Helical CT Scans Research Articles

Construction of a finite element model of normal human foot and ankle

Objective To report the construction of a finite element (FE) model of normal human foot and ankle which can be used for biomechanical research. Methods Helical CT scan images of a 30-year-old male volunteer's right foot were obtained, The 3D structures of 28 bones and surrounding soft tissues of the foot and ankle were reconstructed with Mimics software. After processed by SolidWorks, the Workebench modules of Ansys were imported to establish a meshed accurate geometrical model of the foot and ankle. The articular cartilages, ligaments, plantar fascias, crural interosseous membranes were also simulated in the model according to anatomic and literature data. The normal standing status of the ankle joint was simulated for loading analysis using appropriate boundary conditions. Results The 3D FE model of normal human right foot complex, including bones and surrounding soft tissues, represented the basic anatomic structures and mechanical properties of the human foot and ankle. When a vertical load of 600 N was added on the upper section of the lower tibia at the simulated standing status of the ankle, the stresses on the ankle joint articular surface of the tibia was mainly distributed at the central and anterolateral aspects, with the maximum stress of 3.97 MPa, average contact stress of 1.52 MPa and contact area of 343.6 mm~2. Conclusion The 3D FE foot and ankle model can be constructed and reliably used in the study of foot and ankle injuries. Key words: Foot; Ankle; Finite element analysis; Biomechanics; Digital technology

The impact of intraoperative ultrasonography on the surgical treatment of patients with colorectal liver metastases

IntroductionIntraoperative ultrasonography (IOUS) has been the standard in surgical decision making in oncologic liver surgery. Preoperative imaging techniques have improved substantially in resent years; therefore, the importance of IOUS might change. The current results of IOUS were compared with preoperative high-resolution helical CT scanning and the impact of IOUS on surgical decision making was evaluated.MethodsA total of 100 consecutive patients who underwent open surgery for colorectal liver metastases within 4 weeks after preoperative imaging, performed with high-speed helical CT scanners, were included for this study. During surgery, IOUS was performed by a liver specialized radiologist. The findings on preoperative and intraoperative imaging and surgical exploration were compared regarding number, site, and size of the hepatic lesions. The preoperative surgical plan was compared with the final surgical treatment.ResultsOne hundred patients with CRLM underwent 117 surgical treatments. In 38 patients IOUS differed from preoperative data. In 23 cases IOUS identified more metastatic lesions. In five patients, intraoperative findings identified smaller or less hepatic lesions. Additional information on the localization of the hepatic lesions was gathered by IOUS and changed the surgical treatment in ten cases. IOUS alone altered the surgical strategy 35 times during 117 procedures. In nearly all cases, discrepancy between the preoperative CT scan and IOUS resulted in a change of surgical treatment.ConclusionsDespite improvement in preoperative imaging technology, the intraoperative use of ultrasonography remains of crucial importance. The detection of preoperatively unknown lesions remains high with great consequence on surgical therapy.

A detection method for streak artifacts and radiological noise in a non-uniform region in a CT image

By using the CT images obtained by subtracting two CT images acquired under the same conditions and slice locations, we have devised a method for detecting streak artifacts in non-uniform regions and only radiological noise components in CT images. A chest phantom was scanned using 16- and 64-multidetector row helical CT scanners with various mAs values at 120 kVp. The upper lung slice image was employed as a target image for evaluating the streak artifacts and radiological noise. One hundred parallel line segments with a length of 80 pixels were placed on the subtracted CT image, and the largest CT value in each CT value profile was employed as a feature variable of the streak artifacts; these feature variables were analyzed with the extreme value theory (Gumbel distribution). To detect only the radiological noise, all CT values contained in the 100 line profile were plotted on normal probability paper and the standard deviation was estimated from the inclination of its fitted line for the CT value plots. The two detection methods devised in this study were able to evaluate the streak artifacts and radiological noise in the CT images with high accuracy.

