Variation assessment of deformable registration in stereotactic radiosurgery.

INTRODUCTION: The regular functions of CT-MRI registration include delineation of targets and organs-at-risk (OARs) in radiosurgery planning. The question of whether deformable image registration (DIR) could be applied to stereotactic radiosurgery (SRS) in its place remains a subject of debate. METHODS: This study collected data regarding 16 patients who had undergone single-fraction SRS treatment. All lesions were located close to the brainstem. CT and MRI two image sets were registered by both rigid image registration (RIR) and DIR algorithms. The contours of the OARs were drawn individually on the rigid and deformable CT-MRI image sets by qualified radiation oncologists and dosimetrists. The evaluation metrics included volume overlapping (VO), Dice similarity coefficient (DSC), and dose. The modified demons deformable algorithm (VARIAN SmartAdapt) was used for evaluation in this study. RESULTS: The mean range of VO for OARs was 0.84 ± 0.08, and DSC was 0.82 ± 0.07. The maximum average volume difference was at normal brain (17.18 ± 14.48 cm3) and the second highest was at brainstem (2.26 cm3 ± 1.18). Pearson correlation testing showed that all DIRs' OAR volumes were linearly and significantly correlated with RIRs' volume (0.679-0.992, two tailed, P << 0.001). The 100% dose was prescribed at gross tumor volume (GTV). The average maximum percent dose difference was observed in brainstem (26.54% ± 27.027), and the average mean dose difference has found at same organ (1.6% ± 1.66). CONCLUSION: The change in image-registration method definitely produces dose variance, and is significantly more what depending on the target location. The volume size of OARs, however, was not statistical significantly correlated with dose variance.

Autoradiographic and histopathological studies of boric acid-mediated BNCT in hepatic VX2 tumor-bearing rabbits: Specific boron retention and damage in tumor and tumor vessels.

Hepatoma is a malignant tumor that responds poorly to conventional therapies. Boron neutron capture therapy (BNCT) may provide a better way for hepatoma therapy. In this research, (10)B-enriched boric acid (BA, 99% (10)B) was used as the boron drug. A multifocal hepatic VX2 tumor-bearing rabbit model was used to study the mechanisms of BA-mediated BNCT. Autoradiography demonstrated that BA was selectively targeted to tumors and tumor vessels. Histopathological examination revealed the radiation damage to tumor-bearing liver was concentrated in the tumor regions during BNCT treatment. The selective killing of tumor cells and the destruction of the blood vessels in tumor masses may be responsible for the success of BA-mediated BNCT for liver tumors.

Improvements on a patient-specific dose estimation system in nuclear medicine examination.

The purpose of this paper is to develop a patient-specific dose estimation system in nuclear medicine examination. A dose deposition routine to store the deposited energy of the photons during their flights was embedded in the widely used SimSET Monte Carlo code and a user-friendly interface for reading PET and CT images was developed. Dose calculated on ORNL phantom was used to validate the accuracy of this system. The ratios of S value for (99m)Tc, (18)F and (131)I computed by this system to those obtained with OLINDA for various organs were ranged from 0.93 to 1.18, which were comparable to that obtained from MCNPX2.6 code (0.88-1.22). Our system developed provides opportunity for tumor dose estimation which cannot be known from the MIRD. The radiation dose can provide useful information in the amount of radioisotopes to be administered in radioimmunotherapy.

Prediction of nodal metastasis in head and neck cancer using a 3T MRI ADC map.

BACKGROUND AND PURPOSE: The detection of cervical nodal metastases is important for the prognosis and treatment of head and neck tumors. The purpose of this study was to assess the ability of ADC values at 3T to distinguish malignant from benign lymph nodes. MATERIALS AND METHODS: From July 2009 to June 2010, twenty-two patients (21 men and 1 woman; mean age, 49.8±9.5 years; age range, 28-66 years) scheduled for surgical treatment of biopsy-proved head and neck cancer were prospectively and consecutively enrolled in this study. All patients were scanned on a 3T imaging unit (Verio) by using a 12-channel head coil combined with a 4-channel neck coil. Histologic findings were the reference standard for the diagnosis of lymph node metastasis. RESULTS: The ADC values derived from the signal intensity averaged across images obtained with b-values of 0 and 800 s/mm2 were 1.086±0.222×10(-3) mm2/s for benign lymph nodes and 0.705±0.118×10(-3) mm2/s for malignant lymph nodes (P<.0001). When an ADC value of 0.851×10(-3) mm2/s was used as a threshold value for differentiating benign from malignant lymph nodes, the best results were obtained with an accuracy of 91.0%, sensitivity of 91.3%, and specificity of 91.1%. CONCLUSIONS: The ADC value is a sensitive and specific parameter that can help to differentiate malignant from benign lymph nodes.

Development of an imaging-planning program for screen/film and computed radiography mammography for breasts with short chest wall to nipple distance.

