Adjacent Normal Structures Research Articles

Glomangiopericytoma: The Sinonasal Mimic Of Soft Tissue Hemangiopericytoma

A 42-year old Filipino male with a 10-month history of progressive left nasal obstruction and rhinorrhea and a clinical impression of nasal polyposis underwent endoscopic sinus surgery with partial ethmoidectomy and polypectomy.
 We received several dark-brown, irregular, rubbery tissue fragments with an aggregate diameter of 3 cm. Histopathologic examination shows sheets of spindly tumor cells beneath the respiratory epithelial lining. These spindle cells are closely packed and arranged in short fascicles and storiform clusters surrounding hyalinized large vessels or thin-walled submucosal blood vessels. (Figures 1 and 2) There is no atypia or necrosis. Immunohistochemical studies show strong immunoreactivity to muscle specific actin, and focal reactivity to S-100. (Figure 3) Stains for CD34, caldesmon, cytokeratin, and desmin, are negative. (Figure 4) Based on these features, we diagnosed the case as glomangiopericytoma.
 Glomangiopericytoma is a rare tumor arising from the pericytes surrounding capillaries, and accounts for less than 0.5% of all sinonasal tumors.1 It has a very slight female preponderance, with a peak incidence during the seventh decade of life. The most common symptom is nasal obstruction, or epistaxis, with accompanying difficulty breathing, sinusitis and headache. A mass, or polyp is the most common clinical finding.2
 Hematoxylin–eosin staining shows a well-delineated but unencapsulated cellular tumor underneath the normal respiratory epithelium that effaces or surrounds adjacent normal structures.2 The tumor is composed of closely packed, uniform, oval to spindle-shaped cells, in short fascicles and in storiform, whorled or palisaded patterns. The cells surround numerous branching thin-walled, blood vessels, thus the morphologic resemblance to soft tissue hemangiopericytoma/solitary fibrous tumor. However, in contrast to hemangiopericytoma, glomangiopericytoma shows diffuse reactivity to muscle actins, and non-reactivity to CD34, while hemangiopericytoma shows the reverse reactions. Desmin and caldesmon are likewise non-reactive, distinguishing the tumor from leiomyomas or leiomyosarcomas of the upper aerodigestive tract. Cytokeratin non-reactivity distinguishes it from spindle cell carcinoma. S100, although typically negative, can be focally and weakly positive in a small percentage of tumor.3 
 Glomangiopericytoma is categorized as a borderline low malignancy tumor with an overall survival of >90% in 5 years but which tends to recur in up to 30% of cases. Strict follow-up is thus required, especially if complete resection is not achieved.1

Volumetric Modulated Arc Therapy (VMAT) make a difference in retro-orbital irradiation treatment of patients with bilateral Graves’ ophthalmopathy. Comparative analysis of dosimetric parameters from different radiation techniques

BackgroundGraves’ ophthalmopathy is the commonest extrathyroidal manifestation of Graves’ disease. Treatment options include steroid therapy, corrective/decompressive surgery, radiation therapy or combination of these approaches. AimOur purpose was to investigate if retro-orbital irradiation with Volumetric Modulated Arc Therapy (VMAT) yielded better target coverage and dose sparing to adjacent normal structures compared to 3-Dimensional Conformal Radiotherapy (3DCRT) and Lateral Opposing Conformed Fields (LOCF). MethodsFourteen consecutive patients diagnosed with bilateral Graves’ ophthalmopathy were prospectively recruited into this study from August 2012 until August 2014. An individual VMAT, 3DCRT and LOF plan was created for each patient. Conformity Index (CI), Homogeneity Index (HI) and other dosimetric parameters of the targets and organs-at-risk (OAR) were analyzed in all 28 orbits compared between the different techniques. ResultsCI generated by VMAT was superior to that produced by 3DCRT(p<.001) and LOF (p<.001). As expected, 3DCRT was also superior to LOF (p=.007). Regarding the OARs sparing dose (lens, globes, retina and lacrimal glands), VMAT showed a significant benefit when compared with 3DCRT and LOCF, with no differences between the two latter techniques. ConclusionsVMAT should be preferred over 3DCRT and LOF for bilateral Graves’ ophthalmopathy treatment.

