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PubMed1987

Repeated measures analysis of geometrically constructed and directly determined cephalometric points.

Cephalometric landmarks were directly determined visually from bony anatomy on lateral cephalometric radiographs and compared with geometrically constructed cephalometric landmarks for repeated measures reliability of identification. Three groups of four orthodontists, grouped by level of experience, identified 18 landmarks on each of four cephalometric radiographs. This measurement procedure was repeated four times in 1-week intervals. The variability, main associations and interactions among the variables of tracer experience, quality of radiograph traced, and the anatomic landmarks traced were assessed by means of the repeated measures analysis of variance and follow-up Tukey HSD test. The coefficient of variation was used to compare the relative variability of replicate identification of the 18 cephalometric landmarks. Rank order and statistically significant groupings by variability are listed. The level of observer experience and quality of radiograph were statistically unrelated to landmark variability on replicate examination. The geometrically constructed landmarks tested were not statistically different from the reliability of the directly determined bony-based landmarks. This finding would lend support to the techniques of geometric construction used in the Ricketts cephalometric analysis.

Cephalometry↗
PubMed1986

A comparative evaluation of rare earth screen-film systems. Free-response operating characteristic analysis and anatomic criteria analysis.

Diagnostic accuracy was evaluated in a signal detection experiment that used low-contrast acute lesions in a living dog model. At the high levels of certainty normally used by radiologists, rare earth screen-film systems provided accuracy comparable to that of a reference calcium tungstate screen-film system. Additionally subjective image quality evaluation for a given imaging task (clinical pediatric anterior-posterior chest films) based on visualization of anatomic landmarks and physical parameters has been conducted for several rare earth and one calcium tungstate screen-film system. The correspondence of subjective physical ranking with physical and psychophysical measurements was investigated. Evaluating the visualization of anatomic parameters can provide a clear and objective distinction among systems with comparable physical and psychophysical properties.

Animals↗
PubMed2003

[Anatomic variants of paranasal sinuses].

During the last 15 years period, the development of functional endoscopic sinus surgery underlines the needs of a better knowledge of sinonasal anatomy and consequently, of sinonasal anatomic variations. These anatomic variations are widely spread into the population and commonly encountered in daily CT practice. The difference of anatomic landmarks during endoscopic surgery can result in bony transgression and increase the difficulties of the surgery. In fact, functional endoscopic surgery is a blind surgery leading to severe complications with medico-legal impact. Therefore, the anatomic sinonasal variations should be depicted in all sinonasal CT imaging studies irrespective of the indications. Moreover, some anatomical variants may cause certain symptoms.

Endoscopy↗
PubMed2003

[Anterior radial nerve transposition in humerus midshaft fractures: anatomic and clinical study].

PURPOSE OF THE STUDY: Plate fixation of midshaft humerus fractures raises the risk of radial nerve injury. Anterior transposition of the radial nerve has been proposed as a possible solution but few reports have been published. The purpose of the present study was to validate the effect of transposition on the transposed radial nerve and its branches. MATERIAL AND METHODS: We conducted an anatomic study on 10 cadavers. The length of the radial nerve between 2 anatomic landmarks was determined before and after transposition and plate fixation. A clinical evaluation was performed four years after surgery in 6 patients with midshaft humerus fractures treated with plate fixation after radial nerve transposition. RESULTS: The anatomic study demonstrated a mean gain of 11 mm in the length of the radial nerve with no problem for the transposed nerve or its branches. Clinically, osteosynthesis was facilitated and tension on the nerve was reduced. DISCUSSION: These 2 complementary studies demonstrated the releasing effect of transposition on the radial nerve and the facilitated osteosynthesis reported by others. The benefit of transposition is particularly important when bone fixation is particularly difficult to achieve without risk of injuring the radial nerve. Transposition does however require an extensive dissection, and the patient must be informed. CONCLUSION: The ideal indication for anterior transposition of the radial nerve is an oblique fracture of the mid-third to lower-third of the humeral shaft with radial palsy at onset. A certain degree of comminution facilitates the technique. Indications for this technique could however be widened to include cases of difficult osteosynthesis where the option to transpose the radial nerve is always a peroperative decision.

