Detection of setup uncertainties with 3D surface registration system for conformal radiotherapy of breast cancer

Aim

To investigate the clinical application of a technique for patient set-up verification in breast cancer radiotherapy based on a 3D surface image registration system.

Background

Accurate and reproducible patient set-up is a prerequisite to correctly deliver fractionated radiotherapy. Various approaches are available to verify and correct patient setup for 3D image acquisition in a radiation treatment room.

Materials and methods

The study analyzed the setup reproducibility of 15 patients affected by breast cancer and candidates for conformal radiotherapy by using the AlignRT system (VisionRT, London, UK). At the initial setup, electronic portal imaging device (EPID) images were compared with Digitally Reconstructed Radiographs (DRRs) and a reference three-dimensional (3D) surface image was obtained by AlignRT. Surface images were acquired prior to every subsequent setup procedure. The systematic and random errors along longitudinal and vertical directions were measured and compared for the two systems.

Results

The procedure for surface registration, image acquisition and comparison with the reference image took less than 1 min on average. The T test for systematic error showed no significant difference between the 2 verification systems along the longitudinal (p = 0.69) and vertical (p = 0.67) axes. The T-test for random error showed a significant difference between the 2 systems along the vertical axis (p = 0.05).

Conclusion

AlignRT is fast, simple, non-invasive and seems to be reliable in detecting patient setup errors. Our results suggest that it could be used to assess the setup reproducibility for breast cancer patients.     

Intraoperative Near-Infrared Imaging Can Distinguish Cancer from Normal Tissue but Not Inflammation

Introduction

Defining tumor from non-tumor tissue is one of the major challenges of cancer surgery. Surgeons depend on visual and tactile clues to select which tissues should be removed from a patient. Recently, we and others have hypothesized near-infrared (NIR) imaging can be used during surgery to differentiate tumors from normal tissue.

Methods

We enrolled 8 canines and 5 humans undergoing cancer surgery for NIR imaging. The patients were injected with indocyanine green (ICG), an FDA approved non-receptor specific NIR dye that accumulates in hyperpermeable tissues, 16–24 hours prior to surgery. During surgery, NIR imaging was used to discriminate the tumor from non-tumor tissue.

Results

NIR imaging identified all tumors with a mean signal-to-background ratio of 6.7. Optical images were useful during surgery in discriminating normal tissue from cancer. In 3 canine cases and 1 human case, the tissue surrounding the tumor was inflamed due to obstruction of the vascular supply due to mass effect. In these instances, NIR imaging could not distinguish tumor tissue from tissue that was congested, edematous and did not contain cancer.

Conclusions

This study shows that NIR imaging can identify tumors from normal tissues, provides excellent tissue contrast, and it facilitates the resection of tumors. However, in situations where there is significant peritumoral inflammation, NIR imaging with ICG is not helpful. This suggests that non-targeted NIR dyes that accumulate in hyperpermeable tissues will have significant limitations in the future, and receptor-specific NIR dyes may be necessary to overcome this problem.     

Quantitative Segmentation of Fluorescence Microscopy Images of Heterogeneous Tissue: Application to the Detection of Residual Disease in Tumor Margins

Purpose

To develop a robust tool for quantitative in situ pathology that allows visualization of heterogeneous tissue morphology and segmentation and quantification of image features.

Materials and Methods

Tissue excised from a genetically engineered mouse model of sarcoma was imaged using a subcellular resolution microendoscope after topical application of a fluorescent anatomical contrast agent: acriflavine. An algorithm based on sparse component analysis (SCA) and the circle transform (CT) was developed for image segmentation and quantification of distinct tissue types. The accuracy of our approach was quantified through simulations of tumor and muscle images. Specifically, tumor, muscle, and tumor+muscle tissue images were simulated because these tissue types were most commonly observed in sarcoma margins. Simulations were based on tissue characteristics observed in pathology slides. The potential clinical utility of our approach was evaluated by imaging excised margins and the tumor bed in a cohort of mice after surgical resection of sarcoma.

Results

Simulation experiments revealed that SCA+CT achieved the lowest errors for larger nuclear sizes and for higher contrast ratios (nuclei intensity/background intensity). For imaging of tumor margins, SCA+CT effectively isolated nuclei from tumor, muscle, adipose, and tumor+muscle tissue types. Differences in density were correctly identified with SCA+CT in a cohort of ex vivo and in vivo images, thus illustrating the diagnostic potential of our approach.