Contrast-enhancement ratio on multiphase enhanced computed tomography predicts recurrence of pancreatic neuroendocrine tumor after curative resection.

No previous study has quantitatively investigated the degree of enhancement of pancreatic neuroendocrine tumors (pNETs) using a routine preoperative modality. The aim of this study was to evaluate the contrast-enhancement ratio (CER) of pNETs using multiphase enhanced CT and to assess the impact of the CER on disease recurrence after surgery. A retrospective study was performed using data from 47 consecutive patients with pNETs who had undergone curative surgery. The CER of the tumor was calculated by dividing the CT attenuation value obtained during the maximum-enhanced phase by that obtained during the pre-enhanced phase. A region of interest was placed in the largest tumor dimension plane so as to cover as much surface of the tumor as possible while avoiding adjacent normal structures, calcification, and necrotic areas of the tumor. During a median follow-up period of 51 months (range, 1-132 months), a total of 4 patients (8.5%) developed disease recurrence. The median CER value was significantly lower for the patients with recurrence than for the patients without recurrence (2.9 vs. 4.3, P=0.013). Univariate analyses showed that a CER ≤3.2 was significantly associated with disease recurrence (P<0.001). All the patients with disease recurrence had tumors that were both large (>20mm) and weakly enhanced (CER≤3.2), whereas no recurrences were observed even in patients with tumors >20mm when the CER was greater than 3.2. CER might be a useful predictor of disease recurrence in patients with pNETs.

Stereotactic Radiosurgery for Glioblastoma.

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults and one of the most aggressive of all human cancers. GBM tumors are highly infiltrative and relatively resistant to conventional therapies. Aggressive management of GBM using a combination of surgical resection, followed by fractionated radiotherapy and chemotherapy has been shown to improve overall survival; however, GBM tumors recur in the majority of patients and the disease is most often fatal. There is a need to develop new treatment regimens and technological innovations to improve the overall survival of GBM patients. The role of stereotactic radiosurgery (SRS) for the treatment of GBM has been explored and is controversial. SRS utilizes highly precise radiation techniques to allow dose escalation and delivery of ablative radiation doses to the tumor while minimizing dose to the adjacent normal structures. In some studies, SRS with concurrent chemotherapy has shown improved local control with acceptable toxicities in select GBM patients. However, because GBM is a highly infiltrative disease, skeptics argue that local therapies, such as SRS, do not improve overall survival. The purpose of this article is to review the literature regarding SRS in both newly diagnosed and recurrent GBM, to describe SRS techniques, potential eligible SRS candidates, and treatment-related toxicities. In addition, this article will propose promising areas for future research for SRS in the treatment of GBM.

Prone Partial-Breast Irradiation After Breast Conserving Surgery: Results of 397 Patients at a Median Follow-up of 40 Months

anterior, posterior, superior, and inferior directions. To assess cavity movement from preto post-delivery of each fraction, a total of 100 preand post-fraction MR scans were manually registered based on the cavity, and resultant cavity translations in the longitudinal, vertical, and lateral planes were determined. Results: Onboard sagittal cine MR was visually monitored at the treatment machine and qualitative evaluation demonstrated no significant intrafraction motion of the lumpectomy cavity. In quantitative analysis of intrafraction motion, the mean movement of 4 tracking points placed at the superior, inferior, anterior, and posterior cavity edges was 0.34 0.07, 0.45 0.12, 0.42 0.09, and 0.28 0.07 mm in the ant-post direction; and 0.44 0.09, 0.62 0.10, 0.46 0.08, and 0.61 0.10 mm in the supinf direction, respectively. Overall, the median motion of any tracking point in any direction was < 0.5 mm. Mean translation of the lumpectomy cavity from preto post-fraction scans in the longitudinal, vertical, and lateral planes was 0.44 0.32, 0.40 0.30 and 0.41 0.32 mm, respectively. Conclusion: Analysis of intra-fraction motion of the lumpectomy cavity utilizing continuous on-board cine MR images and preand post-fraction MR imaging confirm minimal cavity motion, on the order of < 0.5 mm, in patients undergoing APBI with MR-IGRT. Given the minimal cavity motion and excellent visualization with onboard MRI, we used a 0 mm margin for setup uncertainty and intra-fraction motion, which maintained the ability to target the cavity and adjacent breast tissue at risk, while treating a smaller resultant PTV. Resultant reductions in dose to the ipsilateral normal breast tissue and adjacent normal structures such as the heart and lungs may impact late effects and cosmesis. This work, to our knowledge, is the first to describe real-time movement of lumpectomy cavities on MRI during radiation therapy. Author Disclosure: B.W. Fischer-Valuck: None. T.R. Mazur: None. S. Acharya: None. H. Wan: None. R. Kashani: None. H. Li: None. I. Zoberi: None. M.A. Thomas: Employee; Washington University.

