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PubMed2006

Integrated PET/CT: current applications and future directions.

For the past 5 years, combined positron emission tomography (PET) and computed tomography (CT), or PET/CT, has grown because the PET portion provides information that is very different from that obtainable with other imaging modalities. However, the paucity of anatomic landmarks on PET images makes a consistent "hardware fusion" to anatomic cross-sectional data extremely useful. Clinical experience indicates a single direction: Addition of CT to PET improves specificity foremost, but also sensitivity, and the addition of PET to CT adds sensitivity and specificity in tumor imaging. Thus, PET/CT is a more accurate test than either of its individual components and is probably also better than side-by-side viewing of images from both modalities. The synergistic advantage of adding CT is that the attenuation correction needed for PET can also be derived from the CT data, an advantage not obtainable by integrating PET and magnetic resonance imaging. This makes PET/CT 25%-30% faster than PET alone with standard attenuation-correction methods, leading to higher patient throughput and a more comfortable examination, which typically last 30 minutes or less. Fluorodeoxyglucose (FDG) PET/CT appears to provide relevant information in the staging and therapy monitoring of many tumors, including lung carcinoma, mesothelioma, colorectal cancer, lymphoma, melanoma, and many others, with the notable exception of prostatic cancer. For prostatic cancer, choline derivatives may become useful radiopharmaceuticals. The published literature on the applications of FDG PET/CT in oncology is still limited, but several well-designed studies have demonstrated the benefits of PET/CT.

Forecasting↗
PubMed2006

Role of PET/PET-CT in the management of sarcomas.

Positron emission tomography (PET) is a functional diagnostic imaging technique that provides very different information from that obtainable with other imaging modalities. The most widely used radiotracer is F-18 fluoro-2-deoxy-D-glucose (FDG), which is an analog of glucose. The FDG uptake in cells is directly proportional to glucose metabolism, which is increased many times in malignant cells. FDG-PET is now the standard of care in initial staging, monitoring the response to therapy and management of various cancers (e.g., breast cancer, lung cancer and lymphoma). However, the paucity of anatomical landmarks on PET images makes a consistent hardware fusion to anatomical cross-sectional data extremely useful. The introduction of combined PET-computer tomography (CT) scanners, which provide not only functional, but also structural information leading to a detection of subcentimeter lesions, made this technique useful in the early detection of the disease process and decreasing false-positive lesions. The aim of this article is to review the clinical applications (i.e., diagnosis, staging, evaluation of treatment response and restaging) using PET in patients with bone and soft-tissue sarcoma.

Fibrosarcoma↗
PubMed2006

Computer-assisted, fluoroscopy-based ventral spondylodesis of thoracolumbar fractures.

OBJECTIVE: To design and evaluate a novel computer-assisted, fluoroscopy-based planning and navigation system for minimally invasive ventral spondylodesis of thoracolumbar fractures. MATERIALS AND METHODS: Instruments and an image intensifier are tracked with the SurgiGATE navigation system (Praxim-Medivision). Two fluoroscopic images, one acquired from anterior-posterior (AP) direction and the other from lateral-medial (LM) direction, are used for the complete procedure of planning and navigation. Both of them are calibrated with a custom-made software to recover their projection geometry and to co-register them to a common patient reference coordinate system, which is established by attaching an opto-electronically trackable dynamic reference base (DRB) on the operated vertebra. A bi-planar landmark reconstruction method is used to acquire deep-seated anatomical landmarks such that an intraoperative planning of graft bed can be interactively done. Finally, surgical actions such as the placement of the stabilization devices and the formation of the graft bed using a custom-made chisel are visualized to the surgeon by superimposing virtual instrument representations onto the acquired images. The distance between the instrument tip and each wall of the planned graft bed are calculated on the fly and presented to the surgeon so that the surgeon could formalize the graft bed exactly according to his/her plan. RESULTS: Laboratory studies on phantom and on 27 plastic vertebras demonstrate the high precision of the proposed navigation system. Compared with CT-based measurement, a mean error of 1.0 mm with a standard deviation of 0.1 mm was found. CONCLUSIONS: The proposed computer assisted, fluoroscopy-based planning and navigation system promises to increase the accuracy and reliability of minimally invasive ventral spondylodesis of thoracolumbar fractures.

