weighted images (n = 9) were obtained. Myocardial infarction mass was depicted as elevated signal intensity or wall motion abnormalities and expressed as a percentage of total left ventricular mass for all modalities. Correlations were tested with correlation coefficients. RESULTS: All patients after subacute infarction and 12 of 15 patients with chronic infarction had an area of elevated (23)Na signal intensity that significantly correlated with wall motion abnormalities (subacute; r = 0.96, P <.001, and chronic; r = 0.9, P <.001); three patients had no wall motion abnormalities or elevated (23)Na signal intensity. Only 10 patients in the subacute and nine in the chronic group revealed late enhancement; significant correlation with (23)Na MR imaging occurred only in subacute group (r = 0.68, P <.05). Myocardial edema in subacute infarction correlated (r = 0.71, P <.05) with areas of elevated (23)Na signal intensity but was extensively larger. CONCLUSION: (23)Na MR imaging demonstrates dysfunctional myocardium caused by subacute and chronic myocardial infarction.

Optimization of automatic bolus tracking for timing of the arterial phase of helical liver CT.

The aim of this study was to optimize bolus tracking for timing of the arterial phase of biphasic helical liver CT and to compare optimized bolus tracking to a standard delay. One hundred fifty patients were examined with six protocols: 5- or 10-s delay after triggering at a threshold of 50 or 75 or 100 HU enhancement in the aorta at the origin of the celiac arteries after injection of 120 ml contrast material at 3 ml/s. Optimal arterial enhancement was defined as 20-30% of hepatic enhancement in portal venous phase. Another 50 patients were examined with the optimized protocol and compared to 50 gender- and age-matched patients who underwent a 25-s standard delay. A 10-s delay after the 75-HU threshold resulted in the most patients with an optimal arterial phase (p < 0.01). Thirty-one of 75 patients examined with this protocol showed optimal early liver enhancement. Bolus tracking compared with standard delay revealed only a trend for a difference (p = 0.07). The outcome of automatic bolus tracking differs depending on the protocol used; however, optimal arterial phase imaging was seen in only 41% of patients, indicating only a trend for superior timing compared with a standard delay.

(31)P-MR Spectroscopy for the evaluation of energy metabolism in intact residual myocardium after acute myocardial infarction in humans.

OBJECTIVE: Experimental studies have demonstrated that acute myocardial infarction (MI) alters energy metabolism even in non-infarcted adjacent tissue. In patients with subacute MI, the influence of the regional ischemic insult on energy metabolism of intact septal myocardium was analyzed using 31P-Magnetic resonance spectroscopy (MRS). PATIENTS AND METHODS: In eight patients with wall motion abnormalities in the anterior wall 31P-spectra were obtained from non-infarcted adjacent septal myocardium, as well as infarcted anterior myocardium (voxel size 25 ccm each) 29+/-8 days after MI using a 3D-CSI technique. Additionally, cardiac function was analyzed using breath-hold cine MRI. MRI was repeated 6 months after revascularization to assess viability of infarcted segments. Eight age-matched healthy volunteers served as control group. RESULTS: According to follow-up MRI 4/8 patients showed regional wall motion recovery. Here, PCr/ATP-ratios were not significantly reduced in intact septal myocardium as well as infarcted anterior myocardium compared to healthy volunteers (1.28+/-0.10 and 1.14+/-0.09 vs. 1.45+/-0.29). No recovery of regional function was detected in 4/8 patients with-therefore-non-viable anterior myocardium. PCr/ATP-ratios were significantly reduced in intact and infarcted myocardium compared with healthy volunteers as well as to patients with wall motion recovery (0.77+/-0.17 and 0.49+/-0.23; P<0.05). DISCUSSION: These preliminary results indicate that energy metabolism is reduced in patients with persisting wall motion abnormalities after myocardial infarction and revascularization in ischemically injured as well as in adjacent non-injured myocardium.