Pictorial review. Magnetic resonance for radiotherapy management and treatment planning in prostatic carcinoma.

MRI has an important role for radiotherapy (RT) treatment planning in prostate cancer (PCa) providing accurate visualization of the dominant intraprostatic lesion (DIL) and locoregional anatomy, assessment of local staging and depiction of implanted devices. MRI enables the radiation oncologist to optimize RT planning by better defining target tumour volumes (thereby increasing local tumour control), as well as decreasing morbidity (by minimizing the dose to adjacent normal structures). Using MRI, radiation oncologists can define the DIL for delivery of boost doses of RT using a variety of techniques including: stereotactic body radiotherapy, intensity-modulated radiotherapy, proton RT or brachytherapy to improve tumour control. Radiologists require a familiarity with the different RT methods used to treat PCa, as well as an understanding of the advantages and disadvantages of the various MR pulse sequences available for RT planning in order to provide an optimal multidisciplinary RT treatment approach to PCa. Understanding the expected post-RT appearance of the prostate and typical characteristics of local tumour recurrence is also important because MRI is rapidly becoming an integral component for diagnosis, image-guided histological sampling and treatment planning in the setting of biochemical failure after RT or surgery.

Pitfalls in Oncologic Imaging: Complications of Chemotherapy and Radiotherapy in the Chest

Advances in cancer chemotherapy and radiation therapy continue to improve patients' lives and affect patient care. Chemotherapy has progressed from cytotoxic agents to newer targeted agents that are geared to attack specific mutations in cancer cells. The toxicities of these newer cytotoxic drugs and targeted agents have specific imaging appearances depending on the mechanism of action. Similarly, advances in radiation therapy allow for better tumor, with less effect on normal adjacent structures. Knowledge of the imaging appearance of toxicities of therapy is crucial for radiologists to accurately diagnose complications of therapy and to avoid imaging pitfalls. Radiologists must use the clinical history and the mechanism of action of the drugs to affect patient care and prevent misdiagnosis. In this article, we review some of the common pitfalls of imaging that arise because of complications of therapy.

Multimodal navigated skull base tumor resection using image-based vascular and cranial nerve segmentation: A prospective pilot study.

Background:Skull base tumors frequently encase or invade adjacent normal neurovascular structures. For this reason, optimal tumor resection with incomplete knowledge of patient anatomy remains a challenge.Methods:To determine the accuracy and utility of image-based preoperative segmentation in skull base tumor resections, we performed a prospective study. Ten patients with skull base tumors underwent preoperative 3T magnetic resonance imaging, which included thin section three-dimensional (3D) space T2, 3D time of flight, and magnetization-prepared rapid acquisition gradient echo sequences. Imaging sequences were loaded in the neuronavigation system for segmentation and preoperative planning. Five different neurovascular landmarks were identified in each case and measured for accuracy using the neuronavigation system. Each segmented neurovascular element was validated by manual placement of the navigation probe, and errors of localization were measured.Results:Strong correspondence between image-based segmentation and microscopic view was found at the surface of the tumor and tumor-normal brain interfaces in all cases. The accuracy of the measurements was 0.45 ± 0.21 mm (mean ± standard deviation). This information reassured the surgeon and prevented vascular injury intraoperatively. Preoperative segmentation of the related cranial nerves was possible in 80% of cases and helped the surgeon localize involved cranial nerves in all cases.Conclusion:Image-based preoperative vascular and neural element segmentation with 3D reconstruction is highly informative preoperatively and could increase the vigilance of neurosurgeons for preventing neurovascular injury during skull base surgeries. Additionally, the accuracy found in this study is superior to previously reported measurements. This novel preliminary study is encouraging for future validation with larger numbers of patients.