Algorithms↗
PubMed1999

Endoscopy of the middle ear through the eustachian tube: anatomic possibilities and limitations.

HYPOTHESIS: This anatomic study was designed to provide otosurgeons with a detailed description of the technique of transtubal middle ear endoscopy and anatomic landmarks facilitating orientation. To establish the role of transtubal endoscopy, its anatomical potentials and limitations were studied. BACKGROUND: Transtubal endoscopy has recently been described as an atraumatic tool for exploring the tympanic cavity. From the nasopharynx, a thin, flexible endoscope is advanced into the middle ear through the Eustachian tube. After the endoscope has been placed, it offers an anteroposterior view of the tympanic structures. METHODS: Temporal bone blocks and whole skulls of recently deceased persons were examined to define the average range of view obtained by transtubal endoscopy. Key structures in each region of the tympanic cavity were chosen for inspection, and positive identifications were noted. RESULTS: With a 0.8-mm, flexible, steerable scope, most mesotympanic structures (stapes suprastructure, incudostapedial joint, tympanic chord, and inner surface of the eardrum) were clearly defined. Areas of the posterior wall that were not accessible with the otomicroscope (lateral tympanic sinus, tympanic sinus, and facial recess) were also seen. Unlike with transtympanic endoscopy, the epitympanum (incudomalleal joint and malleus neck) was also evaluable. The stapes footplate was not seen well and the round window niche was unable to be inspected in the anteroposterior view inherent in the technique. Technical factors (poor illumination and small image size) and the unfamiliar anteroposterior view made orientation in the middle ear difficult. CONCLUSION: Transtubal middle ear endoscopy is a suitable method for exploring the tympanic cavity without traumatizing the eardrum.

Ear, Middle↗
PubMed2000

Evaluation of octree regional spatial normalization method for regional anatomical matching.

The goal of regional spatial normalization is to remove anatomical differences between individual three-dimensional (3D) brain images by warping them to match features of a standard brain atlas. Processing to fit features at the limiting resolution of a 3D MR image volume is computationally intensive, limiting the broad use of full-resolution regional spatial normalization. In Kochunov et al. (1999: Neuro-Image 10:724-737), we proposed a regional spatial normalization algorithm called octree spatial normalization (OSN) that reduces processing time to minutes while targeting the accuracy of previous methods. In the current study, modifications of the OSN algorithm for use in human brain images are described and tested. An automated brain tissue segmentation procedure was adopted to create anatomical templates to drive feature matching in white matter, gray matter, and cerebral-spinal fluid. Three similarity measurement functions (fast-cross correlation (CC), sum-square error, and centroid) were evaluated in a group of six subjects. A combination of fast-CC and centroid was found to provide the best feature matching and speed. Multiple iterations and multiple applications of the OSN algorithm were evaluated to improve fit quality. Two applications of the OSN algorithm with two iterations per application were found to significantly reduce volumetric mismatch (up to six times for lateral ventricle) while keeping processing time under 30 min. The refined version of OSN was tested with anatomical landmarks from several major sulci in a group of nine subjects. Anatomical variability was appreciably reduced for every sulcus investigated, and mean sulcal tracings accurately followed sulcal tracings in the target brain.

Algorithms↗
PubMed1996

Use of a caudal auricular axial pattern flap in cats.

A caudal auricular axial pattern flap was used in 3 cats to successfully reconstruct large cutaneous defects of the head that were a result of trauma or surgical excision of neoplasms. The technique was a convenient, practical, one-stage procedure for closure of the defects, and flaps up to 7.0 x 12.0 cm were developed. All flaps healed without complications. Anatomic landmarks and surgical guidelines for developing the flap were determined through anatomic dissections and angiographic studies of the cutaneous vasculature of the head and neck in feline cadavers. This report confirms findings of a previous study describing a platysma myocutaneous flap.