Simultaneous Treatment of Unresectable Hepatocelluar Carcinoma and Hepatic Artery Aneurysm, Case Report

Hepatic artery aneurysm is uncommon with an estimated incidence of less than 0.25%. Because most patients are asymptomatic, the diagnosis is usually made as an incidental finding on imaging studies performed for other reasons. Because of their propensity to rupture with potential catastrophic intraperitoneal hemorrhage, early diagnosis is important. Herein, relatively asymptomatic aneurysm of the common hepatic artery mostly of atherosclerotic etiology is presented. The importance of imaging findings in the diagnosis of this condition is discussed and relevant literature is reviewed (1, 2). Hepatocellular carcinoma (HCC) ranks among the most common malignancies worldwide, and the prognosis for patients with HCC is typically poor. Chemoembolization has become the mainstay of treatment for patients with unresectable HCC. Transcatheter arterial chemoembolization is intended to deliver a highly concentrated dose of chemotherapy to tumor cells, prolong the contact time between the chemotherapeutic agents and the cancer cells, and minimize systemic toxicity. Ideally, achieving these goals will result in a tumor shrinkage, symptomatic relief, improved quality of life, and increased patient survival (3). We will present a case of male patient, 72 years old, who was referred for transcatheter arterial chemoembolization for unresectable hepatocelluar carcinoma. Helical CT scan showed right lobe mass infiltrating the peritoneum with enhancement in the early arterial phase together with hepatic artery aneurysm that was successfully treated at the same time using emulsion of N-butyl cyanoacylate and lipodol with a concentration of 1:1. Hepatic artery aneurysms are uncommon lesions that have varied clinical presentations. Early diagnosis is essential because the natural tendency of the lesion is to rupture into peritoneal cavity or surrounding organs. Chemoembolization has become the mainstay of treatment for patients with unresectable HCC. Our case is notable, because atherosclerotic aneurysms of the hepatic artery are extremely rare with very few cases reported so far and to diagnose a hepatic artery aneurysm and to treat it in one setting with chemoembolization of unresectable HCC without rupture of the aneurysm is also unusual.

Index of Suspicion

Index of Suspicion

Unenhanced helical CT following excretory urography in the diagnosis of upper urinary tract disease: a little more cost, a lot more value

The objective of the study is to evaluate unenhanced CT following intravenous urography (IVU) for the detection of upper urinary tract (UUT) abnormalities, when IVU fails to provide the qualitative diagnosis. Helical CT scan was performed on patients with suspected disorders of UUT, after the completion of IVU for further diagnoses. In total, 124 cases of definite diagnosis and 71 cases of uncertain diagnosis via IVU were collected from 195 patients with suspected UUT disorders. Among the 71 uncertain cases, 65 patients were consent to undergo immediate or delayed CT scan. CT data were transferred to the workstation for postprocessing. Of all the 65 cases, the major CT diagnoses were the following: stone disease (n = 41), urinary tract infections (n = 4), UUT tumors (n = 7), neighboring invasion or metastasis (n = 2), congenital anomalies (n = 2), and compressed stenosis (n = 6). Among all the results, 62 cases were confirmed by surgery, pathology or clinical follow-up, while three cases (4.6%) left were still uncertain. The diagnose accordance rate of IVU + CT achieved to 95.4%. There was significant difference between IVU and IVU + CT in the determinate diagnosis of UUT diseases (chi (2) = 30.4, P < 0.05). In conclusion, IVU + CT provides more valuable information for the localization and qualitative diagnosis of UUT abnormalities. It is recommended as a cost-effective and time-saving complemental means for IVU.

Reducing radiation dose to selected organs by selecting the tube start angle in MDCT helical scans: A Monte Carlo based study

