Biomedical subjects

Richard A Carlson

Publications and source records attributed to Richard A Carlson.

8 recordsLinked to original sources

PubMed2005

Adding in vivo quantitative 1H MR spectroscopy to improve diagnostic accuracy of breast MR imaging: preliminary results of observer performance study at 4.0 T.

PURPOSE: To determine whether the addition of in vivo quantitative hydrogen 1 (1H) magnetic resonance (MR) spectroscopy can improve the radiologist's diagnostic accuracy in interpreting breast MR images to distinguish benign from malignant lesions. MATERIALS AND METHODS: The study was approved by the institutional review board and, where appropriate, was compliant with the Health Insurance Portability and Accountability Act. All patients provided written informed consent. Fifty-five breast MR imaging cases-one lesion each in 55 patients aged 24-66 years with biopsy-confirmed findings-were retrospectively evaluated by four radiologists. Patients were examined with contrast material-enhanced fat-suppressed T1-weighted 4.0-T MR imaging. The concentration of total choline-containing compounds (tCho) was quantified by using single-voxel 1H MR spectroscopy. For each case, the radiologists were asked to give the percentage probability of malignancy, the Breast Imaging and Reporting Data System category, and a recommendation for patient treatment. Two interpretations were performed for each case: The initial interpretation was based on the lesion's morphologic features and time-signal intensity curve, and the second interpretation was based on the lesion's morphologic features, time-signal intensity curve, and tCho concentration. Receiver operating characteristic (ROC), Wilcoxon signed rank, kappa statistic, and accuracy (based on the area under the ROC curve) analyses were performed. RESULTS: Of the 55 lesions evaluated, 35 were invasive carcinomas and 20 were benign. The addition of 1H MR spectroscopy resulted in higher sensitivity, specificity, accuracy, and interobserver agreement for all four radiologists. More specifically, two of the four radiologists achieved a significant improvement in sensitivity (P=.03, P=.03), and all four radiologists achieved a significant improvement in accuracy (P = .01, P = .05, P = .009, P < .001). CONCLUSION: Current study results suggest that the addition of quantitative 1H MR spectroscopy to the breast MR imaging examination may help to improve the radiologist's ability to distinguish benign from malignant breast lesions.

Adolescent↗

PubMed2004

Breast abscess in lactating women: US-guided treatment.

PURPOSE: To retrospectively evaluate the use of ultrasonography (US)-guided treatment of breast abscesses in lactating women. MATERIALS AND METHODS: One hundred eight consecutive lactating women who were clinically suspected of having a breast abscess were examined with US. Abscesses depicted at US were treated with US guidance, and the success of US-guided treatment was retrospectively determined. RESULTS: Fifty-six abscesses were identified at US in 43 women; all abscesses were treated with US guidance: 23 with needle aspiration and 33 with catheter drainage. Treatment method was determined according to the size of the abscess. Abscesses that were smaller than 3 cm in maximum diameter were treated with needle aspiration, and abscesses that were 3 cm or larger in maximum diameter were treated with catheter insertion. One patient who was treated with needle aspiration subsequently underwent surgical intervention; all others were successfully treated with US intervention. Catheter placement was well tolerated (mean pain score 2.3 in 22 women by using a subjective pain scale of 0-10). CONCLUSION: US-guided needle aspiration of abscesses smaller than 3 cm and US-guided catheter drainage of abscesses 3 cm or larger are successful means of treating breast abscesses.

Abscess↗

PubMed2004

Intentional control of event counting.

Event counting depends on simple, well-learned knowledge but is effortful and error-prone. In 6 experiments, the authors examined event-counting performance, testing a model that suggests that counting is controlled by minimal goal representations coordinated with perceptual events by temporal synchrony. In Experiment 1, they examined self-paced counting with or without delays that disrupted participants' preferred pacing. In subsequent experiments, participants counted computer-paced events occurring at rhythmic or varied intervals, reporting or verifying totals. Several results support the model: Participants counted rhythmic events more accurately, made undetected undercount errors when counting rhythmic events, and made false alarms to undercount or overcount probes presented at different times. These results suggest that intentions that guide fluent counting specify parameters deictically rather than semantically and that error monitoring is implicit.

Decision Making↗

PubMed2003

Egocentric organization of spatial activities in imagined navigation.