Conclusion

The combination of a subcellular-resolution microendoscope, acriflavine staining, and SCA+CT can be used to accurately isolate nuclei and quantify their density in anatomical images of heterogeneous tissue.     

Displacements of fiducial markers in patients with prostate cancer treated with image guided radiotherapy: A single-institution descriptive study

Aim

To describe daily displacements when using fiducial markers as surrogates for the target volume in patients with prostate cancer treated with IGRT.

Background

The higher grade of conformity achieved with the use of modern radiation technologies in prostate cancer can increase the risk of geographical miss; therefore, an associated protocol of IGRT is recommended.

Materials and methods

A single-institution, retrospective, consecutive study was designed. 128 prostate cancer patients treated with daily on-line IGRT based on 2D kV orthogonal images were included. Daily displacement of the fiducial markers was considered as the difference between the position of the patient when using skin tattoos and the position after being relocated using fiducial markers. Measures of central tendency and dispersion were used to describe fiducial displacements.

Results

The implant itself took a mean time of 15 min. We did not detect any complications derived from the implant. 4296 sets of orthogonal images were identified, 128 sets of images corresponding to treatment initiation were excluded; 91 (2.1%) sets of images were excluded from the analysis after having identified that these images contained extreme outlier values. If IGRT had not been performed 25%, 10% or 5% of the treatments would have had displacements superior to 4, 7 or 9 mm respectively in any axis.

Conclusions

Image guidance is required when using highly conformal techniques; otherwise, at least 10% of daily treatments could have significant displacements. IGRT based on fiducial markers, with 2D kV orthogonal images is a convenient and fast method for performing image guidance.     

A Statistical Parametric Mapping Toolbox Used for Voxel-Wise Analysis of FDG-PET Images of Rat Brain

Purpose

PET (positron emission tomography) imaging researches of functional metabolism using fluorodeoxyglucose (¹⁸F-FDG) of animal brain are important in neuroscience studies. FDG-PET imaging studies are often performed on groups of rats, so it is desirable to establish an objective voxel-based statistical methodology for group data analysis.

Material and Methods

This study establishes a statistical parametric mapping (SPM) toolbox (plug-ins) named spmratIHEP for voxel-wise analysis of FDG-PET images of rat brain, in which an FDG-PET template and an intracranial mask image of rat brain in Paxinos & Watson space were constructed, and the default settings were modified according to features of rat brain. Compared to previous studies, our constructed rat brain template comprises not only the cerebrum and cerebellum, but also the whole olfactory bulb which made the later cognitive studies much more exhaustive. And with an intracranial mask image in the template space, the brain tissues of individuals could be extracted automatically. Moreover, an atlas space is used for anatomically labeling the functional findings in the Paxinos & Watson space. In order to standardize the template image with the atlas accurately, a synthetic FDG-PET image with six main anatomy structures is constructed from the atlas, which performs as a target image in the co-registration.

Results

The spatial normalization procedure is evaluated, by which the individual rat brain images could be standardized into the Paxinos & Watson space successfully and the intracranial tissues could also be extracted accurately. The practical usability of this toolbox is evaluated using FDG-PET functional images from rats with left side middle cerebral artery occlusion (MCAO) in comparison to normal control rats. And the two-sample t-test statistical result is almost related to the left side MCA.

Conclusion

We established a toolbox of SPM8 named spmratIHEP for voxel-wise analysis of FDG-PET images of rat brain.     

Cell-by-Cell Alignment of Repeated Specular Microscopy Images from the Same Eye

Purpose

Modern specular microscopes (SM) robustly depict the same central area of the corneal endothelium at different time points through a built-in fixation light. However, repeated image acquisitions slightly shift and rotate because of minute changes in head position in the chin and forehead rest. This prevents the manual retrieval of individual corneal endothelial cells (CECs) in repeated measurements because SM images usually lack obvious landmarks. We devised and validated an image registration algorithm that aligns SM images from the same eye to make corresponding CECs coincide.

Methods

We retrospectively selected 27 image pairs for the presence of significant image overlap. Each image pair had been recorded on the same day and of the same eye. We applied our registration method in each image pair. Two observers independently validated, by means of alternation flicker, that the image pairs had been correctly aligned. We also repeatedly applied our registration method on unrelated image pairs by randomly drawing images and making certain that the images did not originate from the same eye. This was done to assess the specifity of our method.

