Clinical Management of End-Stage Renal Disease Patients on Dialysis Receiving Radioactive Iodine Treatment.

PURPOSE: Radioactive iodine (RAI) is used to treat thyroid cancer patients with a clear paradigm for most patients. End-stage renal disease (ESRD) patients pose several challenges when undergoing RAI treatment, primarily due to the lack of renal clearance. We retrospectively report our experience with RAI treatment in a cohort of patients with ESRD and provide a set of recommendations on aspects such as the need for adjusted dose activity, balancing scheduling between RAI therapy and dialysis, and radiation safety precautions. PATIENTS AND METHODS: In this study, we report on 5 patients (6 cases), with ESRD on dialysis, treated with RAI for thyroid cancer. Retention measurements to determine individual biological clearance of RAI from the patient's body before and after dialysis sessions were assessed using external exposure dose rates measured at 1 m. RESULTS: Delayed biological clearance of RAI, after the first hemodialysis session, resulted in a longer RAI effective half-life as a consequence of longer retention periods, consistent with observations reported in scientific literature. To achieve a much closer radiation exposure compared with a nondialysis patient, one would recommend administering ~20%-30% of the dose activity normally administered to a thyroid cancer patient based on their medical history, histopathology, and uptake with the appropriate dialysis schedule. CONCLUSIONS: Special precautions should be taken with the administration of RAI in ESRD patients by adjusting the prescribed dose activity, dialysis sessions, and paying special attention to wastes. Pooling data from multiple centers may be useful to build a consensus and substantiated recommendations.

The effects of visual magnification and physical movement scale on the manipulation of a tool with indirect vision.

Modern tools often separate the visual and physical aspects of operation, requiring users to manipulate an instrument while viewing the results indirectly on a display. This can pose usability challenges particularly in applications, such as laparoscopic surgery, that require a high degree of movement precision. Magnification used to augment the view and, theoretically, enable finer movements, may introduce other visual-motor disruptions due to the apparent speed of the visual motion on screen (i.e., motion scaling). In this research, we sought to better understand the effects of visual magnification on human movement performance and control in operating a tool via indirect vision. Ten adult participants manipulated a computer mouse to direct a pointer to targets on a display. Results (Experiment 1) showed that, despite increased motion scaling, magnification of the view on screen enabled higher precision control of the mouse pointer. However, the relative effectiveness of visual magnification ultimately depended on the scale of the physical movement, and more specifically the precision limits of the whole-hand grip afforded by the mouse. When the physical scale of the hand/mouse movement was reduced (Experiment 2), fine-precision control began to reach its limits, even at full magnification. The role of magnification can thus be understood as "amplifying" the particular skill level afforded by the effecting limb. These findings suggest a fruitful area for future research is the optimization of hand-control interfaces of tools to maximize movement precision.

Radiation exposure from musculoskeletal computerized tomographic scans.

BACKGROUND: Computerized tomographic scans are routinely obtained to evaluate a number of musculoskeletal conditions. However, since computerized tomographic scans expose patients to the greatest amounts of radiation of all imaging modalities, the physician must be cognizant of the effective doses of radiation that are administered. This investigation was performed to quantify the effective doses of computerized tomographic scans that are performed for various musculoskeletal applications. METHODS: The digital imaging archive of a single institution was retrospectively reviewed to identify helical computerized tomographic scans that were completed to visualize the extremities or spine. Imaging parameters were recorded for each examination, and dosimetry calculator software was used to calculate the effective dose values according to a modified protocol derived from publication SR250 of the National Radiological Protection Board of the United Kingdom. Computerized tomographic scans of the chest, abdomen, and pelvis were also collected, and the effective doses were compared with those reported by prior groups in order to validate the results of the current study. RESULTS: The mean effective doses for computerized tomographic scans of the chest, abdomen, and pelvis (5.27, 4.95, and 4.85 mSv, respectively) were consistent with those of previous investigations. The highest mean effective doses were recorded for studies evaluating the spine (4.36, 17.99, and 19.15 mSv for the cervical, thoracic, and lumbar spines, respectively). In the upper extremity, the effective dose of a computerized tomographic scan of the shoulder (2.06 mSv) was higher than those of the elbow (0.14 mSv) and wrist (0.03 mSv). Similarly, the effective dose of a hip scan (3.09 mSv) was significantly higher than those observed with knee (0.16 mSv) and ankle (0.07 mSv) scans. CONCLUSIONS: Computerized tomographic scans of the axial and appendicular skeleton are associated with substantially elevated radiation exposures, but the effective dose declines substantially for anatomic structures that are further away from the torso.

