A use of a neural network to evaluate contrast enhancement curves in breast magnetic resonance images.
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For the diagnosis of breast cancer using magnetic resonance imaging (MRI), one of the most important parameters is the analysis of contrast enhancement. A three-dimensional MR sequence is applied before and five times after bolus injection of paramagnetic contrast medium (Gd-DTPA). The dynamics of absorption are described by a time/intensity enhancement curve, which reports the mean intensity of the MR signal in a small region of interest (ROI) for about 8 minutes after contrast injection. The aim of our study was to use an artificial neural network to automatically classify the enhancement curves as "benign" or "malignant." We used a classic feed-forward back-propagation neural network, with three layers: five input nodes, two hidden nodes, and one output node. The network has been trained with 26 pathologic curves (10 invasive carcinoma [K], two carcinoma-in-situ [DCIS], and 14 benign lesion [B]). The trained network has been tested with 58 curves (36 K, one DCIS, 21 B). The network was able to correctly identify the test curves with a sensitivity of 76% and a specificity of 90%. For comparison, the same set of curves was analyzed separately by two radiologists (a breast MR expert and a resident radiologist). The first correctly interpreted the curves with a sensitivity of 76% and a specificity of 90%, while the second scored 59% for sensitivity and 90% for specificity. These results demonstrate that a trained neural network recognizes the pathologic curves at least as well as an expert radiologist. This algorithm can help the radiologist attain rapid and affordable screening of a large number of ROIs. A complete automatic computer-aided diagnosis support system should find a number of potentially interesting ROIs and automatically analyze the enhancement curves for each ROI by neural networks, reporting to the radiologist only the potentially pathologic ROIs for a more accurate, manual, repeated evaluation. (+info)
Low field dedicated magnetic resonance imaging in untreated rheumatoid arthritis of recent onset.
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OBJECTIVE: To compare a low field dedicated extremity magnetic resonance imaging system (E-MRI) with x ray and clinical examination, in the detection of inflammation and erosive lesions in wrist and metacarpophalangeal (MCP) joints in newly diagnosed, untreated rheumatoid arthritis (RA). PATIENTS AND METHODS: Twenty five patients (disease duration < or =1 year) and three healthy controls entered the study. An x ray examination and MRI (before and after intravenous injection of a contrast agent) of the 2nd-5th MCP joints and the wrist was performed. The number of erosions on x ray examination and MRI was calculated, and synovitis in the MCP joints and wrists was graded semiquantitatively. RESULTS: E-MRI detected 57 bone erosions, whereas only six erosions were disclosed by x ray examination (ratio 9.5:1). Synovial hypertrophy grades were significantly higher in RA joints with clinical signs of joint inflammation-that is, swelling and/or tenderness (median 3, 5th-95th centile 1-4) than without these clinical signs (median 2, 5th-95th centile 1-3), p < 0.001. 51% of the joints without clinical signs of synovitis showed synovial hypertrophy on E-MRI. There was a positive correlation between MRI scores of synovitis and the number of erosions detected by MRI in the MCP joints (Spearman r(s) = 0.31, p < 0.01). No healthy controls had erosions or synovitis on MRI. CONCLUSION: Joint destruction starts very early in RA and E-MRI allows detailed evaluation of inflammatory and destructive changes in wrists and MCP joints in patients with incipient RA. (+info)
Scaphoid blood flow and acute fracture healing. A dynamic MRI study with enhancement with gadolinium.
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We have investigated whether assessment of blood flow to the proximal scaphoid can be used to predict nonunion in acute fractures of the scaphoid. We studied 32 fractures of the scaphoid one to two weeks after injury, by dynamic fat-suppressed T1-weighted gradient-echo MRI after the intravenous administration of gadopentetate dimeglumine (0.1 mmol/kg body-weight). Steepest slope values (SSV) and percentage enhancement values (%E) were calculated for the distal and proximal fragments and poles. All the fractures were treated by immobilisation in a cast, and union was assessed by CT at 12 weeks. Nonunion occurred in four fractures (12%), and there was no statistically significant difference between the proximal fragment SSV and %E values for the fractures which united and those with nonunion. The difference between the proximal pole SSV and %E values for the union and nonunion groups reached statistical significance (p < 0.05), but with higher enhancement parameters for the nonunion group. Our results suggest that poor proximal vascularity is not an important determinant of union in fractures of the scaphoid. (+info)
Relation between Gd-DTPA contrast enhancement and regional inotropic response in the periphery and center of myocardial infarction.
