U. Mödder

Diffusion- and Perfusion-Weighted MRI Influence of Severe Carotid Artery Stenosis on the DWI/PWI Mismatch in Acute Stroke

BACKGROUND AND PURPOSE Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) have been used increasingly in recent years to evaluate acute stroke in the emergency setting. In the present study, we compared DWI and PWI findings in acute stroke patients with and without severe extracranial internal carotid artery (ICA) disease. METHODS Twenty-seven patients with nonlacunar ischemic stroke were selected for this analysis. DWI, PWI, and conventional MRI were performed in all patients within 24 hours of symptom onset and after 1 week. To exclude patients with partial or complete reperfusion, we included only patients with a PWI deficit larger than the DWI lesion. Severe ICA disease (>70% stenosis) was present unilaterally in 9 and bilaterally in 2 patients. Acute DWI lesion volume, the size of the acute PWI/DWI mismatch, and final infarct size (on T2-weighted images) were determined. RESULTS The PWI/DWI mismatch was significantly larger in patients with severe ICA disease than in patients without extracranial carotid stenosis, both when time-to-peak and mean transit time maps (P<0.01) were used to calculate the mismatch. Quantitative analysis of the time-to-peak delay in the mismatch indicated that a relatively smaller fraction of the total mismatch was critically ischemic in patients with carotid stenosis than in those without. Average lesion volume increased less in the stenosis group (P=0.14), despite the larger PWI/DWI mismatch, and final infarct size was smaller in the stenosis group (P<0.05). In the 2 patients with bilateral ICA disease, variable hemodynamic involvement of the contralateral hemisphere was found in addition to the ipsilateral PWI deficit. CONCLUSIONS In most acute stroke patients with severe ICA stenosis, a considerably smaller fraction of the total PWI/DWI mismatch is at risk than in patients without carotid disease.

MRI-guided LASER-induced interstitial thermotherapy of cerebral neoplasms

Objective Laser-induced interstitial thermotherapy (LITT) using a neodymium:yttrium aluminum garnet (Nd: YAG) laser is a new therapeutic approach in the treatment of brain tumors. The purpose of our study was to determine the value of MRI in monitoring LITT. Materials and Methods Eight patients with intracerebral tumors were treated with LITT. The light guide was inserted via an applicator sheath that was implanted stereotaxically with CT guidance. The laser irradiation was performed within the MR unit and monitored by repetitive measurements of a T1-weighted 2D-FLASH sequence. Results During therapy in all patients, typical changes of signal intensity were seen. A gradually increasing central zone of high signal intensity was surrounded by an increasing peripheral area of reduced signal intensity. The diameter of an enhancing rim at the outer border of the peripheral area after Gd-DTPA was considered as the total lesion size. The lesion size as determined on 2D-FLASH scans during LITT accounted for 88–100% (mean 93.5%) of total lesion size on T1-weighted images after Gd-DTPA acquired immediately after therapy. On T2-weighted images the signal intensities of the two zones were vice versa. Follow-up studies showed a decrease of total lesion size (15–87%). Conclusion Our results demonstrate that MRI is feasible and effective in monitoring LITT. However, the role of LITT in the therapeutic workup of brain tumors still has to be defined in future clinical studies.

Incidentally discovered pituitary lesions : high frequency of macroadenomas and hormone-secreting adenomas : results of a prospective study

With increasing use of computed tomography and magnetic resonance imaging, pituitary adenomas are being discovered incidentally with increasing frequency. However, limited data are available concerning the clinical importance and natural history of such ‘incicentalomas’. We have undertaken a prospective study to investigate changes in adenoma size and endocrine and visual function in patients with incidentally discovered intrasellar masses.

Iron Oxide Particle-Enhanced MRI Suggests Variability of Brain Inflammation at Early Stages After Ischemic Stroke

Background and Purpose— Inflammation contributes to brain damage caused by ischemic stroke. Ultrasmall superparamagnetic iron oxide (USPIO)-enhanced MRI allows noninvasive monitoring of macrophage recruitment into ischemic brain lesions. In this study, we determined the extent of USPIO enhancement during early stages of ischemic stroke. Methods— Twelve consecutive patients with typical clinical signs of stroke underwent multimodal stroke imaging at 1.5-T within 24 hours of symptom onset. They received intravenous USPIO (ferumoxtran) infusion at 26 to 96 hours (mean, 44 hours) after stroke. A total of four follow-up MRI scans were performed 24 to 36 hours, 48 to 72 hours, 7 to 8 days, and 10 to 11 days after USPIO infusion. Results— Nine patients were included in the final analysis. Parenchymal USPIO enhancement occurred in 3 of 9 analyzed patients and was mainly evident on T1-weighted spin-echo images. USPIO-dependent signal changes were spatially heterogeneous, reflecting the distinct patterns of hematogenous macrophage infiltration in different lesion types. Conclusions— Our findings suggest a variable extent and distribution of macrophage infiltration into early ischemic stroke lesions. USPIO-enhanced MRI may help to more specifically target antiinflammatory therapy in patients with stroke.

