Do the cardiovascular risk profile and the degree of arterial wall calcification influence the performance of MDCT angiography of lower extremity arteries?

OBJECTIVES: To retrospectively assess the influence of arterial wall calcifications on the accuracy of run-off computed tomographic angiography (CTA) and to analyse whether cardiovascular risk factors are predictors of compromising calcifications. METHODS: In 200 consecutive patients who underwent run-off CTA, calcifications were assessed in pelvic, thigh and calf arteries using a four-point scale. Fifty-nine patients with digital subtraction angiography (DSA) were assessed by both techniques to estimate a threshold of compromising calcifications, defined as a decrease of sensitivity, specificity, PPV or NPV below the lower 95% confidence interval of overall results. Regression analysis was performed to investigate a potential relationship between compromising calcifications and presence of cardiovascular risk factors, advanced patient age and severe peripheral arterial disease (PAD). RESULTS: The highest Ca(++)-score was chosen as the cut-off for the regression analysis, as a relevant decrease of specificity (0.91; overall: 0.95) above the knee and of sensitivity (0.66; overall: 0.83), specificity (0.65; overall: 0.93), positive predictive value (PPV) and negative predictive value (NPV) below the knee was observed. In the pelvic and thigh arteries, severe PAD (Fontaine Stage >or=III) showed the highest odds ratio for compromising calcifications (2.9), followed by diabetes mellitus (2.4), renal failure (2.1) and smoking (1.7). In the calf, renal failure (12.2) and diabetes mellitus (3.3) were the strongest predictors. CONCLUSIONS: Patients with diabetes and renal failure should be considered as candidates for alternative vessel imaging in order to avoid inconclusive examination results.

The value of combined soft-tissue and vessel visualisation before transarterial chemoembolisation of the liver using C-arm computed tomography.

The purpose of the study was to prospectively evaluate intrahepatic vessel depiction on C-arm CT (CACT) and the influence of the additional combined tissue and three-dimensional vessel visualisation on the positioning of the TACE catheter in comparison to DSA alone. Thirty consecutive patients scheduled for their first transarterial chemoembolisation underwent biphasic CACT and DSA of the liver. After assessing the DSA images for procedure planning, the CACT images were reviewed. The number and origin of the tumour-feeding arteries and the ideal position of the catheter for TACE on both DSA and CACT were assessed and correlated. The number of vessels identified as tumour feeders in each patient was significantly higher using additional CACT than on DSA alone (CACT: 4.0 +/- 1.7; DSA: 3.3 +/- 1.4; P = 0.003, t-test). After considering CACT, in 50% of the patients the catheter position was changed for TACE. Segmental portal vein thrombosis was seen in three patients on CACT, but in only one on DSA. As CACT depicts soft tissue and small vessels with high spatial resolution, tumour vessel allocation is facilitated, and ideal catheter position for TACE can be more accurately identified. The high impact of CACT on the TACE procedure suggests the benefits of its routine use for all patients undergoing their first TACE.

[Flat-detector CT-based electromagnetic navigation]. / Auf Flachdetektor-CT basierende elektromagnetische Navigation.

Flat-detector CT coupled to an angiography device provides an imaging technique for interventions which can be used for electromagnetically navigated percutaneous punctures. This report explains the functionality of an electromagnetic navigation system and describes the course of an electromagnetically navigated puncture and the capabilities of such a system in the clinical routine.

Retrieval of vascular foreign bodies using a self-made wire snare.

BACKGROUND: Foreign bodies in the vascular system have a high potential to cause embolization, perforation, and infection. Therefore, numerous commercially available percutaneous retrieval devices have been developed. PURPOSE: To evaluate the feasibility and efficacy of a self-made wire snare for the retrieval of foreign bodies in the vascular system. MATERIAL AND METHODS: 16 consecutive patients, who underwent percutaneous foreign-body retrieval between 1997 and 2007, were included in this retrospective analysis. Percutaneous extraction was performed using an adjustable wire snare that was fabricated using a 5F diagnostic Headhunter or Multipurpose catheter and a 4-m-long 0.018-g/inch standard heavy-duty wire that was bent in the middle to create an eccentric loop. RESULTS: Percutaneous foreign-body retrieval was successful in all 16 cases. Intraluminal materials including partially fractured venous catheters, guidewires, a stent, and a vena cava filter were removed from various locations. In six cases, mobilization of the intraluminal material via a pigtail catheter was necessary before using the wire snare for removal. Successful retrieval was investigator independent. In no cases were surgical procedures required, and no relevant complications were encountered. CONCLUSION: This snare technique is an effective, feasible, and cost-effective method to retrieve intraluminal material. It is an alternative to commercially available retrieval devices.

