value of MR imaging of the bone marrow in children with haematopoietic malignancies

Malignancies were examined by MRI to detect the bone marrow changes. They were 44 patients with acute leukaemia, 4 patients with chronic myelogenous leukaemia, 4 patients with Hodgkins lymphoma, 3 patients with non. Hodgkin s lymphomta and 2 patients with polycythaemia vera. MRI proved to be highly sensitive in detection of focal or dtffuse bone marrow changes in 52 patients [Sensitivity: 100%] and to exclude any bone marrow affection in 5 patients [Specificity: 100%]. In spite of its high sensitivity in detection of bone marrow pathology, MRI could not defive a certain disease. In all haematopoietic malignancies, MRI revealed focal or diffuse low signal intensity on T1 -weighted images and high signal intensity on T2-weighted images. MRI-guided bone marrow biopsy was performed in 26 patients. All were successful and augmented the MRI diagnosis of persistence or relapse of the disease [19 patients], bone marrow aplation with fat replacement [4 patients] and secondary post therapy myelofibrosis [3 patients]. MR1 was proved to be very valuable tool in follow up of patients and in detection of the therapy complications. Its use should restrict the need for bone marrow biopsy to one time at the initial diagnosis

Computed tomography versus magnetic reasonance imaging in diagnosis of congenital cystic intracranial lesions

Twenty one cases of congenital cystic intracranial lesions [having a range of age 24 days to 15 years] were subjected to CT and MRI examinations. The imaging findings were compared with the final diagnosis obtained by clinical data, operation and follow up. The lesions appeared mostly as hypodense nonenhancing masses of CSF density by CT, exerting mass effect according to the size and no surrounding edema. By MRI, they appeared hypointense in T1WI and hyperintense in T2WI. The pathological varieties encountered were; 2 cases of holoprosencephaly, 2 hydranencephaly, one porencephaly, 8 Dandy walker [DW] complex, 7 arachnoid cysts, and one epidermoid tumour. Both CT and MRI can give similar informations concerning the size, shape, rim thickness and other morphologic characteristics of cystic intracranial lesions. Additional data given by MRI are; superior visualization of cerebellar vermis in cases of Dandy Walker complex hence it could be classified into [type A] with absent vermis and [type B] with present vermis in the axial MRI cuts for the fourth ventricular level. MRI is better for detection of infection in an arachnoid cyst by the presence of high signal intensity inside the cyst, It is also able to predict the nature of the contents of the epidermoid cyst whether protein or triglycerides according to its signal intensity in both T[1] and T[2] WI. MRI can detect abnormal signal intensity in the cyst wall of a porencephalic cyst that helps differentiation from arachnoid cysts. Also MRI has a better performance specially in posterior fossa lesions as it is not affected by beam hardening artifact as CT. Other advantages of MRI include lack of ionizing radiation and direct visualization of blood flow, Muliplanar capability and high soft tissue resolution. CT is superior to MRI in the detection of calcification in certain lesions as epidermoid cyst