Hippocampal EUD in primarily irradiated glioblastoma patients.

BackgroundRadiation delivery for malignant brain tumors is gradually becoming more precise. Particularly the possibilities of sparing adjacent normal structures such as the hippocampus are increasing. To determine its radiation exposure more exactly, the equivalent uniform dose (EUD) of the hippocampus was compared with further treatment parameters. This way sparing options could be found.MethodsFrom the database of the University hospital of Munich 61 glioblastoma patients were selected who received primary radiotherapy in 2011. General data about the etiology, treatment course, survival of the patients and dose parameters were retrieved.ResultsIn a linear regression analysis the side of the tumor (left hippocampus: p < 0.001/right hippocampus: p = 0.009) and its temporal location (left hippocampus: p = 0.015/right hippocampus: p = 0.033) were identified as factors with a significant influence on the EUD of the respective hippocampus. Besides this, the size of the planning target volume (PTV) and the EUD of the hippocampus correlated significantly (p = 0.027; Pearson correlation = 0.291). The median PTV size of the tumor in the right hemisphere was 386.1 ml (range 131.2–910.7 ml), and in the left hemisphere 291.3 ml (range 146.0–588.9 ml) (Kruskal–Wallis test: p = 0.048). A dose quartile analysis showed that 31 patients had a high dose exposure of the hippocampus on one side while having a moderate dose exposure in the other side.ConclusionsThe radiation exposure of the respective hippocampus is dependent on the side where the tumor is located as well as on whether it is temporally located. The exposure of the contralateral hippocampus is further dependent on multiple additional factors – nevertheless a reasonable protection seems to be possible in about half of all cases.

NI-17 * MULTIMODAL NAVIGATED SKULL BASE TUMOR RESECTION USING IMAGE-BASED VASCULAR AND CRANIAL NERVE SEGMENTATION: A PROSPECTIVE VALIDATION STUDY

INTRODUCTION: Skull base tumors frequently encase or invade adjacent normal neural and vascular structures. Preoperative segmentation and planning to identify these anatomical landmarks are essentially important in complex skull base tumor resection for minimizing surgical morbidities. METHODS: Ten patients with skull base tumors underwent preoperative 3TMRI, which included thin sectioned 3D space T2, 3D Time of Flight and MPRAGE sequences. Images were reviewed by an expert independent neuroradiologist. Imaging sequences were loaded in BrainLab iPlanNet (8/10) and Stryker (2/10) for segmentation and pre-operative planning. After patient registration to the intra-op neuronavigation system and surgical exposure, each segmented neural or vascular element was validated by manual placement of the navigation probe. RESULTS: Perfect correspondence between image-based segmentation and microscopic view was found at the surface of the tumor and tumor-normal brain interfaces in all cases. Pre-operative segmentation of the major arteries, veins, and venous sinuses matched with the intra-operative microscopic findings in all cases (Dice-coefficient =1). This information reassured the surgeon and prevented vascular tearing during different stages of tumor resection. This also helped in preventing major intra-operative arterial or venous bleeding. Preoperative segmentation of the related cranial nerves was technically possible in only 80% of cases. However, Image-guidance helped the surgeon to localize the involved cranial nerves in all cases. CONCLUSION: Image-based pre-operative vascular and neural element segmentation, especially with 3D reconstruction, is highly informative preoperatively and could increase the vigilance of neurosurgeons for preventing vascular and neural injury during skull base surgeries. This novel preliminary study is encouraging for future prospective intraoperative validation with larger numbers of patients.

