Assessment of the hepatic veins in poor contrast conditions using dual energy CT: evaluation of a novel monoenergetic extrapolation software algorithm.

PURPOSE: To evaluate a novel monoenergetic post-processing algorithm (MEI+) in patients with poor intrahepatic contrast enhancement. MATERIALS AND METHODS: 25 patients were retrospectively included in this study. Late-phase imaging of the upper abdomen, which was acquired in dual-energy mode (100/140 kV), was used as a model for poor intrahepatic contrast enhancement. Traditional monoenergetic images (MEI), linearly weighted mixed images with different mixing ratios (MI), sole 100 and 140 kV and MEI+ images were calculated. MEI+ is a novel technique which applies frequency-based mixing of the low keV images and an image of optimal keV from a noise perspective to combine the benefits of both image stacks. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the intrahepatic vasculature (IHV) and liver parenchyma (LP) were objectively measured and depiction of IHV was subjectively rated and correlated with portal venous imaging by two readers in consensus. RESULTS: MEI+ was able to increase the SNR of the IHV (5.7 ±â€Š0.4 at 40keV) and LP (4.9 ±â€Š1.0 at 90keV) and CNR (2.1 ±â€Š0.6 at 40keV) greatly compared to MEI (5.1 ±â€Š1.1 at 80keV, 4.7 ±â€Š1.0 at 80keV, 1.0 ±â€Š0.4 at 70keV), MI (5.2 ±â€Š1.1 M5:5, 4.8 ±â€Š1.0 M5:5, 1.0 ±â€Š3.5 M9:1), sole 100 kV images (4.4 ±â€Š1.0, 3.7 ±â€Š0.8, 1.0 ±â€Š0.3) and 140 kV images (2.8 ±â€Š0.5, 3.1 ±â€Š0.6, 0.1 ±â€Š0.2). Subjective assessment rated MEI+ of virtual 40 keV superior to all other images. CONCLUSION: MEI+ is a very promising algorithm for monoenergetic extrapolation which is able to overcome noise limitations associated with traditional monoenergetic techniques at low virtual keV levels and consequently does not suffer from a decline of SNR and CNR at low keV values. This algorithm allows an improvement of IHV depiction in the presence of poor contrast. KEY POINTS: • The evaluated new image-based algorithm for virtual monoenergetic imaging allows calculating low virtual keV images from dual energy datasets with significantly improved contrast-to-noise ratios. • The image based novel monoenergetic extrapolation algorithm applies frequency-based mixing of the low keV images and an image of optimal keV from a noise perspective to combine the benefits of both image stacks.• When compared to traditional monoenergetic images, the novel monoenergetic algorithm has improved contrast-to-noise ratios for both low and high virtual keV images.• Contrast-enhanced dual energy images with poor contrast conditions can be significantly improved, e.g. late phase imaging of the liver.

Assessment of relapse in patients with peritoneal carcinomatosis after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy using F-18-FDG-PET/CT.

PURPOSE: In patients with peritoneal carcinomatosis (PC), cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is an evolving therapeutic approach with curative intention. The differentiation between posttherapeutic findings after HIPEC and relapse of PC is challenging. We evaluated the diagnostic value of F-18-FDG-PET/CT in patients with relapse of PC after HIPEC. MATERIALS AND METHODS: 36 patients with recurring PC after HIPEC were examined on a whole-body PET/CT system (44 examinations). The examination included 3 D F-18-FDG-PET and contrast-enhanced CT. Images were assessed by two experienced readers regarding the presence and the extent of PC using the peritoneal carcinomatosis index (PCI). Imaging results were correlated with surgical findings or follow-up. RESULTS: Relapse was suspected in 40 of 44 examinations. Relapse was missed by F-18-FDG PET/CT in 4 patients and significantly underestimated in 8 patients. The diagnostic accuracy for the detection of PC on a patient basis was 91 %, the sensitivity was 91 % and the positive predictive value was 100 %. The mean PCI was 11.4 ±â€Š11.9 for PET/CT, 8.4 ±â€Š10.3 for CT and 16.6 ±â€Š15.0 in the case of surgical exploration. The extent of PC was underestimated by PET/CT and even more by CT alone (p < 0.05). CONCLUSION: The diagnostic value of F-18-FDG PET/CT after cytoreductive surgery and HIPEC in the detection of recurring PC is superior to contrast-enhanced CT. However, the quantification of the extent of PC is limited due to post-therapeutic tissue alterations. KEY POINTS: • Imaging of recurrent PC after HIPEC is challenging due to posttherapeutic tissue alterations.• The extent of recurrent PC after HIPEC is systematically underestimated by F-18-FDG PET/CT.• F-18-FDG PET/CT provides improved sensitivity for recurrent PC compared to contrast-enhanced CT.• The correlation of the extent of recurrent PC depicted by F-18-FDG PET/CT and surgical exploration is better than that of contrast-enhanced CT and surgical exploration.

