Standard versus low-dose computed tomography for assessment of acetabular fracture reduction using novel step and gap measurement technique

PURPOSE

Quality of reduction is of paramount importance after acetabular fracture and is best assessed on computed tomography (CT). A recently proposed measurement technique for assessment of step and gap displacement is reproducible but has not been validated. The purpose of this study is to validate a well-established measurement technique against known displacements and to determine if it can be used with low dose CT.

METHODS

Posterior wall acetabular fractures were created in 8 cadaveric hips and fixed at known step and gap displacements. CT was performed at multiple radiation doses for each hip. Four surgeons measured step and gap displacement for each hip at all doses, and the measurements were compared to known values.

RESULTS

There were no significant differences in measurements across surgeons, and all measurements were found to have positive agreement. Measurement error < 1.5 mm was present in 58% of gap measurements and 46% of step measurements. Only for step measurements at a dose of 120 kVp did we observe a statistically significant measurement error. There was a significant difference in step measurements made by those with greater and those with fewer years in practice.

CONCLUSION

Our study suggests this technique is valid and accurate across all doses. This is important as it may reduce the amount of radiation exposure for patients with acetabular fractures.

Radiographic detection of lateral plateau involvement in medial tibial plateau fractures (AO/OTA 41-B1.2, 1.3, 3.2 and 3.3)

PURPOSE

To assess the accuracy of radiographs in detecting the lateral plateau involvement of medial tibial plateau fractures as well as describe the impact of CT on preoperative planning for this specific fracture morphology.

METHODS

Radiograph and CT imaging of patients with a Schatzker type IV tibial plateau fractures (AO/OTA 41-B1.2, B1.3 h, B2.2. B3.2, and B3.3) between January 2013 and July 2017 were reviewed by three trauma fellowship-trained orthopedic surgeons to identify fractures of the medial condyle with an intact anterolateral articular surface.

RESULTS

Lateral plateau involvement was identified in 16 (37%) radiographs and 26 (61%) CT images (p = 0.051). Radiographic detection of lateral plateau involvement demonstrated a sensitivity of 62% and specificity of 100%, and radiographs were able to predict the recommendation for surgical intervention for lateral plateau involvement with a positive predictive value (PPV) of 75% and a negative predictive value (NPV) of 60% compared to recommendations based on CT imaging. Radiographs predicted a need for a separate surgical approach with PPV of 63% and NPV of 70% when compared to recommendations based on CT images.

CONCLUSIONS

Radiographs are reliable in ruling in lateral plateau involvement of medial plateau fractures, but occult lateral articular extension may only be identified in CT imaging for some cases. Surgical planning may be impacted by CT imaging for this fracture morphology, but further study is warranted to evaluate the correlation between preoperative planning and clinical outcomes.

LEVEL OF EVIDENCE

III.

Timing of supplementation alters grazing behavior and milk production response in dairy cows

Offering feed supplements to grazing dairy cows results in substitution of pasture; however, previous data indicate that the time at which concentrate supplements are offered might affect the level of substitution. These data indicated that cows grazed more intensely presunset, regardless of the amount of supplement offered. It was, therefore, hypothesized that substitution rate would be less, and response to supplement greater if cows received their supplement at the p.m. rather than the a.m. milking. Forty-eight multiparous, nonpregnant, Holstein-Friesian cows, approximately 60 d in milk, were randomly allocated to 1 of 3 treatments in an incomplete crossover arrangement. Treatments were pasture only, pasture + 3 kg of concentrate supplement dry matter (DM) offered during the a.m. milking (AM-SUP), and pasture + 3 kg of concentrate supplement DM offered during the p.m. milking (PM-SUP). Time spent grazing and calculated pasture DM intake did not differ between the AM-SUP and PM-SUP cows. However, a tendency (0.18 kg of milk/kg of concentrate DM) was observed for an increased marginal milk response (kg of milk/kg of DM supplement) for the AM-SUP cows when compared with PM-SUP cows. Irrespective of when supplements were offered, supplementation reduced total grazing time by a similar amount, and the reduction in time spent grazing was evident throughout the day. Cows in the PM-SUP group ruminated for longer and cows in the AM-SUP group spent more time idle compared with the pasture only groups. Cows in the AM-SUP group grazed for less time during the major a.m. grazing bout following a.m. milking compared with PM-SUP cows; in comparison, the major p.m. grazing bout following p.m. milking was unaffected by supplementation. The results indicated possible improvements in marginal milk response to supplements from altering the timing of delivery.