Results

All automated registrations of the same-day and same-eye image pairs were accurate. However, one single image incorrectly failed to trigger the non-match diagnosis twice in 81 registration attempts between unrelated images. As it turned out, this particular image depicted only 73 CECs. The average number of CECs was 253 (range 73–393).

Conclusion

Repeated non-contact SM images can be automatedly aligned so that the corresponding CECs coincide. Any successful alignment can be considered as proof of the retrieval of identical CECs as soon as at least 100 CEC centroids have been identified. We believe our method is the first to robustly confirm endothelial stability in individual eyes.     

Interactive visual exploration of overlapping similar structures for three-dimensional microscope images

Background

Recent advances in microscopy enable the acquisition of large numbers of tomographic images from living tissues. Three-dimensional microscope images are often displayed with volume rendering by adjusting the transfer functions. However, because the emissions from fluorescent materials and the optical properties based on point spread functions affect the imaging results, the intensity value can differ locally, even in the same structure. Further, images obtained from brain tissues contain a variety of neural structures such as dendrites and axons with complex crossings and overlapping linear structures. In these cases, the transfer functions previously used fail to optimize image generation, making it difficult to explore the connectivity of these tissues.

Results

This paper proposes an interactive visual exploration method by which the transfer functions are modified locally and interactively based on multidimensional features in the images. A direct editing interface is also provided to specify both the target region and structures with characteristic features, where all manual operations can be performed on the rendered image. This method is demonstrated using two-photon microscope images acquired from living mice, and is shown to be an effective method for interactive visual exploration of overlapping similar structures.

Conclusions

An interactive visualization method was introduced for local improvement of visualization by volume rendering in two-photon microscope images containing regions in which linear nerve structures crisscross in a complex manner. The proposed method is characterized by the localized multidimensional transfer function and interface where the parameters can be determined by the user to suit their particular visualization requirements.     

Indirect Magnetic Resonance Imaging Lymphography Identifies Lymph Node Metastasis in Rabbit Pyriform Sinus VX2 Carcinoma Using Ultra-Small Super-Paramagnetic Iron Oxide

Background

USPIO is a contrast agent for MRI that can generate T2W images with low signal intensities. After subcutaneous or intravenous injection of USPIO, normal lymph node tissues uptake these nano-particles, but tumor cells do not. Thus, tumor metastasis can be detected using this contrast agent.

Objective

The aim of this study was to access the feasibility of USPIO enhanced MRI for the detection of cervical lymph node metastasis in a pyriform sinus carcinoma animal model and to investigate the ability of USPIO to enhance images of cervical lymph node metastases.

Methods and Findings

Twenty New Zealand rabbits were randomly divided into tumor and inflammatory groups, and each group contained 10 rabbits. In the inflammatory group, a 0.5 ml egg yolk emulsion was injected into the sub-mandibular muscle of the rabbits to induce an inflammatory reaction in their cervical lymph nodes. In the tumor group, a VX2 tumor tissue suspension was transplanted into the pyriform sinus sub-mucosa of the rabbits using direct laryngoscope. Four weeks after the tumor or egg yolk injection, MRIs were performed before and after USPIO injection to observe the imaging enhancement features of USPIO. After that, a histo-pathological analysis was performed for all rabbits. We found the metastatic lymph nodes had no signal reduced intensity or irregular signal reduced intensity on T2-weighted image by using USPIO enhancement. In the tumor group,the sensitivity and specificity of plain MRI were 57.6% and 60.7%. The corresponding values of USPIO-enhanced MRl were 96.1% and 85.7%. (P<0.05)

Conclusion

The features and the extent of the lymph node metastases corresponded to those observed on USPIO-enhanced MR images. USPIO-enhanced MRI is useful for the detection and estimation of lymph node metastasis in this cervical carcinoma animal model.     

Respiratory Gating during Stereotactic Body Radiotherapy for Lung Cancer Reduces Tumor Position Variability

Purpose

We evaluated the effects of respiratory gating on treatment accuracy in lung cancer patients undergoing lung stereotactic body radiotherapy by using electronic portal imaging device (EPID) images.

