Girth-based administered activity for pediatric 99m Tc-DMSA SPECT

BACKGROUND

Pediatric molecular imaging requires a balance between administering an activity that will yield sufficient diagnostic image quality while maintaining patient radiation exposure at acceptable levels. In current clinical practice, this balance is arrived at by the current North American Consensus Guidelines in which patient weight is used to recommend the administered activity (AA).

PURPOSE

We have previously demonstrated that girth (waist circumference at the level of the kidneys) is better at equalizing image quality than patient weight for pediatric Tc-99m DMSA renal function imaging. However, the correlation between image quality (IQ), AA, and patient girth has not been rigorously and systematically developed. In this work, we generate a series of curves showing the tradeoff between AA and IQ as a function of patient girth, providing the data for standards bodies to develop the next generation of dosing guideline for pediatric DMSA SPECT.

METHODS

An anthropomorphic phantom series that included variations in age (5, 10, and 15 years), gender (M, F), local body morphometry (5, 10, 50, 90, and 95th girth percentiles), and kidney size (±15% standard size), was used to generate realistic SPECT projections. A fixed and clinically challenging defect-to-organ volume percentage (0.49% of renal cortex value) was used to model a focal defect with zero uptake (i.e., full local loss of renal function). Task-based IQ assessment methods were used to rigorously measure IQ in terms of renal perfusion defect detectability. This assessment was performed at multiple count levels (corresponding to various AAs) for groups of patients that had similar girths and defect sizes. Receiver-operating characteristics (ROC) analysis was applied; the area under the ROC curve (AUC) was used as a figure-of-merit for task performance. Curves showing the tradeoff between AUC and AA were generated for these groups of phantoms.

RESULTS

Overall, the girth-based dosing method suggested different amounts of AA compared to weight-based dosing for the phantoms that had a relatively large body weight but a small girth or phantoms with relatively small bodyweight but large girth. Reductions of AA to 62.9% compared to weight-based dosing guidelines can potentially be realized while maintaining a baseline (AUC = 0.80) IQ for certain 15-year-olds who have a relatively small girth and large defect size. Note that the task-based IQ results are heavily dependent on the simulated defect size for the defect detection task and the appropriate AUC value must be decided by the physicians for this diagnostic task. These results are based purely on simulation and are subject to future clinical validation.

CONCLUSIONS

The study provides simulation-based IQ-AA data for a girth-based dosing method for pediatric renal SPECT, suggesting that patient waist circumference at the level of kidneys should be considered in selecting the AA needed to achieve an acceptable IQ. This data may be useful for standards bodies to develop girth-based dosing guidelines.

Quadriceps Muscle Size Following ACL Injury and Reconstruction: A Systematic Review

Image-based assessments of quadriceps muscle size facilitate examination of structural changes after anterior cruciate ligament (ACL) injury and reconstruction (ACLR). Understanding the effects of ACLR on muscle size measures may aid in clarifying the contribution of quadriceps atrophy toward quadriceps strength. The purpose of this study was to systematically review the literature examining the effects of ACLR on quadriceps muscle volume and cross-sectional area (CSA). An online database search was conducted using Web of Science, SportDISCUS, PubMed (Medline), CINHAL (EBSCO), and Cochrane Library limited to articles published after January 1, 1980. Means and standard deviations were extracted for the ACLR limb and the contralateral limb, and sample characteristics from relevant articles. Magnitude of between limb differences were assessed using pooled effect sizes (Hedge's g) and 95% confidence intervals. Eleven articles (five CSA, six muscle volume) were included in this systematic review. Included studies reported negative effective sizes, indicating that the ACLR limb was smaller in CSA or muscle volume compared with the contralateral limb; however, 36% of the included articles reported meaningful difference between the limbs. Quadriceps atrophy may occur following ACL injury and persist after rehabilitation, however, the magnitude of these reductions may not be clinically meaningful and may only partially explain the persistent quadriceps weakness that is ubiquitous among this patient population. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:598-608, 2020.