Animals↗
PubMed2000

Anatomical variations of landmarks for implantation at the cochlear nucleus.

A knowledge of the microanatomy of the cochlear nucleus complex and its variations is essential for successful implantation and for the design of stimulation devices. One hundred cerebellopontine angle specimens were dissected under surgical conditions using the Zeiss NC31 surgical microscope. The topographical anatomy of the exit of the vestibulocochlear nerve, the cochlear nucleus and the surface of the medulla and their relation to the surrounding structures was recorded and measured. The mean distances between the exits of the VIIth and VIIIth cranial nerves were 4.7 +/- 0.9 mm, between the VIIth and IXth 6.3 +/- 1.2 mm and between the VIIIth and IXth 5.5 +/- 1.0 mm. The visible area of the cochlear nucleus covered a square of 10.0 +/- 2.9 by 3.3 +/- 1.0 mm. A major AICA-loop had to be re-routed in 17 per cent of specimens. The taenia of the choroid plexus was present in 92 per cent and had to be cut in 51 per cent in order to enter the foramen of Luschka, that had a mean size of 3.5 by 2.0 mm. It was wide open in 24 per cent, open only after incision of the arachnoid in 53 per cent, functionally closed but opened by extensive dissection in 18 per cent and anatomically occluded in five per cent of the specimens. The typical straight vein at the cochlear nucleus leading to the entrance of the foramen of Luschka was found in 76 per cent of specimens. Constant anatomical landmarks are very helpful for finding the cochlear nucleus, but variations may endanger dissection and implantation in a remarkable number of cases.

Brain Stem↗
PubMed2000

Use of internal fiducial markers in frameless stereotactic navigational systems during spinal surgery: technical note.

OBJECTIVE: The use of frameless stereotaxy has expanded the spine surgeon's ability to perform surgical procedures with instrumentation in areas of narrow anatomic tolerance. In many circumstances, however, it is difficult to register the frameless stereotactic probe using known anatomic landmarks. This occurs typically because landmarks are indistinct, and congenital or surgical defects limit the availability of anatomic fiducials. We propose an accurate and efficient method for registering the frameless stereotactic probe for spinal surgery when a staged procedure is planned. METHODS: During the first stage of a planned two-stage procedure, a minimum of four cranial fiducial screws are implanted in the posterior element of each vertebra in which stereotactic registration is desired. Stage 1 is completed, and all suture closure is performed. A computed tomographic scan formatted for the frameless stereotactic unit is obtained postoperatively. In the second stage of surgery, registration is performed using cranial screws as internal fiducial markers. RESULTS: Registration is performed easily and quickly using cranial screws as internal fiducial markers. No more than four registration points are necessary to calibrate the system to accuracy within 1.5 mm. CONCLUSION: Implantation of fiducial markers during Stage 1 of a complex staged spinal surgery renders the frameless stereotactic navigational system registration extremely fast and accurate. We advocate the technique to enhance the use of frameless navigational systems for reliable and quick registration of the spine.

Bone Screws↗
PubMed1996

The clinical anatomy of laparoscopic inguinal hernia repair.

Laparoscopic approaches for abdominal surgery are being used with increasing frequency. Their advantages are sometimes negated by the disturbing incidence of postoperative sequelae. In the case of inguinal hernia repair, these are often the result of failing to understand that the anatomy of the anterior approach to the abdominal wall cannot necessarily be directly applied to laparoscopy. The inguinal ligament, easily identified in an anterior approach, is only seen laparoscopically after removal of the iliopubic tract, a key structure which lies in the plane of the original defect of most groin hernias. Thus, an understanding of the incompletely trilaminar anterior abdominal wall, including the iliopubic tract, is the foundation for effective inguinal hernia repair using any approach (anterior or posterior) or technique (sutures, mesh or staples). Laparoscopic inguinal hernia repair has produced an increase in the frequency of debilitating neuropathies, most notably of the lateral femoral cutaneous nerve (LFCN). This is directly related to the variable intrapelvic course of this nerve or its branches. In more than 13% of the 114 pelves we examined, the LFCN was within 0.5 cm of the iliopubic tract or in the vertical plane of the anterior superior iliac spine, key lateral landmarks and anchoring sites for mesh in laparoscopic hernia repairs. Medial landmarks also have variable features. These data indicate that the identity of anatomical landmarks and the variability of other structures will continue to be important in the successful development of new laparoscopic techniques.

