Anatomic Slices Research Articles

Metastatic disease involving the discovertebral junction of the spine

Objective To investigate the use of magnetic resonance imaging in the detection of metastatic tumors involving the discovertebral junction of the spine in cadaveric specimens and patients, with histologic findings as the reference standard. Methods Magnetic resonance imaging studies were performed on 30 DVJs in 10 cadavers with documented metastatic bone disease. Anatomic sectioning and histologic evaluations were performed, and anatomic slices were correlated with the magnetic resonance images. For clinical study, magnetic resonance imaging examinations in three patients with vertebral metastasis were reviewed. Results On magnetic resonance imaging, the signal intensity characteristics of vertebral body metastases were variable. Magnetic resonance imaging failed to detect metastatic foci invading the cartilaginous endplates. On microscopic examination, infiltration of the discovertebral junction by tumorous tissue was found in 11 (69%) of the 16 discovertebral junctions that had an irregular contour, and in 5 (31%) disrupted discovertebral junctions. In three specimens and three patients, microscopic examination revealed tumor metastasis to the intervertebral disc. In no specimen magnetic resonance imaging afforded depiction of discal invasion by tumor. Conclusions Our results lend further support to the theory that metastatic tumors can invade the cartilaginous endplate through defects in its substance, allowing direct contact of tumor and disc. Minimal tumor invasion of the discovertebral junction may not be identified at magnetic resonance imaging or gross anatomic inspection, or both, because small metastatic foci may be obscured by abnormalities in the morphology of the cartilaginous endplate.

Communication Between the Proximal Tibiofibular Joint and Knee via the Subpopliteal Recess: MR Arthrography with Histologic Correlation and Stratigraphic Dissection

The anatomy and functional importance of the proximal tibiofibular joint (TFJ) have rarely been emphasized. Specifically, the detailed anatomic basis and MRI findings of the communication between the proximal TFJ and the knee have not been defined in the literature. To investigate such communication, anatomic and histologic correlation with MRI findings in frozen specimens and dissections of embalmed specimens was used in the study. Twelve frozen knees were studied on MR arthrography. MR images of each specimen were compared with anatomic slices and histologic sample analysis. Dissection of an additional 28 embalmed specimens was performed to further investigate communication and the anatomy of the proximal TFJ. Communication between the proximal TFJ and the knee was observed in 27.5% of all anatomic specimens. It occurred via the subpopliteal recess and was related to a defect in the posterior ligament of the fibular head in all specimens. Evidence of an injury was apparent on MR images and was proven on histologic examination in 9% of the anatomic specimens that had such communication. The frequency of the communication between the proximal TFJ and knee via the subpopliteal recess related to a defect in the posterior ligament of the fibular head was found to be 27.5%. Evidence of an injury was present in 9% of anatomic specimens that had such communication. Injury to the posterior ligament of the fibular head and instability of the proximal TFJ may accompany a variety of knee injuries. Knowledge of the detailed anatomic appearance and MRI characteristics of the structures related to the proximal TFJ is key to identifying injuries to these structures.

Comparison of MR-arthrography and CT-arthrography in hyaline cartilage-thickness measurement in radiographically normal cadaver hips with anatomy as gold standard

To compare magnetic resonance (MR)-arthrography and multidetector-spiral-computed-tomography (MDSCT)-arthrography in cartilage-thickness measurement, in hips without cartilage loss, with coronal anatomic slices as gold standard. Institutional review board permission to study cadavers of individuals who willed their bodies to science was obtained. Two independent observers measured femoral and acetabular cartilage thicknesses of 12 radiographically normal hips (six women, five men; age range, 52-98 years; mean age, 76.5 years), on MDSCT-arthrographic and MR-arthrographic reformations, and on coronal anatomic slices, excluding regions of cartilage loss. Inter- and intraobserver reproducibilities were determined. Analysis of variance (ANOVA) was used to test differences between MR-arthrographic and MDSCT-arthrographic measurement errors compared to anatomy. By MR-arthrography, cartilage was not measurable at approximately 50% of points on sagittal and transverse sections, compared to 0-6% of the points by MDSCT-arthrography. In the coronal plane, the difference between MDSCT-arthrographic and MR-arthrographic measurement errors was not significant (P=0.93). In the coronal plane, MR-arthrography and MDSCT-arthrography were similarly accurate for measuring hip cartilage thickness.