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BACKGROUND: Gd-DTPA contrast-enhanced (CE) MRI identifies patterns of early hypoenhancement and delayed hyperenhancement in acute myocardial infarction, but their clinical significance for the prediction of myocardial viability remains controversial. Therefore, we closely examined the relationship between these CE patterns and regional inotropic response to low-dose dobutamine infusion at a regional level. METHODS AND RESULTS: Thirteen dogs underwent CE and tagged MRI at rest and during 5 microg. kg(-1). min(-1) dobutamine 48 hours after MI. CE patterns and 3D regional strains were measured in 96 segments per animal. Segments were categorized as being normofunctional (n=828) if resting circumferential shortening was within the range of remote myocardium, or dysfunctional (n=420) if not. Inotropic response in resting dysfunctional segments was assessed according to CE patterns. Significant improvement of radial thickening (from +12+/-1% [mean+/-SEM] to +22+/-2%, P<0.05) and circumferential shortening (from +1+/-1% to -5+/-1%, P<0.05) strains occurred in dysfunctional myocardium with normal CE pattern but not in myocardium with early hypoenhancement. Delayed hyperenhanced myocardium displayed a more complex behavior. Circumferential stretching improved in the peripheral regions (from +4+/-1% to -2+/-2%, P<0.05), where the infarct was nontransmural (38+/-3% transmurality), but not in centrally hyperenhanced regions (from +4+/-1% to +1+/-1% P=NS), where the infarct was 66+/-3% transmural. CONCLUSIONS: Inotropic reserve was confined to dysfunctional myocardium with normal contrast enhancement but not to myocardium with early hypoenhancement. Inotropic response in delayed hyperenhanced myocardium is influenced by transmurality of necrosis. These observations support the use of CE MRI for the clinical detection of myocardial viability. (+info)
Value of magnetic resonance imaging in predicting efficacy of GnRH analogue treatment for uterine leiomyoma.
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BACKGROUND: Estimating pharmacological efficacy is important when selecting conservative treatment of uterine leiomyoma. Hence, the ability of magnetic resonance (MR) imaging to predict gonadotrophin-releasing hormone (GnRH) analogue efficacy was investigated. METHODS: A total of 85 lesions was studied in 40 patients who were clinically diagnosed as having uterine leiomyoma and treated with GnRH analogue for 24 weeks. To evaluate changes in lesion size, T2-weighted and gadopentetate-dimeglumine (Gd-DTPA)-enhanced, T1-weighted MR images were obtained within 2 weeks before, and immediately after termination of, GnRH analogue treatment. RESULTS: An average 46.3% size reduction was observed in 45 lesions (52.9%); these were seen as low signal intensity on T2-weighted images and enhanced by Gd-DTPA. Also, an average 44.7% size reduction was observed in lesions enhanced by Gd-DTPA, irrespective of signal intensity findings on T2-weighted images. The average size reduction of unenhanced lesions was only 17.8%, and significantly different from enhanced lesions (P < 0.001). The prediction of efficacy was difficult in those lesions not enhanced. CONCLUSIONS: It is considered that evaluation of MR signal intensities, and the presence or absence of Gd-DTPA enhancement, would predict treatment efficacy before GnRH analogue administration. (+info)
Molecular biologic and scintigraphic analyses of somatostatin receptor-negative meningiomas.