Materials and Methods

Our study population consisted of 30 lung cancer patients treated with stereotactic body radiotherapy (48 Gy/4 fractions/4 to 9 days). Of these, 14 were treated with- (group A) and 16 without gating (group B); typically the patients whose tumors showed three-dimensional respiratory motion ≧5 mm were selected for gating. Tumor respiratory motion was estimated using four-dimensional computed tomography images acquired during treatment simulation. Tumor position variability during all treatment sessions was assessed by measuring the standard deviation (SD) and range of tumor displacement on EPID images. The two groups were compared for tumor respiratory motion and position variability using the Mann-Whitney U test.

Results

The median three-dimensional tumor motion during simulation was greater in group A than group B (9 mm, range 3–30 mm vs. 2 mm, range 0–4 mm; p<0.001). In groups A and B the median SD of the tumor position was 1.1 mm and 0.9 mm in the craniocaudal- (p = 0.24) and 0.7 mm and 0.6 mm in the mediolateral direction (p = 0.89), respectively. The median range of the tumor position was 4.0 mm and 3.0 mm in the craniocaudal- (p = 0.21) and 2.0 mm and 1.5 mm in the mediolateral direction (p = 0.20), respectively.

Conclusions

Although patients treated with respiratory gating exhibited greater respiratory tumor motion during treatment simulation, tumor position variability in the EPID images was low and comparable to patients treated without gating. This demonstrates the benefit of respiratory gating.     

Assessment and evaluation of MV image guidance system performance in radiotherapy

Background and aim

The clinical use of imaging system in image guided radiotherapy (IGRT) necessitates performing periodic quality assurance of the system to be confident in applying corrections for patient set-up errors. We aim to develop and implement a quality assurance (QA) programme for megavoltage (MV) based image guidance system and assess its long term performance for a period of 3 years.

Materials and methods

Periodic QA tests were performed for the MV planar and cone beam computed tomography (CBCT) imaging system to assess the system safety, mechanical and geometrical accuracy, image quality and dose. The tests were performed using the equipment supplied by the manufacturer along with the image guidance system and using simple methods developed in-house. The test results were compared with expected or baseline values established during commissioning.

Results

The safety system was found to be functional. The results of mechanical and geometrical tests were in good agreement with the expected results. The system mechanical positioning was stable and reproducible within ±2 mm accuracy. The image quality and the imaging dose of the planar and CBCT imaging were found to agree with the baseline values and the manufacturer specifications.

Discussion

Throughout the three-year period, all the QA tests were within the specification. The mechanical and geometrical tests are most crucial as they directly affect the patient positioning accuracy.

Conclusion

We conclude that the MV image guidance system is efficient to perform IGRT and insist to perform periodic QA tests and calibration for the system.     

Label-Free Delineation of Brain Tumors by Coherent Anti-Stokes Raman Scattering Microscopy in an Orthotopic Mouse Model and Human Glioblastoma

Background

Coherent anti-Stokes Raman scattering (CARS) microscopy provides fine resolution imaging and displays morphochemical properties of unstained tissue. Here, we evaluated this technique to delineate and identify brain tumors.

Methods

Different human tumors (glioblastoma, brain metastases of melanoma and breast cancer) were induced in an orthotopic mouse model. Cryosections were investigated by CARS imaging tuned to probe C-H molecular vibrations, thereby addressing the lipid content of the sample. Raman microspectroscopy was used as reference. Histopathology provided information about the tumor''s localization, cell proliferation and vascularization.

Results

The morphochemical contrast of CARS images enabled identifying brain tumors irrespective of the tumor type and properties: All tumors were characterized by a lower CARS signal intensity than the normal parenchyma. On this basis, tumor borders and infiltrations could be identified with cellular resolution. Quantitative analysis revealed that the tumor-related reduction of CARS signal intensity was more pronounced in glioblastoma than in metastases. Raman spectroscopy enabled relating the CARS intensity variation to the decline of total lipid content in the tumors. The analysis of the immunohistochemical stainings revealed no correlation between tumor-induced cytological changes and the extent of CARS signal intensity reductions. The results were confirmed on samples of human glioblastoma.

Conclusions

CARS imaging enables label-free, rapid and objective identification of primary and secondary brain tumors. Therefore, it is a potential tool for diagnostic neuropathology as well as for intraoperative tumor delineation.     

The Utility of Gadoxetic Acid-Enhanced MR Imaging to Characterize Atypical Cirrhotic Nodules Detected on Dynamic CT Images

Purpose

To evaluate whether gadoxetic acid (Gd-EOB-DTPA)-enhanced MR images of tumors taken during the hepatocyte-specific phase can aid in the differentiation between hepatocellular carcinoma (HCC) and dysplastic nodules (DNs) in patients with atypical cirrhotic nodules detected on dynamic CT images.

