Research Spotlight

Weir, V. J. and J. Zhang (2019). “Technical note using linear and polynomial approximations to correct IEC CTDI measurements for a wide-beam CT Scanner.” Med Phys Sep 4. [Epub ahead of print].

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PURPOSE: Investigate a feasible correction to align the IEC CTDI measurement with other approaches for an accurate measure of radiation output. METHODS: Radiation dose measurements were performed in a GE 256-slice CT scanner using three methods. The first method used a 0.6cc Farmer chamber to measure peak dose and then to calculate dose length integral (DLI). The second method integrated dose profiles with a pencil chamber over 600mm for both body and head phantoms. Both methods achieved scatter equilibrium using a 600mm long body and head phantom. The third method followed IEC recommendations by adjusting traditional CTDI with beam width. We performed measurements using polymethyl methacrylate (PMMA) 32cm diameter body and 16cm diameter head phantoms, combining with various available bowtie filters and at different kV settings. Correction factors using linear or polynomial functions were developed based on these measurements. RESULTS: CTDI measurements using the DLI method and direct integration (DLP) method align with each other with an error of less than 6.7% for the body phantom, and 6.9% for head phantom respectively. The IEC method underestimates radiation dose for body and head phantoms relative to the DLI, with an error range from 8.9% to 19.4%, depending on the phantom and bowtie filter. A correction factor of 0.15 (15%) could be used for body and head phantom measurements with large body, head and pediatric head bowtie filters. While for body phantom with medium filter and head phantom with small body filter which are not routinely used for CTDI measurements, a correction factor of 0.30 (30%) could be used. The proposed correction factors are validated using various kV and filter combinations. Compared to a linear approximation, a polynomial correction is better at adjusting the IEC measurements, with an error of 5.2%. We found that the a1 coefficient of the polynomial correction is approximately equal to Aeq obtained from DLI measurements for all cases studied, with an average percent difference of 6.7%. CONCLUSION: Both linear and polynomial approximations can be used to correct the IEC measurements, aligning them with the direct integration of dose profiles or the point detector method of CT dosimetry on a 256 slice GE Revolution scanner. Using a polynomial correction may potentially bypass the need for an elongated phantom in the DLI method since the a1 coefficients are approximately equal to Aeq obtained from the DLI method.

Roberts, B. J., D. B. Adams and J. P. Baker (2019). “The Pandemic of Work-Related Musculoskeletal Disorders: Can We Stem the Tide in Cardiac Sonography?” J Am Soc Echocardiogr 32(9): 1147-1150.

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In this issue of JASE, Barros-Gomes et al., of the Mayo Clinic (Rochester, MN), have published an article titled “Characteristics and Consequences of Work-Related Musculoskeletal Pain among Cardiac Sonographers Compared with Peer Employees: A Multisite Cross-Sectional Study,” in which they assess the frequency, magnitude, and impact of work-related musculoskeletal pain (WRMSP) among cardiac sonographers compared with a control group of peer employees. Data were gathered from a total of 416 respondents through an electronic survey, 111 cardiac sonographers (27%) and 305 peer employee control subjects (73%), at 10 Mayo Clinic facilities in four states. The control group consisted of a diverse cohort of peer workers within the cardiology department, ranging from patient care personnel to administrative assistants. Pain levels were assessed using a standardized questionnaire. The overall prevalence of WRMSP was compared between the two groups, as well as in specific areas of the body commonly affected, namely and from greatest to least, the neck, shoulder, lower back, hand, upper back, and elbow. The level for statistical significance was adjusted to P < .01 (as opposed to P < .05) because multiple-group comparisons were being made. As seen in Figure 2 in the article, the prevalence of WRMSP was almost double in the sonographer group compared with the control group. Significant differences in pain prevalence also existed in every body part that was assessed: neck, shoulder, lower back, hand, upper back, and elbow. The results of the study can be summarized as follows: 1. WRMSP in sonographers is highly prevalent, with 86% of those surveyed affected. 2. Sonographers' pain is more severe and is worsening at a greater rate compared with the control group. 3. The neck, shoulder, lower back, and hand are the most frequently affected regions. 4. Because of pain, sonographers more often seek medical evaluation and miss workdays. (Excerpt from text, p. 1147; no abstract available.)

Rizkalla, J. M., T. Lines and S. Nimmons (2019). “Classifications in Brief: The Denis Classification of Sacral Fractures.” Clin Orthop Relat Res 477(9): 2178-2181.