Previous work has demonstrated that there are significant dose variations with a sinusoidal pattern on the peripheral of a CTDI 32 cm phantom or on the surface of an anthropomorphic phantom when helical CT scanning is performed, resulting in the creation of "hot" spots or "cold" spots. The purpose of this work was to perform preliminary investigations into the feasibility of exploiting these variations to reduce dose to selected radiosensitive organs solely by varying the tube start angle in CT scans. Radiation dose to several radiosensitive organs (including breasts, thyroid, uterus, gonads, and eye lenses) resulting from MDCT scans were estimated using Monte Carlo simulation methods on voxelized patient models, including GSF's Baby, Child, and Irene. Dose to fetus was also estimated using four pregnant female models based on CT images of the pregnant patients. Whole-body scans were simulated using 120 kVp, 300 mAs, both 28.8 and 40 mm nominal collimations, and pitch values of 1.5, 1.0, and 0.75 under a wide range of start angles (0 degree-340 degrees in 20 degrees increments). The relationship between tube start angle and organ dose was examined for each organ, and the potential dose reduction was calculated. Some organs exhibit a strong dose variation, depending on the tube start angle. For small peripheral organs (e.g., the eye lenses of the Baby phantom at pitch 1.5 with 40 mm collimation), the minimum dose can be 41% lower than the maximum dose, depending on the tube start angle. In general, larger dose reductions occur for smaller peripheral organs in smaller patients when wider collimation is used. Pitch 1.5 and pitch 0.75 have different mechanisms of dose reduction. For pitch 1.5 scans, the dose is usually lowest when the tube start angle is such that the x-ray tube is posterior to the patient when it passes the longitudinal location of the organ. For pitch 0.75 scans, the dose is lowest when the tube start angle is such that the x-ray tube is anterior to the patient when it passes the longitudinal location of the organ. Helical MDCT scanning at pitch 1.5 and pitch 0.75 results in "cold spots" and "hot spots" that are created both at surface and in-depth locations within patients. For organs that have a relatively small longitudinal extent, dose can vary considerably with different start angles. While current MDCT systems do not provide the user with the ability to control the tube start angle, these results indicate that in these specific situations (pitch 1.5 or pitch 0.75, small organs and especially small patients), there could be significant dose savings to organs if that functionality would be provided.

Venous Thromboembolism in the Elderly: Epidemiological Data Overview Based On the 2149-Patients Prospective OPTIMEV Cohort.

Abstract 5063VTE is a multifactorial disease, but one of the strongest risk factor is age. Despite this high incidence, there is surprisingly little known about VTE in this population. So, based on the large OPTIMEV cohort study on VTE, the aim of this study was to focus on epidemiological information regarding VTE among old population.OPTIMEV was a multicentre prospective cohort study of patients referred for clinically suspected VTE throughout France. VTE presentations were categorized using objective tests including ultrasonography, lung scan and helical CT scan. Subjects without a confirmed diagnosis of VTE were used as controls.A total of 8256 patients were included in the OPTIMEV study, among which the aged study population (> 75y) was 2149. The median age of the old group was 81 years (76 - 101 years). Among this cohort, a total of 655 patients (30.5%) were positive cases of VTE, including 203 isolated distal DVT (31%), and 452 (69%) proximal DVT +/- PE. Diagnosis of VTE was ruled out in 1494 patients (69.5%). To identify potential specific risk factors in older patients, we compared VTE positive aged patients to younger. For this purpose, we tested by logistic regression the interaction between age (more or less than 75) and risk factors. Personal or familial history of VTE, travel, cardiac or respiratory insufficiency were not specific of the difference in incidence of VTE in older compared to younger patients. Only male gender (OR 1.4, 95% CI 1.1 – 1.9), bed rest (OR 1.4, 95% CI 1.1 – 1.9), lower limb immobilization (OR 1.1, 95% CI 0.5 – 2.5 and surgery <45d (OR 1.2, 95% CI 0.9 – 1.7) were found to be significantly different risk factors for VTE according to age.Our epidemiological data, based on a large cohort, showed few really specific risk factors in this old population, compared to younger. DisclosuresNo relevant conflicts of interest to declare.

Quantitative evaluation of cone-beam computed tomography in target volume definition for offline image-guided radiation therapy of prostate cancer

Purpose To quantitatively evaluate cone-beam CT (CBCT) in target volume definition in an offline image guidance environment. Methods and materials Fifteen patients each with five helical CTs (HCT) and eight CBCTs were included. A single physician manually delineated prostate and seminal vesicles (SVs) on each CT. The clinical target volume (CTV) was prostate for low risk group (G1), plus SVs for intermediate risk group (G2). The internal target volumes (ITVs) on CBCT (ITV CBCT) were constructed and compared with ITV HCT. The following comparisons were performed: CTV and ITV in HCT and CBCT; similarity of ITVs using overlap index (OI); surface differences between ITVs; quality assurance of ITV CBCT using CTV from weekly CBCT; and dosimetric evaluations of ITV HCT coverage on plans from ITV CBCT. Results There was no statistical significant difference of CTV or ITV. The ITV OIs were 91%/88% for G1/G2 patients. They improved significantly with 1–2 mm margins. Therefore, the ITVs were mostly within 2 mm. The CTVs from weekly CBCT had >95% overlap with ITV CBCT. The ITV dose differences ( D 95, and D mean) were <0.3%. Conclusions It is feasible to use CBCT for target definition in offline image guidance, thereby eliminating the separate helical CT scan process.