Adult↗
PubMed2005

Anatomy of the lateral antebrachial cutaneous and superficial radial nerves in the forearm: a cadaveric and clinical study.

PURPOSE: To define the anatomy of the lateral antebrachial cutaneous nerve (LACN) and the superficial radial nerve (SRN) in relation to easily identifiable landmarks in the dorsoradial forearm to minimize the risk to both nerves during surgical approaches to the dorsal radius. METHODS: In this study 37 cadaveric forearms and 20 patients having distal radius external fixation were dissected to identify these nerves in relation to various anatomic landmarks. RESULTS: Based on these dissections the anatomy was divided into 2 zones that can be identified by easily visible and palpable landmarks. Zone 1 extends from the elbow to the cross-over of the abductor pollicis longus with the extensor carpi radialis brevis and longus. Zone 2 is distal to the cross-over. In zone 1 the 2 nerves can be differentiated through limited incisions based on their depth and anatomic location. Within this zone the SRN is deep to the brachioradialis until 1.8 cm proximal to zone 2 (9 cm proximal to the radial styloid), where it becomes superficial and pierces the fascia of the mobile wad and then remains deep to the subcutaneous fat. In contrast the LACN pierces the fascia between the brachialis and biceps muscles at the level of the elbow. In all specimens the LACN ran parallel to the cephalic vein within the subcutaneous fat. In 31 specimens it ran volar to the vein and in 5 specimens the nerve crossed under the cephalic vein at the elbow and ran dorsal to the vein in the forearm. One specimen had 2 branches with 1 on either side of the vein. Differentiation of these nerves was found to be possible through limited incisions in zone 1 during placement of external fixation pins for distal radius fractures. The LACN always was located in the superficial fat running with the cephalic vein, whereas the SRN was deeper to this nerve either covered by the brachioradialis or closely adherent to it within the investing fascia of the mobile wad. In zone 2 the nerves arborized and ran in the same tissue plane, making differentiation through limited incisions difficult. CONCLUSIONS: Dividing forearm anatomy into zones aids in understanding the complex 3-dimensional anatomy. Recognition of the consistent location of both the LACN and SRN facilitates surgical exposure. This allows localization through limited incisions during nerve repair and hardware placement, thereby enhancing uncomplicated and favorable outcomes.

Cadaver↗
PubMed2001

Diffusion tensor imaging and axonal tracking in the human brainstem.

Diffusion tensor MRI was used to demonstrate in vivo anatomical mapping of brainstem axonal connections. It was possible to identify the corticospinal tract (CST), medial lemniscus, and the superior, medial, and inferior cerebellar peduncles. In addition, the cerebral peduncle could be subparcellated into component tracts, namely, the frontopontine tract, the CST, and the temporo-/parieto-/occipitopontine tract. Anatomical landmarks and tracking thresholds were established for each fiber and, using these standards, reproducibility of automated tracking as assessed by intra- and interrater reliability was found to be high (kappa > 0.82). Reconstructed fibers corresponded well to existing anatomical knowledge, validating the tracking. Information on the location of individual tracts was coregistered with quantitative MRI maps to automatically measure MRI parameters on a tract-by-tract basis. The results reveal that each tract has a unique spatial signature in terms of water relaxation and diffusion anisotropy.

Adult↗
PubMed2004

A methodology to determine margins by EPID measurements of patient setup variation and motion as applied to immobilization devices.