Materials and Methods

Seventy-one patients with 112 nodules showing atypical dynamic enhancement on CT images underwent gadoxetic acid-enhanced MR imaging (MRI) studies. Using a reference standard, we determined that 33 of the nodules were DNs and that 79 were true HCCs. Tumor size, signal intensity on precontrast T1-weighted images (T1WI) and T2WI, and the pattern of dynamic enhancement on MR images taken in the hepatocyte-phase were determined.

Results

There were significant differences in tumor size, hyperintensity on T2WI, hypointensity on T1WI, typical HCC enhancement pattern on dynamic MR images, or hypointensity on hepatocyte-phase images between DNs and HCC. The sensitivity and specificity were 60.8% and 87.9% for T2WI, 38.0% and 87.9% for T1WI, 17.7% and 100% for dynamic MR imaging, 83.5% and 84.9% for hepatocyte-phase imaging, and 60.8% and 87.9% for tumor size (threshold of 1.7 cm).

Conclusion

Gd-EOB-DTPA-enhanced hepatocyte-phase imaging is recommended for patients at high risk of HCC who present with atypical lesions on dynamic CT images.     

Assessment of Still and Moving Images in the Diagnosis of Gastric Lesions Using Magnifying Narrow-Band Imaging in a Prospective Multicenter Trial

Objectives

Magnifying narrow-band imaging (M-NBI) is more accurate than white-light imaging for diagnosing small gastric cancers. However, it is uncertain whether moving M-NBI images have additional effects in the diagnosis of gastric cancers compared with still images.

Design

A prospective multicenter cohort study.

Methods

To identify the additional benefits of moving M-NBI images by comparing the diagnostic accuracy of still images only with that of both still and moving images. Still and moving M-NBI images of 40 gastric lesions were obtained by an expert endoscopist prior to this prospective multicenter cohort study. Thirty-four endoscopists from ten different Japanese institutions participated in the prospective multicenter cohort study. Each study participant was first tested using only still M-NBI images (still image test), then tested 1 month later using both still and moving M-NBI images (moving image test). The main outcome was a difference in the diagnostic accuracy of cancerous versus noncancerous lesions between the still image test and the moving image test.

Results

Thirty-four endoscopists were analysed. There were no significant difference of cancerous versus noncancerous lesions between still and moving image tests in the diagnostic accuracy (59.9% versus 61.5%), sensitivity (53.4% versus 55.9%), and specificity (67.0% versus 67.6%). And there were no significant difference in the diagnostic accuracy between still and moving image tests of demarcation line (65.4% versus 65.5%), microvascular pattern (56.7% versus 56.9%), and microsurface pattern (48.1% versus 50.9%). Diagnostic accuracy showed no significant difference between the still and moving image tests in the subgroups of endoscopic findings of the lesions.

Conclusions

The addition of moving M-NBI images to still M-NBI images does not improve the diagnostic accuracy for gastric lesions. It is reasonable to concentrate on taking sharp still M-NBI images during endoscopic observation and use them for diagnosis.

Trial registration

Umin.ac.jp UMIN-CTR000008048     

Corticospinal tract-sparing intensity-modulated radiotherapy treatment planning

Aim

To establish intensity-modulated radiotherapy (IMRT) planning procedures that spare the corticospinal tract by integrating diffusion tensor tractography into the treatment planning software.

Background

Organs at risk are generally contoured according to the outline of the organ as demonstrated by CT or MRI. But a part of the organ with specific function is difficult to protect, because such functional part of the organ cannot be delineated on CT or conventional sequence of MRI.

Methods

Diagnostic and treatment planning images of glioblastoma patients who had been treated by conventional 3-dimensional conformal radiotherapy were used for re-planning of IMRT. Three-dimensional fiber maps of the corticospinal tracts were created from the diffusion tensors obtained from the patients before the surgery, and were blended with the anatomical MR images (i.e. gadolinium-enhanced T1-weighted images or T2-weighted images). DICOM-formatted blended images were transferred and fused to the planning CT images. Then, IMRT plans were attempted.

Results

The corticospinal tracts could be contoured as organs at risk (OARs), because the blended images contained both anatomical information and fiber-tract maps. Other OARs were contoured in a way similar to that of ordinary IMRT planning. Gross tumor volumes, clinical target volumes, planning target volumes, and other OARs were contoured on the treatment planning software, and IMRT plans were made.