Reduced intercarotid artery distance in acromegaly: pathophysiologic considerations and implications for transsphenoidal surgery

Background The objective of this study is to evaluate the significance of reduced intercarotid artery distance in the C5 segment in acromegalic patients and the implications for transsphenoidal surgery. Methods The skull base with the carotid canal was examined with a helical CT scan in 45 patients with acromegaly and 45 age group–matched controls. The distances between the inner walls (IWs) of the carotid sulcus (CS), the outer walls (OWs) of the CS, and the diameter of the ICA at the C5 segment were assessed. Preoperative IGF-1 and growth hormone levels and concomitant diseases were evaluated and correlated with the biometric findings. Statistical analysis was performed with JMP (JMP version 7.0.2, SAS, Cary, USA). Results The mean distance between the IW was 1.64 ± 0.40 cm in the acromegalic patients and 1.90 ± 0.26 cm in the control group ( P = .0005). The distance between the OW measured 3.01 ± 0.39 and 2.97 ± 0.33 cm in the acromegalics and in the control group, respectively ( P = .6230). The difference in the diameter of the ICA was statistically significant ( P < .0001) between patients and control group. Within the patient group, the distance between the IW of both ICA was significantly smaller in the subgroup with arterial hypertension ( P = .0256). Conclusion Narrowing of the inner borders of the CS between the right and left side is a statistically significant parameter in acromegaly. Attention should be given to an altered vascular course of the ICAs when planning and performing transsphenoidal microsurgery in acromegalic patients. A preoperative skull base CT may furnish important anatomical information and further reduce the risk of vascular injury.

Critical Evaluation of Pulmonary Contusion in the Early Post-Traumatic Period: Risk of Assisted Ventilation

This study attempts to accurately quantify pulmonary contusion and predict those patients most likely to require assisted ventilation early in their hospital course. Patients admitted to a Level I trauma center were evaluated for pulmonary contusion by helical CT scan. Scans were reviewed by a single radiologist who attempted to accurately quantify contusion as a percentage of total lung volume. These patients were then followed for 48 hours in an attempt to use CT measurements of contusion to predict those that would require assisted ventilation early in their hospital course. After using numerous exclusion criteria, 152 patients were included in the study. Of these, 31 patients (20%) required assisted ventilation within 48 hours of hospital admission. Twenty per cent pulmonary contusion proved to be a highly predictive variable leading to need for assisted ventilation. Of patients sustaining <20 per cent contusion, only 7 of 92 (8%) required assisted ventilation versus 24 of 60 (40%) sustaining >20 per cent contusion. Pulmonary contusion is a significant injury especially when contusion volume exceeds 20 per cent of total lung volume. With accurate measurement of contusion, we can identify those patients at high risk of requiring assisted ventilation early in their hospital course.

Is radiography justified for the evaluation of patients presenting with cervical spine trauma?

