Limitations of Weight Velocity Analysis by Commercial Computer Program Growth Analyser Viewer Edition

Commercial software package “Growth Analyser Viewer Edition” (“GAVE”) aims to document, monitor and analyze growth and development in children and adolescents. Although its clinical and scientific use is widespread, there are no published studies that describe the method and its validation. We were informed that GAVE calculates the weight velocity (kg/year) at age t from the weight difference between t and 448 days earlier or at birth, divided by the time difference. We recently discussed a case of false child abuse diagnosis (Pediatric Condition Falsification), resulting in the separation of the child from its parents, in which GAVE played a negative contributing role. To prevent such inappropriate diagnoses, we analyzed GAVE from a schematic representation of the measured clinical weight curve, with precisely defined weight velocities. In conclusion, the 448 days included for weight velocity predictions by GAVE caused the erroneous outcomes. Until the necessary changes to the software are implemented and validated, we advise against the use of GAVE in infants younger than 1.5 years, if multiple weight changes occur within 448 days, and following a long-lasting weight velocity change. Our analysis suggests to discard all medical software packages that lack public description and proof of validation

Weight velocity equations with 14–448 days time separated weights should not be used for infants under 3 years of age

Abnormal growth of infants may indicate disease of the children, thus methods to identify growth disorders are wanted in medicine. We previously showed that two-time-points weight growth velocities at age t, calculated by a commercial software product as [Weight(t)− Weight(t − X)]/X, with X = 448 days, were erroneous due to the long separation of 448 days. We were convinced that shorter X-values would solve this accuracy problem. However, our hypothesis is that: “shorter time separations than 448 days cause a decreased accuracy of numerical weight velocity equations in realistic infant weights until an age of about three years”. Supporting evidence comes from analyzing how shorter X-values will affect the accuracy of two-time-points weight velocity calculations. We systematically varied X between 1 and 448 days of various P50/0SD-related standard weight curves: (a)P50/0SD with the weights separated by 1 day and X = 1,28,224,448 days; (b)P50/0SD with the weights at variable ages and X = 14–448 days; and (c)case (b)and incorporating weight fluctuations typically occurring in infants. Cases (b)and (c)include details observed in a clinical case. Our results show that the combination of weight fluctuations and varying time intervals between consecutive weights make weight velocity predictions worse for shorter X values in children younger than three years. Because these two causes of failure occur naturally in infants whose weight is regularly measured, other weight velocity equations face the same causes for inaccuracy. In conclusion, our hypothesis suggests that any software that predicts weight velocities should be abandoned in infants < 3 years. Practically, it should require that when (commercial)software weight velocity prediction suggests a medical problem, careful clinical checking should be mandatory, e.g. by linking predicted and exact weight velocities at age t (the latter from the mathematical first derivative at age t of standard weight curves)

Endovenous laser ablation (EVLA): a review of mechanisms, modeling outcomes, and issues for debate

Endovenous laser ablation (EVLA) is a commonly used and very effective minimally invasive therapy to manage leg varicosities. Yet, and despite a clinical history of 16 years, no international consensus on a best treatment protocol has been reached so far. Evidence presented in this paper supports the opinion that insufficient knowledge of the underlying physics amongst frequent users could explain this shortcoming. In this review, we will examine the possible modes of action of EVLA, hoping that better understanding of EVLA-related physics stimulates critical appraisal of claims made concerning the efficacy of EVLA devices, and may advance identifying a best possible treatment protocol. Finally, physical arguments are presented to debate on long-standing, but often unfounded, clinical opinions and habits. This includes issues such as (1) the importance of laser power versus the lack of clinical relevance of laser energy (Joule) as used in Joule per centimeter vein length, i.e., in linear endovenous energy density (LEED), and Joule per square centimeter vein wall area, (2) the predicted effectiveness of a higher power and faster pullback velocity, (3) the irrelevance of whether laser light is absorbed by hemoglobin or water, and (4) the effectiveness of reducing the vein diameter during EVLA therapy

Some controversies in endovenous laser ablation of varicose veins addressed by optical-thermal mathematical modeling