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Somatostatin receptor scintigraphy (SRS) using 111In-octreotide has proven useful in the preoperative discrimination of expansive central nervous system lesions. Meningiomas, generally expressing human somatostatin receptor (hsst) on their surface, were detected with a sensitivity of about 100%. This finding was associated with the assumption that meningiomas lack an intact blood-brain barrier. However, this exclusion procedure became questionable when histologically proven meningiomas in which SRS was negative were reported. Therefore, the aim of this study was to discover why these meningiomas gave negative SRS results. METHODS: Before surgery, 46 patients with 47 meningiomas underwent standard MRI and SRS. Thirty-four of these patients with 35 tumors were also examined by 99mTc-diethylenetriaminepentaacetic acid (DTPA) brain scintigraphy. After surgical resection, hsst subtype 2 (hsst2) messenger RNA (mRNA) expression of 4 SRS-positive and 4 SRS-negative meningiomas was estimated semiquantitatively by reverse transcriptase polymerase chain reaction (RT-PCR). Translation of hsst2 mRNA into receptor proteins was proven immunocytochemically on the surface of 1 SRS-positive and 1 SRS-negative meningioma. Tumor specimens used for RNA extraction and RT-PCR and cultivated cells used for hsst2 immunostaining were tested for their meningioma nature by immunochemistry. RESULTS: SRS yielded positive results in 39 meningiomas with a tumor volume of 24.1 +/- 32.8 mL and negative results in 8 meningiomas with a volume of 3.9 +/- 6.5 mL. 99mTc-DTPA scintigraphy visualized 24 of 35 meningiomas. SRS was positive in all of them. In contrast, 11 meningiomas were (99mTc-DTPA negative. In these meningiomas, SRS was negative in 5 cases (5.4 +/- 8.1 mL), whereas the remaining 6 were positive (4.6 +/- 4.5 mL). None of the meningiomas was 99mTc-DTPA positive and SRS negative. RT-PCR revealed no significant difference of hsst2 mRNA expression between SRS-positive and SRS-negative meningiomas but showed varied expression among all meningiomas regardless of SRS results. Furthermore, hsst2 proteins were visualized immunocytochemically on the surface of cultivated cells of SRS-positive and SRS-negative meningiomas. CONCLUSION: SRS-negative meningiomas do express hsst2; thus, in these meningiomas SRS is false-negative. Because an insufficient sensitivity was excluded, 99mTc-DTPA scintigraphy identified a permeability barrier in SRS-negative meningiomas that explains their false-negative SRS results. SRS-negative meningiomas most likely meet the function of their tissue of origin (the meninges) to develop more-or-less intact permeability barriers. (+info)
The susceptibility of tumors to the antivascular drug combretastatin A4 phosphate correlates with vascular permeability.
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The acute effects of the antivascular drug, combretastatin A4 phosphate, on tumor energy status and perfusion were assessed using magnetic resonance imaging (MRI) and spectroscopy. Localized (31)P magnetic resonance spectroscopy showed that LoVo and RIF-1 tumors responded well to drug treatment, with significant increases in the P(i)/nucleoside triphosphate ratio within 3 h, whereas SaS, SaF, and HT29 tumors did not respond to the same extent. This variable response was also seen in MRI experiments in which tumor perfusion was assessed by monitoring the kinetics of inflow of the contrast agent, gadolinium diethylenetriaminepentaacetate. These data were analyzed to give the initial rate and time constant for inflow of contrast agent and the integral under the inflow curve. The differential susceptibility of the tumors to combretastatin A4 phosphate showed a positive correlation with prior MRI measurements of tumor vascular permeability, which was determined by measuring the inflow of a macromolecular contrast agent, BSA-gadolinium diethylenetriaminepentaacetate. (+info)
Magnetic resonance imaging permits in vivo monitoring of catheter-based vascular gene delivery.
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BACKGROUND: Gene therapy is an exciting frontier in modern medicine. To date, most investigations about the imaging of gene therapy have primarily focused on noncardiovascular systems, and no in vivo imaging modalities are currently available for monitoring vascular gene therapy. The purpose of this study was to develop an in vivo imaging tool to monitor a catheter-based vascular gene delivery procedure. METHODS AND RESULTS: We produced gadolinium/blue dye and gadolinium/gene-vector media by mixing Magnevist with a trypan-blue or a lentiviral vector carrying a green fluorescent protein (GFP) gene. The gadolinium was used as an imaging marker for magnetic resonance (MR) imaging to visualize vessel wall enhancement, and the blue dye/GFP was used as a tissue stain marker for histology/immunohistochemistry to confirm the success of the transfer. Using Remedy gene delivery catheters, we transferred the gadolinium/blue dye (n=8) or gadolinium/GFP lentivirus (n=4) into the arteries of 12 pigs, that were monitored under high-resolution MR imaging. The results showed, in all 12 pigs, the gadolinium enhancement of the target vessel walls on MR imaging and the blue/GFP staining of the target vessel tissues with histology/immunohistochemistry. This study shows the potential of using MR imaging to dynamically visualize (1) where the gadolinium/genes are delivered; (2) how the target portion is marked; and (3) whether the gene transfer procedure causes complications. CONCLUSIONS: We present a technical development that uses high-resolution MR imaging as an in vivo imaging tool to monitor catheter-based vascular gene delivery. (+info)