Magnetic resonance imaging of bone marrow changes in Gaucher disease during enzyme replacement therapy: first German long-term results

Abstract.Objective:. Since 1991, enzyme replacement therapy (ERT) has been available for patients with Gaucher disease in Germany. The aim of this study was to analyse the MR pattern of bone marrow involvement and response to ERT in Gaucher disease type I. Patients and design:. Thirty patients with Gaucher disease type I had MRI examinations prior to initiation of ERT with alglucerase/imiglucerase and during follow-up. Median MR follow-up and duration of ERT were 36 months. Coronal T1- and T2-weighted spin-echo images of the lower extremities were obtained to evaluate changes in the appearance of yellow marrow. MR images were categorized as having either a homogeneous (type A) or non-homogeneous patchy (type B) appearance of bone involvement and response to ERT was assessed by two radiologists. Results:. Overall, 19 of 30 patients (63%) showed an increased signal intensity on T1- and T2-weighted images after 36 months of ERT, consistent with partial reconversion of fatty marrow during treatment. Focal bone lesions surrounded by a low signal intensity (SI) rim did not respond to ERT, suggesting bone infarcts. Of the 11 patients with bone infarcts (low SI rim lesion), 82% had the non-homogeneous type B pattern (P=0.0021). In 86% of patients with splenectomy, bone infarcts were seen (P<0.05). Conclusions:. MRI using T1- and T2-weighted spin-echo sequences is a valuable, non-invasive method for monitoring bone marrow response in patients receiving ERT. A non- homogeneous patchy signal intensity of bone marrow involvement correlates with the presence of bone infarcts (P=0.0021).

Detection of changed regional cerebral blood flow in mild cognitive impairment and early Alzheimer's dementia by perfusion-weighted magnetic resonance imaging

The utility of perfusion-weighted magnetic resonance imaging (PW-MRI) for detecting changes in regional cerebral blood flow (rCBF) in patients with mild cognitive impairment (MCI) and early Alzheimers disease (AD) was evaluated. Thirteen cognitively normal (CN) elderly subjects, 35 mostly amnestic MCI subjects and 20 subjects with mild probable AD were enrolled. During i.v. injection of gadopentetate dimeglumine, a dynamic T2*-weighted single-shot EPI sequence was conducted using a 1.5-T scanner. Frontobasal (FROB), temporoparietal (TPAR), mesiotemporal (MTMP), anterior and posterior cingular (ACING, PCING), amygdala (AMYG), thalamus and cerebellar brain regions were studied. rCBF was computed from regional cerebral blood volume and arterial input function and normalised to white matter. Images were analysed by manually placed regions of interest using anatomical coregistration. Significant decreases of rCBF were detected in MCI vs. CN in MTMP (-23%), AMYG (-20%) and ACING (-15%) with no further decline in mild AD. In PCING hypoperfusion (-10%) was confined to AD. These hypoperfusional changes are a possible correlate of localised impairment of CNS function. In FROB no perfusion changes were observed between diagnostic groups, but hyperperfusion was observed in mild dementia stages, possibly reflecting functional compensatory mechanisms. These data suggest that PW-MRI detects specific changes in rCBF not only in AD, but also in amnestic MCI, a disorder suggested to largely represent a pre-dementia stage of AD. This method may thus be useful in both research and clinical applications to detect early functional brain changes in the pathogenesis of dementias.

Management of arterial stenosis affecting kidney graft perfusion: a single-centre study in 53 patients.

We assessed clinical and duplex sonographic (CDS) findings, and outcome in patients with stenosis of the transplant renal artery (TRAS) or the aorto‐iliac segment proximal to the graft (Prox‐TRAS) treated with dilatation (PTA), stenting (PTAS) and surgery. From 1988 to 2002, of 1189 patients with renal transplantations, 117 underwent angiography. Fifty‐three patients with TRAS (n = 37)/Prox‐TRAS (n = 16) were found (4.4%).

