Population-level risks of physical activity: Saving bones and screening hearts

Documented risks of physical activity include reduced bone mineral density at high activity volume, and sudden cardiac death among adults and adolescents. Further illumination of these risks is needed to inform future public health guidelines. The present research seeks to 1) quantify the association between physical activity and bone mineral density (BMD) across a broad range of activity volume, 2) assess the utility of an existing pre-screening questionnaire among US adults, and 3) determine if pre-screening risk stratification by questionnaire predicts referral to physician among Texas adolescents. ^ Among 9,468 adults 20 years of age or older in the National Health and Nutrition Examination Survey (NHANES) 2007-2010, linear regression analyses revealed generally higher BMD at the lumbar spine and proximal femur with greater reported activity volume. Only lumbar BMD in women was unassociated with activity volume. Among men, BMD was similar at activity beyond four times the minimum volume recommended in the Physical Activity Guidelines. These results suggest that the range of activity reported by US adults is not associated with low BMD at either site. ^ The American Heart Association / American College of Sports Medicine Preparticipation Questionnaire (AAPQ) was applied to 6,661 adults 40 years of age or older from NHANES 2001-2004 by using NHANES responses to complete AAPQ items. Following AAPQ referral criteria, 95.5% of women and 93.5% of men would be referred to a physician before exercise initiation, suggesting little utility for the AAPQ among adults aged 40 years or older. Unnecessary referral before exercise initiation may present a barrier to exercise adoption and may strain an already stressed healthcare infrastructure. ^ Among 3181 athletes in the Texas Adolescent Athlete Heart Screening Registry, 55.2% of boys and 62.2% of girls were classified as high-risk based on questionnaire answers. Using sex-stratified contingency table analyses, risk categories were not significantly associated with referral to physician based on electrocardiogram or echocardiogram, nor were they associated with confirmed diagnoses on follow-up. Additional research is needed to identify which symptoms are most closely related to sudden cardiac death, and determine the best methods for rapid and reliable assessment. ^ In conclusion, this research suggests that the volume of activity reported by US adults is not associated with low BMD at two clinically relevant sites, casts doubts on the utility of two existing cardiac screening tools, and raises concern about barriers to activity erected through ineffective screening. These findings augment existing research in this area that may inform revisions to the Physical Activity Guidelines regarding risk mitigation.^

High Resolution Vascular Imaging of the Rat Spine using Liposomal Blood Pool MR Agent

High resolution, vascular magnetic resonance imaging of the spine region in small animals poses several challenges. The small anatomical features, extravascular diffusion, and the low signal-to-noise ratio limit the use of conventional contrast agents. We hypothesize that a long circulating, intravascular liposomal-encapsulated MR contrast agent (liposomal-Gd) would facilitate visualization of small anatomical features of the perispinal vasculature not visible with conventional contrast agent (Gd-DTPA).

High-resolution vascular imaging of the rat spine using liposomal blood pool MR agent.

BACKGROUND AND PURPOSE: High-resolution, vascular MR imaging of the spine region in small animals poses several challenges. The small anatomic features, extravascular diffusion, and low signal-to-noise ratio limit the use of conventional contrast agents. We hypothesize that a long-circulating, intravascular liposomal-encapsulated MR contrast agent (liposomal-Gd) would facilitate visualization of small anatomic features of the perispinal vasculature not visible with conventional contrast agent (gadolinium-diethylene-triaminepentaacetic acid [Gd-DTPA]). METHODS: In this study, high-resolution MR angiography of the spine region was performed in a rat model using a liposomal-Gd, which is known to remain within the blood pool for an extended period. The imaging characteristics of this agent were compared with those of a conventional contrast agent, Gd-DTPA. RESULTS: The liposomal-Gd enabled acquisition of high quality angiograms with high signal-to-noise ratio. Several important vascular features, such as radicular arteries, posterior spinal vein, and epidural venous plexus were visualized in the angiograms obtained with the liposomal agent. The MR angiograms obtained with conventional Gd-DTPA did not demonstrate these vessels clearly because of marked extravascular soft-tissue enhancement that obscured the vasculature. CONCLUSIONS: This study demonstrates the potential benefit of long-circulating liposomal-Gd as a MR contrast agent for high-resolution vascular imaging applications.

Commissioning an Anthropomorphic Spine and Lung Phantom for Remote Dose Verification of Institutions Participating in RTOG 0631

The RPC developed a new phantom to ensure comparable and consistent radiation administration in spinal radiosurgery clinical trials. This study assessed the phantom’s dosimetric and anatomic utility. The ‘spine phantom’ is a water filled thorax with anatomy encountered in spinal radiosurgery: target volume, vertebral column, spinal canal, esophagus, heart, and lungs. The dose to the target volume was measured with axial and sagittal planes of radiochromic film and thermoluminescent dosimeters (TLD). The dose distributions were measured with the radiochromic film calibrated to the absolute dose measured by the TLD. Four irradiations were administered: a four angle box plan, a seven angle conformal plan, a seven angle IMRT plan, and a nine angle IMRT plan (denoted as IMRT plan #1 and plan #2, respectively). In each plan, at least 95% of the defined tumor volume received 8 Gy. For each irradiation the planned and administered dose distributions were registered via pinpricks, and compared using point dose measurements, dose profiles, isodose distributions, and gamma analyses. Based on previous experience at the RPC, a gamma analysis was considering passing if greater than 95% of pixels passed the criteria of 5% dose difference and 3 mm distance-to-agreement. Each irradiation showed acceptable agreement in the qualitative assessments and exceeded the 95% passing rate at the 5% / 3 mm criteria, except IMRT plan #1, which was determined to have been poorly localized during treatment administration. The measured and planned dose distributions demonstrated acceptable agreement at the 5% / 3 mm criteria, and the spine phantom was determined to be a useful tool for the remote assessment of an institution’s treatment planning and dose delivery regimen.

Chondrosarcoma of the mobile spine and sacrum.

Chondrosarcoma is a rare malignant tumor of bone. This family of tumors can be primary malignant tumors or a secondary malignant transformation of an underlying benign cartilage tumor. Pain is often the initial presenting complaint when chondrosarcoma involves the spine. In the mobile spine, chondrosarcoma commonly presents within the vertebral body and shows a predilection for the thoracic spine. Due to the resistance of chondrosarcoma to both radiation and chemotherapy, treatment is focused on surgery. With en bloc excision of chondrosarcoma of the mobile spine and sacrum patients can have local recurrence rates as low as 20%.