Probing liquid distribution in partially saturated porous materials with hydraulic admittance

The distribution of two immiscible fluids in a complex porous material during displacement is often central to understanding its function. Characterization of this distribution is traditionally determined via optically transparent flow cells. However, for opaque or thin porous materials of the order of hundreds of microns, optical visualization proves to be difficult and requires sophisticated imaging techniques that are expensive and difficult to come by. We describe here a bench-top tool that dynamically probes the hydraulic pathways leading to each free-interface within a single capillary and a bundle of seven capillaries at various saturations (i.e., hydraulic path lengths). A small volumetric displacement was applied to each interface such that the interfaces remained pinned at the capillary walls and the resultant oscillatory pressure drop was measured to determine the hydraulic admittance at each applied oscillation frequency. When the magnitude of the hydraulic admittance was plotted vs. applied oscillation frequency, a resonance peak was found for each degenerately filled capillary. The corresponding peaks were represented by a half-loop (100% filled) and full loops (partially filled) in a Nyquist plot. We compared the theoretical and measured admittance curves and found good agreement for both capillary systems at high filled states. The theoretical predictions became worse when the hydraulic path length was comparable to the capillary radius. The analysis for the hydraulic admittance of a bundle of capillaries is developed here and experimentally validated for the first time.

Predicting intrafraction displacement of the prostate during a five-fraction radiotherapy regimen: Implications for stereotactic body radiotherapy

90

Background: Accurate characterization of prostate displacement during stereotactic body radiotherapy (RT) may help optimize margins to maximize complication and disease-free survival. Also, if individual patients with large intrafraction displacement can be identified, additional interventions can be undertaken.

Methods: Fifty-three men treated on a phase I/II study of extreme hypofractionation were selected for the study. A total dose of 35 Gy in 5 fractions was delivered with intensity modulated radiotherapy (IMRT). Daily image guidance was performed using gold seed fiducials. Position verification was obtained with orthogonal electronic portal images taken immediately before and after each fraction. Prostate shifts were recorded in 3 dimensions.

Results: The mean intrafraction prostate displacements were -0.03 ± 0.61 mm (1SD), 0.21 ± 1.50 mm, and -0.86 ± 1.73 mm in the lateral, superior-inferior, and anterior-posterior directions, respectively. The mean intrafraction displacement during the first two fractions is moderately correlated with the displacement in the remaining 3 fractions, with correlation coefficients of 0.63 and 0.47 in the SI and AP directions, respectively.

Conclusions: The mean intrafraction prostate displacement during a course of extreme hypofractionated radiotherapy is small. A strategy using the first two fractions to predict future displacements >5mm shows promise and warrants further validation.

No significant financial relationships to disclose.

Quality of life after pelvic radiotherapy with hypofractionated IMRT boost and long-term hormone therapy for locally advanced prostate cancer

75

Background: Combined radiotherapy (RT) and long-term hormonal therapy (HT) is a standard treatment option for high-risk prostate cancer. Dose escalated RT alone has been shown to improve disease free survival. Increased sensitivity of prostate cancer to high doses per fraction has led to hypofractionation as a method to radiobiologically escalate dose.We report on the quality of life of patients treated with combined hypofractionated RT and HT.

Methods: A prospective phase I/II study enrolling patients with any of: clinical T3, PSA ≥20, or Gleason 8-10. Forty-five Gy (1.8 Gy/fraction) was delivered to the pelvic nodes with a concomitant 22.5 Gy intensity-modulated RT boost to the prostate, for a total of 67.5 Gy (2.7 Gy/fraction) in 25 fractions over 5 weeks. Hormonal therapy was administered for 2-3 years. Patient reported outcomes were measured at baseline and every 6 months using the validated Expanded Prostate Cancer Index Composite (EPIC) questionnaire, which measures urinary, bowel, sexual, and hormonal domains.

Results: Sixty patients with a minimum 24 months of patient-reported outcomes were analyzed. Mean scores comparing baseline to 24 month values are reported. There were no statistically significant changes in the urinary summary scores (86.3 vs. 86.0, p=0.45) or any of the urinary subscales (function, bother, incontinence, irritative/obstructive). Domain summary score decreases were observed in: bowel by 4.4% (94.7 vs. 90.3, p<0.01), sexual by 27% (44.5 vs. 17.5, p<0.01), and hormonal by 11.9% (93.1 vs. 81.2, p<0.01). Examining time trends in outcomes, most changes occurred within the first 6 months with smaller changes thereafter.

Conclusions: Hypofractionated RT combined with long-term HT is associated with good patient-reported urinary and bowel outcomes at 24 months. Sexual and hormonal summary scores are affected, largely due to continued androgen deprivation therapy. Further follow-up is needed to document patient reported outcomes after testosterone recovery.

