IMRT for image-guided single vocal cord irradiation

PURPOSE: We have been developing an image-guided single vocal cord irradiation technique to treat patients with stage T1a glottic carcinoma. In the present study, we compared the dose coverage to the affected vocal cord and the dose delivered to the organs at risk using conventional, intensity-modulated radiotherapy (IMRT) coplanar, and IMRT non-coplanar techniques.

METHODS AND MATERIALS: For 10 patients, conventional treatment plans using two laterally opposed wedged 6-MV photon beams were calculated in XiO (Elekta-CMS treatment planning system). An in-house IMRT/beam angle optimization algorithm was used to obtain the coplanar and non-coplanar optimized beam angles. Using these angles, the IMRT plans were generated in Monaco (IMRT treatment planning system, Elekta-CMS) with the implemented Monte Carlo dose calculation algorithm. The organs at risk included the contralateral vocal cord, arytenoids, swallowing muscles, carotid arteries, and spinal cord. The prescription dose was 66 Gy in 33 fractions.

RESULTS: For the conventional plans and coplanar and non-coplanar IMRT plans, the population-averaged mean dose ± standard deviation to the planning target volume was 67 ± 1 Gy. The contralateral vocal cord dose was reduced from 66 ± 1 Gy in the conventional plans to 39 ± 8 Gy and 36 ± 6 Gy in the coplanar and non-coplanar IMRT plans, respectively. IMRT consistently reduced the doses to the other organs at risk.

CONCLUSIONS: Single vocal cord irradiation with IMRT resulted in good target coverage and provided significant sparing of the critical structures. This has the potential to improve the quality-of-life outcomes after RT and maintain the same local control rates.

On-line cone beam CT image guidance for vocal cord tumor targeting

Background and purpose: We are developing a technique for highly focused vocal cord irradiation in early glottic carcinoma to optimally treat a target volume confined to a single cord. This technique, in contrast with the conventional methods, aims at sparing the healthy vocal cord. As such a technique requires sub-mm daily targeting accuracy to be effective, we investigate the accuracy achievable with on-line kV-cone beam CT (CBCT) corrections. Materials and methods: CBCT scans were obtained in 10 early glottic cancer patients in each treatment fraction. The grey value registration available in X-ray volume imaging (XVI) software (Elekta, Synergy) was applied to a volume of interest encompassing the thyroid cartilage. After application of the thus derived corrections, residue displacements with respect to the planning CT scan were measured at clearly identifiable relevant landmarks. The intra- and inter-observer variations were also measured. Results: While before correction the systematic displacements of the vocal cords were as large as 2.4 ± 3.3 mm (cranial-caudal population mean ± SD Σ), daily CBCT registration and correction reduced these values to less than 0.2 ± 0.5 mm in all directions. Random positioning errors (SD σ) were reduced to less than 1 mm. Correcting only for translations and not for rotations did not appreciably affect this accuracy. The residue random displacements partly stem from intra-observer variations (SD = 0.2-0.6 mm). Conclusion: The use of CBCT for daily image guidance in combination with standard mask fixation reduced systematic and random set-up errors of the vocal cords to <1 mm prior to the delivery of each fraction dose. Thus, this facilitates the high targeting precision required for a single vocal cord irradiation. © 2009 Elsevier Ireland Ltd. All rights reserved.

Four-dimensional CT analysis of vocal cords mobility for highly focused single vocal cord irradiation

Background and Purpose: To quantify respiratory motion of the vocal cords during normal respiration using 4D-CT. The final goal is to develop a technique for single vocal cord irradiation (SVCI) in early glottic carcinoma. Sparing the non-involved cord and surrounding structures has the potential to preserve voice quality and allow re-irradiation of recurrent and second primary tumors. Material and methods: Four-dimensional CTs of 1 mm slice thickness from 10 early glottic carcinoma patients were acquired. The lateral dimensions of the air gap separating the vocal cords were measured anteriorly, at mid-level and posteriorly at each phase of the 4D-CTs. The corresponding anterior-posterior gaps were similarly measured. Cranio-caudal vocal cords movements during breathing were derived from the shifts of the arythenoids. Results: The population-averaged mean gap size ± the corresponding standard deviation due to breathing (SD_B) for the lateral gaps was 5.8 ± 0.7 mm anteriorly, 8.7 ± 0.9 mm at mid-level, and 11.0 ± 1.3 mm posteriorly. Anterior-posterior gap values were 21.7 ± 0.7 mm, while cranio-caudal shift SD_B was 0.8 mm. Conclusion: Vocal cords breathing motions were found to be small relative to their separation. Hence, breathing motion does not seem to be a limiting factor for SVCI. © 2008 Elsevier Ireland Ltd. All rights reserved.