Neighbourhood deprivation and dental service use: a cross-sectional analysis of older people in England

BACKGROUND

Appropriate dental care is an important part of maintaining good oral health. We examined the relationship between socioeconomic status, neighbourhood deprivation levels and older people's dental service use.

METHODS

We used logistic regression analysis to assess the relationship between self-reported dental service use and neighbourhood deprivation, adjusting for individual socioeconomic and health factors, in individuals aged 65+ in the 2005 Health Survey for England (n = 4240).

RESULTS

Among dentulous respondents, 69.9% reported attending for regular check-ups, 6.2% occasional check-ups, 18.4% only saw a dentist when in trouble and 5.6% never went to a dentist. In our adjusted model age, sex, region, education level, occupational social class, self-reported health and smoking status, but not degree of urbanization, were associated with use of dental services. Following adjustment for these other factors those living in the most deprived 20% of neighbourhoods, compared with those in the least deprived, had a relative risk ratio of 2.25 (95% confidence interval 1.59-3.17) of using dental services only when symptomatic, rather than going for regular or occasional check-ups. When alternative outcomes of reporting having recently seen a doctor or been a hospital inpatient were assessed these deprivation-related patterns in service use were not evident.

CONCLUSION

Levels of neighbourhood deprivation are associated with the use of dental services by older people. Action is needed to ensure older people in deprived communities access appropriate and comprehensive dental services.

Magnetic resonance studies of laryngeal tumors implanted in nude mice: effect of treatment with bleomycin and electroporation

Recently, a new type of cancer treatment has been introduced that combines pulsed electric fields (PEF) with anticancer drugs. The proposed mode of action is that PEF create transient pores in the membranes which allow entry of drugs into the cells. This method increases cytotoxicity of some anticancer drugs like bleomycin (BLM) by 2-3 orders of magnitude, which, in turn, reduces systemic drug dosage without decreasing efficacy. In the present study, magnetic resonance imaging (MRI) was used to determine changes in apparent water self-diffusion coefficients (ADC) and spin-lattice (T(1)) and spin-spin (T(2)) relaxation times that occur in an animal laryngeal tumor (HEp-2 cells) model with BLM delivered by PEF. A Bruker 14 Tesla (600 MHz) wide-bore spectrometer with micro-imaging capability was used to generate all the data. Mice carrying approximately 8 mm tumors were treated with several combinations of drug and PEF. All measurements were made on tumor samples excised from mice 24 and 48 hours after treatment with (i) saline, intratumor injection (i.t.), (ii) BLM, i.t., (iii) saline with PEF, and (iv) BLM, i.t., followed by PEF. Although T(1) does not differ between the controls (i, ii, and iii) and full treatment (iv) 6.72 +/- 0.20 s vs. 6.31 +/- 1.7 s, T(2) for (iv) at 24 hours is significantly different from the controls 52.4 +/- 0.91 ms vs. 46.5 +/- 1.54 ms. T(2) differences between treatment and controls disappear at 48 hours. ADC increases significantly from 24 to 48 hours (7.31 +/- 0.16 x 10(-6) to 8.28 +/- 0.28 x 10(-6) cm(2)/sec, p = 0.05). Longer T(2) values may reflect early apoptosis and tumor death when the tumor is structurally less dense. Higher ADC's, associated with the periphery of the tumors and the central region, may indicate loose structural organization and necrosis resulting from the combination treatment.