Assessment of the nature of residual masses at end of treatment in lymphoma patients using volume perfusion computed tomography.

OBJECTIVES: To determine the diagnostic benefit of volume perfusion computed tomography (VPCT) at end of treatment for response assessment in lymphoma patients. METHODS: Seventy-five patients with different lymphoma subtypes were included: 50/75 patients had residual masses at end of treatment, 26/50 patients underwent VPCT at baseline and at end of treatment, and 24/50 patients only had end-of-treatment VPCTs. We evaluated the size of the main lymphoma mass, its blood flow (BF), blood volume (BV) and k-trans, calculated ratios (baseline and end of treatment) as well as sensitivity/specificity/negative (NPV)/positive predictive values (PPV). For VPCT at end of treatment, a cutoff threshold between responders and non-responders was calculated. RESULTS: For patients undergoing VPCT at baseline and end of treatment, reduction in size, BF, BV and k-trans was significant (P < 0.001). Identification of non-response was reached at: <53% reduction in size (sensitivity/specificity/accuracy/PPV/NPV of 88.89%/62.5%/80.77%/84.21%/71.43%), <15% reduction of BF (sensitivity/specificity/accuracy/PPV/NPV of 100%/37.5%/80.77%/0.26%/100%), or <45% reduction of k-trans (sensitivity/specificity/accuracy/PPV/NPV of 88.89%/75%/84.62%/88.89%/75%). In the subgroup undergoing VPCT at end of treatment, BF >18.51 ml/100 ml indicated non-responsiveness (sensitivity 92.86%, specificity 72.73%, accuracy 84%, PPV 81.25%, NPV 88.89%). CONCLUSIONS: VPCT seems adequate for assessment of lymphoma response at end of treatment. The degree of residual lymphoma perfusion at end of treatment helps to identify patients likely to remain in remission 1 year after completion of therapy. KEY POINTS: • Volume perfusion computed tomography (VPCT) offers measurements for assessing tumour response. • Perfusion parameter changes measured by VPCT correlate with antitumour therapy response. • In lymphoma, baseline and end-of-treatment perfusion parameter ratios can predict response. • Perfusion measurements after treatment identify patients likely to remain in remission.

High-pitch dual-source CT angiography of supra-aortic arteries: assessment of image quality and radiation dose.

INTRODUCTION: High-pitch CT angiography (CTA) is a recent innovation that allows significant shortening of scan time with volume coverage of 43 mm per second. The aim of our study was to assess this technique in CTA of the head and neck. METHODS: CTA of supra-aortic arteries was performed in 50 patients using two acquisition protocols: conventional single-source 64-slice (pitch 1.2) and high-pitch dual-source 128-slice CT (pitch 3.2). Subjective and objective image quality of supra-aortic vessel ostia as well as intra- and extra-cranial segments was retrospectively assessed by blinded readers and radiation dose compared between the two protocols. RESULTS: Conventional and high-pitch CTA achieved comparable signal-to-noise ratios in arterial (54.3 ± 16.5 versus 57.3 ± 14.8; p = 0.50) and venous segments (15.8 ± 6.7 versus 18.9 ± 8.9; p = 0.21). High-pitch scanning was, however, associated with sharper delineation of vessel contours and image quality significantly improved at the level of supra-aortic vessel ostia (p < 0.0001) as well as along the brachiocephalic trunk (p < 0.0001), the subclavian arteries (p < 0.0001), proximal common carotid arteries (p = 0.01), and vertebral V1 segments (p < 0.0001). Using the high-pitch mode, the dose-length product was reduced by about 35% (218.2 ± 30 versus 141.8 ± 20 mGy × cm). CONCLUSIONS: Due to elimination of transmitted cardiac motion, high-pitch CTA of the neck improves image quality in the proximity of the aortic arch while significantly lowering radiation dose. The technique thus qualifies as a promising alternative to conventional spiral CTA and may be particularly useful for identification of ostial stenosis.

