Biomedical subjects

Aditya Bharatha

Publications and source records attributed to Aditya Bharatha.

3 recordsLinked to original sources

PubMed2004

Statistical validation of image segmentation quality based on a spatial overlap index.

RATIONALE AND OBJECTIVES: To examine a statistical validation method based on the spatial overlap between two sets of segmentations of the same anatomy. MATERIALS AND METHODS: The Dice similarity coefficient (DSC) was used as a statistical validation metric to evaluate the performance of both the reproducibility of manual segmentations and the spatial overlap accuracy of automated probabilistic fractional segmentation of MR images, illustrated on two clinical examples. Example 1: 10 consecutive cases of prostate brachytherapy patients underwent both preoperative 1.5T and intraoperative 0.5T MR imaging. For each case, 5 repeated manual segmentations of the prostate peripheral zone were performed separately on preoperative and on intraoperative images. Example 2: A semi-automated probabilistic fractional segmentation algorithm was applied to MR imaging of 9 cases with 3 types of brain tumors. DSC values were computed and logit-transformed values were compared in the mean with the analysis of variance (ANOVA). RESULTS: Example 1: The mean DSCs of 0.883 (range, 0.876-0.893) with 1.5T preoperative MRI and 0.838 (range, 0.819-0.852) with 0.5T intraoperative MRI (P < .001) were within and at the margin of the range of good reproducibility, respectively. Example 2: Wide ranges of DSC were observed in brain tumor segmentations: Meningiomas (0.519-0.893), astrocytomas (0.487-0.972), and other mixed gliomas (0.490-0.899). CONCLUSION: The DSC value is a simple and useful summary measure of spatial overlap, which can be applied to studies of reproducibility and accuracy in image segmentation. We observed generally satisfactory but variable validation results in two clinical applications. This metric may be adapted for similar validation tasks.

Analysis of Variance↗

PubMed2002

Quantitative MR imaging assessment of prostate gland deformation before and during MR imaging-guided brachytherapy.

RATIONALE AND OBJECTIVES: The authors performed this study to document the deformations that occur between pretreatment magnetic resonance (MR) imaging and intraoperative MR imaging during brachytherapy. MATERIALS AND METHODS: MR images obtained at 1.5 and 0.5 T in 10 patients with prostate cancer were analyzed for changes in the shape and substructure of the prostate. Three-dimensional models of the prostate were obtained. The authors measured anteroposterior dimension; total gland, peripheral zone, and central gland volumes; transverse dimension; and superoinferior height. RESULTS: Gland deformations were seen at visual inspection of the three-dimensional models. The anteroposterior dimension of the total gland, central gland, and peripheral zone increased from 1.5- to 0.5-T imaging (median dimension, 4.9, 1.5, and 1.8 mm, respectively), and the increase was greatest in the peripheral zone (P < .05, all comparisons). There was a decrease in the transverse dimension from 1.5- to 0.5-T imaging (median, 4.5 mm; P < .005). The total gland volume and the superoinferior height did not show a statistically significant change. CONCLUSION: There were significant deformations in the shape of the prostate, especially in the peripheral zone, between the two imaging studies. The likely causes of the shape change are differences in rectal filling (endorectal coil used in 1.5-T studies vs obturator in 0.5-T studies) and/or changes in patient position (supine vs lithotomy). These findings suggest that pretreatment images alone may not be reliable for accurate therapy planning. It may be useful to integrate pre-and intraoperative data.

Brachytherapy↗

PubMedDate not supplied

Barriers to diagnosis of occupational asthma in Ontario.

BACKGROUND: Occupational asthma (OA) refers to asthma caused by workplace-specific substances. A longer duration of symptoms while continuing to be exposed has been associated with a worse prognosis. Evidence suggests a significant period of time exists between symptom onset and diagnosis of OA, the reasons for which have not been investigated. The purpose of this study was to examine whether primary health care and/or socio-economic factors account for delays in Ontario. METHOD: Two hundred and forty-seven (247) chart reviews were undertaken of patients referred to the University Health Network Asthma Centre for evaluation of OA, with clinic visits from 1997-2002. Forty-two (42) patients fulfilling objective OA criteria were administered a structured telephone interview to examine the chronology and nature of health care consultation and reasons for possible delay in diagnosis. RESULTS: The mean time to diagnosis was 4.9 years (3.4 years excluding 4 outliers). On average, patients waited 7.4 months before discussing the work-relation of symptoms with a physician. Main self-reported reasons for delay were lack of enquiry about work relatedness by the primary care physician (41%) and fear of losing work time (37%). Reported increases in time during secondary care were related to difficulties associated with completion of investigations (35%). Lower education level (p = 0.04) and household income (p = 0.03) were significantly associated with an increased time to diagnosis. INTERPRETATION: Physicians who assess working adults with asthma need to ask pertinent work-related questions when taking a history in order to initiate timely investigations and referral. Socio-economic factors are also associated barriers to early diagnosis of occupational asthma.

Asthma↗