Abdominal Muscles↗
PubMed2002

Fluoroscopic cardiac anatomy for catheter ablation of tachycardia.

The understanding of cardiac anatomy is crucial for the interventional arrhythmologist. In spite of the introduction of several nonfluroscopic navigational tools, some of them capable of reconstructing a computer-based surrogate of the endocardial surface of the heart cavities, simple fluoroscopy with or without the aid of angiographic techniques is still the most widely used method to guide mapping and ablation procedures. In some instances, fluoroscopic and angiographic methods have no possible replacement to unravel certain arrhythmologically useful anatomic landmarks. New interpretations of cardiac architecture show the need to challenge some traditional anatomic views, like the concept of septums within the heart. The fluoroscopic anatomy also needs to be reconsidered in the light of the new attitudinally oriented nomenclature. This article presents an overview of the fluoroscopic anatomy of the heart. When pertinent, some anatomical concepts are discussed in more detail like the triangle of Koch, the pyramidal space, and the interatrial groove. In the sections on the atria and on the ventricles, the authors focus on the anatomic information that is relevant for mapping and ablation from a fluoroscopic viewpoint, providing some hints on how best to depict the morphological features from the stance of the interventional arrhythmologist. The Visible Human Slice and Surface Server using data sets from the Visible Human Male and Female Project, has been used to facilitate the understanding of the fluoroscopic anatomy.

Catheter Ablation↗
PubMedDate not supplied

Use of computed tomography for maxillary nerve block in the treatment of trigeminal neuralgia.

BACKGROUND AND OBJECTIVES: Maxillary nerve block has traditionally been performed by using external anatomic landmarks. However, the classic approach to the nerve may be confounded because of anatomic variability. We describe a technique for the block using the suprazygomatic route guided by computed tomography (CT). CASE REPORT: A 90-year-old woman had a 30-year history of episodic pain in her right maxillary region. We attempted to block the maxillary nerve with classic technique, but we could not identify the nerve by eliciting paresthesia. In addition, bleeding was noted after repeated attempts. To minimize complications and confirm the correct position of the needle tip, we planned the block with a suprazygomatic approach using CT guidance. The needle was inserted without paresthesia. The CT scan showed the needle tip was placed at the entrance of the pterygopalatine fossa and the distribution of contrast medium spread appropriately around the pterygopalatine fossa. After confirming the clinical effect and lack of complications of the block using the local anesthetic, 0.5 mL of 7% phenol was injected. This technique resulted in complete sensory loss in the area innervated by the maxillary nerve, and did so without complications. CONCLUSIONS: A maxillary nerve block guided by a CT imaging is an alternative to classic techniques.

Aged↗
PubMed1991

Three-dimensional face shape analysis of French adults, and its application to the design of protective equipment.

The study's aim was to identify female and male face shape variability in order to establish typical profiles for the design of masks. A specific data acquisition photogrammetric station was used for this purpose. A preliminary survey using anthropometric techniques was conducted on 301 females and 208 males, randomly selected from the French military population, in order to constitute two samples of 30 males and 30 females for the stereometric survey. For each subject, the stereorestitution of face photos was made on three sets of data: (1) 37 anatomical landmarks previously identified by a black point marked on the face; (2) 7 anatomical arcs, also drawn with a black pencil; and (3) 1500-2000 points distributed on horizontal cross-sections at different vertical levels. The analysis only concerned the global face shape, and excluded the central area (eyes, nose and mouth). A common origin and reference axis system was defined. All the three-dimensional (3D) produced data was processed using computer-aided design software, after some adaptations. Subjects were selected iteratively for five levels of cross-section and three anatomical arcs so as to characterize least variation amplitudes, subject by subject. Five groups were identified. All cross-sections were verified to check the validity of the preceding step. By this method, each group was defined by a mean profile form and by the amplitude of this form for each point of the profile. Males and females were present in each group, and for each group, a greater variability was noted at the lower part of the face. This variability can be explained as the result of morphological and functional phenomena. These results can be applied to the design of new protective equipment for the fore-face indeed they were used for the design of a new mask for the French military.