Automated volumetric assessment of the Achilles tendon (AVAT) using a 3D T2 weighted SPACE sequence at 3T in healthy and pathologic cases.

PURPOSE: Achilles tendinopathy has been reported to be frequently associated with increasing volume of the tendon. This work aims at reliable and accurate volumetric quantification of the Achilles tendon using a newly developed contour detection algorithm applied on high resolution MRI data sets recorded at 3T. MATERIALS AND METHODS: A total of 26 healthy tendons and 4 degenerated tendons were examined for this study. Automated identification (AI) of tendon boundaries was performed in transverse slices with isotropic resolution (0.8mm) gained with a T2-weighted SPACE sequence at 3T. For AI a snake algorithm was applied and compared to manual tracing (MT). RESULTS: AI was feasible in all examined tendons without further correction. AI of both tendons was performed in each participant within 2 min (2 × 37 slices) compared to MT lasting 20 min. MT and AI showed excellent agreement and correlation (R(2) = 0.99, p<0.0001). AI provided a reduction of measurement error (0.4 cm(3) vs. 0.5 cm(3)) and coefficient of variation (1% vs. 2%). DISCUSSION: Compared to MT the AI allows assessment of tendon volumes in highly resolved MRI data in a more accurate and reliable time-saving way. Therefore automated volume detection is seen as a helpful clinical tool for evaluation of small volumetric changes of the Achilles tendon.

MRI assessment of cardiac amyloidosis: experience of six cases with review of the current literature.

Cardiac MRI is known to be diagnostically valuable in cardiac amyloidosis. Several features are frequently found, including myocardial hypertrophy, diastolic dysfunction, a faster gadolinium blood wash out, pleural and pericardial effusions, and diffuse myocardial delayed enhancement. Cardiac MR facilitates the detection of cardiac amyloidosis and allows longitudinal assessment of myocardial function. This pictorial review focuses on cases with histologically proven systemic amyloidosis and cardiac involvement in order to illustrate typical findings.

[Cost considerations for whole-body MRI and PET/CT as part of oncologic staging]. / Kostenüberlegungen zur Ganzkörper-MRT und PET-CT im Rahmen des onkologischen Stagings.

PURPOSE: The aim of this study was to evaluate and discuss economic aspects of whole-body MRI and PET/CT in oncologic staging. Considerations from the perspective of the health care system, the radiologist, and the patients are presented. MATERIALS AND METHODS: Costs of both whole-body techniques are compared with the conventional radiologic diagnostic recommendations of the AWFM (Arbeitsgemeinschaft Wissenschaftlich Medizinischer Fachgesellschaften) in oncologic staging of the five most frequent tumor entities. Temporal and monetary aspects are calculated. Invasive, endoscopic, and endosonographic techniques are regarded as essential and cannot be replaced by other techniques. Thus only the minimal potential for cost reduction is quantified. RESULTS: In the German system there is no cipher to correctly balance whole-body MRI and PET/CT. Using the frequently applied ciphers 5700-5730 and 5378, 5489 (factor 1.0) total costs were 440.45 euros, and adding the cipher for additional series 545.37 euros (60 min examination time) for whole-body MRI and 774.74 euros (879.66 euros) (60/90 min examination time) for whole-body PET/CT. Using the common factor 1.8 costs were 981.66 and 1583.38 euros. On the basis of a simple full cost analysis total costs of whole-body PET/CT were higher than of whole-body MRI by a factor of about 2.0 (about 1123 vs 575 euros). There were substantial monetary and temporal differences between tumor entities. In extended bronchial carcinoma 375.32 euros and 55 min can be saved using whole-body MRI in comparison to conventional recommended techniques and using whole-body PET/CT 88.14 euros and 45 min. In tumor entities of lower stages with thus less essential radiologic diagnostics the potential for cost reduction is substantially lower. CONCLUSION: Whole-body imaging techniques make it possible to reduce the number of necessary separate radiologic examinations and thus time in oncologic staging. A substantial reduction of health care costs seems to be possible in many tumor entities but differences between different tumor entities are decisive.