Evaluation of computed tomographic anatomy of the equine metacarpophalangeal joint

To determine the detailed computed tomography (CT) anatomy of the metacarpophalangeal (MCP) joint in healthy horses. 10 cadaveric forelimbs from 10 adult horses without orthopedic disease. CT of the MCP joint was performed on 4 forelimbs. In 1 of the limbs, CT was also performed after intra-articular injection of 30 mL of contrast medium (40 mg of iodine/mL). Transverse slices 1-mm thick were obtained, and sagittal and dorsal planes were reformatted with a slice thickness of 2 mm. The CT images were matched with corresponding anatomic slices from 6 additional forelimbs. The third metacarpal bone, proximal sesamoid bones, and proximal phalanx could be clearly visualized. Common digital extensor tendon; accessory digital extensor tendon; lateral digital extensor tendon; superficial digital flexor tendon (including manica flexoria); deep digital flexor tendon; branches of the suspensory ligament (including its attachment); extensor branches of the suspensory ligament; collateral ligaments; straight, oblique, and cruciate distal sesamoidean ligaments; intersesamoidean ligament; annular ligament; and joint capsule could be seen. Collateral sesamoidean ligaments and short distal sesamoidean ligaments could be localized but not at all times clearly identified, whereas the metacarpointersesamoidean ligament could not be identified. The cartilage of the MCP joint could be assessed on the postcontrast sequence. CT of the equine MCP joint can be of great value when results of radiography and ultrasonography are inconclusive. Images obtained in this study may serve as reference for CT of the equine MCP joint.

Prevalence and MRI-Anatomic Correlation of Bone Cysts in Osteoarthritic Knees

The objectives of this study were to determine the prevalence of cysts in the weight-bearing areas and interspinous bone cysts in tibial plateau specimens derived from knees with advanced osteoarthritis, to perform MRI-anatomic correlation of these cysts, and to define their histologic characteristics. Forty-two tibial plateau specimens were recovered from patients undergoing total knee replacement surgery for severe osteoarthritis (14 men and 28 women; mean age, 74 years; age range, 58-87 years). The tibial specimens underwent MRI with T1- and T2-weighted MR sequences. No radiographic data were available before MRI. Tibial specimens were sectioned using a high-speed rotating diamond disk into 3-mm-thick slices. MR images and anatomic specimens were analyzed for the presence of cysts in the interspinous and weight-bearing areas. Histologic staining methods included routine Harris hematoxylin stain, trichrome stain, and Alcian blue-PAS stain. Twenty-three (54%) of 42 specimens contained one or more cystic areas, with a total of 30 cystic areas. The cysts were distributed in the weight-bearing area (14/30) and interspinous area (16/30). All cysts seen on the anatomic slices could also be depicted on both MRI sequences. Histologic findings were identical for all noncommunicating cysts and revealed necrotic bone fragments with dead denuclearized cells. The cavities were surrounded by a layer of fibrous connective tissue containing adipocytes and osteoblasts. No evidence of epithelial components was found in the lining of the cavities. Interspinous and weight-bearing tibial cysts are common in severe knee osteoarthritis. The cysts contain necrotic bone fragments and are lined by a nonepithelial fibrous wall. Our findings support the hypothesis that interspinous cysts could result from repetitive bone stresses through the cruciate ligaments. Our findings do not support the use of the term "herniation cyst."