Bleeding complications after endovascular therapy of cerebral arteriovenous malformations.

BACKGROUND AND PURPOSE: Intracerebral hemorrhages after embolization of arteriovenous malformations (AVMs) are the most dreaded complications of this well-established therapy. Apart from the known risk factors, our center noticed a high incidence of complications during postinterventional monitoring in medical intensive care units (ICUs) and stroke units. MATERIALS AND METHODS: We report 125 consecutive interventions performed on 66 patients by using flow-dependent microcatheters and n-butyl cyanoacrylate as the embolic agent. Postinterventional intensive care monitoring was performed in an interdisciplinary operative ICU, a stroke unit, or a medical ICU. Patients were compared with regard to bleeding complications, AVM morphology, embolization result, postinterventional monitoring, and demographic factors. RESULTS: Intracerebral hemorrhages occurred in 7 patients. Significant differences in outcome were found between 66 patients monitored in the interdisciplinary operative ICU from medical ICU or stroke unit. This was also true when adjusted for age and extent of AVM reduction by using exact logistic regression. A partial AVM reduction of >60% was a considerable risk factor for hemorrhage (odds ratio [OR] = 18.8; 95% confidence interval [CI] [1.341, not available]. Age was also an essential risk factor. An age difference of 10 years leads to an OR of 2.545 (95% CI [1.56, 7.35]). DISCUSSION: A considerable AVM reduction in one session appears to increase the risk of hemorrhage technically. This suggests a distribution of the interventions in many partial steps.

Evaluation of efficient chemoembolization mixtures by magnetic resonance imaging therapy monitoring: an experimental study on the VX2 tumor in the rabbit liver.

To find effective chemoembolization mixtures, we tested combinations of carboplatin with the embolizates Spherex and Gelfoam in comparison to a therapy with NaCl-solution, a treatment with the cytostatic drug only, and a therapy with each of the embolizates alone. The experiments were carried out using as a model the VX2 tumor in the liver of male chinchilla rabbits (five for each group). Carboplatin was revealed by the 3-(4,5-dimethylthiazole-2)-yl-2,5-diphenyltetrazolium bromide test to be a potent cytostatic drug for VX2 rabbit tumor cells. We used magnetic resonance imaging to examine the tumor volume and signal intensity enhancement up to 15 min after Gd-DTPA administration within the tumor and liver before and after the different therapies. These parameters allowed us to evaluate tumor growth and vitality as well as liver injury for the different therapy types. The results found by magnetic resonance imaging corresponded very well to those obtained by histological analysis of the tumors. The chemoembolization therapies were significantly more efficient than the other therapies, as indicated by the reduction of signal intensity enhancement after contrast agent administration within the tumor and by the histologically determined necrotic fraction after therapy. In addition, we found a significant decrease of the tumor volume and no significant live injury for a therapy with Carboplat and Gelfoam.

[Characterization of an experimental venous thrombus model with MRI, phlebography and histology]. / Charakterisierung eines experimentellen venösen Thrombosemodells mittels MRT, Phlebographie und Histologie.