Axial development and radial non-uniformity of flow in packed columns

Flow inhomogeneity and axial development in low-pressure chromatographic columns have been studied by magnetic resonance imaging velocimetry. The columns studied included (a) an 11.7-mm I.D. column packed with either 50 microm diameter porous polyacrylamide, or 99 or 780 microm diameter impermeable polystyrene beads, and (b) a 5-mm I.D. column commercially packed with 10 microm polymeric beads. The packing methods included gravity settling, slurry packing, ultrasonication, and dry packing with vibration. The magnetic resonance method used averaged apparent fluid velocity over both column cross-sections and fluid displacements greater than one particle diameter and hence permits assessment of macroscopic flow non-uniformities. The results confirm that now non-uniformities induced by the conical distributor of the 11.7-mm I.D. column or the presence of voids at the column entrance relax on a length scale of the column radius. All of the 11.7-mm I.D. columns examined exhibit near wall channeling within a few particle diameters of the wall. The origins of this behavior are demonstrated by imaging of the radial dependence of the local porosity for a column packed with 780 microm beads. Columns packed with the 99-microm beads exhibit reduced flow in a region extending from ten to three-to-five particle diameters from the wall. This velocity reduction is consistent with a reduced porosity of 0.35 in this region as compared to approximately 0.43 in the bulk of the column. Ultrasonicated and dry-packed columns exhibit enhanced flow in a region located between approximately eight and 20 particle diameters from the wall. This enhancement maybe caused by packing density inhomogeneity and/or particle size segregation caused by vibration during the packing process. No significant non-uniformities on length scales of 20 microm or greater were observed in the commercially packed column packed with 10 microm particles.

Rapid analysis of non-uniformly sampled pulsed field gradient data for velocity estimation

Bretthorst's recent generalization of the Lomb-Scargle periodogram shows that a sufficient statistic for frequency estimation from non-uniformly, but simultaneously sampled quadrature data is equivalent to the FFT of those data with the missing samples replaced by zeros. We have applied this concept to the rapid analysis of pulsed field gradient MRI data which have been non-uniformly sampled in the velocity encoding wave vector q. For a small number of q samples, it is more computationally efficient to calculate the periodogram directly rather than using the FFT algorithm with a large number of zeros. The algorithm we have implemented for finding the peak of the generalized periodogram is simple and robust; it involves repeated apodization and grid searching of the periodogram until the desired velocity resolution is achieved. The final estimate is refined by quadratic interpolation. We have tested the method for fully developed Poiseuille flow of a Newtonian fluid and have demonstrated substantial improvement in the precision of velocity measurement achievable in a fixed acquisition time with non-uniform sampling. The method is readily extendible to multidimensional data. Analysis of a 256 by 256 pixel image with 8 q samples and an effective velocity resolution of better than 1/680 of the Nyquist range requires approximately 1 minute computation time on a 400 MHz SUN Ultrasparc II processor.

Effective dose equivalent and effective dose: comparison for common projections in oral and maxillofacial radiology

OBJECTIVES

Effective dose equivalents (H(E)) and effective doses (E) for radiographic projections common in dentistry, calculated from the same organ dose distributions, are presented to determine whether the 2 quantities can be directly compared.

STUDY DESIGN

Doses to all organs and tissues in the head, neck, trunk, and proximal extremities were determined for each projection (intraoral full-mouth radiographic survey, panoramic, cephalometric, temporomandibular tomograms, and submentovertex view) by computer simulation with Monte Carlo methods. H(E) and E were calculated from these complete distributions and by methods prescribed by the International Commission on Radiological Protection (ICRP).

RESULTS

H(E) and E computed from complete dose distributions were found comparable within a few percentage points. However, those computed by strict application of ICRP methods were not.

CONCLUSION

For radiographic projections with highly localized dose distributions, such as those common in dentistry, direct comparison of H(E) and E may not be meaningful, unless both computation algorithms are known.

Prospective study of modified condylotomy for treatment of nonreducing disk displacement

OBJECTIVE

This study was performed to provide an objective assessment of the outcome of modified condylotomy for treatment of the painful temporomandibular joint with nonreducing disk displacement (Wilkes late stage III, IV, V).

STUDY DESIGN

A prospective study of 31 consecutive patients (43 joints) was conducted. All patients had nonreducing disk displacement verified by means of disk imaging. Independent evaluations were performed to assess pain, dysfunction, and progression of disease. The examinations were performed before modified condylotomy and at intervals up to 1 year after the operation. Eighteen patients (26 joints) completed the required examinations. Patient-based assessments were completed for pain and diet on 15 of these 18 patients (23 joints) 3 years after the operation.