Improving fuel economy application of the organic Rankine Cycle on a hybrid bus

Globally vehicle operators are experiencing rising fuel costs and increased
running expenses as governments around the world attempt to decrease carbon dioxide emissions and fossil fuel consumption, due to global warming and the drive to reduce dependency on fossil fuels. Recent advances in hybrid vehicle design have made great strides towards more efficient operation, with regenerative braking being widely used to capture otherwise lost energy. In this paper a hybrid series bus is developed a step further, by installing another method of energy capture on the vehicle. In this case, it is in the form of the Organic Rankine Cycle (ORC). The waste heat expelled to the exhaust and coolant streams is recovered and converted to electrical energy which is then stored in the hybrid vehicles batteries. The electrical energy can then be used for the auxiliary power circuit or to assist in vehicle propulsion, thus reducing the load on the engine, thereby improving the overall fuel economy of the vehicle and reducing carbon dioxide emissions.

The Day After Tomorrow: Transition Management, Spatial Planning & the Low Carbon Economy

Many of the societal challenges that current spatial planning practice claims to be addressing (climate change, peak oil, obesity, aging society etc) encompass issues and timescales that lie beyond the traditional scope planning policy (Campbell 2006). The example of achieving a low carbon economy typifies this in that it demands a process of society-wide transition, involving steering a wide range of factors (markets, infrastructure, governance, individual behaviour etc). Such a process offers a challenge to traditional approaches to planning as they cannot be guided by a fixed blueprint, given the timescales involved (up to 50 years) and an enhanced level of uncertainty, social resistance, lack of control over implementation and a danger of ‘policy lock in’ (Kemp et al 2007). One approach to responding to these challenges is the concept of transition management which has emerged from studies of science, technology and innovation (Geels 2002, Markard et al 2012). Although not without criticism, this perspective attempts to uncertainty and complexity encompassing long term visions that integrates multi-level, multi-actor and multi-domain perspectives (Rotmans et al 2001).
 
Given its origins, research on transition management has tended to neglect spatial contexts (Coenen et al 2012) and, related to this, it’s relationship with spatial planning is poorly understood. Using the example of the low carbon transition, this paper will review the relationships between the concepts, methodologies and goals of transition management and spatial planning to explore whether a closer integration of the two fields offers benefits to achieving the long term challenges facing society.
 

Inter- and Intrafraction Target Motion in Highly Focused Single Vocal Cord Irradiation of T1a Larynx Cancer Patients

PURPOSE: The purpose of this study was to verify clinical target volume-planning target volume (CTV-PTV) margins in single vocal cord irradiation (SVCI) of T1a larynx tumors and characterize inter- and intrafraction target motion.

METHODS AND MATERIALS: For 42 patients, a single vocal cord was irradiated using intensity modulated radiation therapy at a total dose of 58.1 Gy (16 fractions × 3.63 Gy). A daily cone beam computed tomography (CBCT) scan was performed to online correct the setup of the thyroid cartilage after patient positioning with in-room lasers (interfraction motion correction). To monitor intrafraction motion, CBCT scans were also acquired just after patient repositioning and after dose delivery. A mixed online-offline setup correction protocol ("O2 protocol") was designed to compensate for both inter- and intrafraction motion.

RESULTS: Observed interfraction, systematic (Σ), and random (σ) setup errors in left-right (LR), craniocaudal (CC), and anteroposterior (AP) directions were 0.9, 2.0, and 1.1 mm and 1.0, 1.6, and 1.0 mm, respectively. After correction of these errors, the following intrafraction movements derived from the CBCT acquired after dose delivery were: Σ = 0.4, 1.3, and 0.7 mm, and σ = 0.8, 1.4, and 0.8 mm. More than half of the patients showed a systematic non-zero intrafraction shift in target position, (ie, the mean intrafraction displacement over the treatment fractions was statistically significantly different from zero; P<.05). With the applied CTV-PTV margins (for most patients 3, 5, and 3 mm in LR, CC, and AP directions, respectively), the minimum CTV dose, estimated from the target displacements observed in the last CBCT, was at least 94% of the prescribed dose for all patients and more than 98% for most patients (37 of 42). The proposed O2 protocol could effectively reduce the systematic intrafraction errors observed after dose delivery to almost zero (Σ = 0.1, 0.2, 0.2 mm).