Adult↗
PubMed1980

Stereotactic neurosurgery in experimental animals. Use of intracerebral landmarks and an atlas of the cat brain.

A stereotactic method, based on the correlation of intracerebral radiological and anatomical landmarks, was developed for application in experimental animals. To make possible the use of this method, particularly in the cat, a stereotactic atlas was developed with an intracerebral coordinate system, as all currently available stereotactic atlases of experimental animals are based on extracranial landmarks. Advantages of the proposed method compared to the classical Horsley-Clarke method are discussed.

Animals↗
PubMed1999

Extended transbasal approach: anatomy, technique, and indications.

Appropriate indications for the transbasal approach have not been clearly established. The focus of this study is to determine the feasibility of maximal exposure of the clivus and surrounding regions via this strategy. Further, we sought to determine the key anatomical landmarks and morphometric data necessary for safe, radical exposure. In 20 injected cadaveric specimens, anatomical observations were made grossly and microscopically with 4-40 x magnification. The three basic variations of the transbasal craniotomy were compared with regard to surgical exposure. Maximum exposure of the ventral clivus could be obtained by total ethmoidectomy and sphenoidectomy through the extensive transbasal craniotomy. The lateral limits of exposure were found to be the optic nerves, intracavernous carotid arteries, and hypoglossal canals. Inferiorly, the foramen magnum is the limit of exposure. Morphometric measurements were determined between the key landmarks and were found helpful in subsequent dissections due to the lack of bony structures in relation to neural and vascular structures within the bone. The keys to optimizing the transbasal approach are beyond the simple initial steps of the craniotomy. Maximal exposure from the suprasellar compartment to the foramen magnum is possible via the extended transbasal approach.

Journal Article↗
PubMedDate not supplied

The reliability of cecal landmarks during colonoscopy.

Confirming colonoscopic intubation of the cecum can be a laborious, time-consuming, and often frustrating endeavor. Anatomic landmarks may offer visual clues of cecal intubation, but the predictability of this evidence is unclear. The presence of three cecal landmarks, alone and in combination, were evaluated to precisely define their reliability. Between February and October of 1991, 601 of 708 (85%) consecutive colonoscopic examinations were able to be completed to the cecum as confirmed by fluoroscopy. All three cecal landmarks studied were present in 64% (386/601), two cecal landmarks in 32% (189/601), and one cecal landmark in 4% (26/601) of the patients. Therefore, at least two cecal landmarks were identified in 96% (575/601) of the patients. The ileocecal sphincter was identified in 98% (591/601) of patients overall, in 98% (185/189) of patients and 2 cecal landmarks, and in 77% (20/26) of patients with 1 cecal landmark. The appendiceal orifice was seen in 87% (524/601) of patients overall and in 72% (137/189) of patients with 2 cecal landmarks. Transillumination through the abdominal wall was possible in 74% (447/601) of patients overall and in 30% (56/189) of patients with 2 cecal landmarks. In summary, the ileocecal sphincter is the most reliable cecal landmark and is invariably visualized, even when all other landmarks are obscure. While other cecal landmarks, such as the appendiceal orifice and transillumination, are consistently identified, they are most valuable when found in association with the ileocecal sphincter.

Cecum↗
PubMed2005

[The coracoid block: demonstration of a simple approach using the pectoralis minor as landmark].