RESULTS

Visual analog scale (VAS) scores (mean +/- SE) for pain improved from 7.4 +/- 0.4 before modified condylotomy to 2.4 +/- 0.5 1 year later (P <. 001). Joints with degenerative joint disease (Wilkes stage IV, V) had less satisfactory pain relief compared with stage III joints (3. 6 +/- 0.9 vs 1.1 +/- 0.4, P =.05) and an 11-fold higher risk (P <. 04) for serious residual pain (VAS score >4). Dietary restrictions improved from a mean VAS score of 5.3 +/- 0.7 before the operation to 7.7 +/- 0.5 1 year later (P =.02). Minor differences between mean VAS scores at 1 (2.1 +/- 0.5) and 3 (2.1 +/- 0.5) years for pain, and 1 (7.4 +/- 0.6) and 3 (8.1 +/- 0.6) years for diet, were not significant. Mean maximal interincisal opening was 36.7 +/- 2.0 mm before the operation, and this improved to 40.1 +/- 2.0 mm 1 year later (P <.02). Mean contralateral movement was 8.3 +/- 0.5 mm before the operation and 8.4 +/- 0.6 mm 1 year after the operation (P >.05). None of the 12 Wilkes late III joints progressed to Wilkes IV or V, and none of the 14 Wilkes IV, V joints showed evidence of further bone resorption. The rate for reoperation was 4%. Minor complications occurred in 5 patients and were resolved in all but 1 a year later. When these outcomes were judged by 7 American Association of Oral and Maxillofacial Surgeons assessment indices for internal derangement, the mean rate of favorable outcome was 87%.

CONCLUSION

Modified condylotomy is a safe and effective operation for treating pain and diminished function of temporomandibular joints with nonreducing disk displacement. It also seems to be an effective treatment for slowing further progression of the internal derangement and associated pathologic conditions.

One- and three-year prospective outcome study of modified condylotomy for treatment of reducing disc displacement

PURPOSE

This outcomes study was designed to provide a comprehensive evaluation of modified condylotomy for the treatment of the painful temporomandibular joint with reducing disc displacement (Wilkes stage II, early III).

PATIENTS AND METHODS

A prospective study of 48 consecutive patients (79 joints) was conducted. All reducing disc displacements were verified by disc imaging. Independent evaluations were performed to assess pain, dysfunction, and progression of disease before modified condylotomy and at intervals up to 1 year after operation. Thirty-one patients (50 joints) completed the examination before the operation and 1 year later. Patient-based assessments were made for pain and diet in 22 patients (35 joints) 3 years after operation.

RESULTS

The mean (+/- SE) visual analog scale (VAS) score for pain improved from 6.9+/-0.4 before modified condylotomy to 2.0+/-0.4 1 year later (P < .001). Serious pain (VAS score greater than 4) after operation was 7 times more likely (P < .04) when there was persistent disc displacement. The mean frequency of pain each day decreased from 14.6+/-1.4 hours to 4.8+/-1.3 hours (P < .001). Dietary restrictions improved from a mean VAS score of 6.1+/-0.5 before operation to 8.8+/-0.3 at 1 year (P < .001). Small differences between mean VAS scores for pain at 1 (2.0+/-0.5) and 3 (2.7+/-0.5) years and diet at 1 (8.6+/-0.4) and 3 (8.4+/-0.5) years after operation were not significant. Mean maximal incisal opening was 41.7+/-1.2 mm before operation and 43.5+/-1.1 mm 1 year later, but the difference was not statistically significant. Mean contralateral movement improved from 8.1+/-0.3 mm to 8.9+/-0.3 mm 1 year after operation (P < .05). Clicking was reduced from 64% of joints to 16% 1 year after operation (P < .001). The disc was reduced in 72% of joints, healing of an incipient degenerative lesion occurred in 1 joint, and there was no evidence of progression to nonreducing disc displacement (Wilkes late III, IV, V) or DJD (Wilkes IV, V) in any joint 1 year after modified condylotomy. The rate for reoperation was 4%. Complications occurred in 4 patients after operation and were resolved 1 year later. When these outcomes were judged by 7 AAOMS assessment indices for internal derangement, the mean rate of favorable outcome was 94%.

CONCLUSION

Modified condylotomy is an effective operation for treating pain and diminished function of temporomandibular joints with reducing disc displacement. It is also an effective treatment for slowing and, in some cases, reversing the progression of internal derangement.

