Computer- and robot-assisted resection of thalamic astrocytomas in children.

Six children ranging in age from 2 to 10 years who harbored deep benign astrocytomas were operated upon using a computer- and robot-assisted system. A radical excision was achieved in all cases with no significant morbidity nor any mortality. The system consists of an interactive, three-dimensional display of computed tomographic image contours and digitized cerebral angiograms taken using the Brown-Roberts-Wells stereotactic frame. The surgical retractor is held and manipulated using a PUMA 200 robot. The position and orientation of the surgical retractor is displayed on the three-dimensional display. Preoperative planning and simulation are important features of this system. Movement of the brain after removal of the tumor and cerebrospinal fluid is substantial, so the tumor removal is based on visually defined margins. Enhanced computer graphics and robotic devices are important adjuncts to neurosurgical procedures and will find increasing use in the future.

Quantitative Phenotyping of Childhood Leukemia Identifies Variable and Invariable Cell Surface Antigens.

Cells obtained from 75 cases of childhood leukemia were subjected to flow cytometry analysis to estimate the density of several cell surface antigens and derive a quantitative immunological phenotype. Sixty-five cases of acute lymphoblastic leukemia (ALL) including 10 T-ALL, 6 non-T ALL designated groups I and II (HLA-DRCALLA), 48 non-T ALL termed groups III and IV (HLA-DRCALLA) and one B-ALL were studied; 10 cases of acute myeloblastic leukemia (AML) were also analysed. The estimation of the relative fluorescence index (RFI) on leukemic blasts led to the derivation of mean values for each marker in the leukemia subgroups. We have quantitated the levels of the antigens generally used in the classification of these leukemias (CALLA, CD5, CD20, CD13, HLA-DR and CD19) and of other cell surface antigens associated with leukemic cells. For example, CALLA (CD10) level was high (mean RFI value of 26.4) on the leukemic cells of non-T ALL groups III and IV. The CD5 antigen was present on T-ALL, as expected, with an RFI value of 4.5; however, low levels were observed on the more immature non-T ALL of groups I and II (RFI = 2.3 on only 27% of blast cells). The quantitative analysis of the cell surface antigens associated with non-T ALL has revealed molecules such as CALLA, HLA-DR, CD9 and CD44 present at high and variable levels and others such as CD19, CD38, 44G4, 44D7, 44H9 and 44H6 generally of lower intensity, less variable from one patient to another, and with similar mean levels of expression in the different subgroups. These invariable antigens are not altered by the lineage or stage of differentiation of the leukemic cells. The variable antigens could be correlated with the functional and/or differentiation status of the cells and could also be modified by the alterations of regulatory processes associated with malignancy. The quantitation of multiple leukemia-associated antigens, whose structure and function are becoming rapidly established, should help in elucidating the function of these molecules in leukemogenesis and/or disease progression.