INTRODUCTION: Several magnetic resonance (MR) techniques designed to demonstrate the characteristic signal intensity of blood degeneration products of thrombi have been suggested, but the effect of thrombus organization on the MR display, in particular with regard to its temporal evolution, remains to be determined. It is the purpose of this study to develop a stagnation thrombus model in rabbits and to characterize thrombus at different ages with two (MR) imaging techniques, phlebography and histology. MATERIALS AND METHODS: Venous stagnation thrombi were induced in the external jugular veins of rabbits using a minimally invasive radiological technique to produce artificial embolic vascular occlusion and hypercoagulability. Twenty-five animals were divided into 5 groups of 5 animals, and each group underwent 1.5 T MR imaging at 1, 3, 5, 7 and 9 days after thrombus induction using a T1-weighted magnetization-prepared rapid gradient-echo sequence (MP-RAGE: TR 10.4 msec, TE 4.0 msec, FA 15 degrees ) and a T2-weighted fast low-angle shot sequence (FLASH: TR 54 msec, TE 18 msec, FA 15 degrees ). The thrombus length was measured on the T1-weighted images. Thrombus conspicuity, signal intensity, and heterogeneity on T2* weighted images were described using visual scales. Radiographic venography and histology served as reference methods. RESULTS: Thrombi were successfully induced in all animals. The overall thrombus length decreased from 43 +/- 9 (day 1 after induction) to 23 +/- 4 mm (day 9). On 3D-reconstructions of the T1-weighted images, the visible portion of the true thrombus length relative to the overall thrombus length was 0.16 +/- 0.3 (day 1), 0.24 +/- 0.3 (day 3), 0.38 +/- 0.5 (day 5), 0.06 +/- 0.1 (day 7) and 0.00 (day 9). Sixteen of 25 thrombi were detectable with the T2*-weighted technique. The overall thrombus signal intensity decreased with the age of the thrombus from day 1 to day 9. The histological evaluation showed that the rabbit thrombi closely resemble human thrombi morphologically. CONCLUSIONS: The thrombus model closely resembles the human venous stagnation thrombus of different organizational stages. With state-of-the-art MRI techniques, thrombi were only partially displayed with the visibility depending on thrombus age. The model may be suitable for evaluating new and potentially more effective MRI techniques for improved thrombus visualization.

[16-row multidetector CT angiography of the aortoiliac system and lower extremity arteries: contrast enhancement and image quality using a standarized examination protocol]. / Becken-Bein-CT-Angiographie mit der 16-Zeilen-Multislice-Technik: Kontrastmittel-Enhancement und Bildqualität unter Einsatz eines standardisierten Untersuchungsprotokolls.

PURPOSE: To assess the degree of enhancement and image quality of 16-slice multidetector CT angiography (MDCTA) of pelvic and lower limb arteries with a monophasic contrast medium injection protocol. MATERIALS AND METHODS: Fifty patients underwent a CT angiography of the pelvic and lower limb arteries using the following parameters: collimation 16 x 1.5 mm, rotation time 0.5 s, table feed 40 mm/sec, slice thickness 2 mm, reconstruction interval 1.2 mm, 100 ml Iomeprol 400 + 60 ml normal saline, flow rate 4 ml/s, bolus tracking (threshold of 250 DeltaHU in aorta). Arterial enhancement was measured in all arterial segments. Maximum intensity projections (MIP) together with axial images were reviewed by two radiologists (consensus). If the results were inconclusive for stenosis, additional curved multiplanar reformations (MPR) were performed. RESULTS: The mean arterial enhancement values were aorta: 314 +/- 69, pelvis: 342 +/- 105, thigh: 347 +/- 139, calf: 231 +/- 109 DeltaHU. The image quality was judged as excellent in 346 (77.6 %), adequate in 76 (17 %), and inadequate in 24 (5.4 %, all but one in calf and foot) of 446 arterial territories. An override of the contrast bolus below the knee occurred in 2 patients rendering the calf arteries nondiagnostic. Venous enhancement occurred in 13 patients but this compromised the diagnostic assessment in only one case. Additional MPRs were required accurately to assess stenoses in 22 of 200 arterial levels in 16 patients with marked arterial calcifications. CONCLUSION: 16-slice MDCTA with a monophasic contrast bolus of Iomeprol 400 provided good arterial enhancement and diagnostic image quality in 94.6 % of the depicted arterial segments. The majority (67 %) of nondiagnostic segments were below the ankle. MPRs were required in patients with marked calcification for accurate assessment of stenosis.

A new concept for melatonin deficit: on pineal calcification and melatonin excretion.

Even though exogenous melatonin has proven to influence sleep and circadian parameters, low endogenous melatonin is not related to sleep disturbances, nor does it predict response to melatonin replacement therapy. In this manuscript, we present a new concept towards a definition of a melatonin deficit. The purpose of the study was to introduce a marker for an intra-individual decrease in melatonin production. Therefore, we developed a method to quantify the degree of pineal calcification (DOC) using cranial computed tomography. Combining pineal DOC with the organs's size, we estimated the uncalcified pineal gland volume. This estimation was positively and significantly associated with 6-sulfatoxymelatonin (aMT6s), collected over 24 hours in urine, in 26 subjects. Data yielded evidence that the decline in aMT6s excretion with age can be sufficiently explained by an increased pineal calcification. These results suggest that DOC might be useful as an indicator of an intra-individual, decreased capability of the pineal gland to produce melatonin. DOC might prove to be a response-marker for melatonin replacement therapy and a vulnerability marker of the circadian timing system.

