Ablative radiotherapy improves survival but does not cure autochthonous mouse models of prostate and colorectal cancer.

Background: Genetically engineered mouse models (GEMMs) of cancer are powerful tools to study mechanisms of disease progression and therapy response, yet little is known about how these models respond to multimodality therapy used in patients. Radiation therapy (RT) is frequently used to treat localized cancers with curative intent, delay progression of oligometastases, and palliate symptoms of metastatic disease.

Methods: Here we report the development, testing, and validation of a platform to immobilize and target tumors in mice with stereotactic ablative RT (SART).

Improved dosimetry in prostate brachytherapy using high resolution contrast enhanced magnetic resonance imaging: a feasibility study.

Purpose: To assess detailed dosimetry data for prostate and clinical relevant intra- and peri-prostatic structures including neurovascular bundles (NVB), urethra, and penile bulb (PB) from postbrachytherapy computed tomography (CT) versus high resolution contrast enhanced magnetic resonance imaging (HR-CEMRI).

Material And Methods: Eleven postbrachytherapy prostate cancer patients underwent HR-CEMRI and CT imaging. Computed tomography and HR-CEMRI images were randomized and 2 independent expert readers created contours of prostate, intra- and peri-prostatic structures on each CT and HR-CEMRI scan for all 11 patients.

Accuracy of endorectal magnetic resonance/transrectal ultrasound fusion for detection of prostate cancer during brachytherapy.

Objective: To evaluate the effectiveness of 3 Tesla endorectal magnetic resonance imaging (erMRI) with fusion to real-time transrectal ultrasound to detect a dominant cancer focus within the prostate gland.

Materials And Methods: The safety and effectiveness of identifying suspicious lesions using erMRI was assessed in men undergoing brachytherapy perineal implants. Suspicious lesions identified on erMRI fused to real-time transrectal ultrasound were biopsied at brachytherapy seed placement.

Frameless angiogram-based stereotactic radiosurgery for treatment of arteriovenous malformations.

Purpose: Stereotactic radiosurgery (SRS) is an effective alternative to microsurgical resection or embolization for definitive treatment of arteriovenous malformations (AVMs). Digital subtraction angiography (DSA) is the gold standard for pretreatment diagnosis and characterization of vascular anatomy, but requires rigid frame (skull) immobilization when used in combination with SRS. With the advent of advanced proton and image-guided photon delivery systems, SRS treatment is increasingly migrating to frameless platforms, which are incompatible with frame-based DSA.

Relationship between radiation treatment time and overall survival after induction chemotherapy for locally advanced head-and-neck carcinoma: a subset analysis of TAX 324.

Purpose: To analyze the relationship between overall survival (OS) and radiation treatment time (RTT) and overall treatment time (OTT) in a well-described sequential therapy paradigm for locally advanced head-and-neck carcinoma (LAHNC).

Methods And Materials: TAX 324 is a Phase III study comparing TPF (docetaxel, cisplatin, and fluorouracil) with PF (cisplatin and fluorouracil) induction chemotherapy (IC) in LAHNC patients; both arms were followed by carboplatin-based chemoradiotherapy (CRT). Prospective radiotherapy quality assurance was performed.

Bicalutamide alone prior to brachytherapy achieves cytoreduction that is similar to luteinizing hormone-releasing hormone analogues with less patient-reported morbidity.

Objectives: To compare the impact of bicalutamide (B) vs. luteinizing hormone-releasing hormone analogues (LHRHa) on prostate volume, patient-reported side effects, and postimplant urinary toxicity in the setting of interstitial brachytherapy for early-stage prostate cancer.

Methods: Between May 1998 and January 2004, 81 patients received androgen-deprivation therapy (ADT) for cytoreduction prior to interstitial brachytherapy alone.

Androgen deprivation-mediated cytoreduction before interstitial brachytherapy for prostate cancer does not abrogate the elevated risk of urinary morbidity associated with larger initial prostate volume.

Purpose: We examined whether prostate volume reduction after a short course of androgen deprivation (AD) lowered the risks of acute and chronic urinary morbidity related to radioactive seed implantation for low-risk prostate cancer.

Methods And Materials: Eighty-one patients received AD for cytoreduction before interstitial brachytherapy alone. Urinary morbidity was carefully assessed for all patients during a median followup of 53 (range, 23-78) months after treatment.

Real-time computed tomography dosimetry during ultrasound-guided brachytherapy for prostate cancer.

Purpose: Ultrasound-guided implantation of permanent radioactive seeds is a treatment option for localized prostate cancer. Several techniques have been described for the optimal placement of the seeds in the prostate during this procedure. Postimplantation dosimetric calculations are performed after the implant.

Effect of random seed placement error in permanent transperineal prostate seed implant.

Background And Purpose: Random seed placement error may adversely effect dose distribution in transperineal prostate seed implants. In this study, we investigated the extent to which individual seed activity influences dose-distribution degradation due to random seed placement error.

Patients And Methods: Separate initial treatment plans were prepared for three prostate sizes, 27.

Automatic detection of linear artifacts in medical images.

Our purpose in this study is to describe an algorithm for the automatic detection of linear artifacts in medical images. Linear artifacts arise as a result of many different forms of tissues and tissue boundaries within the imaging volume. Additionally, linear artifacts can arise for artificial structures such as radioactive seeds and radioactive linear sources.