Dosimetric comparison of 3DCRT versus IMRT in whole breast irradiation of early stage breast cancer

Purpose: The counseling regarding the treatment option is an important objective in the management of early stages breast cancer. In this study, we attempt to compare and analyze the dosimetric aspects of 3DRT over IMRT in the whole breast radiotherapy. Methods and Materials: Both right and left sided computed tomography simulations of 14 women with early stage breast cancer were used for our retrospective study to compare the 3DCRT and IMRT. The dose prescribed was 50 Gy in 25 fractions to the whole breast PTV. The PTV was defined by adding unequal margins to the directional safety margin status of each lumpectomy cavity (i.e., medial, lateral, superior, inferior and deep margins measured from the tumor front after the examination of the surgical specimen: 2, 1.5, and 1 cm for resection margins 2cm, respectively). And than modified so that it was no longer closer than 3mm to the skin surface and was no deep than the lung –chest interface. The prescribed dose delivered in 5 fractions per week schedule. Treatment plans were compared for target minimum dose, maximum dose, mean dose, conformity index, heterogeneity index and doses to organs at risk were compared and analysed. Results: The target coverage was achieved with 90% prescription to the 95% of the PTV. Conformity to the PTV was significantly higher with 3DCRT technique than IMRT. 3DCRT technique seems better in sparing critical organs parameters like lung V 20 and Mean, heart, V 25 , Maximum, both lungs V 20 , Mean and Dose to the Normal Healthy tissue. Conclusion: We conclude from our study that treatment technique selection for whole Breast irradiation is an important factor in sparing the adjacent normal structures and in determining the associated risk. 3DCRT produces better conformity and heterogeneity indices of the target volume, also reduces dose to OARs the 3DCRT reduces the risk of radiation induced heart diseases. Cite this article as: Ashraf M, Janardhan N, Bhavani P, Shivakumar R, Ibrahim S, Reddy PY, Surrendharen J, Sarangnathan B, Johnson B, Madhuri B, Dar RA. Dosimetric comparison of 3DCRT versus IMRT in whole breast irradiation of early stage breast cancer. Int J Cancer Ther Oncol 2014; 2 (3):020318. DOI: 10.14319/ijcto.0203.18

Abstract 4536: Combination external beam and internal radiation via 131I-CLR1404 in the treatment of head and neck squamous cell carcinoma xenografts.

Abstract Radiotherapy (RT) is a central treatment modality for head and neck cancer (HNC). However, optimal outcome is commonly limited by the radiation tolerance of adjacent normal tissue structures. Radiation is sometimes valuable in the setting of locoregional tumor recurrence, however the risk of significant normal tissue toxicity is substantial with repeat irradiation and can have a profound adverse impact on patient quality of life. Although technical advances including intensity modulated radiotherapy (IMRT) can reduce normal tissue effects, the problem of repeat exposure of normal tissues to radiation is frequently limiting. The radiolabeled drug 124/131I-CLR1404 is a phospholipid ether analogue (PLE) that accumulates preferentially within malignant tumors and enables internal delivery of radiation. This allows a combination of external and internal radiotherapy delivery with a goal of improving treatment outcome without enhanced normal tissue toxicities. In this study, we characterized the ability of 131I-CLR1404 to augment RT response using xenografted mice harboring human squamous cell carcinomas (SCC). We determined tumor growth delay as well as tumor and normal tissue dose distribution of 131I-CLR-1404 via Monte Carlo simulation using PET data generated with 124I-CLR1404 imaging. Tumor growth delay was extended by 15.5 days using combined 3.7MBq 131I-CLR1404 and RT compared to RT or 131I-CLR1404 alone. In combination therapy, single dose administration of 7.4 MBq 131I-CLR1404 as well as split dosing with 2 x 3.7 MBq separated by one week showed the same additional growth delay of 27 days compared to single dose of 3.7 MBq. Monitoring drug distribution via PET/CT showed high tumor selectivity with a tumor-to-liver ratio of 6.2±0.65 and a tumor-to-muscle ratio of 6.7±0.21. These data illustrate the tumor selectivity of the CLR1404 PLE delivery platform as well as augmentation of tumor response with combined RT and 131I-CLR1404 treatment. De-intensification of external beam radiation dose, with attendant reduction in normal tissue toxicities so common in HNC patients represents a central objective to be tested in controlled clinical trials with the ultimate goal of improving treatment outcome and quality of life for HNC patients. Citation Format: Jarob Saker, Eric Armstrong, Bryan Bednarz, Mohammed Farhoud, Abigail Besemer, Jamey Weichert, Paul Harari. Combination external beam and internal radiation via 131I-CLR1404 in the treatment of head and neck squamous cell carcinoma xenografts. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4536. doi:10.1158/1538-7445.AM2013-4536