Minimally invasive treatment of varicose veins by endovenous laser ablation (EVLA) becomes more and more popular. However, despite significant research efforts performed during the last years, there is still a lack of agreement regarding EVLA mechanisms and therapeutic strategies. The aim of this article is to address some of these controversies by utilizing optical–thermal mathematical modeling. Our model combines Mordon's light absorption-based optical–thermal model with the thermal consequences of the thin carbonized blood layer on the laser fiber tip that is heated up to temperatures of around 1,000 °C due to the absorption of about 45 % of the laser light. Computations were made in MATLAB. Laser wavelengths included were 810, 840, 940, 980, 1,064, 1,320, 1,470, and 1,950 nm. We addressed (a) the effect of direct light absorption by the vein wall on temperature behavior, comparing computations by using normal and zero wall absorption; (b) the prediction of the influence of wavelength on the temperature behavior; (c) the effect of the hot carbonized blood layer surrounding the fiber tip on temperature behavior, comparing wall temperatures from using a hot fiber tip and one kept at room temperature; (d) the effect of blood emptying the vein, simulated by reducing the inside vein diameter from 3 down to 0.8 mm; (e) the contribution of absorbed light energy to the increase in total energy at the inner vein wall in the time period where the highest inner wall temperature was reached; (f) the effect of laser power and pullback velocity on wall temperature of a 2-mm inner diameter vein, at a power/velocity ratio of 30 J/cm at 1,470 nm; (g) a comparison of model outcomes and clinical findings of EVLA procedures at 810 nm, 11 W, and 1.25 mm/s, and 1,470 nm, 6 W, and 1 mm/s, respectively. Interestingly, our model predicts that the dominating mechanism for heating up the vein wall is not direct absorption of the laser light by the vein wall but, rather, heat flow to the vein wall and its subsequent temperature increase from two independent heat sources. The first is the exceedingly hot carbonized layer covering the fiber tip; the second is the hot blood surrounding the fiber tip, heated up by direct absorption of the laser light. Both mechanisms are about equally effective for all laser wavelengths. Therefore, our model concurs the finding of Vuylsteke and Mordon (Ann Vasc Surg 26:424–433, 2012) of more circumferential vein wall injury in veins (nearly) devoid of blood, but it does not support their proposed explanation of direct light absorption by the vein wall. Furthermore, EVLA appears to be a more efficient therapy by the combination of higher laser power and faster pullback velocity than by the inverse combination. Our findings suggest that 1,470 nm achieves the highest EVLA efficacy compared to the shorter wavelengths at all vein diameters considered. However, 1,950 nm of EVLA is more efficacious than 1,470 nm albeit only at very small inner vein diameters (smaller than about 1 mm, i.e., veins quite devoid of blood). Our model confirms the efficacy of both clinical procedures at 810 and 1,470 nm. In conclusion, our model simulations suggest that direct light absorption by the vein wall is relatively unimportant, despite being the supposed mechanism of action of EVLA that drove the introduction of new lasers with different wavelengths. Consequently, the presumed advantage of wavelengths targeting water rather than hemoglobin is flawed. Finally, the model predicts that EVLA therapy may be optimized by using 1,470 nm of laser light, emptying of the vein before treatment, and combining a higher laser power with a greater fiber tip pullback velocity

Endovenous laser ablation (EVLA) : a review of mechanisms, modeling outcomes, and issues for debate

Endovenous laser ablation (EVLA) is a commonly used and very effective minimally invasive therapy to manage leg varicosities. Yet, and despite a clinical history of 16 years, no international consensus on a best treatment protocol has been reached so far. Evidence presented in this paper supports the opinion that insufficient knowledge of the underlying physics amongst frequent users could explain this shortcoming. In this review, we will examine the possible modes of action of EVLA, hoping that better understanding of EVLA-related physics stimulates critical appraisal of claims made concerning the efficacy of EVLA devices, and may advance identifying a best possible treatment protocol. Finally, physical arguments are presented to debate on long-standing, but often unfounded, clinical opinions and habits. This includes issues such as (1) the importance of laser power versus the lack of clinical relevance of laser energy (Joule) as used in Joule per centimeter vein length, i.e., in linear endovenous energy density (LEED), and Joule per square centimeter vein wall area, (2) the predicted effectiveness of a higher power and faster pullback velocity, (3) the irrelevance of whether laser light is absorbed by hemoglobin or water, and (4) the effectiveness of reducing the vein diameter during EVLA therapy