Multi-class medical image segmentation using one-vs-rest graph cuts and majority voting.

Semi-automatic image segmentation is still a valuable tool in clinical applications since it retains the expert oversights legally required. However, semi-automatic methods for simultaneous multi-class segmentation are difficult to be clinically implemented due to the complexity of underlining algorithms. We purpose an efficient one-vs-rest graph cut approach of which the complexity only grows linearly as the number of classes increases.

Semiautomatic tumor segmentation with multimodal images in a conditional random field framework.

Volumetric medical images of a single subject can be acquired using different imaging modalities, such as computed tomography, magnetic resonance imaging (MRI), and positron emission tomography. In this work, we present a semiautomatic segmentation algorithm that can leverage the synergies between different image modalities while integrating interactive human guidance. The algorithm provides a statistical segmentation framework partly automating the segmentation task while still maintaining critical human oversight.

Are fiducial markers useful surrogates when using respiratory gating to reduce motion of gastroesophageal junction tumors?

Background: Radiation therapy (RT) is an integral component of the management of gastroesophageal junction (GEJ) tumors. We evaluated the use of implanted radiopaque fiducials as tumor surrogates to allow for more focal delivery of RT to these mobile tumors when using respiratory gating (RG) to reduce motion.

Material And Methods: We analyzed four-dimensional computed tomography scans of 20 GEJ patients treated with RG and assessed correlation between tumor and implanted fiducial motion over the whole respiratory cycle and within a clinically realistic gate around end-exhalation.

Kilovoltage Imaging of Implanted Fiducials to Monitor Intrafraction Motion With Abdominal Compression During Stereotactic Body Radiation Therapy for Gastrointestinal Tumors.

Purpose: To assess intrafraction respiratory motion using a commercial kilovoltage imaging system for abdominal tumor patients with implanted fiducials and breathing constrained by pneumatic compression during stereotactic body radiation therapy (SBRT).

Methods And Materials: A pneumatic compression belt limited respiratory motion in 19 patients with radiopaque fiducials in or near their tumor during SBRT for abdominal tumors. Kilovoltage images were acquired at 5- to 6-second intervals during treatment using a commercial system.

Safety considerations for IGRT: Executive summary.

Radiation therapy is an effective cancer treatment that is constantly being transformed by technological innovation. Dedicated devices for fraction-by-fraction imaging and guidance within the treatment room have enabled image guided radiation therapy (IGRT) allowing clinicians to pursue highly conformal dose distributions, higher dose prescriptions, and shorter fractionation schedules. Capitalizing on IGRT-enabled accuracy and precision requires a strong link between IGRT practices and planning target volume (PTV) design.

Semi-automatic medical image segmentation with adaptive local statistics in Conditional Random Fields framework.

Planning radiotherapy and surgical procedures usually require onerous manual segmentation of anatomical structures from medical images. In this paper we present a semi-automatic and accurate segmentation method to dramatically reduce the time and effort required of expert users. This is accomplished by giving a user an intuitive graphical interface to indicate samples of target and non-target tissue by loosely drawing a few brush strokes on the image.

Low-dose megavoltage cone-beam computed tomography for lung tumors using a high-efficiency image receptor.

We report on the capabilities of a low-dose megavoltage cone-beam computed tomography (MV CBCT) system. The high-efficiency image receptor consists of a photodiode array coupled to a scintillator composed of individual CsI crystals. The CBCT system uses the 6 MV beam from a linear accelerator.

Integrating respiratory gating into a megavoltage cone-beam CT system.

We have previously described a low-dose megavoltage cone beam computed tomography (MV CBCT) system capable of producing projection image using one beam pulse. In this study, we report on its integration with respiratory gating for gated radiotherapy. The respiratory gating system tracks a reflective marker on the patient's abdomen midway between the xiphoid and umbilicus, and disables radiation delivery when the marker position is outside predefined thresholds.

Interfractional anatomic variation in patients treated with respiration-gated radiotherapy.

As quality assurance for respiration-gated treatments using the Varian RPM system, we monitor interfractional diaphragm variation throughout treatment using extra anterior-posterior (AP) portal images. We measure the superior-inferior (SI distance between one or more bony landmarks and the ipsilateral diaphragm dome in each such radiograph and calculate its difference, D, from the corresponding distance in a planning CT scan digitally reconstructed radiograph (DRR). For each patient, the mean of D represents the systematic diaphragm displacement, and the standard deviation of D represents random diaphragm variations and is a measure of interfractional gating reproducibility.

Tumor motion control in the treatment of non small cell lung cancer.

Tumor motion due to respiration during radiation therapy for non-small cell lung cancer is a significant problem. This article reports on two techniques used to control tumor motion: respiratory gating and the deep inspiration breath hold technique. This technique was implemented in 40 patients without significant difficulties and there are encouraging clinical outcomes.