Transdermal water mobility in the presence of electrical fields using MR microscopy

Magnetic resonance microscopy of skin from hairless rats under the influence of electrical fields was conducted for two cases: 1) low voltage constant electrical fields and 2) high-voltage short pulse, electrical fields. Under conditions of the low voltage and low current iontophoresis, i.e., 0 to 20 V, and 0 to 0.5 mA/cm2, it was found that the skin structure, as observed by magnetic resonance microscopy, did not significantly change until 20 Volts were applied across the 0.1 cm thick skin. Under these conditions, the viable epidermis appeared to swell, and this result corresponded to observations from scanning electron microscopy and other research from the literature. High voltage electrical fields, i.e., 220 V 1 ms pulses repeated once per second, appeared to hydrate the stratum corneum as is consistent with published literature on electroporation. In the case of iontophoresis, water self-diffusion coefficients in the epidermis and hair follicle regions at all voltages were affected by the electrical field. Statistical analysis at the 95% confidence level for the comparison of the average differences between diffusion coefficients with the electrical field on and with the electrical field off for pair matched pixels for the viable epidermis show that for 5 V (p = 0.00377), 10 V (p = 0.0108), 20 V (p = 0.0219) regimes there are statistically significant (p < or = 0.05) changes due to the applied electric field. The same analysis for the hair follicle region at 5 V (p = 6.89 x 10(-7)), 10 V (p = 1.42 x 10(-5)), 20 V (p = 3.23 x 10(-3)) also show statistically significant changes (p < or = 0.05). When the electroporation pulse was applied, the water diffusion coefficients increased by about 30% to 6.6 x 10(-6) cm2/s +/- 2.4 x 10(-7) cm2/s and 8.3 x 10(-6) cm2/s +/- 3.7 x 10(-7) cm2/s, for the epidermis and hair follicle regions, respectively. Significant differences were noted between diffusion coefficients in the viable epidermis and the hair follicles for all cases.

Xenon-131 surface sensitive imaging of aerogels in liquid xenon near the critical point

In recent years, optically pumped xenon-129 has received a great deal of attention as a contrast agent in gas-phase imaging. This report is about the other NMR active xenon isotope (i.e., xenon-131, S = 32) which exhibits distinctive features for imaging applications in material sciences that are not obtainable from xenon-129 (S = (1/2)). The spin dynamics of xenon-131 in gas and liquid phases is largely determined by quadrupolar interactions which depend strongly on the surface of the surrounding materials. This leads to a surface dependent dispersion of relaxation rates, which can be substantial for this isotope. The dephasing of the coherence due to quadrupolar interactions may be used to yield surface specific contrast for imaging. Although optical pumping is not practical for this isotope because of its fast quadrupolar relaxation, a high spin density of liquid xenon close to the critical point (289 K) overcomes the sensitivity problems of xenon-131. We report the first xenon-131 magnetic resonance images and have tested this technique on various meso-porous aerogels as host structures. Aerogels of different densities and changing levels of hydration can clearly be distinguished from the images obtained.

A protocol for magnetic resonance imaging of the temporomandibular joints

The complex concepts and procedures of magnetic resonance imaging (MRI) are unfamiliar to many dentists. Similarly, many radiologists lack understanding of the clinical requirements of the dentist for accurate assessment of TMJ abnormalities. Thus, TMJ imaging procedures may be inadequate or incomplete, may vary from facility to facility, and sometimes from patient to patient in a given facility. A protocol for TMJ imaging is presented which meets dental requirements and is rapidly performed in the MRI facility. The protocol may be copied and attached to the prescription to the imaging center. It may be modified or expanded to accommodate specific patient requirements or equipment performance.

Rapid MRI and velocimetry of cylindrical Couette flow

A narrow-gap, temperature-controlled Couette flow rheometer has been developed to study fluid velocities within the annular gap between two concentric cylinders by nuclear magnetic resonance (NMR) imaging and velocimetry. Alternative pulsed-field-gradient-based nuclear magnetic resonance imaging strategies which may be used for measurement of velocity within the Couette flow device have been evaluated. These include two-dimensional (2-D) imaging techniques with acquisition times of several minutes and a one-dimensional (1-D) projection method which exploits the symmetry of the device to reduce overall measurement time to less than 1 min. Velocity measurements made using each technique are presented for a Newtonian fluid undergoing Couette flow at shear rates of approximately 20 and 60 s(-1).