Conventional radiography has been for decades the standard method of evaluation for cervical spine trauma patients. However, currently available helical multidetector CT scanners allow multiplanar reconstruction of images, leading to increased diagnostic accuracy. The purpose of this study was to determine the relative benefit/risk ratio between cervical spine CT and cervical spine radiography and between cervical spine CT and cervical spine radiography, followed by CT as an adjunct for positive findings. A decision analysis model for the determination of the optimum imaging technique was developed. The sensitivity and specificity of CT and radiography were obtained by dedicated meta-analysis. Lifetime attributable risk of mortal cancer from CT and radiography was calculated using updated organ-specific risk coefficients and organ-absorbed doses. Patient organ doses from radiography were calculated using Monte Carlo techniques, simulated exposures performed on an anthropomorphic phantom, and thermoluminescence dosimetry. A prospective patient study was performed regarding helical CT scans of the cervical spine. Patient doses were calculated based on the dose-length-product values and Monte Carlo-based CT dosimetry software program. Three groups of patient risk for cervical spine fracture were incorporated in the decision model on the basis of hypothetical trauma mechanism and clinical findings. Radiation effects were assessed separately for males and females for four age groups (20, 40, 60, and 80 yr old). Effective dose from radiography amounts to 0.050 mSv and from a typical CT scan to 3.8 mSv. The use of CT in a hypothetical cohort of 106 patients prevents approximately 130 incidents of paralysis in the low risk group (a priori fracture probability of 0.5%), 500 in the moderate risk group (a priori fracture probability of 2%), and 5100 in the high risk group (a priori fracture probability of 20%). The expense of this CT-based prevention is 15-32 additional radiogenic lethal cancer incidents. According to the decision model calculations, the use of CT is more favorable over the use of radiography alone or radiography with CT by a factor of 13, for low risk 20 yr old patients, to a factor of 23, for high risk patients younger than 80 yr old. The radiography/CT imaging strategy slightly outperforms plain radiography for high and moderate risk patients. Regardless of the patient age, sex, and fracture risk, the higher diagnostic accuracy obtained by the CT examination counterbalances the increase in dose compared to plain radiography or radiography followed by CT only for positive radiographs and renders CT utilization justified and the radiographic screening redundant.

Estimation of urinary stone composition by automated processing of CT images

The objective of this article was developing an automated tool for routine clinical practice to estimate urinary stone composition from CT images based on the density of all constituent voxels. A total of 118 stones for which the composition had been determined by infrared spectroscopy were placed in a helical CT scanner. A standard acquisition, low-dose and high-dose acquisitions were performed. All voxels constituting each stone were automatically selected. A dissimilarity index evaluating variations of density around each voxel was created in order to minimize partial volume effects: stone composition was established on the basis of voxel density of homogeneous zones. Stone composition was determined in 52% of cases. Sensitivities for each compound were: uric acid: 65%, struvite: 19%, cystine: 78%, carbapatite: 33.5%, calcium oxalate dihydrate: 57%, calcium oxalate monohydrate: 66.5%, brushite: 75%. Low-dose acquisition did not lower the performances (P < 0.05). This entirely automated approach eliminates manual intervention on the images by the radiologist while providing identical performances including for low-dose protocols.

Quality Improvement Guidelines for the Treatment of Lower Extremity Deep Vein Thrombosis with Use of Endovascular Thrombus Removal

Suresh Vedantham, MD, Akhilesh K. Sista, MD, Seth J. Klein, MD, Lina Nayak, MD, Mahmood K. Razavi, MD, Sanjeeva P. Kalva, MD, Wael E. Saad, MD, Sean R. Dariushnia, MD, Drew M. Caplin, MD, Christine P. Chao, MD, Suvranu Ganguli, MD, T. Gregory Walker, MD, and Boris Nikolic, MD, MBA, for the Society of Interventional Radiology and Cardiovascular and Interventional Radiological Society of Europe Standards of Practice Committees

Osteoid osteoma of the odontoid process of the axis associated with atlanto-axial fusion

Osteoid osteoma is a primary benign bone tumour with characteristic imaging and pathological features. In about 10% of the cases it involves the spine, especially the posterior elements. We report a pathologically proven case of osteoid osteoma of the odontoid process of the second cervical vertebra associated with atlanto-axial fusion. The case was diagnosed pre-operatively using plain radiography, multiplanar helical CT, contrast-enhanced MRI and radioisotope bone scanning.

