Image-guided small animal radiation research platform: calibration of treatment beam alignment

Matinfar, Mohammad; Ford, Eric; Iordachita, Iulian; Wong, John W.; Kazanzides, Peter

doi:10.1088/0031-9155/54/4/005

Cited by 73 publications

(78 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This level of targeting accuracy is comparable to that achieved by other systems. For example, the Stanford modified micro-CT system is able to achieve an accuracy of Ϯ0.1 mm in each direction 16 and the SARRP unit 17 an accuracy of 0.2 mm. The micro-IGRT has been in active use for research since its installation, in both an IGRT and a diagnostic capacity.…”

Section: Discussionmentioning

confidence: 99%

Characterization of image quality and image‐guidance performance of a preclinical microirradiator

et al. 2011

View full text Add to dashboard Cite

Purpose:To assess image quality and image-guidance capabilities of a cone-beam CT based smallanimal image-guided irradiation unit ͑micro-IGRT͒. Methods: A micro-IGRT system has been developed in collaboration with the authors' laboratory as a means to study the radiobiological effects of conformal radiation dose distributions in small animals. The system, the X-Rad 225Cx, consists of a 225 kVp x-ray tube and a flat-panel amorphous silicon detector mounted on a rotational C-arm gantry and is capable of both fluoroscopic x-ray and cone-beam CT imaging, as well as image-guided placement of the radiation beams. Image quality ͑voxel noise, modulation transfer, CT number accuracy, and geometric accuracy characteristics͒ was assessed using water cylinder and micro-CT test phantoms. Image guidance was tested by analyzing the dose delivered to radiochromic films fixed to BB's through the endto-end process of imaging, targeting the center of the BB, and irradiation of the film/BB in order to compare the offset between the center of the field and the center of the BB. Image quality and geometric studies were repeated over a 5-7 month period to assess stability. Results: CT numbers reported were found to be linear ͑R 2 Ն 0.998͒ and the noise for images of homogeneous water phantom was 30 HU at imaging doses of approximately 1 cGy ͑to water͒. The presampled MTF at 50% and 10% reached 0.64 and 1.35 mm −1 , respectively. Targeting accuracy by means of film irradiations was shown to have a mean displacement error of ͓⌬x,⌬y,⌬z͔ = ͓−0.12, −0.05, −0.02͔ mm, with standard deviations of ͓0.02, 0.20, 0.17͔ mm. The system has proven to be stable over time, with both the image quality and image-guidance performance being reproducible for the duration of the studies. Conclusions:The micro-IGRT unit provides soft-tissue imaging of small-animal anatomy at acceptable imaging doses ͑Յ1 cGy͒. The geometric accuracy and targeting systems permit dose placement with submillimeter accuracy and precision. The system has proven itself to be stable over 2 yr of routine laboratory use ͑Ͼ1800 irradiations͒ and provides a platform for the exploration of targeted radiation effects in small-animal models.

show abstract

Section: Discussionmentioning

confidence: 99%

Characterization of image quality and image‐guidance performance of a preclinical microirradiator

et al. 2011

View full text Add to dashboard Cite

show abstract

“…1,2 However with the development of conformal radiotherapy, intensity modulated radiation therapy, and image-guided radiation therapy, new conformal small animal radiation therapy systems simulating clinical dose delivery methods have been designed. [3][4][5][6][7] While systems developed at Princess Margaret Hospital and John Hopkins University use 225 kV x-ray tubes for irradiation of small animals, preclinical radiation therapy at Washington University, originally done with a 192 Ir source, has been recently conducted with a 320 kV x-ray tube. At Stanford University, a kilovoltage (kV) GE eXplore Locus microCT scanner (GE Healthcare, London, Ontario, Canada) has been modified for delivery of therapeutic doses to small animals.…”

Section: Introductionmentioning

confidence: 99%

The importance of tissue segmentation for dose calculations for kilovoltage radiation therapy

Bazalova

Graves

2011

Med. Phys.