Studies on spatial frameworks suggest that the way we locate objects in imagined environments is influenced by the physical and functional properties of the world and our body. The present study provides evidence that such an influence also characterizes imagined navigation. In Experiment 1, participants followed spatial directions to construct an imagined path, while either keeping constant or updating their orientation at each step. A pattern of step times diagnostic of spatial frameworks was obtained in the updated-orientation but not in the constant-orientation condition. In Experiment 2, participants performed the updated-orientation condition with two levels of external support for the reference frame being used. Step times conformed to the predictions of spatial frameworks in both conditions. Both experiments also provided support that the processes involved in imagined navigation exhibit the operator-operand dynamics of other mental skills previously documented in the mental arithmetic domain. These results reinforce Piaget's (1954) notion that spatial displacements and integer arithmetic share a set of structural characteristics

Female↗

PubMed2003

Information acquisition strategies and the cognitive structure of arithmetic.

In three experiments, we examined the sensitivity of information acquisition strategies to the underlying cognitive structure of arithmetic tasks. Previous work has shown that individuals solve arithmetic problems more quickly when they consider operators before operands. The operators establish the goal, and the operands are then assimilated into that goal. In the present experiments, participants performed arithmetic tasks in which they controlled the display of operators and operands, using separate keystrokes. The participants chose to see the operator before the operands in most conditions. This ordering was more likely when task constraints made it easier to achieve, when feedback emphasized execution time, and in a more complex multiple-step task. These results extend previous research on strategy selection and information acquisition, supporting the idea that coordination between the environment and ongoing cognition is an important feature of cognitive skill.

Cognition↗

PubMed2003

Viewpoint alignment and response conflict during spatial judgment.

Spatial judgment (e.g., identifying the relative location, such as left or right, of a target) from a reference point becomes more difficult with increasing disparity between the relevant allocentric viewpoint and the observer-centered viewpoint. The viewpoint alignment hypothesis suggests that this misalignment effect is due to a realignment process that reconciles two viewpoints, implying that providing an advance cue for a viewpoint should facilitate the subsequent judgment. We examined whether advance viewpoint information can reduce the misalignment effect and whether the misalignment effect reflects response conflict, as well as realignment of viewpoints. In Experiment 1, the misalignment effect decreased with advance viewpoint information, suggesting that the misalignment effect indeed reflects viewpoint realignment. In Experiment 2, the misalignment effect was greater with spatial response codes that might conflict with the spatially arranged response keys than with arbitrary responses with no such conflict. These results suggest that the misalignment effect may arise from both viewpoint realignment and response conflicts.

Attention↗

PubMed2003

Implicit temporal tuning of working memory strategy during cognitive skill acquisition.

Complex cognitive tasks such as multiple-step arithmetic entail strategies for coordinating mental processes such as calculation with processes for managing working memory (WM). Such strategies must be sensitive to factors such as the time needed for calculation. In 2 experiments we tested whether people can learn the timing constraints on WM demands when those constraints are implicitly imposed. We varied the retention period for intermediate results using the well-known digit size effect: The larger the operands, the longer it takes to perform addition. During learning participants practiced multiple-step arithmetic routines combined with large or small digits. At transfer, they performed both practiced and novel combinations. Practice performance was affected by digit size and WM demands. However, the transfer performance was not fully explained by the digit size effect or the practice effect. We argue that participants acquired temporal tuning of the WM strategy to the implicit retention interval imposed by the digit size and kept using the tuning mode to unpracticed data set.

Cognition↗

PubMed2002

Temporal tuning in the acquisition of cognitive skill.

The temporal tuning hypothesis suggests that individuals adjust the timing of cognitive performances to achieve temporal coordination of mental processes and the data on which they operate, and that this adjustment becomes more precise with practice. Participants in two experiments performed self-paced multiple-step arithmetic tasks in which the information needed for each step was briefly displayed at the participants' request. Timing constraints were manipulated by varying between subjects the delay between requests and displays of information. In Experiment 1, both operators and operands appeared step by step, and participants achieved a modest degree of temporal adjustment that did not change with practice. In Experiment 2, participants could preview operators while operands appeared step by step. In that experiment, participants achieved more precise temporal adjustment, and the amount of adjustment increased with practice. These results demonstrate the phenomenon of temporal tuning in symbolic cognitive skills and suggest some constraints on the ability to anticipate the time course of one's mental processes.

Adult↗