Assessment of coronary artery bypass grafts by magnetic resonance imaging.

This study evaluated graft patency and flow at rest/stress in patients with coronary artery bypass grafts using MR flow measurements and MR angiography (MRA). 45 symptomatic patients with 86 grafts (46 arterial, 40 venous) were examined 5.5 years after surgery. MRA was used to assess bypass patency. Flow measurements were performed at rest and after stress induction with dipyridamole. All graft segments were evaluated at MRA for stenosis, and were additionally evaluated by the combination of flow measurements and MRA. Conventional coronary angiography or multidetector computed tomography was regarded as a reference standard. No significant stenosis was observed in 49 grafts (Group A), whereas significant stenosis was observed in 37 grafts (Group B). Sensitivity, specificity, and positive and negative predictive values for stenosis in arterial grafts were 95.2%, 96.8%, 80% and 99.4%, respectively, and in venous grafts were 100%, 97.8%, 87.5% and 100%, respectively. The mean blood flow rate at baseline/stress in Group B was significantly lower than that in Group A (p<0.002/p<0.001). With the combined MR method, 84 of 86 (97%) grafts could be correctly classified. In conclusion, MRI allows a combined assessment of graft status, including bypass patency and flow, in symptomatic patients after revascularization.

Sixty-four-slice CT in the assessment of global and regional left ventricular function: comparison with MRI in a porcine model of acute and subacute myocardial infarction.

The purpose was to assess 64-slice CT in the analysis of global and regional ventricular function, using a model of acute and subacute myocardial infarction in comparison with cine-MRI. Seven pigs underwent standard MSCT and MRI examination a median 1 and 21 days following creation of reperfused myocardial infarction. Endocardial and epicardial contours were manually defined and ventricular volumes calculated according to Simpson's method. Results were compared by Pearson's correlation coefficient and Blant-Altman analysis. Wall motion was assessed on cine-images and evaluated by kappa statistics. MSCT revealed a strong correlation with cine-MRI regarding quantification of end-diastolic volume (EDV; r = 0.97), end-systolic volume (ESV; r = 0.97), stroke volume (SV; r = 0.94), ejection fraction (EF; r = 0.95) or myocardial mass (MM; r =0.94 ). Minor overestimation was observed for EDV and ESV (bias -1.7 ml; -1.5 ml; P=0.095; 0.025), whilst the mean difference for EF was found to be negligible (bias 0.9%; P = 0.18). Both modalities showed a 96.2% segmental agreement in regional wall motion (weighted-kappa 0.91 for 238 segments). This was true for both acute and subacute infarct phase and MSCT, and thereby enabled accurate intraindividual follow-up of segmental dysfunction. Sixty-four-slice CT allows for reliable analysis of global cardiac function and, moreover, provides accurate evaluation of wall motion in acute and subacute myocardial infarct.

[CT-based assessment score after ventral spondylodesis for thoracolumbar spine fracture]. / CT-basierter Auswertungsscore nach ventraler Spondylodese bei thorakolumbalen Wirbelfrakturen.

BACKGROUND: Dorsoventral stabilization is a common procedure to treat thoracolumbar spine fractures. Especially in respect of the evaluation of alternative procedures to autogenous bone graft, a standardized evaluation score for ventral spondylodesis is necessary. PATIENTS AND METHODS: In a group of 44 patients a follow-up CT scan was evaluated with a standardized scoring system by four different independent evaluators (a trauma surgeon, an orthopedic surgeon, and two radiologists). The score is based on the morphologic classification of the region between graft and vertebral body. It allows a classification of the spondylodesis as sufficient, partial, and not sufficient. RESULTS: The statistical evaluation of the classification of the different evaluators shows very good interobserver agreement in monosegmental fusion and good agreement in bisegmental fusion. CONCLUSION: The demonstrated score is easy to handle, does not need special equipment for CT scans, and shows good interobserver agreement in the classification of spinal fusion after ventral spondylodesis for thoracolumbar spine fracture.