Assessment of clinic and site specific margins are essential for the effective use of three-dimensional and intensity modulated radiation therapy. An electronic portal imaging device (EPID) based methodology is introduced which allows individual and population based CTV-to-PTV margins to be determined and compared with traditional margins prescribed during treatment. This method was applied to a patient cohort receiving external beam head and neck radiotherapy under an IRB approved protocol. Although the full study involved the use of an EPID-based method to assess the impact of (1) simulation technique, (2) immobilization, and (3) surgical intervention on inter- and intrafraction variations of individual and population-based CTV-to-PTV margins, the focus of the paper is on the technique. As an illustration, the methodology is utilized to examine the influence of two immobilization devices, the UON thermoplastic mask and the Type-S head/ neck shoulder immobilization system on margins. Daily through port images were acquired for selected fields for each patient with an EPID. To analyze these images, simulation films or digitally reconstructed radiographs (DRR's) were imported into the EPID software. Up to five anatomical landmarks were identified and outlined by the clinician and up to three of these structures were matched for each reference image. Once the individual based errors were quantified, the patient results were grouped into populations by matched anatomical structures and immobilization device. The variation within the subgroup was quantified by calculating the systematic and random errors (sigma(sub) and sigma(sub)). Individual patient margins were approximated as 1.65 times the individual-based random error and ranged from 1.1 to 6.3 mm (A-P) and 1.1 to 12.3 mm (S-I) for fields matched on skull and cervical structures, and 1.7 to 10.2 mm (L-R) and 2.0 to 13.8 mm (S-I) for supraclavicular fields. Population-based margins ranging from 5.1 to 6.6 mm (A-P) and 3.7 to 5.7 mm (S-I) were calculated for the corresponding skull/cervical field and 9.3 to 10.0 mm (L-R) and 6.3 to 6.6 mm (S-I) for the supraclavicular fields, respectively. The reported CTV-to-PTV margins are comparable to a value 7-15 mm based on traditional Mayo margins, but in some cases exceed the default values established in RTOG Head and Neck studies. The data suggests that the population-based margins provide sufficient coverage for the majority of the patients. However, the population-derived margins are excessive for some patients and insufficient for others, suggesting that a re-evaluation of current treatment margins for individual patients is warranted. Finally, this methodology provides direct evidence of treatment variation and thus can demonstrate with confidence, the superiority of one technique over another.

Algorithms↗
PubMed2001

Patellofemoral complications following total knee arthroplasty.

Patellofemoral complications following TKA are largely avoided with proper surgical technique. A variety of surgical exposures, including the midvastus and subvastus approach, has resulted in good clinical success. It is critical to maintain the integrity of the extensor mechanism. The surgeon should be prepared to use specific surgical techniques to assist in exposing the stiff knee and to avoid injury to the patellar tendon. These techniques may include the quadriceps snip, modified V-Y quadriceps turndown, and tibial tubercle osteotomy. When tibial tubercle osteotomy is necessary, the technique of Whiteside, using wire fixation of the osteotomy, is preferred. Selection of the proper femoral component size is important. In general, the surgeon should avoid selecting an excessively large femoral component and overstuffing the patellofemoral compartment. Similarly, the surgeon should restore the patella-implant composite to the original patellar thickness or slightly less when possible. Femoral component positioning is critical to proper patellofemoral tracking. The femoral component rotation should be aligned with the transepicondylar axis of the femur. The anteroposterior axis of the femur as described by Whiteside and Arima is a useful secondary landmark to ensure proper femoral component placement. A slightly lateral femoral component position is favored when possible to further facilitate proper patellar tracking. Proper rotation of the tibial component is important. A variety of surgical techniques and anatomic landmarks may be used to establish proper tibial component rotation. The surgeon must avoid internal rotation of the tibial component leading to an increased quadriceps angle and lateral maltracking of the patella. The patellar osteotomy may be performed using either a calibrated cutting system or an eyeball technique. The surgeon should avoid an oblique osteotomy placing the patellar component on the lateral facet. A cemented all-polyethylene component placed in a medialized position to improve patellar tacking is preferred. Proper soft-tissue tension may require a lateral retinacular release in a small percentage of cases. The superior lateral genicular artery is preserved when possible with the release. Proper patellofemoral tracking must be obtained at the time of the primary TKA. The diagnosis and treatment of the more frequent complications of the extensor mechanism following TKA have been discussed. Although these complications may be successfully treated, most may be largely avoided with proper surgical technique and prosthetic component design.