The CT motion quantitation of lung lesions and its impact on PET-measured SUVs.

Unlabelled: We previously reported that respiratory motion is a major source of error in quantitation of lesion activity using combined PET/CT units. CT acquisition of the lesion occurs in seconds, rather than the 4-6 min required for PET emission scans. Therefore, an incongruent lesion position during CT acquisition will bias activity estimates using PET.

Dosimetric effect of respiratory motion in external beam radiotherapy of the lung.

Background And Purpose: To study the effect of breathing motion on gross tumor volume (GTV) coverage for lung tumors using dose-volume histograms and relevant dosimetric indices.

Patients And Methods: Treatment plans were chosen for 12 patients treated at our institution for lung carcinoma. GTV volumes of these patients ranged from 1.

Deep inspiration breath hold and respiratory gating strategies for reducing organ motion in radiation treatment.

We examine 2 strategies for reducing respiration-induced organ motion in radiation treatment: deep inspiration breath hold (DIBH) and respiratory gating. DIBH is a controlled breathing technique in which the patient performs a supervised breath hold during treatment. The technique offers 2 benefits: reduced respiratory motion from the breath hold and increased normal tissue sparing from the increased lung volume.

Technological advances in external-beam radiation therapy for the treatment of localized prostate cancer.

The relative inability of conventional radiotherapy to control localized prostate cancer results from resistance of subpopulations of tumor clonogens to dose levels of 65 to 70 Gy, the maximum feasible with traditional two-dimensional (2D) treatment planning and delivery techniques. Several technological advances have enhanced the precision and improved the outcome of external-beam radiotherapy. The three-dimensional conformal radiotherapy (3D-CRT) approach has permitted significant increases in the tumor dose to levels beyond those feasible with conventional techniques.

Evaluation of rapid dose map acquisition of a scanning liquid-filled ionization chamber electronic portal imaging device.

Purpose: We evaluated the performance of a new dosimetry module in the LC250 scanning liquid-filled ionization chamber (SLIC) electronic portal imaging device (EPID) for intensity-modulated radiotherapy (IMRT) verification. This module permits one to convert EPID readings to two-dimensional (2D) maps of IMRT dose rate in real time, and to integrate them over time to produce a profile of accumulated dose for treatment verification.

Methods And Materials: The EPID was calibrated using an iterative procedure, from which a lookup table for dose integration was generated and transferred to the image-acquisition hardware.

Development of a semi-automatic alignment tool for accelerated localization of the prostate.

Purpose: Delivering high dose to prostate with external beam radiation has been shown to improve local tumor control. However, it has to be carefully performed to avoid partial target miss and delivering excessive dose to surrounding normal tissues. One way to achieve safe dose escalation is to precisely localize prostate immediately before daily treatment.

Optimization of conformal thoracic radiotherapy using cone-beam CT imaging for treatment verification.

Purpose: Megavoltage cone-beam computed tomography (MVCBCT) has been proposed for treatment verification in conformal radiotherapy. However, the doses required for such imaging may compromise the quality of the delivered dose distribution. The present paper explores the effect of cone-beam imaging on dose homogeneity and critical organ dose and the use of our new tool, adapted intensity-modulated radiation therapy (AIMRT).

Respiratory gating for liver tumors: use in dose escalation.

Purpose: To determine the clinical impact of the Varian Real-Time Position Monitor (RPM) respiratory gating system for treatment of liver tumors.

Methods And Materials: Ten patients with liver tumors were selected for evaluation of this passive system, which tracks motion of reflective markers mounted on the abdomen with an infrared-sensitive camera. At simulation, a fluoroscopic movie, breathing trace, and CT scans synchronized at end-expiration (E-E) and end-inspiration were acquired in treatment position using the RPM system.

Time trends in organ position and volume in patients receiving prostate three-dimensional conformal radiotherapy.

Using multiple computed tomography (CT) scans, 50 patients undergoing prostate radiotherapy were tested for clinically significant time trends in the target and surrounding critical structures. Significant trends were observed toward increasing bladder volume and increasing bowel-to-planning target volume separation; however, no trends were observed in the prostate, seminal vesicles, or rectum. The subset of patients undergoing hormone therapy was also tested and did not independently exhibit any significant time trends.

Intensity-modulated radiotherapy.

Intensity-modulated radiotherapy represents a recent advancement in conformal radiotherapy. It employs specialized computer-driven technology to generate dose distributions that conform to tumor targets with extremely high precision. Treatment planning is based on inverse planning algorithms and iterative computer-driven optimization to generate treatment fields with varying intensities across the beam section.