TH-C-303A-04: Evaluation of 3D Surface Camera System in Patient Setup for HN RT

Purpose: To evaluate the usefulness of a 3D surface camera system (AlignRT) in detecting rigid and non‐rigid setup errors during head and neck radiotherapy.Methods and Materials: To evaluate the accuracy of AlignRT's surface registration algorithm, both translational and rotational movements of a known magnitude were manually applied in Pinnacle to transform a helical CT scan. The skin contours of both the primary helical CT scan and the transformed helical CT scan were transferred to AlignRT, where the transformed surface was registered to the primary surface. The changes that were reported by the AlignRT system were compared to the manually applied motions from Pinnacle. To evaluate the usefulness of AlignRT for rigid and non‐rigid patient setup, a retrospective analysis was performed on the helical CT scans of eleven patients. The registrations in Pinnacle based on bony (either skull (rigid) or vertebrae (non‐rigid)) anatomy were compared to the surface (either head (rigid) or shoulder (non‐rigid)) registrations in AlignRT. Results: The accuracy of AlignRT's surface registration algorithm was, on average, 0.041 ± 0.036 degrees and 0.075 ± 0.100 mm. The accuracy of the optical system was, on average, 0.087 ± 0.912 degrees and −0.153 ± 1.996 mm. For shoulder (non‐rigid) guidance, if we use 2*standard deviation for 95% confidence level, the accuracy of the optical system was within 3 degrees for rotations in the vertical and longitudinal directions, but 5 degrees for the lateral direction. For translations, the accuracy was more than 10 mm. Conclusion: While the feasibility of using the AlignRT system for head (rigid) guidance in the setup of HN patients was demonstrated, the use of the system in non‐rigid patient setup yielded undesirable results.

TU‐C‐304A‐06: Reducing Dose to a Small Organ by Varying the Tube Start Angle in a Helical CT Scan

Purpose: Previous work demonstrated that there are significant dose variations on the peripheral, or surface of either a CTDI 32cm phantom or an anthropomorphic phantom when helical CT scanning is performed. The purpose of this work is to investigate the effectiveness of exploiting these variations to reduce dose to targeted radiosensitive organs solely by varying the tube start angle in CT scans. Method and Materials: Radiation dose to several radiosensitive organs (including breasts, thyroid, uterus, gonads, lens of eyes) from a MDCT CT scanner were estimated using Monte Carlo simulation methods on GSF Baby phantom. Whole body scans were simulated using 120kVp, 300mAs, 28.8 mm nominal collimation, pitch 1.5 under a wide range of start angles (0 to 340 degrees in 20 degree increments). The relationship between tube start angle and organ dose was examined for each organ and the potential dose reduction was calculated. Results: The organ dose shows obvious variation depending on the tube start angle. For small peripheral organs, (e.g. the lens of eyes), the minimum dose can be 35% lower than the maximum dose, depending on tube start angle. For pitch 1.5 scans, the dose is usually lowest when the tube start angle is such that the x‐ray tube is posterior to the patient when it passes the longitudinal location of the organ. Conclusion: Helical MDCT scanning results in “cold spots” and “hot spots” that are created both at surface and even in‐depth locations within patients. If organs have a relatively small longitudinal extent, their dose may be reduced by selecting the tube start angle such that the location of these “cold spots” may be manipulated by appropriately selecting the tube start angle. This dose reduction should not have any implications for image quality as there is no change in mAs or total mAs.

Artifacts in spiral CT protocols: The importance of the spatial reconstruction

Purpose This study recorded and analysed streak and motion artifacts in spiral CT examinations and evaluated the elimination and minimization of them by the use of segmental reconstruction with and without alterations of the initial examination protocol. Materials and methods One hundred CT scans of the chest and 300 CT scans of the brain have been included in this study. All studies were performed by a helical CT scanner (Philips 5000 SR) with the standard protocol and were randomly selected due to the presence of either streak or motion artifacts. Segmental reconstruction was applied in all cases by the same experienced radiographer. Image evaluation was performed by two experienced radiologists using a scoring system for each artifact and a grading system for classifying post-processing images. Results Among series of images that were evaluated after the application of segmental reconstruction, brain examinations demonstrated the following results: 10.9% of the cases showed no artifact improvement, 19.6% showed slight artifact improvement 31.5% showed moderate improvement and 38% showed significant improvement. The results of chest examinations were as follows: 27% of the cases showed no artifact improvement, 23% showed slight artifact improvement, 26% showed moderate improvement and 24% of showed significant improvement. Spatial reconstruction was useless in brain CT images when a patient moved during the entire scan and in chest CT images when streak and motion artifacts co-existed. Conclusions Spatial reconstruction may improve the image quality in brain and chest CT examinations and thus may contribute to more diagnostic images. Elimination of motion artifacts is also suggested due to the limitation of intravenous contrast medium that can be administered per patient per day and in cases of non-cooperative patients.

