RESUMEN
The growth of the global terrestrial sink of carbon dioxide has puzzled scientists for decades. We propose that the role of land management practices-from intensive forestry to allowing passive afforestation of abandoned lands-have played a major role in the growth of the terrestrial carbon sink in the decades since the mid twentieth century. The Forest Transition, a historic transition from shrinking to expanding forests, and from sparser to denser forests, has seen an increase of biomass and carbon across large regions of the globe. We propose that the contribution of Forest Transitions to the terrestrial carbon sink has been underestimated. Because forest growth is slow and incremental, changes in the carbon density in forest biomass and soils often elude detection. Measurement technologies that rely on changes in two-dimensional ground cover can miss changes in forest density. In contrast, changes from abrupt and total losses of biomass in land clearing, forest fires and clear cuts are easy to measure. Land management improves over time providing important present contributions and future potential to climate change mitigation. Appreciating the contributions of Forest Transitions to the sequestering of atmospheric carbon will enable its potential to aid in climate change mitigation.
Asunto(s)
Bosques , Árboles , Biomasa , Secuestro de Carbono , Agricultura ForestalRESUMEN
PURPOSE: The use of T2 MR for postimplant dosimetry (PID) after prostate brachytherapy allows more anatomically accurate and precise contouring but does not readily permit seed identification. We developed a reproducible technique for performing MR-CT fusion and compared the resulting dosimetry to standard CT-based PID. METHODS AND MATERIALS: CT and T1-weighted MR images for 45 patients were fused and aligned based on seed distribution. The T2-weighted MR image was then fused to the aligned T1. Reproducibility of the fusion technique was tested by inter- and intraobserver variability for 13 patients. Dosimetry was computed for the prostate as a whole and for the prostate divided into anterior and posterior sectors of the base, mid-prostate, and apex. RESULTS: Inter- and intraobserver variability for the fusion technique showed less than 1% variation in D90. MR-CT fusion D90 and CT D90 were nearly equivalent for the whole prostate, but differed depending on the identification of superior extent of the base (p = 0.007) and on MR/CT prostate volume ratio (p = 0.03). Sector analysis showed a decrease in MR-CT fusion D90 in the anterior base (ratio 0.93 ±0.25, p < 0.05) and an increase in MR-CT fusion D90 in the apex (p < 0.05). The volume of extraprostatic tissue encompassed by the V100 is greater on MR than CT. Factors associated with this difference are the MR/CT volume ratio (p < 0.001) and the difference in identification of the inferior extent of the apex (p = 0.03). CONCLUSIONS: We developed a reproducible MR-CT fusion technique that allows MR-based dosimetry. Comparing the resulting postimplant dosimetry with standard CT dosimetry shows several differences, including adequacy of coverage of the base and conformity of the dosimetry around the apex. Given the advantage of MR-based tissue definition, further study of MR-based dosimetry is warranted.
Asunto(s)
Braquiterapia/métodos , Imagen por Resonancia Magnética/métodos , Neoplasias de la Próstata/radioterapia , Tomografía Computarizada por Rayos X/métodos , Braquiterapia/instrumentación , Humanos , Masculino , Variaciones Dependientes del Observador , Paladio/uso terapéutico , Próstata/diagnóstico por imagen , Próstata/patología , Próstata/efectos de la radiación , Neoplasias de la Próstata/diagnóstico por imagen , Neoplasias de la Próstata/patología , Radioisótopos/uso terapéutico , Radiometría/métodos , Dosificación Radioterapéutica , Reproducibilidad de los ResultadosRESUMEN
Like cities, forests grow by spreading out or by growing denser. Both inventories taken steadily by a single nation and other inventories gathered recently from many nations by the United Nations confirm the asynchronous effects of changing area and of density or volume per hectare. United States forests spread little after 1953, while growing density per hectare increased national volume and thus sequestered carbon. The 2010 United Nations appraisal of global forests during the briefer span of two decades after 1990 reveals a similar pattern: A slowing decline of area with growing volume means growing density in 68 nations encompassing 72% of reported global forest land and 68% of reported global carbon mass. To summarize, the nations were placed in 5 regions named for continents. During 1990-2010 national density grew unevenly, but nevertheless grew in all regions. Growing density was responsible for substantially increasing sequestered carbon in the European and North American regions, despite smaller changes in area. Density nudged upward in the African and South American regions as area loss outstripped the loss of carbon. For the Asian region, density grew in the first decade and fell slightly in the second as forest area expanded. The different courses of area and density disqualify area as a proxy for volume and carbon. Applying forestry methods traditionally used to measure timber volumes still offers a necessary route to measuring carbon stocks. With little expansion of forest area, managing for timber growth and density offered a way to increase carbon stocks.