Proton Diffusion and T1 Relaxation in Polyacrylamide Gels: A Unified Approach Using Volume Averaging

The structure of polyacrylamide gels was studied using proton spin-lattice relaxation and PFG diffusion methods. Polyacrylamide gels, with total polymer concentrations ranging from 0.25 to 0.35 g/ml and crosslinker concentrations from 0 to 10% by weight, were studied. The data showed no effect of the crosslinker concentration on the diffusion of water molecules. The Ogston-Morris and Mackie-Meares models fit the general trends observed for water diffusion in gels. The diffusion coefficients from the volume averaging method also fit the data, and this theory was able to account for the effects of water-gel interactions that are not accounted for in the other two theories. The averaging theory also did not require the physically unrealistic assumption, required in the other two theories, that the acrylamide fibers are of similar size to water molecules. Contrary to the diffusion data, T1 relaxation measurements showed a significant effect of crosslinker concentration on the relaxation of water in gels. The model developed using the Bloch equations and the volume averaging method described the effects of water adsorption on the gel medium on both the diffusion coefficients and the relaxation measurements. In the proposed model the gel medium was assumed to consist of three phases (i.e., bulk water, uncrosslinked acrylamide fibers, and a bisacrylamide crosslinker phase). The effects of the crosslinker concentration were accounted for by introducing the proton partition coefficient, Keq, between the bulk water and crosslinker phase. The derived relaxation equations were successful in fitting the experimental data. The partition coefficient, Keq, decreased significantly as the crosslinker concentration increased from 5 to 10% by weight. This trend is consistent with the idea that bisacrylamide tends to form hydrophobic regions with increasing crosslinker concentration. Copyright 1998 Academic Press.

Initial TMJ disk recapture with anterior repositioning appliances and relation to dental history

Fifty-eight consecutive patients in a referral based practice seeking treatment for complex chronic painful temporomandibular joint (TMJ) disease were enrolled in a prospective study to assess the recapture of displaced disks by anterior repositioning appliances (ARA) and the improvement in disk position in those disks that did not fully recapture. After standard clinical workup, including assessment of pain, maxillary and mandibular ARAs were constructed which repositioned condyles to the Gelb 4/7 position as determined by cephalometrically-corrected linear tomograms. Multi-planar magnetic resonance imaging (MRI) was performed immediately before and after insertion of the mandibular ARA, showing three-dimensional recapture of disks in 85% and improved disk position in 6% of reducing displacements. Disk position was improved in 28% of nonreducing joints, but none were totally recaptured. Recapture or improvement was achieved in 91% of reducing, 28% of nonreducing, and 63% of all joints with internal derangements. Initial disk position, reduction on opening and recapture by ARA were statistically independent of patient age, number of teeth missing, number of third molars missing, malocclusion (Angle's class), overjet, overbite, prosthetic appliances, and previous orthodontic treatment. It was concluded that ARA therapy provided effective recapture of displaced TMJ disks that reduce upon mouth opening. In this population of patients with chronic TMJ pain, previous dental treatment had no statistically significant effect on the incidence of internal derangement or on disk recapture by ARA therapy. There was no evidence of adverse effect from orthodontics, prosthetics, or any other dental care.

Imaging of the temporomandibular joint: a position paper of the American Academy of Oral and Maxillofacial Radiology

Various imaging techniques for the temporomandibular joint are discussed with respect to uses, strengths, and limitations. An imaging protocol is outlined for evaluating patients with a wide variety of temporomandibular joint related signs and symptoms.

Strategies for Rapid NMR Rheometry by Magnetic Resonance Imaging Velocimetry

Strategies for NMR-based rheometry are discussed with particular attention given to ease of implementation, robustness, and measurement speed. The techniques are based on NMR velocimetry of Poiseuille flow, and together with measurements of the pressure drop, the velocimetric data may be processed to yield measures of the shear viscosity over the range of shear rates present in the Poiseuille flow field of the test fluid. Methods for NMR velocimetry are briefly reviewed, and three methods all based on the pulsed-field-gradient technique are compared experimentally; they involve (1) direct two-dimensional imaging of the tube cross section, (2) one-dimensional imaging of a Cartesian projection of the tube cross section followed by Abel inversion to obtain radial profiles, and (3) measurement of the bulk velocity spectrum of the tube cross section and conversion to the radial velocity profile. The second and third of these techniques allow the most rapid measurements (potentially less than one minute) and show promise for on-line NMR rheometry.