Low-cost data transfer from a questionnaire to standard software using a barcode pen.

Computer-aided transfer of questionnaire data simplifies the analysis of questionnaires. We present a solution based on an inexpensive barcode pen and its decoder, the software tool Barcode Wizard included in CorelDRAW, and a self-developed application written using Microsoft Visual Basic for Applications. The barcode may be provided on the questionnaire or on a transparency. Error correction is done by means of two different procedures. The present solution can be applied while looking over the completed questionnaire and thus allows time-saving, economic, and precise data transfer from the completed questionnaire directly into computer software.

Assessment of peripheral arterial occlusive disease: comparison of multislice-CT angiography (MS-CTA) and intraarterial digital subtraction angiography (IA-DSA).

PURPOSE: The aim of the study was to assess the arterial vascular system of the lower extremities in patients with peripheral arterial occlusive disease using Multislice-CT angiography (MS-CTA) and to compare the results with the standard of reference, intraarterial digital subtraction angiography (IA-DSA). MATERIALS AND METHODS: MS-CTA and IA-DSA of the lower extremities were carried out on 23 patients with peripheral arterial occlusive disease (Fontain Stage IIb: 18, III: 3, IV: 2). MS-CTA comprised a 4 x 2.5 mm collimation, 15 mm table feed/rotation, 0.5 sec rotation time and 3 mm slice thickness (1.5 mm reconstruction increment). Delay time was determined by bolus tracking. 150 ml of contrast media were injected intravenously at a flow rate of 3 ml/sec. Maximum intensity projection (MIP) reformations were performed using a semi-automatic vessel tracking program. MS-CTA (axial and MIP-reformatted images) and IA-DSA were reviewed by two radiologists. The grade of vascular stenosis as well as occlusion were rated on a scale of 0 to 3 (0=0-50% stenosis, 1 = 51-75% stenosis, 2 = 76-99% stenosis, 3 = occlusion). RESULTS: For MS-CTA, the mean delay time was 30.2 s (23-40 s), mean scan time was 37.4 (33-42 s). Data analysis was based upon a total of 1136 vascular segments for both methods (568 each). A comparison of all the evaluated segments in both techniques revealed a MS-CTA / IA-DSA 86.3% match. Out of 442 segments proximal the trifurcation, 386 were correctly assessed in MS-CTA (87.3%) and distal the trifurcation, 101 out of 126 segments were rated correctly (80.2%). In MS-CTA, an overall confidence interval of 95% can be achieved in 83.2% to 89.0% for correctly rated stenosis grading. CONCLUSIONS: In patients with peripheral arterial occlusive disease, MS-CTA of the lower extremity is a promising minimal-invasive method for detection of relevant arterial stenoses. However, the technique was limited to routine diagnostic purposes due to severe calcifications and time consuming reconstruction procedures.

[Quantitative assessment of therapy related effects after breast conserving therapy with dynamic MRI of the breast]. / Quantitative Erfassung von Gewebsveränderungen der Mamma nach brusterhaltender Therapie mit der dynamischen MR-Mammographie *