Conclusions

IMRT plans with diminished doses to the corticospinal tract were attained. This technique enabled us to spare specific neuron fibers as OARs which were formerly “invisible” and to reduce the probability of late morbidities.     

In-vivo visualization of tumor microvessel density and response to anti-angiogenic treatment by high resolution MRI in mice

Purpose

Inhibition of angiogenesis has shown clinical success in patients with cancer. Thus, imaging approaches that allow for the identification of angiogenic tumors and the detection of response to anti-angiogenic treatment are of high clinical relevance.

Experimental Design

We established an in vivo magnetic resonance imaging (MRI) approach that allows us to simultaneously image tumor microvessel density and tumor vessel size in a NSCLC model in mice.

Results

Using microvessel density imaging we demonstrated an increase in microvessel density within 8 days after tumor implantation, while tumor vessel size decreased indicating a switch from macro- to microvessels during tumor growth. Moreover, we could monitor in vivo inhibition of angiogenesis induced by the angiogenesis inhibitor PTK787, resulting in a decrease of microvessel density and a slight increase in tumor vessel size.

Conclusions

We present an in vivo imaging approach that allows us to monitor both tumor microvessel density and tumor vessel size in the tumor. Moreover, this approach enables us to assess, early-on, treatment effects on tumor microvessel density as well as on tumor vessel size. Thus, this imaging-based strategy of validating anti-angiogenic treatment effects has high potential in applications to preclinical and clinical trials.     

MicroPure Imaging for the Evaluation of Microcalcifications in Gouty Arthritis Involving the First Metatarsophalangeal Joint: A Preliminary Study

Objective

To assess the value of MicroPure, a new ultrasound image processing technique, in identifying microcalcifications (formed by monosodium urate crystals) in the first metatarsophalangeal joints attacked by gout compared to gray-scale ultrasound images.

Materials and Methods

Thirty-six patients who fulfilled the study inclusion criteria underwent gray-scale ultrasound and MicroPure examinations of the first metatarsophalangeal joints attacked by gout. Static images of the target areas were acquired using gray-scale ultrasound and MicroPure. Two independent and blinded investigators analyzed the images to determine the number of microcalcifications and to score for image quality and artifacts.

Results

The two investigators observed significantly more microcalcifications with MicroPure compared to gray-scale ultrasound (ρ<0.001). The level of agreement between the investigators consistently increased from gray-scale ultrasound to MicroPure imaging (gray-scale interclass correlation coefficient of 0.69 vs. MicroPure interclass correlation coefficient of 0.81). One investigator preferred the MicroPure image quality over gray-scale ultrasound (ρ<0.001), but the other investigator disagreed (ρ<0.001). Both investigators observed fewer artifacts with MicroPure than with gray-scale ultrasound (ρ<0.009).

Conclusion

MicroPure imaging identified significantly more microcalcifications than gray-scale ultrasound.     

A Feasibility Study of an Intravascular Imaging Antenna to Image Atherosclerotic Plaques in Swine Using 3.0 T MRI

Purpose

To investigate the feasibility of an intravascular imaging antenna to image abdominal aorta atherosclerotic plaque in swine using 3.0T magnetic resonance imaging (MRI).

Methods

Atherosclerotic model was established in 6 swine. After 8 months, swine underwent an MR examination, which was performed using an intravascular imaging guide-wire, and images of the common iliac artery and the abdominal aorta were acquired. Intravascular ultrasound (IVUS) was performed in the right femoral artery; images at the same position as for the MR examination were obtained. The luminal border and external elastic membrane of the targeted arteries were individually drawn in the MR and IVUS images. After co-registering these images, the vessel, lumen, and vessel wall areas and the plaque burden in the same lesions imaged using different modalities were calculated and compared. The diagnostic accuracy of intravascular MR examination in delineating the vessel wall and detecting plaques were analyzed and compared using IVUS.

Results

Compared with IVUS, good agreement was found between MRI and IVUS for delineating vessel, lumen, and vessel wall areas and plaque burden (r value: 0.98, 0.95, 0.96 and 0.91, respectively; P<0.001).

Conclusion

Compared with IVUS, using an intravascular imaging guide-wire to image deep seated arteries allowed determination of the vessel, lumen and vessel wall areas and plaque size and burden. This may provide an alternative method for detecting atherosclerotic plaques in the future.     