Long-term follow-up of modified condylotomy for internal derangement of the temporomandibular joint

OBJECTIVES

The purpose of this study was to evaluate disk position and patient response 10 years after modified condylotomy for symptomatic reducing disk displacement.

STUDY DESIGNS

Questionnaires and invitations to return for examination and temporomandibular joint magnetic resonance imaging were mailed to 39 consecutive patients 10 years after modified condylotomy.

RESULTS

On a 10-point scale the mean pain experienced by the 17 respondents (27 joints) to the questionnaire was 2.0. Ninety percent of 20 joints (12 patients) examined were free of tenderness to palpation. Magnetic resonance imaging in 10 patients (17 joints) showed disk reduction in 59%, displacement with reduction in 29%, and displacement without reduction in 12%. Eighty-five percent of the joints met American Association of Oral and Maxillofacial surgeons criteria for a successful therapeutic outcome.

CONCLUSIONS

The study suggests a role for modified condylotomy in the long-term management of symptoms associated with reducing disk displacement. Further, modified condylotomy can frequently reverse an internal derangement and seems to protect against the natural progression of osteoarthrosis.

Radiology: closing a century, opening a millennium

As we close the file on the first century of radiology, we honor the pioneers and reflect on the progress they started. We also open a new file, not just a new century, but a new millennium of opportunity. The dramatic technologic advances in diagnostic imaging within recent decades have provided the foundation for expanding our activities in Oral and Maxillofacial Radiology. We are no longer just dental radiology; we can no longer rest on the teaching and practice of conventional dental radiography. We can summarize in one word the direction our efforts must take in opening the millennium: research. Only with research at the fundamental as well as clinical level we can continue to expand our service to the public, to our patients, and to our colleagues.

A pilot study to evaluate the cost-effectiveness of ondansetron and granisetron in fractionated total body irradiation

The duration of the antiemetic effect of granisetron was examined in a pilot study of patients (n = 26) undergoing a standard emetogenic stimulus in the form of total body irradiation fractionated over 3-4 days, in a randomized comparison with twice-daily ondansetron. A single intravenous dose of granisetron at the onset of therapy was effective over the entire follow-up period in 50% (6/12) of patients, compared with 77% (10/13) prescribed twice-daily oral ondansetron for 3 or 4 days. The response rate within the first 24 hours from the start of irradiation was 67% (8/12) for granisetron and 77% (10/13) for ondansetron. Granisetron and ondansetron were therefore of similar efficacy within the first 24-hour period, but granisetron was less efficaceous more than 24 hours after the onset of therapy. Patients who required a second dose of granisetron did so at intervals of 12, 42, 47 and 48 hours following the first fraction of radiotherapy. The cost per patient in this study was pound 48 for granisetron and pound 54 for ondansetron, but the dose scheduling we used cannot be recommended in view of the lower effectiveness of granisetron.

Studies of soil-water transport by MRI

Sequential spin-echo spin-warp MRI pulse sequences have been used to study soil-water transport processes including infiltration, redistribution, and drainage of water in soil columns. Those images provide a means for monitoring and quantifying spatial and temporal changes of soil-water distributions and the movement of wetting fronts. In addition, temporal-geometric changes of unstable wetting fronts during water redistribution were estimated from 2D images and the temporal development of the longest length of finger was described by a fractal relation t approximately L1.38. Bulk dispersion-time-dependent displacement and velocity spectra, as well as 2D maps of flow velocities and dispersion coefficients in soil macropores during saturated steady-state flow, were reconstructed from data obtained using the alternating-pulsed-field-gradient (APFG) pulse sequences.

