Early CT detection of intracranial seeding from medulloblastoma

Since 1975, intracranial subarachnoid metastases of medulloblastoma have been detected in seven of 23 initial contrast-enhanced computed tomographic (CT) scans in children with proven medulloblastoma. Furthermore, four of the seven cases with subarachnoid seeding were diagnosed after the introduction of high-resolution contrastenhanced CT. Only three cases of seeding had been detected in the previous 17 lowresolution cases studied with CT. Thus, it is quite likely that the incidence of subarachnoid metastases may be substantially more than the overall figure of 30% indicated by this series. This may have an impact on the treatment of these patients, since the frequent appearance of metastases may indicate the need for more vigorous chemotherapeutic regimens. One should be aware of the possibility of early intracranial subarachnoid seeding and that it can be demonstrated by contrast-enhanced CT. This is particularly true when using high-resolution scanners in conjunction with 5 mm sections through the posterior fossa . At the Childrens Hospital of Los Angeles , medulloblastoma is the most common posterior fossa brain tumor Materials and Methods We retrospecti vely reviewed surgically proven cases of medullobl astoma at Childrens Hospital of Los Angeles between 1975 and September 1983 . Since 1975 . when an EMI scanner was installed at this institution . 23 cases of medulloblastoma have been diagnosed with the aid of an initial CT scan . Several other cases either had no ini tial CT , or the initial record s could not be retrieved. The 23 cases that were available for review were scruti ni zed for evidence of subarachnoid seeding of tu mor . The primary criterion of metastases was subarachnoid enhancement on the postcontrast scan. An area of increased density on the precontrast scan and obliteration of the subarachnoid space were also considered manifestations of metastases. The scanning procedure recommended with high-resolution CT machines includes 5 mm slices through the posterior fossa before and after infusion of contrast material. Conray 60 was admini stered by drip infusion at the rate of 2 ml/ kg . It should be mentioned that this protocol was not in use during the earlier phases of this retrospective survey (before the introduction of high-resolution scanning)

The Motion Artifact Suppression Taechnique (MAST) in magnetic resonance imaging: Clinical results

The Motion Artifact Suppression Technique (MAST) is a method which uses a series of gradient echos that are computed to cancel velocity, acceleration and pulsatility components of involuntary motion in MR imaging. A total of 916 patient studies were performed over a nine month period using MAST sequences with a TE 40, 60, 80, 100, 120, and 26 112 . There was considerable improvement in long TR, long TE images. Cerebrospinal fluid flow artifacts were reduced. Body and spine images had reduced flow and respiratory artifacts. Spin rephasing in blood vessels caused increased intraluminal signal. This might be useful for cardiovascular imaging