Combined functional and viability cardiac MR imaging in a single breathhold

The combination of cardiac viability and functional information enhances the identification of different heart tissues in the setting of ischemic heart disease. A method has recently been proposed for obtaining black-blood delayed-enhancement (DE) viability images using the stimulated-echo acquisition mode (STEAM) MRI pulse sequence in a single short breathhold. The method was validated against conventional inversion-recovery (IR) DE images for identifying regions of myocardial infarction (MI). The method was based on the acquisition of three consecutive images of the same anatomical slice. One image has T(1)-weighted contrast in which infarction appears bright. The two other images are used to construct an anatomical image of the heart, which is combined with the first image to produce a black-blood viability image. However, using appropriate modulation and demodulation frequencies, the latter two images bear useful information about myocardial deformation that results in a cardiac strain-encoding (SENC) functional image. In this work, a method is proposed for obtaining three consecutive SENC images in a single acquisition that can be combined to produce a composite image of the heart, which shows both functional and viability information. The proposed technique reduces scan time by one-half, compared with separate acquisitions of functional and viability images, and alleviates misregistration problems caused by separate breathholds.

Performance of a novel piezoelectric motor at 4.7 T: applications and initial tests

The focus of this report was to test the performance of a novel piezoelectric motor under high magnetic field strength conditions and to investigate its potential applications in small animal magnetic resonance imaging (MRI). The device is made entirely of nonferrous materials and consists of four piezoelectric ceramic plates connected to a threaded metal tube through which a screw migrates. Ultrasonic vibrations of the threads inherent to the tube result in rotational and translational motion of the screw. Potential applications of the piezoelectric motor were investigated at 4.7 T. Firstly, phantom studies showed the motor was capable of accurately delivering low injection volumes ( approximately 0.01 ml). Dynamic contrast-enhanced MRI (DCE-MRI) studies performed in vivo using serially acquired T1-weighted, spin-echo imaging demonstrated the ability of the motor to reliably administer MR contrast-enhancing agent into live tumor-bearing mice without the introduction of image artifacts. In a second set of experiments, the motor allowed for controlled, dynamic repositioning of an anatomic slice of interest in a live animal to magnetic field isocenter, which resulted in reduced geometric distortion and image artifact due to improved radiofrequency and gradient field homogeneity. In conclusion, piezoelectric motors are MR compatible and offer great potential for improving MRI efficiency and throughput, particularly in a preclinical setting. Further investigation into applications such as automated capacitor tuning and impedance matching for MR transceiver coils is warranted.

Magnetic Resonance Imaging Protocol Optimization for Detection of Endometriotic Lesions

transmit-receive extremity RF coil; previous medical history and investigation indicated compartment syndrome was suspected in the anterior tibialis region. High resolution T1-weighted SPGR images were acquired prior to functional imaging. Mid-calf axial BOLD images were acquired using a Gradient Echo sequence with an EPI readout (∝=70o, TE/TR=35/250ms, FOV 24cm, 64x64 matrix). 3072 contiguous images were acquired over 12.8 minutes at a rate of 4 per second (4Hz). Data acquisition was performed prior to and immediately following 30 minutes of intense exercise. BOLD data obtained from muscle regions of interest (ROIs; soleus, gastrocnemius, anterior tibialis) were spatially aligned with anatomical slices and Fourier transformed into frequency spectra using in-house programs written in Matlab (The Mathworks, Natick MA).

Peri-Stent Reference Segment Plaque Burden Is Associated With Disease Progression in Saphenous Vein Grafts (A Serial Intravascular Ultrasound Assessment)