Adult↗
PubMed1995

Uncomplicated central vein catheterization of high risk patients with real time ultrasound guidance.

Internal jugular vein cannulation has become a routine and clinically important aspect of medical care of critically ill patients. The landmark guided technique usually affords rapid and easy vascular access, but is not always successful and may be complicated by arterial puncture, hematoma, or pneumothorax. Some categories of patients, in particular patients with no external landmarks and patients with coagulopathies, appear to be at an increased risk of complications. We report the experience of internal jugular vein cannulation by a single operator with the external landmark technique in 10 patients and with ultrasound guidance in 31 patients, including 12 high risk patients. These patients had severe coagulopathies due to hepatic failure, HELLP syndrome, excess of anticoagulation treatment, or they had no external anatomic landmarks because of anasarca or obesity, were unable to maintain the horizontal position, or were external landmark catheterization failures. With the availability of the ultrasound device, success and complication rates improved markedly, suggesting that the ultrasound technique is easy to learn and rapidly produces an improvement over the external landmark method. In particular the 13 cannulations performed in 12 high risk patients were all successful at the first attempt, with no complications. In the overall population successful cannulations improved from 80% to 100%, first attempt success from 20% to 87% and carotid punctures decreased from 33% to 3.2%. Our results confirm that ultrasound guided cannulation of the internal jugular vein allows safer operation in high risk patients or when access problems are anticipated.

Adult↗
PubMed1994

[Anatomy of the superficial parts of the face and neck].

The author presents four chapters concerning classical anatomy, an anatomical contribution to new facelifts, aesthetic anatomy, which recalls the aesthetic relations of the face, and finally a brief review of the mode of ageing of the face. The embryology of the superficial plane of the face and neck shows that the development of muscles of facial expression, deep and superficial fatty tissues, the facial nerve and the parotid is the result of divergent migratory movements and confluences. The anatomy is discussed in two parts: the first concerns conventional anatomy, and reviews the anatomical data acquired to date, the second proposes anatomical conclusions adapted to new surgical techniques of rejuvenation. The branches of the facial nerve are unusual in terms of their great variability. However, by using anatomical landmarks, it is possible to localize them precisely. The blood supply of the superficial tissues of the face and neck has been the subject of many studies. Deep monoblock facelifts, by sparing the blood supply of certain anatomical planes, allow the perfectly safe creation of extensive skin flaps. Some muscles of the face and neck are useful surgically. The orbicularis oculi muscle is also a muscle of the orbital margins by its depressing action on the eyebrows and levator action on the superficial malar adipose tissue. The corrugator muscle is a central element of new frontal endoscopy techniques. Elevation of the eyebrows is then ensured by the occipitofrontal complex which occupies only the medial two-thirds of the eyebrows. The zygomaticus major muscle must be released over its entire length because excessive traction on a SMAS flap can induce a disorder of facial expression. The platysma muscle plays an increasingly important role in cervical surgery and constitutes the deep guarantee of the cervical corset. The four fixed osteocutaneous points of the face: zygomatic (Mac Gregor), mandibular (Furnas), orbital (Psillakis) and masseteric play an antigravitational and functional role in facial expression. A macroscopic anatomical and histological study, performed on 60 dissections of hemifaces with several preparations defined the anatomy of the superficial musculoaponeurotic system (SMAS), jugomalar adipose planes and the nasolabial fold. The SMAS is a strictly superficial surgical anatomy structure derived from the primitive platysma muscle, and does not possess any bony insertion. It is composed exclusively of platysma and risorius muscles. There is no parotid aponeurosis. The parotid is surrounded by a capsule. Its is limited in depth by the superficial cervical aponeurosis which lines the styloid curtain (Jost, Levet).(ABSTRACT TRUNCATED AT 400 WORDS)

Esthetics↗
PubMed1998

Observer-independent registration of perspective projection prior to subtraction of in vivo radiographs.