Evaluation of gadobutrol in a rabbit model as a new lanthanide contrast agent for computed tomography.

RATIONALE AND OBJECTIVES: The efficacy of the neutral lanthanide contrast agent gadobutrol was compared to that of the iodinated contrast agent iopromide in rabbits. METHODS: The computed tomography (CT) attenuation of increasing concentrations of gadolinium (Gd) (gadobutrol) and iodine (I) (iopromide) was measured in Hounsfield units (HU) in aqueous solution at 80, 120, and 137 kV. The peak enhancement (net increase in CT attenuation compared with baseline) and the time-enhancement product in the aorta and in the renal parenchyma of the outer and inner cortex were measured in rabbits over a 5-minute period after the animals were given single intravenous injections of 0.7, 1.0, and 1.5 mmol Gd/kg of gadobutrol and 1.0 and 2.4 mmol I/kg of iopromide. RESULTS: In vitro, the CT attenuation of gadolinium was 40% higher than that of iodine at equivalent mass concentrations (120 kV). The mean peak enhancements in the aorta after the injections of 0.7, 1.0, and 1.5 mmol Gd/kg and 1.0 and 2.4 mmol I/kg were 216, 313, 591, 224, and 498 HU, respectively. In addition, a 30-second injection of the high dose of gadobutrol resulted in an attenuation profile that was suitable for a three-dimensional reconstruction of the aorta and the renal vasculature. CONCLUSIONS: Because of the higher CT attenuation of gadolinium compared with that of iodine, the neutral macrocyclic chelate gadobutrol is a more effective contrast agent than iopromide for CT at lower doses of the imaging atom.

Functional hepatobiliary imaging with gadolinium-EOB-DTPA. A comparison of magnetic resonance imaging and 153gadolinium-EOB-DTPA scintigraphy in rats.

RATIONALE AND OBJECTIVES: Gadolinium-EOB-DTPA (Gd-EOB-DTPA) is a hepatobiliary magnetic resonance (MR) imaging contrast medium designed to detect focal liver lesions. The objective of this study was to evaluate dynamic Gd-EOB-DTPA-enhanced MR imaging as a new method for assessing liver excretory function and to compare it with a scintigraphic method, the gold standard. METHODS: Changes in scintigraphic liver activity or MR liver signal intensity were intraindividually monitored over time after intravenous injection of 50 mumol Gd/kg of Gd-EOB-DTPA in controls and rats with common bile duct obstruction or L-ethionine-induced fatty liver (n = 6). RESULTS: A comparison of liver scintigraphy and MR imaging revealed that elimination half-lives of Gd-EOB-DTPA were significantly longer in rats with common bile duct obstruction (scintigraphy: 100 +/- 27 minutes; MR imaging: 59 +/- 18 minutes) or fatty liver (scintigraphy: 94 +/- 30 minutes; MR imaging: 72 +/- 32 minutes) than in controls (scintigraphy: 20 +/- 2 minutes; MR imaging: 18 +/- 3) (P < 0.05). CONCLUSIONS: Like liver scintigraphy, functional MR liver imaging using Gd-EOB-DTPA is feasible and can differentiate normal controls from models of biliary and hepatocyte disease.

Iron-oxide-enhanced magnetic resonance imaging of atherosclerotic plaques: postmortem analysis of accuracy, inter-observer agreement, and pitfalls.