We are aware of no studies of peri-stent disease progression or luminal compromise in saphenous vein graft (SVG) lesions. We used serial intravascular ultrasound (IVUS) to assess disease progression in peri-stent saphenous vein bypass graft reference segments. We studied 37 peri-stent SVG reference segments in 21 patients; 16 were proximal and 21 were distal to the stent. The same anatomic image slice was analyzed after the intervention and at follow-up; this site was 3.68 +/- 2.22 mm from the stent edge. Graft age was 10.1 +/- 5.4 years, and mean follow-up duration was 13 months (range 3 to 61). Overall, change in SVG area, change in lumen area, and change in plaque burden correlated with postintervention plaque burden (r = 0.448, p = 0.005; r = -0.584, p <0.001; and r = 0.507, p = 0.001, respectively). For the proximal edge, change in lumen area correlated with change in plaque area (r = -0.951, p <0.001), but not with change in SVG area (r = -0.337, p = 0.201). For the distal edge, change in lumen area correlated more strongly with change in plaque area (r = -0.982, p <0.001) than with change in SVG area (r = -0.624, p = 0.003). When peri-stent reference segments were divided into 2 groups according to postintervention plaque burden (>50% [n = 20] vs <50% [n = 17]), there was a greater decrease in lumen area (-1.12 +/- 0.81 vs -0.33 +/- 0.26 mm(2), p <0.001) and greater increases in SVG area (0.26 +/- 0.29 vs 0.09 +/- 0.09 mm(2), p = 0.027), plaque area (1.37 +/- 0.96 vs 0.42 +/- 0.30 mm(2), p <0.001), and plaque burden (8.2 +/- 5.6% vs. 2.8 +/- 1.6%, p <0.001) in segments with a plaque burden >50%. In conclusion, peri-stent reference segment SVG disease progression and lumen loss were more significant in segments with a greater postintervention plaque burden after implantation of a bare metal stent or drug-eluting stent.

SONOGRAPHIC ANATOMY OF THE PALMARODISTAL ASPECT OF THE EQUINE DIGIT

Although ultrasonography is widely used in equine orthopedics, its use in the distal portion of the digit is still limited. The purpose of this descriptive study was to document the normal ultrasonographic appearance of the palmarodistal aspect of the digital area imaged between the bulbs of the heels. Ultrasonographic images were obtained with a 7.5 MHz microconvex transducer in 10 fresh equine cadaver forelimbs and five soundhorses. Sagittal, parasagittal, and transverse images were obtained from the proximal aspect of the middle phalanx to the distal sesamoid bone. Anatomic sections were obtained from five cadaver specimens to correlate the sonographic appearance with the anatomic findings. The remaining cadaver limbs were dissected to confirm normalcy. Ultrasonographic examinations were possible on all digits but distal images were more difficult to obtain in digits with long heels. Bony structures (palmar surface of the middle phalanx and proximal border of the distal sesamoid bone) and soft tissue structures (deep digital flexor tendon, digital tendon sheath, proximal palmar recess of the distal interphalangeal joint, proximal recess of the podotrochlear bursa, collateral sesamoidean ligaments) identified on the anatomic slices were seen on the matched sonographic images. Ultrasonography provides good anatomic details of the palmarodistal aspect of the digit. The images of this study will serve as a reference for clinical studies on ultrasonography of the palmarodistal aspect of the digit.

Hyaline Cartilage Thickness in Radiographically Normal Cadaveric Hips: Comparison of Spiral CT Arthrographic and Macroscopic Measurements

To assess spiral multidetector computed tomographic (CT) arthrography for the depiction of cartilage thickness in hips without cartilage loss, with evaluation of anatomic slices as the reference standard. Permission to perform imaging studies in cadaveric specimens of individuals who had willed their bodies to science was obtained from the institutional review board. Two independent observers measured the femoral and acetabular hyaline cartilage thickness of 12 radiographically normal cadaveric hips (from six women and five men; age range at death, 52-98 years; mean, 76.5 years) on spiral multidetector CT arthrographic reformations and on coronal anatomic slices. Regions of cartilage loss at gross or histologic examination were excluded. CT arthrographic and anatomic measurements in the coronal plane were compared by using Bland-Altman representation and a paired t test. Differences between mean cartilage thicknesses at the points of measurement were tested by means of analysis of variance. Interobserver and intraobserver reproducibilities were determined. At CT arthrography, mean cartilage thickness ranged from 0.32 to 2.53 mm on the femoral head and from 0.95 to 3.13 mm on the acetabulum. Observers underestimated cartilage thickness in the coronal plane by 0.30 mm +/- 0.52 (mean +/- standard error) at CT arthrography (P < .001) compared with the anatomic reference standard. Ninety-five percent of the differences between CT arthrography and anatomic values ranged from -1.34 to 0.74 mm. The difference between mean cartilage thicknesses at the different measurement points was significant for coronal spiral multidetector CT arthrography and anatomic measurement of the femoral head and acetabulum and for sagittal and transverse CT arthrography of the femoral head (P < .001). Changes in cartilage thickness from the periphery to the center of the joint ("gradients") were found by means of spiral multidetector CT arthrography and anatomic measurement. Spiral multidetector CT arthrography depicts cartilage thickness gradients in radiographically normal cadaveric hips.