An automatic seed finder for brachytherapy CT postplans based on the Hough transform.

Purpose: The purpose of the work is to describe a new algorithm for the automatic detection of implanted radioactive seeds within the prostate. The algorithm is based on the traditional Hough transform. A method of quality assurance is described as well as a quantitative phantom study to determine the accuracy of the algorithm.

A comparison of the precision of seeds deposited as loose seeds versus suture embedded seeds: a randomized trial.

Purpose: Brachytherapy for prostate cancer with permanent low-dose-rate seeds has been shown to be an effective treatment for early stage prostate cancer. Due to the rapid falloff of dose, accurate seed placement is critical for optimal dosimetry. One approach to achieve optimal dosimetry is the use of seeds embedded in suture material.

Real time MRI-ultrasound image guided stereotactic prostate biopsy.

To report a technique for target directed transperineal ultrasound guided biopsy using high resolution endorectal MRI images Ultrasound fusion. Two patients presented after external beam irradiation for prostate cancer with a rising PSA. An Endorectal MRI using a 1.

Intraoperative treatment planning for radioactive seed implant therapy for prostate cancer.

We describe a procedure for intraoperative treatment planning for seed implantation. One hundred seven treatment plans have been analyzed at the Beth Israel Deaconess Medical Center and affiliated hospitals. The average time for the intraoperative procedure was 1.

Analysis of prostate seed loading for permanent implants.

The goal of radioactive seed implantation in prostate cancer is to treat the tumor to the necessary dose while minimizing the dose to adjacent normal structures. The uniform and peripheral loading schemes used in the past have serious limitations. However, with the availability of three-dimensional treatment-planning systems, it has become possible to do custom volume loading based on volumetric ultrasound imaging of the gland.

Calculated prostate cancer volume: the optimal predictor of actual cancer volume and pathologic stage.

Objectives: A new clinical pretreatment quantity called the calculated prostate cancer volume has been defined. The correlation between the calculated parameter and the actual prostate cancer volume, and its ability to predict for pathologic Stage T3 disease in patients with clinically localized disease, is tested.

Methods: Prostate cancer volume measurements were obtained using a 3-dimensional computerized morphometric reconstruction technique on 104 whole-mounted radical prostatectomy specimens.

Ultrasound image fusion for external beam radiotherapy for prostate cancer.

Purpose: To determine whether real-time ultrasound imaging and targeting system for the treatment of prostate cancer was feasible. The initial phase of this project included a study to develop and determine (a) software for the fusion of ultrasound images to standard x-rays obtained during simulation, and (b) the potential reduction in field size with real-time imaging.

Methods And Materials: During 13 patient simulations a transrectal ultrasound image was obtained.

Magnetic resonance image-directed stereotactic neurosurgery: use of image fusion with computerized tomography to enhance spatial accuracy.

Distortions of the magnetic field, such as those caused by susceptibility artifacts and peripheral magnetic field warping, can limit geometric precision in the use of magnetic resonance (MR) imaging in stereotactic procedures. The authors have routinely found systematic error in MR stereotactic coordinates with a median of 4 mm compared to computerized tomography (CT) coordinates. This error may place critical neural structures in jeopardy in sme procedures.

Image fusion for stereotactic radiotherapy and radiosurgery treatment planning.

Purpose: We describe an image fusion application that addresses two basic problems that previously limited the use of magnetic resonance imaging (MRI) for geometric localization in stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). The first limitation is imposed by the use of a relocatable, MRI-incompatible, stereotactic frame for stereotactic radiotherapy. The second limitation is an inherent lack of geometric fidelity in current MRI scanners that invalidates the use of MRI for stereotactic localization.

Effect of set-up error on the dose across the junction of matching cranial-spinal fields in the treatment of medulloblastoma.

Purpose: The effect of systematic and stochastic setup error on the dose delivered to the gap region for the three field radiation treatment of medulloblastoma is studied. The consequences of such setup error is discussed.

Methods And Materials: The treatment of medulloblastoma is typically a 3 field technique, in which two lateral cranial fields are matched with a spine field.

A geometric algorithm for medical image correlations.

An automatic image correlation algorithm is discussed for the cranial region which is based on the geometric properties of the second moment tensor associated with a volume. The second moment tensor of two identical volumes represented in two different coordinate frames is evaluated to obtain the set of translations, rotations, and anisotropic scaling operators which relate the two coordinate frames. The theory is presented along with a discussion of quantitative error analysis to measure the usefulness of such an algorithm in the clinical setting.

Treatment planning for stereotactic radiosurgery of intra-cranial lesions.

Stereotactic radiosurgery of intra-cranial lesions is a treatment modality where a well defined target volume receives a high radiation dose in a single treatment. Our technique delivers this dose using a set of non-coplanar arcs and small circular collimators. We use a standard linear accelerator in our treatments, and the adjustable treatment parameters are: isocenter location, gantry arc rotation interval, couch angle, collimator field size, and dose.

Spherical harmonic expansion of cranial surfaces.

A three-dimensional analytical technique for the representation of the cranial surface based on a spherical harmonic expansion is presented. The analytical surface representation is used in conjunction with a sample iterative ray-intersection algorithm to compute the dose calculation depth. The technique is compared to other conventional techniques and it is determined that the spherical harmonic approach of approximating the cranial surface decreases the depth calculation time by approximately a factor of 60.