PURPOSE: To quantify therapy related effects after breast conservation therapy (BCT) with dynamic MRI of the breast. METHODS: Twenty patients (median age 51 years) with breast conserving tumor excision were included. Contrast enhanced dynamic MRI was performed before and 3, 6 and 12 months after adjuvant radiation therapy (RT) with a total dose of 50.0 to 50.4 Gy. The following sequences were applied: axial fat-suppressed T(2)-weighted; coronal contrast enhanced 3D spoiled gradient-echo (first measurement prior to the administration of 0.16 mmol/kg Gd-DTPA, six repetitive measurements); sagittal T(1)-weighted Flash3D. Enhancement data were obtained using a computer software with automated segmentation of regions of interest (ROIs). After defining ROIs for skin, parenchyma and pectoral muscle of each breast the early enhancement after the first post contrast measurement (E(1)) and the slope of enhancement between the second and last postcontrast measurement (SE(2-L)) were calculated. The edema was quantified by assessing the signal intensities (SI) in the T(2)-weighted images. The thickness of the skin was measured in the sagittal T(1)-weighted images. RESULTS: Three months after RT statistically significant increases between 51 and 179 % of the SI and E(1) quotients were detected for all tissues compared to the examinations prior to RT. Six months after RT the skin still presented a by 102 % significantly higher E(1) quotient, and a by 140 % significantly increased SI quotient. No significant differences for SI and E(1) quotients could be observed 12 months after RT compared to the examinations prior to RT. A significant increase of the SE(2-L) difference for the skin from 0.0225 to 0.0691 and 0.0665 was found 3 and 6 months after RT, respectively. No significant differences between the initial MR examination and the follow-up examinations 3, 6 and 12 months could be detected for the SE(2-L) differences of the parenchyma. CONCLUSION: Early therapy related effects after BCT can be exactly quantified with dynamic MRI using an automated ROI-segmentation and whole breast analysis software. Both edema formation and early enhancement show peaks 3 months after RT, and after 12 months there is no statistically significant difference compared with baseline.

[2D-phase contrast flow evaluation and contrast-enhanced MR angiography for perioperative assessment of internal mammary artery grafts]. / 2D-Phasenkontrast-Flussquantifizierung und kontrastangehobene 3D-MR-Angiographie zur perioperativen Untersuchung des Arteria-mammaria-interna-Bypasses.

PURPOSE: To evaluate LV functional parameters, graft flow and patency in patients with IMA grafts using a combined MR protocol with phase-contrast technique and contrast enhanced MR angiography. MATERIAL AND METHODS: Using a 1.5 T MR system 27 patients with 27 left internal mammary artery (LIMA) and 41 venous grafts were examined before and 6 months after CABG surgery. A T(1)w-TSE sequence (slice thickness 5 mm) was applied for morphological imaging. LV function (EF, CO) was evaluated on cine images (segmented FLASH 2D, TR(eff) 11 ms, TE 4.8 ms, flip angle 25 degrees ). A phase-contrast FLASH 2D (TR 24 ms, TE 5 ms, flip angle 20 degrees ) sequence was applied for aortic and IMA flow measurements. Postoperatively, a contrast enhanced FLASH 3D MR angiography (TR 3.8 ms, TE 1.4 ms, flip angle 30 degrees ) with 25 ml Gd-DTPA was performed to assess bypass patency. RESULTS: In patients with reduced LV function (ejection fraction < 50 %) an improvement of the ejection fraction from 38.4 +/- 10.3 % to 49.8 +/- 15.3 % (p < 0.05) was found postoperatively. LIMA grafts were occluded in 1/27 patients, while 6/41 venous grafts were occluded. Distal LIMA anastomoses were demonstrated in 33 % by MRA. Flow of LIMA decreased from 21.2 +/- 11 ml/min/m(2) preoperatively to 14.4 +/- 9.6 ml/min/m(2) postoperatively (p < 0.01). CONCLUSION: MR imaging allows accurate combined assessment of LV function, bypass patency and flow. The protocol of this study may be applicable for perioperative follow-up studies in patients after CABG surgery.

Subacute myocardial infarction: assessment by STIR T2-weighted MR imaging in comparison to regional function.

PURPOSE: Increased T2 signal intensity (SI) can be regularly observed in myocardial infarction. However, there are controversial reports about the relationship of elevated T2 SI to myocardial viability and some authors propose that high T2 SI serves as a sign of irreversible myocardial injury. This study investigates increased T2 SI compared to myocardial function in patients with reperfused subacute myocardial infarction. Preserved function was used as criterion for viability. METHODS: Ten healthy volunteers and 17 patients with myocardial infarction and patent infarct related coronary artery were examined on a 1.5 T Magnetom Vision system (Siemens). For T2-weighted MR imaging a breath-hold STIR sequence with dark-blood preparation was used. Cine FLASH 2D imaging was applied to assess myocardial function. Signal-to-noise (S/N) in STIR T2 images was measured in normal and infarcted regions and subsequently identified by two independent observers. Based on a 20 segment model of the left ventricle findings were compared to regional myocardial function. RESULTS: Elevated STIR T2 SI was found in all 17 patients and observed in 27% (204/754) of segments. S/N of normal myocardium was 5.1 +/- 0.7 in volunteers and 4.9 +/- 0.8 in patients (P = NS). Infarcted myocardium presented with significantly increased S/N 12.8 +/- 1.9 (P < 0.0001). Significant transmural elevation of T2 SI was noted in 32% of segments with preserved systolic function. CONCLUSION: Increased STIR T2 SI can be observed transmurally in post-ischemic myocardial regions with preserved function. It therefore cannot be used as an exclusive marker for the non-viable region.