Kinematic analysis of multiple constraints on a pointing task.

The current experiment suggests that the speed/accuracy tradeoff is composed of two classes of constraints, effector and task. We examined the effects of movement distance, target size, orientation of the movement in the workspace, and C-D gain on the kinematics of discrete pointing movements made with computer mouse. It was found that target size influenced the shape of velocity profiles by elongating the duration of the corrective sub-movement phase, while movement distance scaled the entire velocity curve without affecting its shape. C-D gain and orientation of the movement exhibited two kinds of effects: an overall scaling of the velocity curve and a change in its shape. We conclude that target size is a task constraint and movement distance is an effector constraint, while movement orientation exhibited characteristics of both. C-D gain by itself was not a constraint, but interacted with both task and effector constrains. These results highlight the roles of biomechanical and information processing factors in the speed/accuracy tradeoff.

Development of a statewide hospital plan for radiologic emergencies.

Although general guidelines have been developed for triage of victims in the field and for hospitals to plan for a radiologic event, specific information for clinicians and administrators is not available for guidance in efficient management of radiation victims during their early encounter in the hospital. A consensus document was developed by staff members of four Connecticut hospitals, two institutions of higher learning, and the State of Connecticut Department of Environmental Protection and Office of Emergency Preparedness, with assistance of the American Society for Therapeutic Radiology and Oncology. The objective was to write a practical manual for clinicians (including radiation oncologists, emergency room physicians, and nursing staff), hospital administrators, radiation safety officers, and other individuals knowledgeable in radiation monitoring that would be useful for evaluation and management of radiation injury. The rationale for and process by which the radiation response plan was developed and implemented in the State of Connecticut are reviewed. Hospital admission pathways are described, based on classification of victims as exposed, contaminated, and/or physically injured. This manual will be of value to those involved in planning the health care response to a radiologic event.

Altered coordination patterns in parkinsonian patients during trunk-assisted prehension.

We examined whether coordination between movement components during trunk-assisted prehension was compromised in PD patients in response to varying constraints (experiment 1: reach speed, object size, movement amplitude; experiment 2: movement sequence). In general, both PD patients and controls responded similarly to the changes in these three variables. PD patients, however, demonstrated less synchronized movements in terms of timing between onsets and offsets of aperture formation, endpoint motion and trunk motion. In addition, PD patients used a pattern different from that of controls in specifying the relative contribution of trunk and arm to the endpoint motion. A significant group difference was observed in that controls tended to synchronize the involved movement components together, whereas PD patients did not show such a trend. These data suggest that PD patients have intact parameterization capabilities, although they have a reduced capability to coordinate multiple neuromotor synergies as a single unit.

Effects of target height and width on 2D pointing movement duration and kinematics.

This study examined the impact of target geometry on the trajectories of rapid pointing movements. Participants performed a graphic point-to-point task using a pen on a digitizer tablet with targets and real time trajectories displayed on a computer screen. Circular- and elliptical-shaped targets were used in order to systematically vary the accuracy constraints along two dimensions. Consistent with Fitts Law, movement time increased as target difficulty increased. Analysis of movement kinematics revealed different patterns for targets constrained by height (H) and width (W). When W was the constraining factor, movements of greater precision were characterized by a lower peak velocity and a longer deceleration phase, with trajectories that were aimed relatively farther away from the center of the target and were more variable across trials. This indicates an emphasis on reactive, sensory-based control. When H was the constraining factor, however, movements of greater precision were characterized by a longer acceleration phase, a lower peak velocity, and a longer deceleration phase. The initial trajectory was aimed closer to the center of the target, and the trajectory path across trials was more constrained. This suggests a greater reliance on both predictive and reactive control.