View full text Add to dashboard Cite

Purpose: The aim of this work was to evaluate the effect of tissue segmentation on the accuracy of Monte Carlo (MC) dose calculations for kilovoltage radiation therapy, which are commonly used in preclinical radiotherapy studies and are also being revisited as a clinical treatment modality. The feasibility of tissue segmentation routinely done on the basis of differences in tissue mass densities was studied and a new segmentation scheme based on differences in effective atomic numbers was developed. Methods: MC dose calculations in a cylindrical mouse phantom with small cylindrical inhomogeneities consisting of 34 ICRU-44 tissues were performed using the EGSnrc/BEAMnrc and DOSXYZnrc codes. The dose to tissue was calculated for five different kilovoltage beams currently used in small animal radiotherapy: a microCT 120 kV beam, two 225 kV beams filtered with either 4 mm of Al or 0.5 mm of Cu, a heavily filtered 320 kV beam, and a 192Ir beam. The mean doses to the 34 ICRU-44 tissues as a function of tissue mass density and effective atomic number and beam energy were studied. A treatment plan for an orthotopic lung tumor model was created, and the dose distribution was calculated for three tissue segmentation schemes using 4, 8, and 39 tissue bins to assess the significance of the simulation results for kilovoltage radiotherapy.Results: In our model, incorrect assignment of adipose tissue to muscle caused dose calculation differences of 27%, 13%, and 7% for the 120 kV beam and the 225 kV beams filtered with 4 mm Al and 0.5 mm Cu, respectively. For the heavily filtered 320 kV beam and a 192 Ir source, potential dose calculation differences due to tissue mis-assignment were below 4%. There was no clear relationship between the dose to tissue and its mass density for x-ray beams generated by tube potentials equal or less than 225 kV. A second order polynomial fit approximated well the absorbed dose to tissue as a function of effective atomic number for these beams. In the mouse study, the 120 kV beam dose to bone was overestimated by 100% and underestimated by 10% for the 4 and 8-tissue segmentation schemes compared to the 39-tissue segmentation scheme, respectively. Dose to adipose tissue was overestimated by 30% and underestimated by 10%, respectively. In general, organ at risk (OAR) doses were overestimated in the 4-tissue and the 8-tissue segmentation schemes compared to the 39-tissue segmentation. Conclusions: Tissue segmentation was shown to be a key parameter for dose calculations with kilovoltage beams used in small animal radiotherapy when an x-ray tube with a potential 225 kV is used as a source. A new tissue segmentation scheme with 39 tissues based on effective number differences derived from mass density differences has been implemented.

show abstract

“…Several laboratories are addressing this issue by developing methods for more precise small animal radiation therapy, including groups at Johns Hopkins University, [4][5][6][7][8][9][10] Princess Margaret Hospital, 11 and Washington University. [12][13][14][15][16] Our group has previously developed a method for precision irradiation of small animals by adapting an existing small animal microCT scanner with an x-ray tube operating at 70-120 kVp using a variable-aperture collimator with an aperture range of 1-102 mm at isocenter.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the effects of treatment planning variables in small animal radiotherapy dose distributions

et al. 2010

View full text Add to dashboard Cite

Purpose: Methods used for small animal radiation treatment have yet to achieve the same dose targeting as in clinical radiation therapy. Toward understanding how to better plan small animal radiation using a system recently developed for this purpose, the authors characterized dose distributions produced from conformal radiotherapy of small animals in a microCT scanner equipped with a variable-aperture collimator. Methods: Dose distributions delivered to a cylindrical solid water phantom were simulated using a Monte Carlo algorithm. Phase-space files for 120 kVp x-ray beams and collimator widths of 1-10 mm at isocenter were generated using BEAMnrc software, and dose distributions for evenly spaced beams numbered from 5 to 80 were generated in DOSXYZnrc for a variety of targets, including centered spherical targets in a range of sizes, spherical targets offset from centered by various distances, and various ellipsoidal targets. Dose distributions were analyzed using dose volume histograms. The dose delivered to a mouse bearing a spontaneous lung tumor was also simulated, and dose volume histograms were generated for the tumor, heart, left lung, right lung, and spinal cord. Results: Results indicated that for centered, symmetric targets, the number of beams required to achieve a smooth dose volume histogram decreased with increased target size. Dose distributions for noncentered, symmetric targets did not exhibit any significant loss of conformality with increasing offset from the phantom center, indicating sufficient beam penetration through the phantom for targeting superficial targets from all angles. Even with variable collimator widths, targeting of asymmetric targets was found to have less conformality than that of spherical targets. Irradiation of a mouse lung tumor with multiple beam widths was found to effectively deliver dose to the tumor volume while minimizing dose to other critical structures. Conclusions: Overall, this method of generating and analyzing dose distributions provides a quantitative method for developing practical guidelines for small animal radiotherapy treatment planning. Future work should address methods to improve conformality in asymmetric targets.

show abstract

Image-guided small animal radiation research platform: calibration of treatment beam alignment

Cited by 73 publications

References 20 publications

Characterization of image quality and image‐guidance performance of a preclinical microirradiator

Characterization of image quality and image‐guidance performance of a preclinical microirradiator

The importance of tissue segmentation for dose calculations for kilovoltage radiation therapy

Investigation of the effects of treatment planning variables in small animal radiotherapy dose distributions

Contact Info

Product

Resources

About