Primary mucosal sinonasal melanoma—Case report and review of the literature. The role of complex treatment-surgery and adjuvant radiotherapy

Aim

The place of adjuvant radiotherapy in the treatment of sinonasal melanoma.

Background

Sinonasal mucosal melanoma is a rare disease with poor prognosis and requires a complex treatment. Elective neck dissection in patients with N0 and adjuvant radiotherapy has been a source of controversy. High late regional recurrence rates rise questions about elective irradiation of the neck nodes in patients with N0 stage disease.

Methods

We present our two years’ follow up in a case of locally advanced sinonasal melanoma and literature review of the treatment options for mucosal melanoma.

Results

In locally advanced sinonasal melanoma treated with surgical resection, postoperative radiotherapy and chemotherapy we had local tumor control. Two years later, a regional contralateral recurrence without distant metastasis occurred.

Conclusions

Literature data for frequent neck lymph nodes recurrences justify elective neck dissection. Postoperative elective neck radiotherapy for patients with locally advanced sinonasal melanoma and clinically N0 appears to decrease the rate of late regional recurrences.     

Respiratory Motion Reduction in PET/CT Using Abdominal Compression for Lung Cancer Patients

Purpose

Respiratory motion causes substantial artifacts in reconstructed PET images when using helical CT as the attenuation map in PET/CT imaging. In this study, we aimed to reduce the respiratory artifacts in PET/CT images of patients with lung tumors using an abdominal compression device.

Methods

Twelve patients with lung cancer located in the middle or lower lobe of the lung were recruited. The patients were injected with 370 MBq of ¹⁸F-FDG. During PET, the patients assumed two bed positions for 1.5 min/bed. After conducting free-breathing imaging, we obtained images of the patients with abdominal compression by applying the same setup used in the free-breathing scan. The differences in the standardized uptake value (SUV)_max, SUV_mean, tumor volume, and the centroid of the tumors between PET and various CT schemes were measured.

Results

The SUV_max and SUV_mean derived from PET/CT imaging using an abdominal compression device increased for all the lesions, compared with those obtained using the conventional approach. The percentage increases were 18.1% ±14% and 17% ±16.8% for SUV_max and SUV_mean, respectively. PET/CT imaging combined with abdominal compression generally reduced the tumor mismatch between CT and the corresponding attenuation corrected PET images, with an average decrease of 1.9±1.7 mm over all the cases.

Conclusions

PET/CT imaging combined with abdominal compression reduces respiratory artifacts and PET/CT misregistration, and enhances quantitative SUV in tumor. Abdominal compression is easy to set up and is an effective method used in PET/CT imaging for clinical oncology, especially in the thoracic region.     

A Tri-Modality Image Fusion Method for Target Delineation of Brain Tumors in Radiotherapy

Purpose

To develop a tri-modality image fusion method for better target delineation in image-guided radiotherapy for patients with brain tumors.

Methods

A new method of tri-modality image fusion was developed, which can fuse and display all image sets in one panel and one operation. And a feasibility study in gross tumor volume (GTV) delineation using data from three patients with brain tumors was conducted, which included images of simulation CT, MRI, and ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) examinations before radiotherapy. Tri-modality image fusion was implemented after image registrations of CT+PET and CT+MRI, and the transparency weight of each modality could be adjusted and set by users. Three radiation oncologists delineated GTVs for all patients using dual-modality (MRI/CT) and tri-modality (MRI/CT/PET) image fusion respectively. Inter-observer variation was assessed by the coefficient of variation (COV), the average distance between surface and centroid (ADSC), and the local standard deviation (SD_local). Analysis of COV was also performed to evaluate intra-observer volume variation.

Results

The inter-observer variation analysis showed that, the mean COV was 0.14(±0.09) and 0.07(±0.01) for dual-modality and tri-modality respectively; the standard deviation of ADSC was significantly reduced (p<0.05) with tri-modality; SD_local averaged over median GTV surface was reduced in patient 2 (from 0.57 cm to 0.39 cm) and patient 3 (from 0.42 cm to 0.36 cm) with the new method. The intra-observer volume variation was also significantly reduced (p = 0.00) with the tri-modality method as compared with using the dual-modality method.

Conclusion

With the new tri-modality image fusion method smaller inter- and intra-observer variation in GTV definition for the brain tumors can be achieved, which improves the consistency and accuracy for target delineation in individualized radiotherapy.