Conventional high resolution versus fast T(2)-weighted MR imaging of the heart: assessment of reperfusion induced myocardial injury in an animal model.

Cardiac image quality in terms of spatial resolution and signal contrast was assessed for conventional and newly developed T(2)-weighted fast spin-echo imaging with high k-space segmentation. The capability in revealing regional myocardial edema and cellular damage was examined by a porcine model using histopathologic correlation. Twelve porcine hearts were excised from slaughtered animals and instantly perfused with 1000 mL cold cardioplegic solution. After 4 h of cold ischemia the hearts were reperfused for one hour using a "Langendorff" perfusion model followed by MR imaging at 1.5 Tesla. Three additional pig hearts served as controls and were studied by MR directly after harvesting. Histopathological analysis of regional tissue changes was performed macro- and microscopically. Short axis T(2)-weighted (3000/45 and 90) high quality fast spin-echo (FSE) images were recorded without cardiac action and signal intensity was correlated with histology. These images also served as gold standard for evaluation of newly developed faster sequences allowing measuring times shorter than 20 s. Fast T(2)-weighted imaging comprised single-slice fast spin echo (moderate echo train length of 23 echoes, FSE(m)), and multi-slice single-shot half-Fourier fast spin-echo (71 echoes, FSE(HASTE)) sequences, supplemented by versions with inversion recovery preparation (FSE(m)IR and FSE(HASTE)IR). Systolic function after reperfusion was restored in 10 porcine hearts. Tissue alterations included myocardial edema and contraction band necrosis which was found to be most severe in myocardium with maximum T(2) SI. Especially FSE(m) and FSE(m)IR sequences allowed differentiation of all categories of tissue damage on a high level of significance. In contrast, single-shot FSE(HASTE) and FSE(HASTE)IR sequences did not provide sufficient image quality to discriminate moderate and severe myocardial damage (p > 0.05). Different degrees of myocardial injury after ischemia and reperfusion can be staged by MR imaging, especially using conventional high resolution T(2)-weighted FSE sequences. The animal study indicates that fast T(2)-weighted FSE(m) and FSE(m)IR sequences lead to superior image quality and diagnostic accuracy compared to FSE(HASTE) and FSE(HASTE)IR imaging.

MR imaging in the presence of vascular stents: A systematic assessment of artifacts for various stent orientations, sequence types, and field strengths.

A systematic evaluation of the potential quality of magnetic resonance images recorded in the presence of metallic stents was performed on a low-field open imager operating at 0.2 T and on a high-field closed unit operating at 1.0 T. Eight different stent types were examined by two-dimensional gradient-echo sequences with echo times of 4 and 10 msec and by a fast spin-echo technique. In addition, a three-dimensional gradient-echo sequence was applied with an echo time of 2.4 msec. A set of sequence and slice parameters was used on both scanners. Thus, artifacts due to susceptibility effects depending on the magnetic field strength could be distinguished from radiofrequency shielding effects in the lumen of the stents (independent of the field strength). Nine different orthogonal orientations of the stent axis and the image (in terms of slice, read, and phase-encoding direction) were tested, and the artifacts (extension of signal void and visibility of the lumen) were compared. The optimal strategy for visualization of vascular and perivascular regions outside the stents was fast spin-echo imaging with the stent axis and read direction parallel to the static field. Susceptibility-induced signal void in gradient-echo images was minimal using the three-dimensional approach. Increased transmitter amplitudes above usual values provided clearly improved insight in the lumen using gradient-echo sequences.