No significant financial relationships to disclose.

Pharmaceutical care: cultural, practice and professional perspectives

Focal points

Pharmaceutical care for older people: recording and review of medication following admission to hospital

Focal points

Comparison of helical and average computed tomography for stereotactic body radiation treatment planning and normal tissue contouring in lung cancer

AIMS

To compare average computed tomography (CT(AVE)) datasets with free breathing helical computed tomography (CT(HEL)) for contouring organs at risk (OARs) and radiation treatment planning in patients receiving stereotactic body radiation therapy (SBRT) in the lung.

MATERIALS AND METHODS

Ten SBRT patients with peripheral stage I non-small cell lung cancer underwent a CT(HEL) and a four-dimensional computed tomography scan in the treatment position. CT(AVE) datasets were generated from the four-dimensional computed tomography scan. The following OARs were delineated on the CT(HEL) and CT(AVE) datasets of each patient: lung minus internal target volume, trachea/main bronchus, heart, oesophagus and spinal cord. Volumes and geometric centres of the OARs, as well as the dosimetric impact of planning with these different datasets, were examined.

RESULTS

There were no statistical differences in the OAR geometric centre coordinates nor in the OAR volumes between the CT(HEL) and CT(AVE) datasets, except that CT(AVE)-defined trachea/main bronchus and lung minus internal target volume mean volumes were larger than those defined on the CT(HEL) (46, 43 cm³ and 3516, 3378 cm³, respectively, P<0.05). Despite this, there were no significant differences in the mean and maximum doses to the OAR contours when using the CT(HEL) or CT(AVE) for planning (<4% average change in the maximum and mean doses for all OARs, P>0.05). There were also no significant differences in the locations of the hotspots within OARs among the CT(HEL) or CT(AVE) datasets (P>0.05).

CONCLUSIONS

CT(AVE) datasets may be used in place of CT(HEL) for OAR contouring and dose calculations. When four-dimensional computed tomography is available, it may not be necessary to acquire a separate CT(HEL) scan for OAR contouring or dosimetric purposes.

Femoral tunnel widening after quadrupled hamstring anterior cruciate ligament reconstruction

PURPOSE

To evaluate the extent of femoral tunnel widening after quadrupled hamstring anterior cruciate ligament reconstruction using femoral cross pin fixation in contrast to bioabsorbable screw fixation augmented with Endopearl.

METHODS

16 patients underwent cross pin femoral fixation and the next 15 underwent bioabsorbable screw fixation augmented with Endopearl. The patients were evaluated radiographically for femoral tunnel widening. Standard posteroanterior radiographs of the knee in full extension were taken at postoperative year 2 and 5. The tunnel width was measured at the opening, the widest and the most proximal parts of the femoral tunnel.

RESULTS

In the femoral cross pin and bioabsorbable screw fixations, the mean femoral tunnel sizes were 7.6 and 8.0 mm, respectively. The overall mean tunnel widening at all measured sites were 2.7 and 1.8 mm at the 2-year follow-up and were 2.5 and 1.8 mm at the 5-year follow-up, respectively. The femoral tunnel widening was greater in the cross pin than the bioabsorbable screw group, but only the difference in the most proximal part was significant (p=0.01 at year 2 and p<0.001 at year 5).

CONCLUSION

Femoral tunnel widening was greater in femoral cross pin fixation, probably related to the windshield-wiper and bungee-cord effects. It usually occurred in the first 2 years after the operation and remained static thereafter.

Modeling evidence of episodic intercontinental long-range transport of lindane

Two global atmospheric transport models for persistent toxic substances were employed to quantify the intercontinental atmospheric transport of lindane in 2005 using a recently constructed global lindane emission inventory. The focus of this numerical investigation was to identify, on an intercontinental scale, the major sources of lindane that contributed to the contamination of North America and the Arctic. Both models simulated several strong episodic trans-Pacific atmospheric transport events of lindane from its sources in Asia to the western seaboard of North America. Modeling results also detected, forthe firsttime, an important atmospheric pathway for persistent toxic substances from Western Africa/Western Europe to the Caribbean, the southern United States, and the eastern seaboard of North America. Several episodic lindane transAtlantic atmospheric transport events were found from May to October. These events were associated primarily with the easterly trade winds and the African easterly wave that extends from the subtropical eastern Atlantic to the Caribbean. This atmospheric pathway for toxic chemicals has a substantial implication for the level of toxic substances in North America. Atmospheric mechanisms contributing to these transport events are briefly discussed. Multiple modeling scenarios were studied to assess the contribution of lindane sources in Europe, Asia, and North America to its fate in the Arctic. Results show that these continental contributions are season-dependent with the highest contribution from Europe in the spring.