Dose Enhancement for the Flattening-Filter-Free and Flattening-Filter Photon Beams in Nanoparticle-Enhanced Radiotherapy: A Monte Carlo Phantom Study

Monte Carlo simulations were used to predict the dose enhancement ratio (DER) using the flattening-filter-free (FFF) and flattening-filter (FF) photon beams in prostate nanoparticle-enhanced radiotherapy, with multiple variables such as nanoparticle material, nanoparticle concentration, prostate size, pelvic size, and photon beam energy. A phantom mimicking the patient’s pelvis with various prostate and pelvic sizes was used. Macroscopic Monte Carlo simulation using the EGSnrc code was used to predict the dose at the prostate or target using the 6 MV FFF, 6 MV FF, 10 MV FFF, and 10 MV FF photon beams produced by a Varian TrueBeam linear accelerator (Varian Medical System, Palo Alto, CA, USA). Nanoparticle materials of gold, platinum, iodine, silver, and iron oxide with concentration varying in the range of 3–40 mg/ml were used in simulations. Moreover, the prostate and pelvic size were varied from 2.5 to 5.5 cm and 20 to 30 cm, respectively. The DER was defined as the ratio of the target dose with nanoparticle addition to the target dose without nanoparticle addition in the simulation. From the Monte Carlo results of DER, the best nanoparticle material with the highest DER was gold, based on all the nanoparticle concentrations and photon beams. Smaller prostate size, smaller pelvic size, and a higher nanoparticle concentration showed better DER results. When comparing energies, the 6 MV beams always had the greater enhancement ratio. In addition, the FFF photon beams always had a better DER when compared to the FF beams. It is concluded that gold nanoparticles were the most effective material in nanoparticle-enhanced radiotherapy. Moreover, lower photon beam energy (6 MV), FFF photon beam, higher nanoparticle concentration, smaller pelvic size, and smaller prostate size would all increase the DER in prostate nanoparticle-enhanced radiotherapy.

Neonatal Size and Birth Canal Dimensions

The limitation of the fetal growth process during pregnancy is supposed to be an adaptative response to a physical or a physiological constraint: the pelvic size or the maternal resources and metabolism. In this study 131 mother-infant dyads were recruited. We investigate correlation between maternal traits (height, BMI) pelvic variables (conjugate diameter, inter-spinous diameter, sub-pubic angle) and neonatal traits (gestational age, birthweight, head, suboccipito-brematic and abdominal girth). We found that the three neonatal variables are significantly inter-correlated. Among maternal traits, height is highly correlated with conjugate and inter-spinous diameters. Subpubic angle is correlated with inter-spinous diameter. Among neonatal and pelvimetry correlations, conjugate diameter is highly correlated with suboccipito-bregmatic girth. The pelvic size seems to be the primary constraint to the fetal growth process. This adjustement of fetus size to the birth canal dimensions limits the risk of dystocia. But the way this adjustement occurs at the end of pregnancy is unclear. We assume that the uterus expansion limitation may be an intermediate mechanism explaining the high correlation between pelvic and neonatal traits.

Ultrasound evaluation of the renal pelvis in cats with ureteral obstruction treated with a subcutaneous ureteral bypass: a retrospective study of 27 cases (2010–2015)

Objectives The objective of the study was to measure the preoperative and postoperative renal pelvic size and describe the ultrasound findings following successful decompression of a ureteral obstruction using the subcutaneous ureteral bypass (SUB) device in cats. Methods This retrospective study assessed the measurement of the renal pelvis of 27 cats with unilateral (n = 21) or bilateral (n = 6) ureteral obstruction before (pre-t0) and after placement of a SUB during short- (before t0 + 3 months) and long-term (after t0 + 3 months) follow-up. Several qualitative ultrasound parameters were recorded for each cat. At both intervals, the last ultrasound examination was used for qualitative criteria and the mean pelvic size was recorded. The complications observed during follow-up were divided into obstructive and non-obstructive. Results No qualitative ultrasound parameter was statistically significant. The presence of retroperitoneal or peritoneal effusion was rarely seen (n = 4/25 during the short term and n = 1/14 during the long term). Hyperechogenicity of the perirenal adipose tissue decreased in the long term. A statistically significant decrease in the width of the renal pelvis was noted in the short- (2.4 mm, range 0–7.0 mm) and long-term (1.7 mm, range 0–3.5 mm) follow-ups compared with the preoperative value (11.7 mm, range 0.9–41 mm). Three months following SUB placement, each cat without an obstructive complication had a pelvic width ⩽3.5 mm. Conclusions and relevance Renal pelvic distension is at least partially reversible when ureteral obstruction is treated by placement of a SUB. Ultrasound monitoring is a useful tool to detect obstructive complications.

Maternal pelvic size, fetal growth and risk of stroke in adult offspring in a large Swedish cohort

Earlier research suggests that maternal pelvic size is associated with offspring’s stroke risk in later life. We followed 6362 men and women from Uppsala, Sweden, born between 1915 and 1929 from 1964 to 2008 to assess whether maternal pelvic size was associated with incidence of thrombotic stroke (TS), haemorrhagic stroke (HS) and other stroke (OS). Offspring whose mothers had a flat pelvis had lower birth weight and birth-weight-for-gestational-age compared with those who did not. Inverse linear associations of birth-weight-for-gestational-age were observed with TS and OS. Female offspring whose mothers had a flat pelvis had increased risk of TS, but flat pelvis was not associated with other types of stroke. A smaller difference between intercristal and interspinous diameters and a smaller external conjugate diameter were independently associated with HS, whereas no pelvic measurements were associated with OS. We conclude that a smaller pelvis in women may impact the health of their offspring in adulthood.

Smaller pelvic size in pregnant adolescents contributes to lower birth weight

Adolescent pregnancy is associated with low birth weight. This has been explained by socioeconomic or emotional factors. However, an adolescent’s pelvis may not be completely developed and this can contribute to impairing fetal growth. Our aim was to compare the relationship between pelvic size and birth weight among adolescents and adult mothers. A cross-sectional study was carried out at Instituto de Medicina Infantil Professor Fernando Figueira (IMIP), Brazil. We studied 125 healthy adolescents and 207 healthy adult women, all of whom were primiparous with a singleton term and low-risk pregnancy. The conjugate, intercristal and interspinous diameters were assessed by the Collins pelvimeter. The effect of pelvic size on the birth weight was evaluated using principal component analysis and multiple linear regression model. The mean pelvic size was smaller in adolescent mothers compared to adult ones (35.1 cm vs. 37.5 cm; p<0.001; t-test). After adjusting for other confounding variables, the predicted birth weights corresponding to these mean values of pelvic size were: 3020±27 g for adolescent mothers and 3145±26 g for adult mothers and showed a significant difference (p<0.001). We concluded that a pelvis that is less than fully developed in adolescents, as assessed by pelvic size, may contribute to lower birth weight in adolescent mothers.