Statistical evaluation of diffusion‐weighted imaging of the human kidney

The signal of diffusion‐weighted imaging of the human kidney differs from the signal in brain examinations due to the different microscopic structure of the tissue. In the kidney, the deviation of the signal behavior of monoexponential characteristics is pronounced. The aim of the study was to analyze whether a mono‐ or biexponential or a distribution function model fits best to describe diffusion characteristics in the kidney. To determine the best regression, different statistical parameters were utilized: correlation coefficient (R2), Akaikes information criterion, Schwarz criterion, and F‐test (Fratio). Additionally, simulations were performed to analyze the relation between the different models and their dependency on signal noise. Statistical tests showed that the biexponential model describes the signal of diffusion‐weighted imaging in the kidney better than the distribution function model. The monoexponential model fits the diffusion‐weighted imaging data the least but is the most robust against signal noise. From a statistical point of view, diffusion‐weighted imaging of the kidney should be modeled biexponentially under the precondition of sufficient signal to noise. Magn Reson Med, 2010.

Prospective randomized trial of operative vs interventional treatment for renal artery ostial occlusive disease (RAOOD)

INTRODUCTION AND OBJECTIVES Patients with either renovascular hypertension (RVH) and/or renal insufficiency (RI) due to renal artery ostial occlusive disease (RAOOD) can successfully undergo an open surgical reconstruction procedure (OSRP), but since the publication of Blum et al(1) percutaneous balloon stent angioplasty (PTRA + stent) leaving a small part of the stent within the aorta has become very popular. However, balloon dilatation and stenting does not remove the atherosclerotic plaque, which is often heavily calcified but leads to disruption of the plaque causing myointimal hyperplasia and recurrent stenosis. Therefore, a comparison of the two treatment modalities concerning complications and durability in a prospective randomized design was felt to bring more insight to the discussion. METHODS From 1998 to 2004, we performed OSRP in 330 patients with RVH and/or RI for various locations of RAOOD. During this time period, 50 patients (female 18, male 32, mean age 64.4 years) with RAOOD of at least 70% stenosis (DSA and duplex criteria) in one or both renal arteries, who did not require other aorto/mesenteric/iliac reconstructive procedures agreed and were randomized to either OSRP (n = 25 patients, 49 arteries) or PTRA + stent (n = 25 patients, 28 arteries). Two patients crossed over to surgical treatment. Patients were followed on a regular basis for 4 years and longer. Endpoints were re-occurrence of RAOOD and impairment of either kidney function or RVH. RESULTS We approached 77 arteries. There was no early mortality in either group, but directly procedure-related morbidity was 13% in the interventional group and 4% in the surgical group. Four-year follow-up mortality was 18% in the interventional group and 25% in the surgical group. Both groups showed significant improvement of RVH (P < .001 in each group) as well as improvement or stabilization in patients with insufficient renal function. Freedom from recurrent RAOOD (>70%) was achieved in 90.1% of the surgical group and 79.9% of the interventional group. CONCLUSION Both treatment modalities showed good early results concerning RVH, kidney function, and renal perfusion. Despite a higher number of bilateral renal artery reconstructions in patients undergoing OSRP, which was probably due to the preferred technique of transaortic endarterectomy eliminating the plaque originating in the aorta and usually extending into both renal arteries, mortality was not higher and procedure-related morbidity was even lower compared to PTRA + stent. These findings and also longer durability of OSRP imply that surgical reconstruction remains the gold standard for patients with RAOOD before PTRA + stent may be considered.

Comparison of cerebral blood volume measurements using the T1 and T2* methods in normal human brains and brain tumors

PURPOSE Regional cerebral blood volume (rCBV) can be determined after bolus injection of a contrast agent by utilizing the susceptibility effect (T2* method) or the relaxation effect (T1 method). The aim of this study was to apply both methods in groups of normal subjects and tumor patients and to compare the results. METHOD CBVs in different brain areas were determined from groups of 18 normal subjects and 21 patients with different histologically classified tumors. Measurements were performed using GE sequences on a 1.5 T scanner without echo planar imaging capability. As a measure of quality of a single examination, the temporal behavior of the contrast agent bolus was characterized using parameters such as rise time, peak value, fall time, and full width at half-maximum of the concentration-time curves. RESULTS The quality of the T2* measurements was inferior to that obtained with the T1 method. A mean CBV value of 4.1 + 1.1 vol% averaged over the entire brain area was found in the normal collective with the T1 method. The value obtained with the T2* method was 2.6 +/- 1.1 vol%. Similar underestimations of the CBV values were also found using the T2* method when evaluating regions of interest in tumor patients. CONCLUSION Both methods are able to determine rCBV in routine clinical studies. If the goal is to obtain quick, qualitative multislice information, the T2* method is adequate. For quantitative evaluations, however, the T1 method should be preferred.