OBJECTIVES: To prove that the model of perspective projection allows precise registration of intra-oral radiographs regardless of whether they have been acquired with or without individual adjustment aids and independent of the human observer or computer algorithm marking corresponding landmarks in the images and, based on in vivo radiographs, to introduce and evaluate a model-based registration method. METHODS: Five observers (three experts and two non-experts) were asked to define corresponding points in 24 pairs of in vivo dental radiographs from the same region of the same patient. The landmarks were used to fit the model of perspective projection applying the least squares method. Misplaced landmarks were detected and suppressed by analysing the quality of all subsets of landmarks with respect to the minimal residual (leaving one out method). In addition, local correlation was used to optimize the quality of registration as well as observer independence. RESULTS: Using six or more corresponding landmarks in both radiographs the correlation of the images registered was > 0.95 (S.D. < 0.063) irrespective of the observers' expertise. CONCLUSIONS: Perspective projection is a reliable model for sequentially acquired intra-oral radiographs. The co-ordinates of anatomical landmarks are useful for determining the parameters of perspective projection. Local correlation and leaving one out techniques improve the geometrical adjustment as well as observer independence. Registration is nearly independent of the actual position of the landmarks and hence independent of the observer. Our algorithm will also be useful for registration techniques based on automatically detected landmarks.

Humans↗
PubMed1997

Interactive image guidance in skull base surgery using an opto-electronic device.

The applicability of an image guidance frameless system based on an opto-electronic sensor device in skull base surgery was explored in this study. Five embalmed heads with external fiducial markers placed in noncoplanar points were scanned (CT scan) and different skull base approaches were reproduced in these specimens. The opto-electronic system is comprised of an infrared camera, a local rigid body, and a 24-light-emitting diode probe attached to different surgical instruments. DOS-based calibration and transformation software and Unix-based surgical planning software were also used. The anatomic landmarks identified during the dissection were matched with the corresponding points derived from computed tomographic (CT) scans. This information allowed the surgeon to develop a three-dimensional representation of the surgical field and to anticipate the next anatomic structure encountered during the dissection. This infrared device operated in real time, is not affected by external factors with regard to its accuracy, and does not interfere with standard neurosurgical techniques. This frameless system is helpful in minimizing the risk of morbidity and provides an accurate guide during the approach, as well as unobstructed access to the surgical field.

Journal Article↗
PubMed2003

Differences between pelvic skin and bone landmark identification in different seated positions on spinal-cord injured subjects.

The purpose of this paper was to determine the differences between internal and external pelvic landmark locations in different seating positions. A computer tool developed for the registration of two series of images was used to obtain the internal geometry. First, images of the pelvis were acquired by magnetic resonance imaging (MRI) for each subject, in a supine position; internal landmarks were then identified on the images. Second, ultrasound images of the iliac crests were acquired in four seated positions. A registration algorithm was applied to obtain the transformation matrix between the two image reference systems. The MRI anatomical landmarks were, therefore, transferred into the ultrasound referential, to obtain their three-dimensional (3-D) location in the different seating positions. The external landmarks in those seated positions were identified with a 3-D digitizer. The results revealed that generally the internal and external coordinates of corresponding landmarks are statistically different. The differences are not only due to soft tissue thickness but also to different interpretations of the landmarks' locations between the supine and the seated postures. However, these differences generally did not affect significantly the accuracy with which orientation indexes can be estimated (pelvic tilt, obliquity, transverse rotation). Correlations were found between the internal and external coordinates, implying that linear regressions can be established.

Adolescent↗
PubMed2000

Complications of Chiari and Salter osteotomies: a cadaver study.