MR-Guided High-Intensity Focused Ultrasound: Current Status of an Emerging Technology

The concept of ideal tumor surgery is to remove the neoplastic tissue without damaging adjacent normal structures. High-intensity focused ultrasound (HIFU) was developed in the 1940s as a viable thermal tissue ablation approach. In clinical practice, HIFU has been applied to treat a variety of solid benign and malignant lesions, including pancreas, liver, prostate, and breast carcinomas, soft tissue sarcomas, and uterine fibroids. More recently, magnetic resonance guidance has been applied for treatment monitoring during focused ultrasound procedures (magnetic resonance-guided focused ultrasound, MRgFUS). Intraoperative magnetic resonance imaging provides the best possible tumor extension and dynamic control of energy deposition using real-time magnetic resonance imaging thermometry. We introduce the fundamental principles and clinical indications of the MRgFUS technique; we also report different treatment options and personal outcomes.

American College of Radiology (ACR) and American Society for Radiation Oncology (ASTRO) Practice Guideline for Intensity-modulated Radiation Therapy (IMRT)

Intensity-modulated radiation therapy (IMRT) is a complex technique for the delivery of radiation therapy preferentially to target structures while minimizing doses to adjacent normal critical structures. It is widely utilized in the treatment of a variety of clinical indications in radiation oncology, including tumors of the central nervous system, head and neck, breast, prostate, gastrointestinal tract, and gynecologic organs, as well as in situations where previous radiation therapy has been delivered, and has allowed for significant therapeutic advances in many clinical areas. IMRT treatment planning and delivery is a complex process. Safe and reliable delivery of IMRT requires appropriate process design and adherence to quality assurance (QA) standards. A collaborative effort of the American College of Radiology and American Society for Therapeutic Radiation Oncology has produced a practice guideline for IMRT. The guideline defines the qualifications and responsibilities of all the involved personnel, including the radiation oncologist, physicist, dosimetrist, and radiation therapist. Factors with respect to the QA of the treatment planning system, treatment-planning process, and treatment-delivery process are discussed, as are issues related to the utilization of volumetric modulated arc therapy. Patient-specific QA procedures are presented. Successful IMRT programs involve integration of many processes: patient selection, patient positioning/immobilization, target definition, treatment plan development, and accurate treatment delivery. Appropriate QA procedures, including patient-specific QA procedures, are essential to ensure quality in an IMRT program and to assure patient safety.

Comparative analysis of dosimetric parameters of three different radiation techniques for patients with Graves’ ophthalmopathy treated with retro-orbital irradiation

BackgroundWe would like to investigate the if IMRT produced better target coverage and dose sparing to adjacent normal structures as compared with 3-dimensional conformal radiotherapy (3DCRT) and lateral opposing fields (LOF) for patients with Graves’ ophthalmopathy treated with retro-orbital irradiation.MethodsTen consecutive patients diagnosed with Graves’ ophthalmopathy were prospectively recruited into this study. An individual IMRT, 3DCRT and LOF plan was created for each patient. Conformity index (CI), homogeneity index (HI) and other dosimetric parameters of the targets and organs-at-risk (OAR) generated by IMRT were compared with the other two techniques.ResultsMann–Whitney U test demonstrated that CI generated by IMRT was superior to that produced by 3DCRT and LOF (p=0.005 for both respectively). Similarly HI with IMRT was proven better than 3DCRT (p=0.007) and LOF (p=0.005). IMRT gave rise to better dose sparing to some OARs including globes, lenses and optic nerves as compared with 3DCRT but not with LOF.ConclusionsIMRT, as compared with 3DCRT and LOF, was found to have a better target coverage, conformity and homogeneity and dose sparing to some surrounding structures, despite a slight increase but clinically negligible dose to other structures. Dosimetrically it might be a preferred treatment technique and a longer follow up is warranted to establish its role in routine clinical use.