INTRODUCTION: Contrast-enhanced magnetic resonance (MR) imaging using ultra small superparamagnetic iron oxide (USPIO) particles is a new noninvasive modality for imaging inflammatory atherosclerotic plaques. We determined the accuracy, interobserver agreement, and potential sources of error of this technique by means of postmortem MR imaging of aortic preparations. MATERIAL AND METHODS: Anesthetized atherosclerotic Watanabe heritable hyperlipidemic (WHHL) rabbits were studied after administration of different dosages of intravenous USPIO (DDM 43/34, IDF Berlin, Germany) and different postcontrast time intervals. A (n = 5) received 0 micromol Fe/kg. B (n = 5) received 50 micromol Fe/kg, 8-hour postcontrast interval. C (n = 5) received 50 micromol, 24 hours. D received 200 micromol, 48 hours. The aortas were removed and 3-mm segments prepared for postmortem examination by MR imaging using a T2-weighted gradient-echo sequence (TR/TE/FA; 41 milliseconds/11 milliseconds/15 degrees ), radiography (mammography), and histology (iron staining). USPIO accumulation was defined as the presence of 20 iron-positive cells per microscopic view (x100 magnification). Two independent readers analyzed the MR images and rated their confidence level for a positive MRI finding, defined as a focal signal loss, on a 5-point scale. The results were evaluated by receiver-operator characteristic (ROC) analysis. RESULTS: Of a total of 621 vessel segments technically acceptable for evaluation, 534 were histologically negative and 87 positive. Accuracy, expressed as the area under the ROC curve, was 0.85 for reader 1 and 0.88 for reader 2. Interobserver agreement was 0.67. False-positive findings were established by at least one reader for 121 of the 621 segments, false-negative findings for only 15 segments. Calcifications and mural thrombi were identified as potential sources of error of the method. CONCLUSION: Postmortem USPIO-enhanced MR imaging of atherosclerotic plaques showed a high accuracy and good interobserver agreement in the animal model used here. Further optimization of the method should aim at reducing the rather high percentage of false-positive results.

Superparamagnetic iron oxide-enhanced MRI of atherosclerotic plaques in Watanabe hereditable hyperlipidemic rabbits.

RATIONALE AND OBJECTIVES: Inflammatory atherosclerotic plaques are characterized by increased endothelial permeability and multiple macrophages. Blood-pool MRI contrast agents like superparamagnetic iron oxide (SPIO) have an affinity for the monocyte-macrophage system and thus, may label inflammatory plaques. The objective was to demonstrate SPIO uptake in plaques of atherosclerotic rabbits by MRI and histology. METHODS: Aortas of anesthetized Watanabe hereditable hyperlipidemic rabbits were studied with a moderately T2*-weighted gradient-echo sequence at 1.5 T. Four groups of five animals each were studied: (1) without ultrasmall SPIO (carboxydextran coating; particle size, 25 nm; estimated plasma half-life, 6 hours) or with imaging after intravenous injection of SPIO at a dose (micromol Fe/kg) and postcontrast time delay (hours) of 50/8 (2), 50/24 (3), or 200/48 (4). In vivo MRI was compared with corresponding ex vivo histological iron stains. RESULTS: Animals receiving 200 micromol Fe/kg demonstrated areas of focal signal loss clearly confined to the aortic wall on a mean of 24 +/- 9 (31% +/- 11%) of 76 +/- 5 images compared with 0 +/- 0 of 76 +/- 5 images in controls (P = 0.009). The number of images with this finding in groups 2 and 3 was not significantly different compared with controls. By microscopy, SPIO-iron was seen in the endothelial cells and subendothelial intimal macrophages of atherosclerosis-prone aortic wall segments. Atherosclerotic lesions demonstrating iron uptake also showed a high macrophage content. CONCLUSIONS: SPIO accumulates in aortic plaques of atherosclerotic rabbits, producing a characteristic MRI finding. As SPIO accumulates in plaques with increased endothelial permeability and a high macrophage content, two established features of plaque inflammation, it may have a potential for noninvasive assessment of inflammatory atherosclerotic plaques.

Magnetic resonance imaging-controlled laser-induced interstitial thermotherapy.

RATIONALE AND OBJECTIVES: Laser-induced interstitial thermotherapy (LITT) may become an attractive modality for minimally invasive tumor therapy. Magnetic resonance imaging (MRI) could be used to assist this procedure. METHODS: A T1-weighted turbo fast low-angle shot (FLASH) sequence for on-line monitoring of the laser-influenced region (liver, muscle) was investigated. Sequence parameters were optimized for maximal image contrast. Magnetic resonance imaging-controlled LITT was performed in vitro, in vivo (rabbits), and in 8 human investigations (6 patients). Special laser applicators were used to establish a uniform laser light distribution. RESULTS: With the MRI sequence used, the LITT region is visualized as a bright area outlined by a dark border. This dark border corresponds to an isotherm of 45 +/- 2 degrees C depending on the sequence parameters used. CONCLUSION: With the T1-weighted turbo-FLASH sequence, MRI can be used for on-line monitoring of interstitial laser-induced thermotherapy in moving organs.