Fat- and water-selective MR cine imaging of the human heart: assessment of right ventricular dysplasia.

RATIONALE AND OBJECTIVES: The purpose of this study was to develop and implement MR sequences for chemical shift-selective breath-hold cine imaging of the heart. Fibroadipose conversion of myocardium in cases suspected of right ventricular dysplasia should be revealed in fat- and water-selective MR images of high quality. METHODS: Frequency-selective saturation of one chemical shift component was applied in modified k-space-segmented, electrocardiography-gated sequences, allowing high-quality cine imaging of the human heart in a single breath-hold. Phantom studies and human examinations in eight normal subjects (aged 24-62 years) and in seven patients (aged 31-47 years) with suspected right ventricular dysplasia were performed. The patients showed suspicious findings, such as a dyskinetic and dilated right ventricle combined with ventricular arrhythmia, and underwent MR imaging after exclusion of other possible reasons (eg, coronary artery disease or pulmonary hypertension). RESULTS: High selectivity to the desired chemical shift component was confirmed by test measurements in a phantom containing water and lipids. In the human subjects, minor problems with magnetic field inhomogeneities appeared in the thoracic walls only. Four patients with suspected right ventricular dysplasia showed clearly abnormal signal behavior of the right myocardial wall in both fat- and water-selective cine images. Bright transmural structures were exhibited in fat-selective images, but the origin of the fat (epicardium or infiltrated myocardium) was often difficult to assess. CONCLUSIONS: Right ventricular areas with fibrosis and fatty degeneration often show normal signal intensity in standard T1-weighted images but can be differentiated from normal tissue by the new chemical shift-selective breath-hold cine techniques.

Assessment of the composition of bone marrow prior to and following autologous BMT and PBSCT by magnetic resonance.

Lumbar bone marrow was assessed by means of magnetic resonance (MR) in 23 examinations of eight patients who underwent autologous bone marrow transplantation (ABMT) or peripheral blood stem cell transplantation (PBSCT). Various imaging and spectroscopic techniques were applied for measurements carried out prior to conditioning for ABMT/PBSCT and in the course of reconstitution and correlated with clinical and blood chemistry data in these patients. The signal intensity from lumbar bone marrow was determined in T1-weighted and water- and fat-selective MR images. The distribution of the magnetic field was demonstrated by a field-mapping method. Localized proton spectroscopy was performed from volume elements of 2 ml located in the central region of vertebral bodies in order to evaluate the fraction of the water signals, the transverse relaxation times T2 of the signals from water and lipids, and the line widths of the spectral signals. Regions of bone marrow after inflammatory conditions or intensive irradiation are shown to be not involved in marrow reconstitution. Additional information about marrow composition was obtained by the magnetic field mapping and by the line widths in the spectra. Considerable alterations of the amount of paramagnetic hemosiderin were revealed following transplantation. Patients with low water signal and strong local inhomogeneities of the magnetic field in the marrow prior to transplantation had a delayed hematopoietic reconstitution compared with the patients lacking these MR features.

Hematopoietic reconstitution after bone marrow transplantation: assessment with MR imaging and H-1 localized spectroscopy.

Magnetic resonance (MR) studies were performed in 14 patients as early as possible (21-110 days) after bone marrow transplantation (BMT). MR characteristics of lumbar vertebral bone marrow were studied with T1-weighted spin-echo imaging, water- and fat-selective imaging with a frequency-selective excitation technique, and point-resolved spatially localized proton spectroscopy. Signals from water and fat protons and their T1 and T2 values were analyzed. Water proton signal intensity correlated well with cellularity within bone marrow, as determined with parallel iliac crest biopsies. The fraction of signal from water in red bone marrow of patients with allogeneic transplants from siblings (four cases) was significantly higher than in four patients with autologous transplants. The latter showed very low cellularity in the period of about 4 weeks after BMT because of the cytotoxic pretreatment of the bone marrow. The MR results in six patients with allogeneic transplants from unrelated donors ranged widely, depending on the complications after BMT. Analysis of data obtained with the different techniques showed that water- and fat-selective MR imaging and spectroscopic methods are useful for noninvasive monitoring of hematopoietic reconstitution after BMT.