The contribution of ascitic fluid to body weight in patients with liver cirrhosis, and its estimation using girth: a cross-sectional observational study

BACKGROUND

There is a high prevalence of malnutrition among people with decompensated liver disease. Standard nutritional screening tools use weight and body mass index (BMI) to identify risk, although these are difficult to measure for those with ascites, often secondary to liver cirrhosis. Dietetic guidance suggests adjusting for ascitic weight by 2.2-14 kg, although there is a lack of evidence to substantiate these values. The present study aimed to measure the contribution of ascitic fluid weight and compare this with the current guidance, as well as to examine whether girth circumference can be used to estimate ascitic weight.

METHODS

A cross-sectional, observational study was conducted over 13 weeks. Participants attending for paracentesis were weighed, their girths measured, and BMI was calculated pre- and post-paracentesis. Fluid removed via paracentesis was recorded. Ethical approval was received (IRAS project ID: 218747).

RESULTS

Eighteen participants underwent paracentesis. The range of ascitic fluid drained was 3.8-19 L [mean (SD) = 8.7 (3.7) L]. Weight difference between pre- and post-paracentesis was in the range 4.5-20 kg [mean (SD) = 8.7 (3.9) kg]. Ascitic fluid weight is shown to be higher in each category (minimal, moderate, severe ascites) than the current guidance values. Weight difference was greater than 14 kg in 11% (n = 2) of participants. A strong, statistically significant relationship (rho = 0.68, P ≤ 0.01) between ascitic weight and pre-paracentesis girth was found. An equation was formulated to enable the estimation of ascitic fluid from pre-paracentesis girth.

CONCLUSIONS

Current dietetic guidance should be re-evaluated to reflect the greater weight differences identified. Measuring girth pre-paracentesis may help to inform dry weight estimation. Further research is required to verify the accuracy of estimating ascitic weight from pre-paracentesis girth.

Am I normal? A systematic review and construction of nomograms for flaccid and erect penis length and circumference in up to 15,521 men

OBJECTIVE

To systematically review and create nomograms of flaccid and erect penile size measurements.

METHODS

Study key eligibility criteria: measurement of penis size by a health professional using a standard procedure; a minimum of 50 participants per sample.

EXCLUSION CRITERIA

samples with a congenital or acquired penile abnormality, previous surgery, complaint of small penis size or erectile dysfunction. Synthesis methods: calculation of a weighted mean and pooled standard deviation (SD) and simulation of 20,000 observations from the normal distribution to generate nomograms of penis size.

RESULTS

Nomograms for flaccid pendulous [n = 10,704, mean (SD) 9.16 (1.57) cm] and stretched length [n = 14,160, mean (SD) 13.24 (1.89) cm], erect length [n = 692, mean (SD) 13.12 (1.66) cm], flaccid circumference [n = 9407, mean (SD) 9.31 (0.90) cm], and erect circumference [n = 381, mean (SD) 11.66 (1.10) cm] were constructed. Consistent and strongest significant correlation was between flaccid stretched or erect length and height, which ranged from r = 0.2 to 0.6.

LIMITATIONS

relatively few erect measurements were conducted in a clinical setting and the greatest variability between studies was seen with flaccid stretched length.

CONCLUSIONS

Penis size nomograms may be useful in clinical and therapeutic settings to counsel men and for academic research.

A new metric for measuring condition in large predatory sharks

A simple metric (span condition analysis; SCA) is presented for quantifying the condition of sharks based on four measurements of body girth relative to body length. Data on 104 live sharks from four species that vary in body form, behaviour and habitat use (Carcharhinus leucas, Carcharhinus limbatus, Ginglymostoma cirratum and Galeocerdo cuvier) are given. Condition shows similar levels of variability among individuals within each species. Carcharhinus leucas showed a positive relationship between condition and body size, whereas the other three species showed no relationship. There was little evidence for strong differences in condition between males and females, although more male sharks are needed for some species (e.g. G. cuvier) to verify this finding. SCA is potentially viable for other large marine or terrestrial animals that are captured live and then released.