Neurogenic hypertension. A new MRI protocol for the evaluation of neurovascular compression of the cranial nerves IX and X root-entry zone.

OBJECTIVE: Neurovascular compression of the rostral ventrolateral medulla (RVLM) has been implicated in the pathogenesis of essential hypertension. Although MRI has been widely used to evaluate the morphologic relation of structures in this region, spatial resolution of the previously used techniques was limited. This article describes the use of a new MRI protocol that combines two sequences with improved spatial resolution and complementary image information as well as a set of defined criteria for image analysis. METHODS: MRI of the brain stem was performed in 60 hypertensive and 50 normotensive subjects using a 3D-CISS and a 3D-FISP-MRA sequence. Neurovascular contact in the RVLM was independently assessed by four readers using predefined criteria and compared with a consensus finding. Agreement was expressed by kappa statistics on a 0 to 1 scale. RESULTS: Left-sided neurovascular contact within the RVLM was found in 13 (22%) hypertensive and 6 (12%) control subjects. The inter-reader agreement for positive and negative findings ranged from 0.47 to 0.79; agreement to the consensus finding ranged from 0.65 to 0.90. CONCLUSIONS: The combination of 3D-CISS and arterial flow-sensitive 3D-FISP, together with the evaluation criteria defined in this study, can be used for describing the finer anatomic features of the brain stem, and in particular for investigation of neurovascular contact of the IX/X cranial nerve root-entry zone. The high quality of images and the substantial or almost perfect reader-consensus agreement should make this protocol useful for future investigations of the neurovascular compression syndrome in patients with essential hypertension and possibly in other neurovascular compression syndromes, such as trigeminal neuralgia and hemifacial spasm.

Color-coded duplex sonography for noninvasive diagnosis and grading of renal artery stenosis.

The accuracy of color-coded duplex sonography (CCDS) in screening hypertensive patients for renal artery stenosis (RAS) was assessed using a semi-quantitative waveform analysis. Our special aims were to separate between moderate and high grade stenoses and to evaluate the accuracy of the method in imaging both the whole course of the renal arteries and accessory renal arteries. Included in the prospective, angiographically controlled study were 135 consecutive patients with 268 renal arteries, of which 195 arteries (73%) could be visualized both proximally and distally by CCDS. Only three of 15 accessory renal arteries could be identified by CCDS. In 42 RAS > or = 50% sensitivity of CCDS was 93%, specificity 92%, and overall accuracy 92%. The sensitivity in identifying RAS > or = 75% was 92%, and none of the high grade stenoses were missed. Because of difficulties in visualizing the middle portion of the renal artery, we carefully examined this part of the artery in 116 additional patients. Whereas the proximal and the distal parts could be visualized in 77% of the renal arteries, signals from the middle third could be derived only in 60% on the right, and in 39% on the left side. Provided that the renal arteries were visualized both proximally and distally, a hemodynamically effective RAS could be excluded with high probability. Moreover, exact grading of high-grade stenoses was possible in all cases but one. An advantage of CCDS over conventional duplex sonography appears to be the time-saving examination. Since a low prevalence of RAS impairs the positive predictive value of CCDS, the examination should be reserved for patients with a strong clinical suspicion of renovascular hypertension.

fMRI shows multiple somatotopic digit representations in human primary somatosensory cortex.

Using electrical finger nerve stimulation in normal human subjects, fMRI detected separate representations for all 5 fingers in the primary somatosensory cortex. Responses were located in the posterior wall of the deep central sulcus (most likely corresponding to Brodmann Area (BA) 3b), and the anterior (BA 1) or posterior crown of the postcentral gyrus (BA 2) with rare activations in BA 3a and 4. In BA 3b we found a regular somatotopic mediolateral digit arrangement for fingers 5 to 1 with a mean Euclidean distance of 16 mm between fingers 1 and 5. In contrast BA 1/2 showed a greater number of adjacent activation foci with significantly more overlap and partly even reversed ordering of neighbouring fingers.

fMRI assessment of somatotopy in human Brodmann area 3b by electrical finger stimulation.