Comparison of Maximum Induced Current and Electric Field from Transcranial Direct Current and Magnetic Stimulations of a Human Head Model

As important non-invasive techniques in brain stimulation, transcranial direct cur- rent stimulation (tDCS) and transcranial magnetic stimulation (TMS) have been studied and compared in this paper by employing impedance method and a 3D human head model. The quantitative analysis of distributions of current density and electric fleld by tDCS and TMS have been presented. Results are compared and potential applications are discussed. DOI: 10.2529/PIERS060906193504 In this paper we use a 3D human head model obtained from Brooks Air Force Laboratory, USA. The model which has 24 difierent tissues is based on anatomical slices from a male cadaver and it is originally obtained from the Visible Human Project. The electrical properties are modeled using the 4-Cole-Cole model (5). Typical sliced layer in the head model and tissue colour palette for part of the tissues are shown in Fig. 1. Conductivities of some important tissues used in the present paper are given in Table 1.

Rehaussement des structures du système nerveux central par traitement des coupes anatomiques avec le chlorure ferrique

The authors have described a new method of coloration on anatomic slices of the central nervous system realised on formolated subjects. They have presented their first results on their experiences carried out on the different levels of the brain, and this simple method of proceeding shows how interesting it could be for all practicians of Neurosciences and for the teaching of Neuroanatomy.

Sliding multislice (SMS): A new technique for minimum FOV usage in axial continuously moving‐table acquisitions

A novel technique for axial continuously moving-table scans is described that minimizes the required extension of the scanner's field of view (FOV) along the direction of table motion (z) by applying a segmented multislice acquisition technique. Any anatomical slice is acquired by applying the same phase-encoding steps at the same spatial positions along the scanner FOV. The full k-space data set of any anatomical slice is collected while the slice moves through the scanner from one scan position to the next. Simultaneous acquisition of multiple slices is realized by shifting the acquisition trajectories of different slices in time. It is demonstrated how the image artifact behavior that relates to varying imaging properties along the distance the table traverses during the acquisition of any given anatomical slice can be optimized simultaneously for all images. Discontinuities between the images along the slice axis are avoided because all z-dependent scan properties are encoded identically for all slices. Flexible spatial acquisition patterns are proposed to enable data oversampling and overlapping slice acquisitions at reduced table speeds. A framework of equations is presented by which matched parameter combinations for sliding multislice acquisitions can be applied to both single- and multiecho sequences. The new technique is validated on phantom and in vivo measurements using a T1-weighted fast low-angle shot (FLASH) sequence as well as a T2-weighted multi-spin-echo sequence of variable echo train lengths.

Technical note: the design of a stereotactic frame for direct MRI-anatomical correlation of the brachial plexus

The purpose of this study was to identify optimal magnetic resonance imaging (MRI) conditions to visualize discrete alterations of brachial plexus components, as part of a biomechanical study of minor nerve compression syndromes. A method was developed allowing direct comparison between the MRI image and the subsequently obtained matching anatomic section of the same specimen. We designed a stereotactic frame to obtain the precise orientation of the MRI plane with reference to the specimen and adapted a vertical band saw for multiplanar sectioning of cadaveric specimens. Two cadaveric upper quadrants were examined by MRI (TR 450 ms, TE 13 ms, pixel matrix 512 x 512 and FOV 23-26 cm) and anatomical slices were produced. One specimen was sectioned axially, while the second specimen was sectioned in an oblique plane corresponding to the natural longitudinal axis of the upper part of the brachial plexus. MR images and the corresponding slices exhibited a strong correlation. This correlation was checked by using vitamin A pearls as landmarks. MR images revealed more detail after the correlating anatomical slices were analyzed. The present study shows that the method is suited for direct MRI-anatomic comparison of the brachial plexus and is also proposed for application to other topographical regions.