CONCLUSIONS: With adequate image guidance and CTV-PTV margins in LR, CC, and AP directions of 3, 5, and 3 mm, respectively, excellent target coverage in SVCI could be ensured.

Stability in a Network Economy: The Role of Institutions

We consider an economy in which agents are embedded in a network of potential value-generating relationships. Agents are assumed to be able to participate in three types of economic interactions: Autarkic self-provision; bilateral interaction; and multilateral collaboration through endogenously provided platforms.
We introduce two stability concepts and provide sufficient and necessary conditions on the network structure that guarantee existence, in cases of the absence of externalities, link-based externalities and crowding externalities. We show that institutional arrangements based on socioeconomic roles and leadership guarantee stability. In particular, the stability of more complex economic outcomes requires more strict and complex institutional rules to govern economic interactions. We investigate strict social hierarchies, tiered leadership structures and global market places.

Socialized credit and the working-class family economy: a comparative history of Britain and France 1900-2000

This paper provides a comparative analysis of working class consumer credit in Britain and France from the early twentieth century through to the 1980s. It indicates a number of similarities between the two nations in the earlier part of the period: in particular, in the operation of doorstep credit systems. For the British case study, we explore consumer finance offered by credit drapers (sometimes known as tallymen) whilst in France the paper explores a similar system that functioned in the coalmining communities around the city of Lens. Both methods operated on highly socialised relationships that established the trust on which credit was offered and long-term creditor/borrower relationships established. In the second part of the paper, we analyse the different trajectories taken in post-war France and Britain in this area of working class credit. In France this form of socialized credit gradually dwindled due to factors such as ‘Bancarisation’, which saw the major banks emerge as modern bureaucratized providers of credit for workers and their families. In contrast, in Britain the tallymen (and other related forms of doorstep credit providers) were offered a new lease of life in the 1960s and 1970s. This was a period during which British credit providers utilised multiple methods to evade the hire purchase controls put in place by post-war governments. Thus, whilst the British experience was one of fragmented consumer loan types (including the continuation of doorstep credit), the French experience (like elsewhere in Europe) was one of greater consolidation. The paper concludes by reflecting on the role of these developments in the creation of differential experiences of credit inclusion/exclusion in the two nations and the impact of this on financial inequality.

The Dark Side of Nudging: The Ethics, Political Economy, and Law of Libertarian Paternalism

Libertarian paternalism, as advanced by Cass Sunstein, is seriously flawed, but not primarily for the reasons that most commentators suggest. Libertarian paternalism and its attendant regulatory implications are too libertarian, not too paternalistic, and as a result are in considerable tension with ‘thick’ conceptions of human dignity. We make four arguments. The first is that there is no justification for a presumption in favor of nudging as a default regulatory strategy, as Sunstein asserts. It is ordinarily less effective than mandates; such mandates rarely offend personal autonomy; and the central reliance on cognitive failures in the nudging program is more likely to offend human dignity than the mandates it seeks to replace. Secondly, we argue that nudging as a regulatory strategy fits both overtly and covertly, often insidiously, into a more general libertarian program of political economy. Thirdly, while we are on the whole more concerned to reject the libertarian than the paternalistic elements of this philosophy, Sunstein’s work, both in Why Nudge?, and earlier, fails to appreciate how nudging may be manipulative if not designed with more care than he acknowledges. Lastly, because of these characteristics, nudging might even be subject to legal challenges that would give us the worst of all possible regulatory worlds: a weak regulatory intervention that is liable to be challenged in the courts by well-resourced interest groups. In such a scenario, and contrary to the ‘common sense’ ethos contended for in Why Nudge?, nudges might not even clear the excessively low bar of doing something rather than nothing. Those seeking to pursue progressive politics, under law, should reject nudging in favor of regulation that is more congruent with principles of legality, more transparent, more effective, more democratic, and allows us more fully to act as moral agents. Such a system may have a place for (some) nudging, but not one that departs significantly from how labeling, warnings and the like already function, and nothing that compares with Sunstein’s apparent ambitions for his new movement.

Review of Mark F. Chingono. The State, Violence and Development. The Political Economy of War in Mozambique, 1975–1992.

Book review of: Mark F. Chingono. The State, Violence and Development. The Political Economy of War in Mozambique, 1975–1992. Avebury (Aldershot, Brookfield USA, Hong Kong, Singapore, Sydney), 1996. 291 pp. Foreword by Keith Hart. Tables. Appendix. Selected Bibliography. Index. £42.00. $71.95. Cloth.