Magnetic resonance imaging-based treatment planning for prostate brachytherapy.

Transrectal ultrasound (TRUS) is the standard imaging modality for planning prostate brachytherapy. However, magnetic resonance imaging (MRI) provides greater anatomic detail than TRUS. We compared treatment plans generated using TRUS, endorectal coil MRI (erMRI), and standard body array coil MRI (sMRI). Treatment plans were used from patients treated with permanent, stranded-seed (125)I brachytherapy in a prospective trial. All men underwent pretreatment planning based on TRUS, and all underwent erMRI before treatment and sMRI 30 days after the implant. Treatments for 20 consecutive patients were replanned on sMRI and erMRI images by investigators blinded to TRUS-based plans. Prostate volume/dimensions, radioactivity-to-prostate-volume ratio, and dosimetric parameters were compared. Compared with TRUS, mean prostate volume measured by erMRI was smaller, medial-lateral diameter was larger, and anterior-posterior diameter was smaller, suggesting that the endorectal coil produced anatomic distortions. Craniocaudal prostate length was smaller on both types of MRI thanon TRUS, suggesting that TRUS overestimates prostate length. Activity per volume was 7.5% lower for plans based on sMRI than on TRUS (0.901 vs. 0.974mCi/cm(3), p<0.001). sMRI plans had similar coverage of the planning target volume (PTV) (dose to 90% of the prostate [D(90)] 116.6% sMRI vs. 117.5% TRUS, p=0.526) and improved dose homogeneity (percentage of PTV receiving 150% of the prescription dose [V(150)] 47.4% sMRI vs. 53.8% TRUS, p=0.001 and percentage of PTV receiving 200% of the prescription dose [V(200)] 16.6% sMRI vs. 19.2% TRUS, p<0.001). Staging erMRI should not be routinely used for treatment planning because it produces anatomic distortion. sMRI may have treatment planning advantages over TRUS because of superior soft-tissue delineation of the prostate and adjacent normal tissue structures.

SU-E-T-229: Monte Carlo Dosimetric Study of SAVI HDR Applicator for Partial Breast Irradiation.

To investigate the dosimetric variation by Monte Carlo and experimentally simulating the situation with and without tissue invagination and the potential translation and rotation of the SAVI applicator for partial breast irradiation. The SAVI applicator with the cavity filled with air and water was merged into a water phantom and the delivered dose was simulated by MCNP monte carlo program. The results verified using an ion chamber and film were compared with a homogenous dose calculation by the treatment planning system. A dose variation from the SAVI translational shift was simulated and measured by moving an ion chamber along with the central axis direction. A dose change from the SAVI rotation was simulated and measured by placing an ion chamber at a fixed point while rotating the SAVI device about the central axis. The dosimetric variations for the SAVI device were found to be related to the cavity dimension, source arrangement, and dwell times. For the single dwell source placed in the center of the applicator, the maximum difference of the dose with the air cavity at 1cm away from the air-water boundary is about 7% higher than that with water filling in the cavity. But the simulation and measurements with nearly fully loaded multi-sources for the same situation show a difference of less than 3%. The 3% dose variation in average was found from either the 3 mm translation or 3 degree rotation of the SAVI applicator. The maximum dosimetric effect of an air cavity is 7% off compared with a water filled cavity when a single dwell source position is used in the center of the central catheter. Multiple catheters of the SAVI applicator with a nearly fully loaded dwell source position produce the discrepancy of less than 3% and allow for optimal and conformal dose distribution to a lumpectomy cavity while minimizing the dose to adjacent normal structures.

SU-E-T-309: Dosimetric Study and Clinical Implementation of an HDR Applicator of SAVI for Partial Breast Irradiation.