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In their original description, Denis et al. described three zones of injury: Zone I: injuries located lateral to the neuroforamina; Zone II: injuries that involve the neuroforamina, but not the spinal canal; and Zone III: injuries that extend into the spinal canal, with primary or associated fracture lines. The study found that neurologic injuries occurred in 5.9% of fractures lateral to the sacral foramina (Zone 1). In transforaminal fractures (Zone 2), 28.4% of patients had a neurologic deficit. Meanwhile, central fractures (Zone 3) had the highest likelihood of neurologic injury (56.7%) [6] (Fig. 1). Furthermore, Zone III fractures are often divided into four different types, including: (1) flexion fracture with anterior angulation, (2) flexion fracture with anterior angulation and posterior displacement, (3) extension fractures with anterior displacement, and (4) comminuted fracture of the upper segment of the sacrum without displaced alignment of sacrum. (Excerpt from text, p. 2179; no abstract available.)

Kiselica, A. M. and J. F. Benge (2019). “Quantitative and qualitative features of executive dysfunction in frontotemporal and Alzheimer’s dementia.” Appl Neuropsychol Adult Aug 19: 1-15. [Epub ahead of print].

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Behavioral variant fronto-temporal degeneration (bvFTD) is typically distinguished from Alzheimer’s disease (AD) by early, prominent dysexecutive findings, in addition to other clinical features. However, differences in executive functioning between these groups are not consistently found. The current study sought to investigate quantitative and qualitative differences in executive functioning between those with bvFTD and AD in a large sample, while controlling for dementia severity and demographic variables. Secondary data analyses were completed on a subset of cases from the National Alzheimer’s Coordinating Center collected from 36 Alzheimer’s Disease Research Centers and consisting of 1,577 individuals with AD and 406 individuals with bvFTD. Groups were compared on 1) ability to complete three commonly administered executive tasks (letter fluency, Trail Making Test Part B [TMTB], and digits backward); 2) quantitative test performance; and 3) errors on these tasks. Findings suggested that individuals with bvFTD were less likely to complete letter fluency, chi(2)(2) = 178.62, p < .001, and number span tasks, chi(2)(1) = 11.49, p < .001), whereas individuals with AD were less likely to complete TMTB, chi(2)(2) = 460.38, p < .001. Individuals with bvFTD performed more poorly on letter fluency, F(1) = 28.06, p = .013, but there were not group differences in TMTB lines per second or number span backwards. Errors generally did not differentiate the diagnostic groups. In summary, there is substantial overlap in executive dysfunction between those with bvFTD and AD, though individuals with bvFTD tend to demonstrate worse letter fluency performance.

Tolia, V. N., K. A. Ahmad, J. Jacob, A. S. Kelleher, N. McLane, R. W. Arnold and R. H. Clark (2019). “Two-Year Outcomes of Infants with Stage 2 or Higher Retinopathy of Prematurity: Results from a Large Multicenter Registry.” Am J Perinatol Sep 3. [Epub ahead of print].

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OBJECTIVE: To define the incidence of ophthalmologic morbidities in the first 2 years of life among infants diagnosed with stage 2 or higher retinopathy of prematurity (ROP). STUDY DESIGN: We prospectively enrolled premature infants with stage 2 or higher ROP. The infants were followed up for 2 years, and we report on data collected from outpatient ophthalmology and primary care visits. RESULTS: We enrolled 323 infants who met inclusion criteria, of which 112 (35%) received treatment with laser surgery (90) or bevacizumab (22). Two-year follow-up was available for 292 (90%) of the cohort. The most common ophthalmologic conditions at follow-up were hyperopia (35%), astigmatism (30%), strabismus (21.9%), myopia (19.2%), anisometropia (12%), and amblyopia (12%). Severe ophthalmologic morbidities such as retinal detachment and cataracts were rare, but occurred in both treated and untreated infants. Overall, 22.6% of the infants were wearing glasses at 2 years, including 8.5% of the untreated infants. CONCLUSION: Patients with stage 2 or higher ROP remain at significant risk for ophthalmological morbidity through 2 years of age. Infants with regression of subthreshold ROP who do not require treatment represent an underrecognized population at long-term ophthalmological risk. CLINICALTRIALS. GOV IDENTIFIER: NCT01559571.