To evaluate the dosimetric impact of heterogeneity corrections on both conventional and volume-optimized high-dose-rate (HDR) ¹⁹²Ir brachytherapy tandem-and-ovoid treatment plans.
Both conventional ...and volume-optimized treatment plans were retrospectively created using eight unique CT data sets. In the volume-optimized plans, the clinical target volume (CTV) and organs-at-risk (rectum, bladder, and sigmoid) were contoured on the CT data sets by a single physician. For each plan, dose calculations representing homogeneous water medium were performed using the Task Group (TG-43) formalism and dose calculations with heterogeneity corrections were performed using a commercially available treatment planning system.
For the conventional plans, the change in dose between TG-43 and heterogeneity-corrected calculations was assessed for the following points: Point-A (left and right) and International Commission on Radiation Units and Measurements (ICRU) 38 defined rectum and bladder points. It was found that the dose to the ICRU bladder decreased the most (-2.2±0.9%), whereas ICRU rectum (-1.7±0.8%), Point-A right (-1.1±0.4%), and Point-A left (-1.0±0.3%) also showed decreases with heterogeneity-corrected calculations. For the volume-optimized plans, the change in dose between TG-43 and heterogeneity-corrected calculations was assessed for the following dose-volume histogram parameters: D(90) of the CTV and D(2cc) of the rectum, bladder, and sigmoid. It was found that D(90) of the CTV decreased by -1.9±0.7% and D(2cc) decreased by -2.6±1.4%, -1.0±0.4%, and -2.0±0.6% for the rectum, bladder and sigmoid, respectively, with heterogeneity-corrected calculations.
Heterogeneity corrections on high-dose rate plans were found to have only a small dosimetric impact over TG-43-based dose calculations for both conventional Point-A and volume-optimized plans.
Previously, our team used Monte Carlo simulation to demonstrate that a gamma camera could potentially be used as an online image guidance device to visualize seeds during permanent breast seed ...implant procedures. This could allow for intraoperative correction if seeds have been misplaced. The objective of this study is to describe an experimental evaluation of an online gamma-camera imaging of permanent seed implantation (OGIPSI) prototype. The OGIPSI device is intended to be able to detect a seed misplacement of
5
mm
or more within an imaging time of
2
min
or less. The device was constructed by fitting a custom built brass collimator (
16
mm
height,
0.65
mm
hole pitch,
0.15
mm
septal thickness) on a 64 pixel linear array CZT detector (eValuator-2000, eV Products, Saxonburg, PA). Two-dimensional projection images of seed distributions were acquired by the use of a digitally controlled translation stage. Spatial resolution and noise characteristics of the detector were measured. The ability and time needed for the OGIPSI device to image the seeds and to detect cold spots was tested using an anthropomorphic breast phantom. Mimicking a real treatment plan, a total of 52
Pd
103
seeds of
65.8
MBq
each were placed on three different layers at appropriate depths within the phantom. The seeds were reliably detected within
30
s
with a median error in localization of
1
mm
. In conclusion, an OGIPSI device can potentially be used for image guidance of permanent brachytherapy applications in the breast and, possibly, other sites.
Traditionally, cervical brachytherapy has been prescribed to point A. However, since the Groupe Européen de Curiethérapie and European Society for Radiotherapy＆ Oncology guidelines were published, ...image-guided brachytherapy has become an emerging technique. The purpose of this study was to evaluate the high-risk clinical target volume （HR-CTV） coverage and analyze dose-volume histograms for organs at risk in point A prescription of high-dose-rate brachytherapy. A total of 68 patients with locally advanced cervical cancer were treated with three-dimensional conformal external beam radiation therapy and brachytherapy from December 2012 to March 2017. Fractions of 6Gy for a total of 12-24Gy were delivered at point A by brachytherapy to all patients. Following each brachytherapy application, a pelvic computed tomography scan was performed and imported into a three-dimensional brachytherapy treatment planning system. In this study, the HR-CTV, bladder, and rectum were re-delineated according to Report 89 of the International Commission on Radiation Units and Measurements using the magnetic resonance images at the time of diagnosis, and the dose-volume histogram of each structure was analyzed. The median age of patients at diagnosis was 67 years （range, 31-91 years）. Mean HR-CTV D90 for all patients was 558.3cGy （range, 228.7-1005.1cGy） and the mean HR-CTV D90 within each clinical T stage was: Ib, 646.4cGy; 2a, 579.3cGy; 2b, 545.2cGy; 3a, 556.6cGy; 3b, 451.3cGy; and 4, 497.9cGy. HR-CTVD90 was correlated with HR-CTV. The mean D2cm3 was 678.1cGy for the bladder and 511.9cGy for the rectum. Using point A-based dose prescription, HR-CTV coverage was insufficient, especially in cases with a large tumor volume or a high T stage. Image-guided brachytherapy is expected to improve HR-CTV coverage while keeping rectal and bladder doses within acceptable levels.
