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Purpose: In situ drug release concurrent with radiation therapy has been proposed to enhance the therapeutic ratio of permanent prostate brachytherapy. Both brachytherapy sources and brachytherapy spacers have been proposed as potential eluters to release compounds, such as nanoparticles or chemotherapeutic agents. The relative effectiveness of the approaches has not been compared yet. This work models the physical dose enhancement of implantable eluters in conjunction with brachytherapy to determine which delivery mechanism provides greatest opportunity to enhance the therapeutic ratio. Materials and methods: The combined effect of implanted eluters and radioactive sources were modeled in a manner that allowed the comparison of the relative effectiveness of different types of implantable eluters over a range of parameters. Prostate geometry, source, and spacer positions were extracted from treatment plans used for 125I permanent prostate implants. Compound concentrations were calculated using steady‐state solution to the diffusion equation including an elimination term characterized by the diffusion‐elimination modulus (ϕb). Does enhancement was assumed to be dependent on compound concentration up to a saturation concentration (csat). Equivalent uniform dose (EUD) was used as an objective to determine the optimal configuration of eluters for a range of diffusion‐elimination moduli, concentrations, and number of eluters. The compound delivery vehicle that produced the greatest enhanced dose was tallied for points in parameter space mentioned to determine the conditions under whether there are situations where one approach is preferable to the other. Results: The enhanced effect of implanted eluters was calculated for prostate volumes from 14 to 45 cm3, ϕb from 0.01 to 4 mm−1, csat from 0.05 to 7.5 times the steady‐state compound concentration released from the surface of the eluter. The number of used eluters (ne) was simulated from 10 to 60 eluters. For the region of (csat, Φ)‐space that results in a large fraction of the gland being maximally sensitized, compound eluting spacers or sources produce equal increase in EUD. In the majority of the remaining (csat, Φ)‐space, eluting spacers result in a greater EUD than sources even where sources often produce greater maximal physical dose enhancement. Placing eluting implants in planned locations throughout the prostate results in even greater enhancement than using only source or spacer locations. Conclusions: Eluting brachytherapy spacers offer an opportunity to increase EUD during the routine brachytherapy process. Incorporating additional needle placements permits compound eluting spacer placement independent of source placement and thereby allowing a further increase in the therapeutic ratio. Additional work is needed to understand the in vivo spatial distribution of compound around eluters, and to incorporate time dependence of both compound release and radiation dose. [ABSTRACT FROM AUTHOR]

Purpose: To balance dose reduction and image registration accuracy in breast setup imaging. In particular, the authors demonstrate the relationship between scan angle and dose delivery for cone beam tomosynthesis (CBTS) when employed for setup verification of breast cancer patients with surgical clips. Methods: The dose measurements were performed in a female torso phantom for varying scan angles of CBTS. Setup accuracy was measured using three registration methods: Clip centroid localization accuracy and the accuracy of two semiautomatic registration algorithms. The dose to the organs outside of the ipsilateral breast and registration accuracy information were compared to determine the optimal scan angle for CBTS for breast patient setup verification. Isocenter positions at the center of the patient and at the breast-chest wall interface were considered. Results: Image registration accuracy was within 1 mm for the CBTS scan angles θ above 20° for some scenarios and as large as 80° for the worst case, depending on the imaged breast and registration algorithm. Registration accuracy was highest based on clip centroid localization. For left and right breast imaging with the isocenter at the chest wall, the dose to the contralateral side of the patient was very low (<0.5 cGy) for all scan angles considered. For central isocenter location, the optimal scan angles were 30°–50° for the left breast imaging and 40°–50° for the right breast imaging, with the difference due to the geometric asymmetry of the current clinical imaging system. Conclusions: The optimal scan angles for CBTS imaging were found to be between 10° and 50°, depending on the isocenter location and ipsilateral breast. Use of the isocenter at the breast-chest wall locations always resulted in greater accuracy of image registration (<1 mm) at smaller angles (10°–20°) and at lower doses (<0.1 cGy) to the contralateral organs. For chest wall isocenters, doses delivered to organs outside of the target breast were much smaller than the scattered and leakage doses of the treatment beams. The complete volumetric information of all clips in the region of interest, combined with the small dose to the contralateral organs and the small scan angle, could result in an advantage for small angle CBTS with off center isocenters over simple orthogonal pairs. [ABSTRACT FROM AUTHOR]

The article discusses the intubation training using Northwick Park drill. The Northwick Park drill uses the Macintosh method but instead of watching the tip of the bougie enter the trachea. Macintosh used a tube with a bevel rotated 90 degrees. Failed intubation in obstetrics provides a valuable yardstick of trainee performance.

A response by R. S. Cormack to a letter to the editor about his article "Intubation training in the real world" in the 2007 issue is presented.