SU‐FF‐I‐45: An Automatic Method for Reduction of Metal Artifacts Caused by Metallic Implants

Purpose: To develop an automatic method for metal artifact reduction (MAR) from small objects such as brachytherapy (BT) seeds. Method and Materials: A phantom made of agar (water‐like) and consisting of 6 slices of 5 mm in which 75 seeds (activity at background level) were implanted for imaging purposes. The phantom was scanned on a helical CT scanner (Siemens Somatom) to produce continuous 1 mm and 3 mm slices of the full phantom. The proposed method is based on the interpolation of missing projections by directly using raw CT data (sinogram). First, an initial image was reconstructed from the raw projection data. Then, the metal objects segmented from the reconstructed image were re‐projected into the same sinogram. The Steger method was used to precisely determine the position and edges of the seed traces in raw CT data. By combining the use of Steger detection and re‐projections, the missing projections were finally detected and further replaced by interpolation of non‐missing neighbouring projections. Results: In both phantom experiment and patient studies, the missing projections have been well detected and the artifacts caused by metallic objects in the image reconstructed using the corrected sinogram have been significantly reduced. The performance of the algorithm has been also proven after a quantitative evaluation by comparing the intensity uniformity between the uncorrected and corrected phantom images. Conclusion: An efficient algorithm for MAR in seed brachytherapy was developed. The challenge of detecting and correcting artifacts from 60 to 120 tiny objects in sinogram space has been successfully demonstrated. The detected traces can be further processed to extract, from a large sample of points, the position and orientation of each seed with high precision. This should enable a more accurate use of advance brachytherapy dose calculations, such as Monte Carlo simulations.

Sentinel and axillary nodes of the breast distinguished from those of the arm by 3D-CT lymphography and selectively dissected by endoscopic surgery

616 Background: In early breast cancer, the presence of metastasis in axillary lymph nodes (AN) is an important factor in prognosis and further treatment. However, AN dissection causes many complications such as contracture of shoulder joint, lymph edema, and paralysis of upper extremities. Sentinel node (SN) biopsy provides us valuable information about no need to dissect AN for node-negative patients. However, on node-positive patients, the conventional AN dissection has been performed. 3D-CT lymphography (LG) can show the precise individual lymphatic flow not only from the breast tumor to SN but also from SN to venous angle, which means breast lymphatic channel. We applied 3D-CT LG to distinguish them from the arm channel to avoid any arm complications. Methods: 3D-CT LG was performed on the day before surgery to mark SN on the skin. Above the tumor and near the areola and the arm pit, 2 ml of Iopamidol 300 was injected subcutaneously. Images of 16-channel multidetector-row helical CT scan were taken at 1, 3, and 5 min after injection. They were reconstructed to produce a 3D image of lymph ducts and lymph nodes. SN biopsy and AN sampling were performed by dye-staining method using endoscopy. Results:We performed SN biopsy with 3D-CT LG on 160 patients. 3D-CT LG clearly showed the precise lymphatic flow from the tumor to SN. It can show SN at only one min after injection. But following up to 5 min, we can follow the lymph ducts beyond SN into the second to the fifth node groups toward the venous angle with complex plexus, observed in the surrounding anatomical architecture. Detection rate was 100% for SN; 80% for the third group; and 30% for the fifth group. The arm lymph flow was distinguished by the connections between the breast and the arm flow, observed 39% and 71% in the fourth and the fifth group. SN was shared from between the breast and the arm in 5 patients (3.1%). They complained arm edema only by SN biopsy. We can distinguish and sample AN drained from the breast, guided by 3D-CT LG and dye-staining using endoscopy. Conclusions:By 3D-CT LG, we can recognize the accurate and more precise lymph flow in the surrounding anatomical architecture. It helps us easily to pursuit lymph flow and to remove SN and AN from the breast selectively using endoscopic surgery. No significant financial relationships to disclose.