There has been increased interest in implementing image-guided brachytherapy to better define the structures of interest and assess the radiation dose distribution in tumors and surrounding normal ...tissues. This is particularly helpful in the treatment of pelvic malignancies such as cervix cancer and prostate cancer, in which the tumor lies in close relationship to the bladder and rectosigmoid. This provides a forum for the collaboration of diagnostic radiologists and radiation oncologists.
The further development of image-guided brachytherapy as modern interventional radiation therapy is strongly depend from the capability of diagnostic equipment and procedures to meet special demands ...of image-guided brachytherapy. The basic aspect and principles of brachytherapy and hence most important demands of diagnostic equipment and procedures dedicated for the image-guided brachytherapy are identified and discussed. It is evident, that all currently available diagnostic procedures such Ultrasound, CT, MRI or PET-CT can only partially meet the special requirements of brachytherapy. The challenge for developers of new hardware’s and software’s of diagnostic equipment / procedures for image-guided brachytherapy is simply first further develop each imaging procedures in accordance with these special requirements and second to make possible the match easily images of everybody diagnostic device each together and so by integration of pre-operative CT, PET-CT or MRI images generate a precise real-time three-dimensional anatomical model of the site.
Braquiterapia guiada por imagen Vila Viñas, Meritxell; Rico Osés, Mikel; Villafranca Iture, Elena ...
Anales del sistema sanitario de Navarra,
2009, 20090001, Letnik:
32, Številka:
2
Journal Article
Odprti dostop
La braquiterapia consiste en la administración de
radiación en contacto íntimo con el tumor, con una baja
exposición de los tejidos sanos circundantes. Empezó a
utilizarse a comienzos del siglo XX y ...desde entonces ha
ido desarrollándose: diferentes radioisótopos, sistemas
de tratamiento a distancia, programas informáticos que
permiten un cálculo individualizado de la dosis.
Los cambios en los últimos años dentro de la braquiterapia
han afectado a dos aspectos. En primer lugar,
la incorporación de las técnicas de imagen como la ecografía,
la tomografía computarizada (TC) y la resonancia
magnética (RM), imprescindibles para el diagnóstico y
la estadificación tumoral. Su utilización mientras se realiza
el implante ayuda a guiarlo y realizarlo con mayor
precisión. En segundo lugar, la utilización de TC, RM y
ecografía permiten mejorar la cobertura del tumor o reducir
la dosis a los órganos sanos. Se utilizan dentro de
sistemas de planificación inversa, que realizan el cálculo
de dosis a partir de las recomendaciones de las dosis
a administrar al tumor y a los órganos sanos. En estos
programas de planificación es posible hacer los cálculos
con mucha rapidez, teniendo en cuenta la colocación en
cada momento de la fuente. Esta técnica, llamada planificación
en tiempo real, empieza a mostrar ventajas en el
tratamiento de los cánceres de próstata.
La incorporación de las técnicas de imagen y las
mejoras en los sistemas de cálculo han hecho que en la
actualidad la braquiterapia juegue un papel importante
en el tratamiento del cáncer de próstata, cérvix, mama,
tumores de cabeza y cuello, bronquio o esófago.
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