OBJECTIVE: Imaging breasts with a short chest wall to nipple distance (CWND) using a traditional mammographic X-ray unit is a technical challenge for mammographers. The purpose of this study is the development of an imaging-planning program to assist in determination of imaging parameters of screen/film (SF) and computed radiography (CR) mammography for short CWND breasts. METHODS: A traditional mammographic X-ray unit (Mammomat 3000, Siemens, Munich, Germany) was employed. The imaging-planning program was developed by combining the compressed breast thickness correction, the equivalent polymethylmethacrylate thickness assessment for breasts and the tube loading (mAs) measurement. Both phantom exposures and a total of 597 exposures were used for examining the imaging-planning program. RESULTS: Results of the phantom study show that the tube loading rapidly decreased with the CWND when the automatic exposure control (AEC) detector was not fully covered by the phantom. For patient exposures with the AEC fully covered by breast tissue, the average fractional tube loadings, defined as the ratio of the predicted mAs using the imaging-planning program and mAs of the mammogram, were 1.10 and 1.07 for SF and CR mammograms, respectively. The predicted mAs values were comparable to the mAs values, as determined by the AEC. CONCLUSION: By applying the imaging-planning program in clinical practice, the experiential dependence of the mammographer for determination of the imaging parameters for short CWND breasts is minimised.

A method incorporating 4DCT data for evaluating the dosimetric effects of respiratory motion in single-arc IMAT.

This study introduces a method incorporating 4DCT data to determine the impact of respiratory motion in single-arc intensity-modulated arc therapy (IMAT). Simulation was done by re-warping the static dose distribution of all phases of a 4DCT image set with a 3D deformation map to reference CT images at end-inspiration and end-expiration. To calculate the dose received during respiration under IMAT, the control points were interpolated and re-distributed into separate IMAT plans corresponding to each respiratory phase. This study also investigated the role that plan complexity may play in the dosimetric impact of the respiratory motion in the delivery of IMAT. The dosimetric impact of organ motion was evaluated by analyzing the degradation of D(95,) D(50) and D(05) of the CTV and PTV. From the results shown for the patients in this study who had maximum organ motion displacement approximately 15 mm, the dosimetric impact is rather small. Therefore, our preliminary results suggest that respiratory motion of less than 1.5 cm may be ignored for both moderately and highly modulated IMAT, irrespective of the number of fractions. Specifically, highly modulated plans only increased the degradation of D(95) of the DVH curves for a single fraction by 2% in the CTV and 9% in the PTV compared to the expected value of the multi-fraction plan.

Simple empirical formula for predicting range variation of central-axis parameters in small electron fields.

The depth of central-axis percent dose Rx (except R100) and practical range, Rp, for small field electron beams can be calculated by the proposed empirical formula: Rx = Rxo x [1 - (1 - r/Rpo)m], where Rxo and Rpo are the broad beam percentage dose depth and practical range respectively; r is the small field cutout side when it is less than the maximum lateral scatter equivalent range, and m is the exponent term relative to the decreasing curvature. Five electron beams from a Varian CL-2100CD linear accelerator were used to verify this formula. The difference between measured and calculated depth dose range is within +/- 1 mm when cutout side reduced to 2 x 2 cm2. This formula offers a simple and time-saving method to quickly determine the useful treatment percentage dose depth of small field electron beams.

Spinal intramedullary pseudocyst. Case report.

The authors describe a case of a spinal intramedullary pseudocyst at T-1 that did not communicate with the surrounding spaces. The cystic wall was composed of dense connective tissue without epithelial or neoplastic cells. The patient's condition improved dramatically after surgical removal of the cyst. The literature on spinal intramedullary cystic lesions is reviewed and the etiology of pseudocysts is discussed. This case is believed to be the first in which a pseudocyst has been demonstrated within the spinal cord.

Both dopaminergic and adrenergic receptors in the brain are involved in the behavioural excitation induced by dibutyryl 3',5'-adenosine monophosphate and aminophylline in the rat.

Following administration of dibutyryl cyclic-AMP or aminophylline, but not vehicle solution, into the lateral cerebral ventricle of rats produced locomotor stimulation, head and body rearing, circling, (as indicated by an enhancement of gross movement), increased grooming, head swaying and scratching (as indicated by an enhancement of fine movement), tail elevation, piloerection and convulsion. The behavioural excitation produced by either dibutyryl cyclic-AMP or aminophylline was antagonized by pretreatment with intraventricular injection of either two alpha-adrenergic antagonists (phentolamine and yohimbine) or a dopaminergic antagonist (haloperidol), but not with either a beta-adrenergic antagonist (propranolol) or a narcotic antagonist (naloxone). In addition, direct administration of dibutyryl cyclic-AMP into either the anterior hypothalamus, the nucleus accumbens or the caudate-putamen complex of rats produced the same behavioural responses as those produced by the intraventricular injection. Again, the behavioural responses induced by intracerebral injection of dibutyryl cyclic-AMP was antagonized by pretreatment with either alpha-adrenergic antagonists or a dopaminergic antagonist. The present data indicate that both the dopaminergic and the adrenergic receptors in the brain are involved in the behavioural excitation induced by dibutyryl cyclic-AMP and aminophylline in the rat.