T1-and T2-weighted Images Research Articles

Spinal xanthogranuloma in a child: Case report

A case of a patient with a xanthogranuloma in the thoracic spine is presented. Magnetic resonance imaging revealed an intradural extramedullary tumor between T6 and T9 as a low-intensity mass on both T1-and T2-weighted images. Total removal of this tumor was achieved through a laminoplastic laminectomy. Differentiation of this disease from other xanthogranulomas in the central nervous system is discussed.

脊椎骨粗しょう症を伴う圧迫骨折のＭＲＩ像の検討

Twenty female pahents (averaging 75.5years) with compression fractures associated with spinal osteoporosis were examined by magnetic resonance (MR) imaging, Newly diagnosed cases presented low and high signals in T1-and T2-weighted images, respectively. Image normalization was noted from peribody (especially posterior margin)after 1-3months of treatment, gradually leading to iso-luminance in mixed presence of high and low signals. Seven cases showed no roentgenographic euidence of fractures, but did show signal changes in MRI. Two cases also developed such changes in the adjacent vertebral bodies in the course of treatment, showing the need for diagnostic care.

Infarction of the Kidney

Magnetic resonance imaging was performed on nine kidneys in six patients with renal infarction caused by renal arterial embolism secondary to cardiac valvular disease. The time interval between the onset of the symptoms attributable to renal infarction and the date of MRI was 2-23 days. On both T1- and T2-weighted images the signal intensity of the infarcted area was lower than that of the noninfarcted area in six kidneys and higher in three kidneys. Postcontrast T1-weighted images demonstrated the extent of the infarction except in the kidney in which the infarcted areas had high signal intensity on precontrast T1-weighted images.

Granulomatous prostatitis: a pitfall in MR imaging of prostatic carcinoma

Granulomatous prostatitis is an uncommon disease that can prostatic carcinoma on both digital rectal examination and transrectal ultrasound. Four patients who underwent magnetic resonance imaging of the prostate had a histological diagnosis of graanulomatous prostatitis; three of them had recent urinary tract infections. The other patient had an associated midline prostatic cyst and a focus of malignancy. T1-and T2-weighted spin-echo images were obtained in all cases. Peripheral zone lesions of decreased signal intensity, suggestive of carcinoma,were found in all four patients on T2-weighted images. Granulomatous prostatitis should be considered in the differential diagnosis of low signal intensity areas with prostatic magnetic resonance imaging.

術後性上顎嚢胞のＭＲＩ

Magnetic resonance images of 47 patients with postoperative maxillary cyst were analyzed for size, location, and signal intensity. The smallest cyst was confirmed at surgery to be 1cm×1cm×1cm and the largest 5cm×5cm×5cm.The cysts were usually found in the superomedial and inferomedial parts of the maxillary sinus (44%). Many patients (60%) had multiple cysts or bilateral cysts (30%).In most the signal intensiy was low in the T1-weighted SE (500/40) images and high in the T2-weighted SE (2000/80) images.Cysts with a hemorrhagic component, though rare, showed high signal intensity in both T1-and T2-weighted images.

MRI of the pancreas transplant: Lack of correlation between imaging and clinical status

Twenty-five MRI scans were performed on 14 patients with cadaveric pancreatic transplants to determine the role of this modality in the evaluation of transplant dysfunction. Our population included 12 normal transplants and 13 recipients with pancreatic graft dysfunction (either rejection or pancreatitis). Six of the latter patients had two or more scans permitting reassessment of the same transplant in various states of health. T1-and T2-weighted MR images were evaluated qualitatively and quantitatively to see if certain patterns were associated with clinical status. We found that although MRI was capable of producing excellent images of the in situ pancreatic transplant, this modality was unable to reliably distinguish the normal from the abnormal transplant. This conclusion differs from prior assessments; possible reasons for this are discussed.

Fibrous dysplasia: Magnetic resonance imaging appearance at 1.5 tesla

Fibrous dysplasia has been described in a small number of cases in the literature as showing low signal intensity on T1- and T2-weighted magnetic resonance images. We reviewed magnetic resonance scans of 13 patients with fibrous dysplasia to determine if there might be a characteristic appearance. All lesions had sharply defined borders and were of intermediate signal intensity on T1-weighted images. With T2 weighting, six lesions (46%) showed high signal intensity, four (31%) showed persistent intermediate signal intensity, and three (23%) showed mixed intermediate and high signal intensity. Ten lesions (77%) had inhomogeneous signal intensity and three (23%) had homogeneous signal intensity. We concluded that fibrous dysplasia does not have a characteristic appearance on magnetic resonance imaging. However, magnetic resonance may be helpful in establishing the diagnosis of fibrous dysplasia if low to intermediate signal intensity is seen on both T1-and T2-weighted images. This situation occurred in 54%, of our cases, whereas the other 46% had nonspecific signal characteristics indistinguishable from many other bone lesions.

<I>Computed Tomography and Magnetic Resonance Imaging of Nonhemorrhagic, Metastatic Melanoma of the Brain</I>

Malignant melanoma frequently metastasizes to the central nervous system. Characteristic features of such lesions are increased density on computed tomography (CT) and shortening of the T1 and T2 on magnetic resonance (MR) imaging. Intratumoral hemorrhage, rather than melanin, is considered to be mainly responsible for these unique radiological features. The authors report a case involving a nonhemorrhagic, metastatic intracerebral melanoma. CT revealed a high-density mass, and MR imaging demonstrated a hyperintense mass both on T1- and T2-weighted images. These observations suggest that melanin is in fact a major determinant of the increased density on CT scans and the high signal intensity on T1-weighted MR images. On T2-weighted images, the paramagnetic effect appears to vary according to the melanin content.

Common pharmaceuticals alter tissue proton NMR relaxation properties.

Differences in the tissue properties of water are the basis for the detailed anatomic visualization of internal body structures produced by NMR imaging. Physiological and pathological events have the potential to alter proton nuclear magnetic resonance relaxation properties through changes in water environment. In this study, the parenteral injection of pharmaceuticals produced significant changes (12-21%) in proton NMR relaxation times in tissues of treated rats. The extent of relaxation time change was both tissue specific and drug specific. Therefore, the effects of common pharmaceuticals should be considered in the interpretation of T1- and T2-weighted NMR images.