A Method to Estimate Brain Volume from Head CT Images and Application to Detect Brain Atrophy in Alzheimer Disease

BACKGROUND AND PURPOSE

Total brain volume and total intracranial volume are important measures for assessing whole-brain atrophy in Alzheimer disease, dementia, and other neurodegenerative diseases. Unlike MR imaging, which has a number of well-validated fully-automated methods, only a handful of methods segment CT images. Available methods either use enhanced CT, do not estimate both volumes, or require formal validation. Reliable computation of total brain volume and total intracranial volume from CT is needed because head CTs are more widely used than head MRIs in the clinical setting. We present an automated head CT segmentation method (CTseg) to estimate total brain volume and total intracranial volume.

MATERIALS AND METHODS

CTseg adapts a widely used brain MR imaging segmentation method from the Statistical Parametric Mapping toolbox using a CT-based template for initial registration. CTseg was tested and validated using head CT images from a clinical archive.

RESULTS

CTseg showed excellent agreement with 20 manually segmented head CTs. The intraclass correlation was 0.97 (P < .001) for total intracranial volume and 0.94 (P < .001) for total brain volume. When CTseg was applied to a cross-sectional Alzheimer disease dataset (58 with Alzheimer disease patients and 58 matched controls), CTseg detected a loss in percentage total brain volume (as a percentage of total intracranial volume) with age (P < .001) as well as a group difference between patients with Alzheimer disease and controls (P < .01). We observed similar results when total brain volume was modeled with total intracranial volume as a confounding variable.

CONCLUSIONS

In current clinical practice, brain atrophy is assessed by inaccurate and subjective "eyeballing" of CT images. Manual segmentation of head CT images is prohibitively arduous and time-consuming. CTseg can potentially help clinicians to automatically measure total brain volume and detect and track atrophy in neurodegenerative diseases. In addition, CTseg can be applied to large clinical archives for a variety of research studies.

Old people in the emergency room: age-related differences in emergency department use and care

Little is known about how the care received in emergency departments (ED) by the elderly population differs from that received by younger people. We prospectively abstracted ED records of 1620 consecutive patients visiting a large community hospital ED over a 22-day period in 1984 for demographic and medical variables. Charts of patients presenting with five specific complaints (dyspnea, chest pain, abdominal pain, syncope, and motor vehicle accidents) were also analyzed for process of care variables and, for patients hospitalized, the accuracy of the ED diagnosis. Older people (ie, those greater than or equal to 65 years of age) do not seem to be overutilizers of the ED for minor complaints, in fact, they tend to be more acutely ill on presentation than younger people. Older people were more likely to be hospitalized (46% v 10%, P less than .001), to arrive by ambulance (35% v 10%, P less than .001), and to have an identified source of primary care (95% v 64%, P less than .01). Older people stayed longer in the ED than younger people if they were eventually released home but shorter if admitted to the hospital. Test ordering patterns for specific complaints varied by patient age (eg, older patients had more electrocardiograms performed for chest pain and fewer urinalyses for abdominal pain than younger patients). Therapy for specific complaints showed less age effect. Although generally more diagnostic tests were performed on older patients, the ED diagnosis tended to be more accurate for younger patients. Our data indicate that the process of ED care may be substantially different for the elderly population and have implications for future planning and financing of medical care.