Feasibility of a fast inverse dose optimization algorithm for IMRT via matrix inversion without negative beamlet intensities

A fast optimization algorithm is very important for inverse planning of intensity modulated radiation therapy (IMRT), and for adaptive radiotherapy of the future. Conventional numerical search algorithms such as the conjugate gradient search, with positive beam weight constraints, generally require numerous iterations and may produce suboptimal dose results due to trapping in local minima. A direct solution of the inverse problem using conventional quadratic objective functions without positive beam constraints is more efficient but will result in unrealistic negative beam weights. We present here a direct solution of the inverse problem that does not yield unphysical negative beam weights. The objective function for the optimization of a large number of beamlets is reformulated such that the optimization problem is reduced to a linear set of equations. The optimal set of intensities is found through a matrix inversion, and negative beamlet intensities are avoided without the need for externally imposed ad-hoc constraints. The method has been demonstrated with a test phantom and a few clinical radiotherapy cases, using primary dose calculations. We achieve highly conformal primary dose distributions with very rapid optimization times. Typical optimization times for a single anatomical slice (two dimensional) (head and neck) using a LAPACK matrix inversion routine in a single processor desktop computer, are: 0.03 s for 500 beamlets; 0.28 s for 1000 beamlets; 3.1 s for 2000 beamlets; and 12 s for 3000 beamlets. Clinical implementation will require the additional time of a one-time precomputation of scattered radiation for all beamlets, but will not impact the optimization speed. In conclusion, the new method provides a fast and robust technique to find a global minimum that yields excellent results for the inverse planning of IMRT.

SU‐FF‐T‐110: Fast Inverse Dose Optimization (FIDO) for IMRT Via Matrix Inversion Without Negative Beamlet Intensities

Purpose: To optimize an IMRT treatment plan by a matrix inversion method that is very fast, robust and yields a global optimization minimum without negative intensities. Given the availability of online imaging tools, the conformal dose distributions obtained through IMRT and its dynamic delivery features, adaptive radiotherapy becomes an important factor to be considered. A fast and reliable optimization algorithm is crucial not only for designing good radiation treatment plans but also for the successful implementation of future interactive adaptive treatment techniques. Method and Materials: The objective function for the optimization of a large number of beamlets is reformulated such that the optimization problem is reduced to a linear set of equations. The optimal set of intensities is found through a matrix inversion, and negative beamlet intensities are avoided without the need for externally imposed ad‐hoc constraints. The objective function remains quadratic and the optimal result obtained corresponds to a single global minimum. Results: The method has been demonstrated with a test phantom and a few clinical radiotherapy cases using primary photons in the dose calculation only. We have showed that the new method is not only faster but also gives better optimization results. Typical optimization times for a single anatomical slice (2D) (head and neck) using a standard LAPack matrix inversion routine in a single processor desktop computer, are: 0.03 sec. for 500 beamlets; 0.28 sec. for 1,000 beamlets; 3.1 sec. for 2,000 beamlets and 12 sec for 3,000 beamlets. Conclusion: We have developed a fast and robust technique to find a global minimum of an objective function that yields excellent results for the inverse optimization problem for the radiation treatment of tumours with IMRT.

Computed tomography and cross-sectional anatomy of the thorax in clinically normal dogs

To provide a detailed anatomic description of the thorax in clinically normal dogs by means of computed tomography. 4 clinically normal adult German Shepherd Dogs weighing 28 to 37 kg. Dogs were anesthetized and positioned in ventral recumbency for computed tomographic (CT) examination of the thorax. A CT image from the thoracic inlet to the diaphragm was made by use of a third-generation scanner with a slice thickness of 5 mm. Individual images were reviewed by use of soft tissue (window width, 250 Hounsfield units; window level, 35 Hounsfield units) and lung (window width, 1,000 Hounsfield units; window level, -690 Hounsfield units) settings. One dog, weighing 28 kg, was euthanatized, bound on a wooden frame in the same position as used for CT examination, and frozen at -14 degrees C until solid. By use of an electric band saw, the frozen thorax was sectioned at 10-mm-thick intervals. Slab sections were immediately cleaned, photographed, and compared with corresponding CT images. Anatomic sections were studied, and identified anatomic structures were matched with structures on corresponding CT images. Except for some blood vessels and details of the heart, most of the bony and soft tissue structures of the thorax discerned on anatomic slices could be found on matched CT images. Because CT images provide detailed information on most structures of the canine thorax, results of our study could be used as a guide for evaluation of CT images of the thorax of dogs with thoracic diseases.