Previous investigations of the Chiari and Salter osteotomies showed that intraoperative vessel and nerve injuries are described repeatedly in the case of both pelvic osteotomies. The aim of our investigations was the exposure of each operation step in anatomic specimens to show the anatomic landmarks and potential risks. We performed nine Chiari osteotomies and five Salter osteotomies on formalin-fixed cadavers. The operation steps were made consecutively to assess the risks to the vessels and nerves as well as the determination of anatomically important reference points. In both procedures an injury of the lateral femoral cutaneous nerve at the anterior access route is feasible. By ensuring that the skin including the lateral femoral cutaneous nerve is pulled medially, injury can be avoided. Additionally, too long retraction of the tensor fasciae latae muscle injures its nutrient vessels. An inadequate subperiosteal approach during the pull on the Hohmann's retractor leads to crushing and irritation of the sciatic nerve. Moreover, there is a risk that the superior gluteal nerve as well as the superior gluteal artery may be injured. An inadequate subperiosteal application of the medial Hohmann's retractor can endanger the obturator nerve. In the Chiari osteotomy there is a risk of injury to the articular branch of the superior gluteal nerve, which supplies parts of the ventral hip joint capsule. By inserting the K-wire too far medially the internal oblique muscle is endangered. Too prolonged retraction of the iliopsoas muscle in a Salter osteotomy can lead to compression of the femoral nerve. The form of the osteotomy has an influence on the stability of the hip joint in the course of exposure of the hip joint. On account of the narrow spatial connection between the anatomic pathways and the osteotomy area, strict subperiosteal dissection and careful use of the retractor are essential to avoid nerve and vessel injuries.

Aged↗
PubMed1988

Vascularization of the myocutaneous latissimus dorsi flap. Injection study on the thoracodorsal artery.

This study reports on investigations of the thoracodorsal artery by injection studies. This artery has a long proximal extramuscular course before it enters the muscle. A consistent neurovascular hilum was found at a considerably constant location on the inferior muscle surface, 2-3 cm medial to its lateral edge and about 5 cm distal to the inferior scapular border. A constant branching pattern of the thoracodorsal artery into a lateral and a medial vessel stem was found. A high number of muscle-perforating arteries from a dense network in the cutaneous and subcutaneous layer. The thoracodorsal artery supplies the whole cutaneous area adjacent to the latissimus dorsi muscle plus a streak of about 2 cm at the medial and distal muscle borders. The presented anatomical landmarks are useful for locating the neurovascular hilum, and the intramuscular course of the thoracodorsal artery for exploration of the vessel by Doppler sonography or dissection. The length of the pedicle and the relatively big vessel gauge are good anatomical markers for the free transfer of a latissimus dorsi flap.

Humans↗
PubMed1997

[Computerized tomography of paranasal sinuses--a preoperative check list].

BACKGROUND: Computed tomography (CT) is being used increasingly both to evaluate location and extent of sinus disease and to detect anatomic abnormalities prior to surgery. Analysis of the CT scan should be undertaken in a routine, standardized fashion to ensure that important details are not missed. To aid in this evaluation, a checklist has been developed which focuses on the most salient and potentially dangerous areas of the paranasal sinuses. Regular preoperative analysis using this system may prevent unforeseen technical difficulties and excess morbidity. MATERIALS AND METHODS: Before obtaining a CT scan, the patient is placed on optimal medical therapy including antibiotics, and topical and occasionally systemic steroids. Coronal scans are then performed with 3 mm sections through the frontal and sphenoid sinuses and 2 mm sections through the ethmoid region. Intravenous contrast is used. The study is then analyzed focusing on specific critical anatomic landmarks. When additional information is required due to severe pathology or atypical anatomy, axial sections are added. RESULTS: Out of 300 CT examinations that where analyzed, a preoperative checklist was developed with eight items that must be evaluated preoperatively. Methods for the identification and analysis of this anatomy as well as the types of anatomic variation are discussed. We have found this evaluation to be extremely useful and efficacious in preventing morbidity in endoscopic sinus surgery. CONCLUSIONS: Evaluation of the preoperative CT examination with a strictly applied checklist of important details and landmarks allows the recognition of hazardous anatomy and pathology which should increase the safety and efficacy of paranasal sinus surgery.

Chronic Disease↗
PubMed1997

Simulation of 3D-treatment plans in head and neck tumors aided by matching of digitally reconstructed radiographs (DRR) and on-line distortion corrected simulator images.