Asunto(s)
Conservación de los Recursos Naturales/estadística & datos numéricos , Recolección de Datos , Internacionalidad , Árboles/crecimiento & desarrollo , Carbono/metabolismo , Dinámica Poblacional , Estados UnidosRESUMEN
PURPOSE: Accurate target delineation of the nodal volumes is essential for three-dimensional conformal and intensity-modulated radiotherapy planning for endometrial cancer adjuvant therapy. We hypothesized that atlas-based segmentation ("autocontouring") would lead to time savings and more consistent contours among physicians. METHODS AND MATERIALS: A reference anatomy atlas was constructed using the data from 15 postoperative endometrial cancer patients by contouring the pelvic nodal clinical target volume on the simulation computed tomography scan according to the Radiation Therapy Oncology Group 0418 trial using commercially available software. On the simulation computed tomography scans from 10 additional endometrial cancer patients, the nodal clinical target volume autocontours were generated. Three radiation oncologists corrected the autocontours and delineated the manual nodal contours under timed conditions while unaware of the other contours. The time difference was determined, and the overlap of the contours was calculated using Dice's coefficient. RESULTS: For all physicians, manual contouring of the pelvic nodal target volumes and editing the autocontours required a mean±standard deviation of 32±9 vs. 23±7 minutes, respectively (p=.000001), a 26% time savings. For each physician, the time required to delineate the manual contours vs. correcting the autocontours was 30±3 vs. 21±5 min (p=.003), 39±12 vs. 30±5 min (p=.055), and 29±5 vs. 20±5 min (p=.0002). The mean overlap increased from manual contouring (0.77) to correcting the autocontours (0.79; p=.038). CONCLUSION: The results of our study have shown that autocontouring leads to increased consistency and time savings when contouring the nodal target volumes for adjuvant treatment of endometrial cancer, although the autocontours still required careful editing to ensure that the lymph nodes at risk of recurrence are properly included in the target volume.
Asunto(s)
Neoplasias Endometriales/diagnóstico por imagen , Neoplasias Endometriales/radioterapia , Ganglios Linfáticos/diagnóstico por imagen , Ilustración Médica , Neoplasias Endometriales/cirugía , Femenino , Humanos , Pelvis , Oncología por Radiación/normas , Planificación de la Radioterapia Asistida por Computador/métodos , Radioterapia Adyuvante , Radioterapia de Intensidad Modulada/métodos , Factores de Tiempo , Tomografía Computarizada por Rayos X/métodosRESUMEN
BACKGROUND: Sublobar lung resection and brachytherapy seed placement is gaining acceptance for T1 non-small cell lung cancer (NSCLC) in select patients with comorbidities precluding lobectomy. Our institution first reported utilization of the da Vinci system for robotic brachytherapy developed experimentally in swine and applied to high-risk patients 5 years ago. We now report seed dosimetrics and midterm follow-up. METHODS: Eleven high-risk patients with stage IA NSCLC who were not candidates for conventional lobectomy underwent limited resection of 12 primary tumors. To reduce locoregional recurrence, (125)I brachytherapy seeds were robotically sutured intracorporeally over resection margins to deliver 14,400 cGy 1 cm from the implant plane. Patients were followed with dosimetric computed tomography scans at 30 +/- 16 days. Survival and sites of recurrence were documented. RESULTS: Resected tumor size averaged 1.48 +/- 0.38 cm (range, 1.1 to 2.1 cm). Perioperative mortality was 0% and recurrence was 9% (1 of 11 [margin recurrence at 6 months with resultant mortality at 1 year]). Follow-up duration was 31.82 +/- 17.35 months. Dosimetrics confirmed 14,400 cGy delivery using 24.21 +/- 4.6 (125)I seeds (range, 17 to 30 seeds) over a planning target volume of 10.29 +/- 2.39 cc(3). Overall, 84.1% of the planning target volume was covered by 100% of the prescription dose (V100), and 88.2% was covered by 87% of the prescription dose (V87), comparable to open dosimetric data at our institution. Follow-up imaging confirmed seed stability in all patients. CONCLUSIONS: Robotic (125)I brachytherapy seed placement is a feasible adjuvant procedure to reduce the incidence of recurrence after sublobar resection in medically compromised patients. Tailored robotic seed placement delivers an exact dosing regimen in a minimally invasive fashion with equivalent precision to open surgery.