An automatic CT-guided adaptive radiation therapy technique by online modification of multileaf collimator leaf positions for prostate cancer

To propose and evaluate online adaptive radiation therapy (ART) using in-room computed tomography (CT) imaging that detects changes in the target position and shape of the prostate and seminal vesicles (SVs) and then automatically modifies the multileaf collimator (MLC) leaf pairs in a slice-by-slice fashion. For intensity-modulated radiation therapy (IMRT) using a coplanar beam arrangement, each MLC leaf pair projects onto a specific anatomic slice. The proposed strategy assumes that shape deformation is a function of only the superior-inferior (SI) position. That is, there is no shape change within a CT slice, but each slice can be displaced in the anteroposterior (AP) or right-left (RL) direction relative to adjacent slices. First, global shifts (in SI, AP, and RL directions) were calculated by three-dimensional (3D) registration of the bulk of the prostate in the treatment planning CT images with the daily CT images taken immediately before treatment. Local shifts in the AP direction were then found using slice-by-slice registration, in which the CT slices were individually registered. The translational shift within a slice could then be projected to a translational shift in the position of the corresponding MLC leaf pair for each treatment segment for each gantry angle. Global shifts in the SI direction were accounted for by moving the open portal superiorly or inferiorly by an integral number of leaf pairs. The proposed slice-by-slice registration technique was tested by using daily CT images from 46 CT image sets (23 each from 2 patients) taken before the standard delivery of IMRT for prostate cancer. A dosimetric evaluation was carried out by using an 8-field IMRT plan. The shifts and shape change of the prostate and SVs could be separated into 3D global shifts in the RL, AP, and SI directions, plus local shifts in the AP direction, which were different for each CT slice. The MLC leaf positions were successfully modified to compensate for these global shifts and local shape variations. The ART method improved geometric coverage of the prostate and SVs compared with the couch-shift method, particularly for the superior part of the prostate and all the SVs, for which the interfraction shape change was the largest. The dosimetric comparison showed that the ART method covered the target better and reduced the rectal dose more than a simple couch-translation method. ART corrected for interfraction changes in the position and shape of the prostate and SVs and gave dose distributions that were considerably closer to the planned dose distributions than could be achieved with simple alignment strategies that neglect shape change. The ART proposed in this investigation requires neither contouring of the daily CT images nor extensive calculations; therefore, it may prove to be an effective and clinically practical solution to the problem of interfraction shape changes.

Cross-sectional and functional imaging of the temporomandibular joint: radiology, pathology, and basic biomechanics of the jaw.

The temporomandibular joint (TMJ) is a common site of complaint. Clicking sounds and pain are indicators of a frequent condition called internal derangement, most often affecting females. As a general term, internal derangement describes a structural abnormality within an articulation. The internal derangement of the TMJ is a specific term defined as an abnormal positional and functional relationship between the disk and articulating surfaces. Imaging of the joint is an important element in the diagnostic work-up. Trauma and inflammatory arthritis account for most of the other TMJ problems. A thorough understanding of joint anatomy and normal function is a prerequisite for perceiving abnormalities and making the correct diagnosis. The authors elucidate joint anatomy, correlating cadaveric specimen and anatomic slices with conventional and cross-sectional imaging studies. TMJ biomechanics are illustrated with schematics and animations, and an overview of imaging strategies and techniques is presented. Common abnormalities are described and illustrated, and a brief discussion of therapeutic options is included.