Functional magnetic resonance imaging (fMRI) is capable of detecting focal brain activation induced by electrical stimulation of single fingers in human subjects. In eight subjects somatotopic arrangement of the second and fifth finger was found in Brodmann area 3b of the primary somatosensory cortex. In four subjects the representation area of the second finger was located lateral and inferior to the fifth finger; in one subject the somatotopy was reversed. In three subjects representation areas of the two fingers in Brodmann area 3b were found overlapping. Additional activated areas were found on the crown of ipsilateral and contralateral postcentral gyrus (Brodmann areas 1 and 2) and posterior parietal cortex.

Hypertensive heart disease: quantitative evaluation of response to therapy with cine MR imaging.

RATIONALE AND OBJECTIVES: To assess the ability of cine magnetic resonance (MR) imaging to help detect and quantity changes in left ventricular parameters in patients receiving antihypertensive therapy. MATERIALS AND METHODS: After undergoing baseline cine MR imaging of the heart, 16 (12 men, four women) hypertensive patients participating in a prospective drug trial began isradipine therapy. Follow-up serial cine MR imaging was performed at 3 months and 6 months. Myocardial mass, end-systolic volume, end-diastolic volume, stroke volume, and ejection fraction were measured. Results from transaxially acquired three-dimensional data sets and monoplanar imaging were compared. RESULTS: Three dimensional data showed reductions of 11% in end-systolic volume (P = .0051) and 17% in end-diastolic volume (P = .0023). These changes were not detected with monoplanar imaging. Changes in myocardial mass, stroke volume, and ejection fraction were not statistically significant. CONCLUSION: Three-dimensional cine MR imaging can depict small yet statistically significant reductions in left ventricular volumes in response to antihypertensive therapy.

Magnetic resonance lymphography in rats: effects of muscular activity and hyperthermia on the lymph node uptake of intravenously injected superparamagnetic iron oxide particles.

RATIONALE AND OBJECTIVES: We investigated the influence of muscular activity and regional body temperature changes on the accumulation of intravenously (i.v.) administered, dextran-coated superparamagnetic iron oxide (SPIO) particles in the lymph nodes of rats. METHODS: Four groups of rats (N = 21) were used. Five rats were allowed to move freely after i.v. contrast administration (group 1). In another five rats, muscular inactivity (group 2) was induced during i.v. injection of SPIO particles and for up to 2 hr thereafter by anesthesia. In seven rats (likewise anesthetized), the contrast agent was administered while the extremities of one side of the body were warmed in a water bath for 2 hr (group 3). The rats in groups 1-3 received 100 mumol Fe/kg of the contrast agent. Four rats not given SPIO particles served as the control group (group 4). The lymph nodes of all animals were removed 24 hr after SPIO administration and were embedded in an agar matrix for magnetic resonance imaging at 1.5 T using a proton-density-weighted spin-echo (PD-SE) sequence and a T2*-weighted gradient-recalled echo (T2* GRE) sequence. RESULTS: Signal loss varied widely among the different lymph nodes in group 1. A pronounced signal reduction was observed in the mesenteric (PD-SE = 20 +/- 6%, T2* GRE = 55 +/- 19%), iliac (PD-SE = 13 +/- 13%, T2* GRE = 44 +/- 24%), and popliteal (PD-SE = 24 +/- 7%, T2* GRE = 70 +/- 11%) lymph nodes and only a moderate reduction in the mandibular (PD-SE = 4 +/- 7%, T2* GRE = 42 +/- 15%), axillary (PD-SE = 0 +/- 4%, T2* GRE = 8 +/- 7%), and inguinal (PD-SE = 5 +/- 5%, T2* GRE = 34 +/- 18%) lymph nodes. The least pronounced signal loss occurred in the peripheral lymph nodes of group 2, ranging from 0 +/- 3% for PD-SE sequences and 10 +/- 11% for T2* GRE sequences to 13 +/- 15% for PD-SE sequences and 41 +/- 19% for T2* GRE sequences. In group 3, the uptake of contrast material in the peripheral lymph nodes of the hyperthermal side was significantly more pronounced than on the contralateral side (p < .01), and the contrast agent was distributed more evenly to the different lymph node groups than in group 1. CONCLUSION: Muscular activity and regional hyperthermia markedly influence the accumulation of SPIO particles in different lymph node groups in rats. These findings must be considered in preclinical studies and in the clinical administration of MR lymphography.