Subtraction MR Venography Acquired from Time-Resolved Contrast-Enhanced MR Angiography: Comparison with Phase-Contrast MR Venography and Single-Phase Contrast-Enhanced MR Venography

OBJECTIVE: To evaluate the image characteristics of subtraction magnetic resonance venography (SMRV) from time-resolved contrast-enhanced MR angiography (TRMRA) compared with phase-contrast MR venography (PCMRV) and single-phase contrast-enhanced MR venography (CEMRV). MATERIALS AND METHODS: Twenty-one patients who underwent brain MR venography (MRV) using standard protocols (PCMRV, CEMRV, and TRMRA) were included. SMRV was made by subtracting the arterial phase data from the venous phase data in TRMRA. Co-registration and subtraction of the two volume data was done using commercially available software. Image quality and the degree of arterial contamination of the three MRVs were compared. In the three MRVs, 19 pre-defined venous structures (14 dural sinuses and 5 cerebral veins) were evaluated. The signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the three MRVs were also compared. RESULTS: Single-phase contrast-enhanced MR venography showed better image quality (median score 4 in both reviewers) than did the other two MRVs (p < 0.001), whereas SMRV (median score 3 in both reviewers) and PCMRV (median score 3 in both reviewers) had similar image quality (p ≥ 0.951). SMRV (median score 0 in both reviewers) suppressed arterial signal better than did the other MRVs (median score 1 in CEMRV, median score 2 in PCMRV, both reviewers) (p < 0.001). The dural sinus score of SMRV (median and interquartile range [IQR] 48, 43-50 for reviewer 1, 47, 43-49 for reviewer 2) was significantly higher than for PCMRV (median and IQR 31, 25-34 for reviewer 1, 30, 23-32 for reviewer 2) (p < 0.01) and did not differ from that of CEMRV (median and IQR 50, 47-52 for reviewer 1, 49, 45-51 for reviewer 2) (p = 0.146 in reviewer 1 and 0.123 in reviewer 2). The SNR and CNR of SMRV (median and IQR 104.5, 83.1-121.2 and 104.1, 74.9-120.5, respectively) were between those of CEMRV (median and IQR 150.3, 111-182.6 and 148.4, 108-178.2) and PCMRV (median and IQR 59.4, 49.2-74.9 and 53.6, 43.8-69.2). CONCLUSION: Subtraction magnetic resonance venography is a promising MRV method, with acceptable image quality and good arterial suppression.

Clinical silent cerebral infarct (SCI) in patients with thalassemia diseases assessed by magnetic resonance imaging (MRI).

BACKGROUND: Silent cerebral infarct (SCI) could be detected on magnetic resonance imaging. It seems to be associated with the risk of stroke. Ischemic stroke has been reported in sickle cell anemia. Sickle red cell in hypoxic state associated with hypercoagulopathy is the risk factor of blood vessel occlusion leading to ischemic stroke. Hypercoagulable state has been documented in patients with beta thalassemia/Hb E disease, which their red cells are abnormal in deformity. OBJECTIVE: Explore SCI in patients with beta thalassemia/Hb E disease and provide a guideline for prevention of stroke. MATERIAL AND METHOD: Sixty-seven patients (29 males and 28 females, age 10-59 yrs, with a mean age of 31) with beta-thal/Hb E disease who were in the steady state without any neurological sign and symptom and no other associated stroke related disease such as DM, HT were included for MRI scanning. The cerebral MRI protocals were axial Flair, T2 Gre and 3DTOFMRA (3-dimension time of flight magnetic resonance angiography) of the brain. RESULTS: 67 patients (29 males and 28 females) with beta-thal/Hb E disease who were in the steady state without any neurological sign and symptom and no other associate stroke related disease such as DM, HT were included for MRI scanning. The ages of the patients were 10 to 59 years with a mean of 31 years. The abnormalities of the brain were found in 16 of 67 (24%). Most of the lesions were lacunar infarcts with varying amounts in the deep cerebral white matter. One cortical and subcortical infarct was observed with irregularity and stenosis of the intracranial vessels noted by MRA. All cases showed increased vascularity compared to the normal control subject. CONCLUSION: This preliminary prevalence of 24% of SCI in this genotype of thalassemia was higher than found in sickle cell disease (11%). It may be associated with coagulopathy and deformity of the red cell. Further study is needed.

Pre-operative evaluation with magnetic resonance imaging in tetralogy of fallot and pulmonary atresia with ventricular septal defect.

BACKGROUND: Preoperative evaluation of patients with pulmonary atresia and ventricular septal defect (PA/ VSD) are generally done by echocardiogram and cardiac catheterization. The authors' objective of the present study was to compare the findings of Gadolinium (Gd) enhanced cardiac magnetic resonance angiography (MRA) with cardiac catheterization. MATERIAL AND METHOD: Patients who had PA/VSD were prospectively evaluated using cardiac catheterization and cardiac MRA. A branch of the pulmonary arteries was divided into: main pulmonary artery (MPA), left and right branch pulmonary artery (LPA & RPA), major aortopulmonary collateral arteries (MAPCA) and minor collaterals. Each study was interpreted blindly. The agreement of findings was compared using Kappa statistics. RESULTS: There were 43 patients who received both cardiac catheterization and cardiac MRI within a 2 month period The average age was 13.8 +/- 8.4 (2-30) years-old. There was an agreement among measurement of both MPA and LPA & RPA with Kappa statistics of more than 0.8. Gd-enhanced MRA was able to identify more branches of MAPCA when compared to cardiac catheterization. CONCLUSIONS: The results of the present study indicate that Gd-enhanced MRA is a feasible, fast and accurate technique for identification of all sources of pulmonary blood supply in patients with complex pulmonary atresia. The present study was a noninvasive alternative to cardiac catheterization. Gd-enhanced MRA can better delineate small (minor) branches of collateral.

Angiografía por Resonancia Magnética con un equipo de campo ultra bajo / MR angiography with an ultra low field equipment

Se presenta el desarrollo de una versión de software en etapa beta test, con una secuencia para la Angiografía por Resonancia Magnética, utilizando la técnica de Phase test, en un equipo de campo ultra bajo (0,064 Telsa), con imán permanente, de tipo vertical, abierto (Access, Toshiba, Toshiba America Inc., South San Francisco). El software provisto por Toshiba America, se encuentra en el período de Beta Test. (Testeo clínico, previo a la aprobación, dependiente de la FDA, para la comercialización del producto). El equipo es un resonador magnético a imán permanente, vertical y abierto, de campo ultra bajo = 0.064 Telsa. Los pacientes estudiados, en un período de tres meses, mayo a julio de 1994, fueron todos sujetos voluntarios, sanos, libres de enfermedad, y pacientes con diagnóstico clínico de enfermedad vascular cervical y/o cerebral. Los resultados demuestran que la secuencia de Phase Contrast, para la obtención de imágenes de los vasos del cuello y de la irrigación cerebral, presenta muy buena calidad de imagen, muy buena certeza diagnóstica, con buena reproducción de la anatomía y la patología. La Angiografía por Resonancia Magnética es un excelente método, no invasivo, para el estudio de la enfermedad vascular en el cuello y cerebro. La secuencia desarrollada, demuestra el potencial de los equipos de campo bajo en este terreno