To present clinical implementation and quality assurance for a new HDR applicator of Strut-Adjusted Volume Implant (SAVI) for partial breast irradiation and the higher-order DVH examined. The SAVI applicator with multi-peripheral struts can be differentially loaded with the HDR source for a conformal dose distribution to the lumpectomy cavity. The treatment plan is evaluated by a dose volume histogram (DVH) as follows: V90 > 90%, V150 < 50 cc, and V200 < 20 cc. A higher-order DVH which may reflect radiation-induced toxicity, such as V300, was studied. The SAVI device status was verified by the 3D CT images and image fusion. Tissue invagination was investigated using an ion chamber and film with the cavity filled with air and water merged into a water phantom. Twenty-nine patients to date at Mercy Medical Center, Baltimore, Maryland were treated with SAVI device. The dosimetric data demonstrated the achievements of greater than 90% coverage for V90 at 96.8% and 94.1% for V95 while keeping a low V150 at 33.9 cc and V200 at 16.5 cc. V300 was found to be 2.7 cc in average. Potential uncertainties introduced by the SAVI applicator motion were a 3% variation in dose caused either by a 3-mm} translation or a rotation of 3 degree. Multiple catheters of the SAVI applicator allows for optimal and conformal dose distribution around a lumpectomy cavity while minimizing the dose to adjacent normal structures such as skin and ribcage. Multiple imaging techniques are capable to verify cavity variation, strut collapse or relative motion, and device shift. A nearly fully loaded dwell source position produced the discrepancy of less than 3% and allow for optimal and conformal dose distribution to a lumpectomy cavity. Advantages of the SAVI applicator have been shown in treating breast cancer with the shallower, elliptical, and asymmetric cavity.

Intensity modulated radiation therapy for definitive treatment of paraortic relapse in patients with endometrial cancer

PurposeThe paraortic nodes are a common site of recurrence of endometrial cancer, especially among patients previously treated with pelvic radiation. Intensity modulated radiation therapy (IMRT) can be used to deliver a tumoricidal dose to paraortic disease while minimizing dose to normal adjacent structures. In this study, we reviewed the outcomes of patients treated with IMRT for unresected or incompletely resected paraortic recurrences of primary uterine cancer. Methods and MaterialsBetween 2000 and 2009, 27 patients with unresected (19 patients) or incompletely resected (8 patients) paraortic relapse of endometrial cancer were treated with curative intent using IMRT. The paraortic basin was generally treated to a dose of 45-50 Gy, and gross disease was treated to a mean total dose of 61.7 Gy (range, 54-66 Gy). Seventeen patients (63%) received neoadjuvant or adjuvant chemotherapy. Fifteen (56%) received cisplatin concurrently with IMRT. Rates of overall survival and progression-free survival following salvage IMRT were determined using the Kaplan-Meier method, and differences between subgroups were assessed using the log-rank statistic. ResultsOf the 27 patients, 19 (70%) had local control of paraortic disease after a median follow-up time of 25 months (range, 4-83 months). Two-year actuarial overall survival and progression-free survival rates were 63% and 53%, respectively. Five patients (19%) experienced severe late gastrointestinal toxic effects (grade 3-5). ConclusionsIMRT can serve as salvage therapy of paraortic recurrence of endometrial cancer. However, the risk of severe gastrointestinal toxic effects is high, and care should be taken during treatment planning to minimize the dose to the small bowel.

Clinical use of a neuronavigation system in hemangioblastoma resection of posterior cranial fossa

The aim of this study was to retrospectively evaluate the effectiveness of the Stryker Leibinger neuronavigation system in surgical resection of hemangioblastomas of the posterior fossa. The study included 16 cases of solid hemangioblastoma of posterior cranial fossa treated since we began using Stryker Leibinger neuronavigation system-assisted microneurosurgery in 2003. These cases were compared on the basis of time, blood loss, and complications to 19 similar cases of solid hemangioblastoma that underwent conventional microneurosurgical resection prior to 2003. All patients in the experimental (neuronavigation-assisted) group underwent surgical resection without complications while the control groups' resections all involved blood loss related to the longer operation time. Neuronavigation also resulted in a clear field of surgical vision and clear lesion boundaries, making it easier to remove lesions and reduce accidental injury of adjacent normal structures. The application of navigation technology is very valuable for solid hemangioblastoma operations not only by shortening operative time, thereby significantly reducing operative blood loss, but also by making surgical excision easier, reducing damage to adjacent normal structures, and decreasing surgical complications and mortality.