BACKGROUND AND PURPOSE: Simulation of 3D-treatment plans for head and neck malignancy is difficult due to complex anatomy. Therefore, CT-simulation and stereotactic techniques are becoming more common in the treatment preparation, overcoming the need for simulation. However, if simulation is still performed, it is an important step in the treatment preparation/execution chain, since simulation errors, if not detected immediately, can compromise the success of treatment. A recently developed PC-based system for on-line image matching and comparison of digitally reconstructed radiographs (DRR) and distortion corrected simulator monitor images that enables instant correction of field placement errors during the simulation process was evaluated. The range of field placement errors with non-computer aided simulation is reported. MATERIALS AND METHODS: For 14 patients either a primary 3D-treatment plan or a 3D-boost plan after initial treatment with opposing laterals for head and neck malignancy with a coplanar or non-coplanar two- or three-field technique was simulated. After determining the robustness of the matching process and the accuracy of field placement error detection with phantom measurements, DRRs were generated from the treatment planning CT-dataset of each patient and were interactively matched with on-line simulator images that had undergone correction for geometrical distortion, using a landmark algorithm. Translational field placement errors in all three planes as well as in-plane rotational errors were studied and were corrected immediately. RESULTS: The interactive matching process is very robust with a tolerance of <2 mm when suitable anatomical landmarks are chosen. The accuracy for detection of translational errors in phantom measurements was <1 mm and for in-plane rotational errors the accuracy had a maximum of only 1.5 degrees. For patient simulation, the mean absolute distance of the planned versus simulated isocenter was 6.4 +/- 3.9 mm. The in-plane rotational error in both planes was <3 degrees with one exception. Three large field placement errors (two patients with 11.5 and 16.0 mm distances of the planned versus simulated isocenter, respectively and one patient with a 7 degree rotational error) were detected and, as with the smaller errors, were immediately corrected. CONCLUSION: On-line image matching of treatment planning CT-derived DRRs and distortion corrected treatment simulator images is a precise and reliable method to reduce field placement errors in the simulation of complex 3D-treatment plans for head and neck malignancy and thus enhances accuracy in the first step of the treatment preparation/execution chain. However, out-of-plane rotational errors could not be assessed and assumedly they are comparatively small since due to rigid fixation, detected in-plane errors were small.

Computer Simulation↗
PubMed2001

Atrial reentrant tachycardia after surgery for congenital heart disease: endocardial mapping and radiofrequency catheter ablation using a novel, noncontact mapping system.

BACKGROUND: The purpose of the present study was to determine the role of a novel, noncontact mapping system for assessing a variety of atrial reentrant tachycardias (ART) in patients after the surgical correction of congenital heart disease. METHODS AND RESULTS: In 14 patients, an electrophysiological study using the Ensite 3000 system was performed to assess ARTs resistant to medical treatment. Sixteen different forms of ART were inducible in the 14 patients studied. The reentrant circuit of all ARTs could be characterized and localized with respect to anatomic landmarks such as atriotomy scars, intraatrial patches/baffles, and cardiac structures. In 15 of the 16 ARTs (in 13 of the 14 patients), a target area of the reentrant circuit for radiofrequency current application (ie, an area of conduction between 2 anatomical obstacles such as surgical barriers and cardiac structures of electrical isolation) could be localized within the systemic venous atrium. Nine patients exhibited macroreentry, and 4 showed microreentry. In 12 patients, ART could be terminated by creating linear radiofrequency current lesions (75 degrees C, 180 to 390 s). Completeness of linear lesions after radiofrequency current delivery was proven by analyzing color-coded isopotential maps of atrial activation while applying atrial pacing techniques. The mean duration of the procedures was 286 minutes (range, 130 to 435 minutes); fluoroscopy time ranged from 7 to 33.8 minutes (mean, 17.4 minutes). CONCLUSIONS: In patients with ART after the surgical correction of congenital heart disease, the use of the noncontact mapping system allows for characterization of the tachycardia and guidance for effective radiofrequency current delivery.

Adolescent↗