OBJECTIVE: Despite their recognized advantages, infraclavicular blocks, especially with the pericoracoid approach, are underutilized because the lack of simple anatomical landmarks. The goal of this study is to determine a simple, reliable and reproducible reference point by means of magnetic resonance imaging (MRI), using the anterior extremity of the coracoid process, and the pectoralis minor as a tactile reference point. METHOD: Sagittal and para-sagittal MRI sections at the coracoid process were performed on 11 patients. The relationships between the coracoid process, the nerve-vessel bundle, the pectoralis minor and the skin were measured. RESULTS: The optimal puncture point for a needle introduced strictly in an anterio-posterior direction in a supine, alert patient is located 2 cm within and 2.5 cm below the coracoid process. The injection point, defined as the distance between the skin and the tip of the needle lying in the centre of the visualized nerve-vessel bundle, is located an average of 5 cm from the skin (mean 5.02 cm, with a standard deviation of 1.03 and a confidence interval of 0.91). This injection point goes from 0.4 cm (at the most anterior part of the bundle) and 1.75 cm (at the most posterior part), with an average 1 cm from the posterior surface of the pectoralis minor (tactile reference point). Neither body mass index nor sex influence significantly the variables measured. CONCLUSIONS: The reference points defined here could allow easy and reproducible performance of this relatively simple block and make it more effective.

Adult↗
PubMed2002

Superficial surgical landmarks for the frontal sinus.

OBJECT: There is a lack of reports in the literature that contain descriptions of superficial anatomical landmarks for the identification of the internally located frontal sinus. Neurosurgeons must often enter the cranium through the frontal bone and knowledge of the frontal sinus is essential to minimize complications. METHODS: Seventy adult cadaveric frontal sinuses were evaluated. Measurements included both the lateral and superior extent of the frontal sinus in reference to a midpupillary line, and the superior extent of the frontal sinus from the nasion. Frontal sinuses were found bilaterally in all specimens. The mean height of the frontal sinus superior to the nasion was 2.8 cm. In 71.4% and 74.3% of specimens the lateral extent of the frontal sinus was found to be medial to the left and right midpupillary line, respectively. Distances superior to a plane drawn through the supraorbital ridges at a midpupillary line included a mean of 2.5 mm for the left side and 1.8 mm for the right side. CONCLUSIONS: Of 70 sinuses, none extended more than 5 mm lateral to a midpupillary line. At this same midpupillary line and at a plane drawn through the supraorbital ridges, the frontal sinus was never higher than 12 mm. Finally, in the midline the frontal sinus never reached more than 4 cm above the nasion. These measurements will assist surgeons who must manipulate the frontal bone.

Adult↗
PubMed2000

Observation study of electronic portal images for off-line verification.

PURPOSE: The goals of this study were to evaluate the use of electronic portal imaging device (EPID) paper images as off-line verification tools and to assess the feasibility of replacing portal films by EPID printed images. MATERIALS AND METHODS: Electronic portal images were acquired using a video-based imaging system. After contrast enhancement, these images were printed and compared to portal films when prescribed, and judged about their usefulness for off-line verification. A total of 2025 images were acquired from 322 fields on 137 patients. The images were shown to eight radiation oncologists and two senior residents in radiation oncology, each one of them judging fields relevant to his (her) daily practice. The questions asked were related to the choice of important anatomical structures and the visibility of such structures, the usefulness of the printed images, the comparison with portal films and the possible replacement of such films by paper images. RESULTS: Answers to the different questions were treated as quantitative scores. For the visibility question, means and standard deviations were calculated for each individual structure, then a global score was obtained for a given treatment site. Means and standard deviations were also computed for the comparison question. Proportions and confidence intervals were used for the other questions. The results show that EPID paper images are useful for some treatment sites such as breast, thorax, prostate, abdomen, pelvis (other than rectum) and axilla. The image quality remains insufficient for some other sites such as head and neck and spine. CONCLUSION: Although global anatomical landmarks scores are good, the usefulness score is not always as high because some essential anatomical structures scores must be taken into account. There is also a strong habit factor related to acceptance of EPID printed images as verification tools. As long as they see more and more images, radiation oncologists can more easily visualize anatomical structures and are less stringent when evaluating the efficiency of EPID paper images as off-line verification tools.

Electronics, Medical↗