Recapture of temporomandibular joint disks using anterior repositioning appliances: an MRI study

Thirty consecutive patients seeking treatment for painful temporomandibular joint (TMJ) disease were enrolled in a prospective study to assess the relationship between the recapture of displaced disks by anterior repositioning appliances (ARA) and the relief of symptoms. After standard clinical workup including assessment of pain, maxillary and mandibular ARAs were constructed that repositioned condyles to the Gelb 4/7 position. Magnetic resonance imaging (MRI) was performed before and immediately after the insertion of ARAs. Initial MRI findings showed 26 joints with reducing disk displacements in 17 patients, seven partially-reducing joints in four patients, 14 nonreducing joints in 11 patients, and 13 normal joints in eight patients. Postinsertion MRI showed recapture of disks in 25 of 26 reducing displacements (96%), but no recapture in partially-reducing or nonreducing joints. All but one of the normal joints remained unchanged. Pain assessment showed significant relief of symptoms in all three categories. The degree of pain relief was significantly greater in recaptured reducing disks than the other categories (p < 0.05). ARA therapy provides effective pain relief regardless of disk status, although a greater degree of relief may be achieved in recaptured reducing internal derangements.

Brain proton magnetic resonance spectroscopy studies in recently abstinent alcoholics

Chronic alcohol-dependent patients have reduced brain volumes and concomitant neurobehavioral deficits that may recover during abstinence. In 10 chronic alcoholic patients, using localized proton magnetic resonance spectroscopy, we found reliable increases during the first 3-4 weeks of abstinence in the concentrations within the superior cerebellar vermis of choline (Cho)-containing compounds relative to the neuronal marker, N-acetylaspartate (NAA). Lesser changes were observed following 1 month of abstinence, and in one of the patients studied longitudinally over 3 months, a marked reduction in the Cho/NAA ratio was associated with relapse. After detoxification, the Cho/NAA ratio correlated with a composite clinical impression of brain functions. The lowest Cho/NAA was observed in a patient with persisting alcoholic dementia, in striking contrast to reduced relative concentrations of NAA reported in dementia of the Alzheimer's type. Possible molecular explanations for these brain metabolic changes are discussed.

Disk position before and after modified condylotomy in 80 symptomatic temporomandibular joints

OBJECTIVE

Our primary objective was to determine the frequency of disk reduction after modified condylotomy and whether the type of displacement affected outcome.

DESIGN

We classified reducing disk displacements from magnetic resonance images of 80 symptomatic temporomandibular joints before modified condylotomy. Disk position was reassessed after surgery.

RESULTS

The disk and condyle typically move in reciprocal directions. The disk was reduced by surgery in 79% of the joints. The rate of reduction varied by the type of displacement, but the differences between the groups were not statistically significant.

CONCLUSION

This finding reaffirms that modified condylotomy has a high rate of disk reduction. The unexpected observation that the increase in joint space resulting from the surgery typically permitted a variable degree of spontaneous movement of the disk has implications for the nature of osteoarthrosis and internal derangement and for surgical treatments intended to reduce the risk.

Hodgkin's disease, follicular non-Hodgkin's lymphoma and a high grade B cell non-Hodgkin's lymphoma in the same patient

We report an unusual patient with a 21 year history of lymphoma of three different histological varieties: a low grade follicular non-Hodgkin's lymphoma, mixed cellularity Hodgkin's disease and a high grade B cell monocytoid non-Hodgkin's lymphoma.

Seminoma and squamous cell carcinomas in association with lymphopenia

A patient with a seminoma, squamous cell carcinomas of the skin and anus, Bowen's disease and lymphopenia is reported. The underlying aetiology is thought to be impaired cell mediated immunity and susceptibility to viral infections.

Partially restricted diffusion in a permeable sandstone: observations by stimulated echo PFG NMR

We demonstrate a variant, insensitive to eddy current effects, of an alternating pulsed field gradient technique designed to null the effect of background gradients in liquid-saturated porous media, using a 38 mm diameter sample of a natural sandstone. Measurements of the effective diffusivity confirm predictions of a decline as the square root of an effective diffusion time. A value of the ratio S/Vp for the dominant pores is extracted, yielding with T1 a value for the surface relaxivity. We test also a geometry-dependent data collapse recently suggested for a range of diffusion times and wavenumbers. The data agree with a sheet-like pore model for this granular sandstone, and fail to agree with a tube-like model; a pore length scale is also extracted.

Pore geometry information via pulsed field gradient NMR

Studies of echo attenuation at long diffusion times in pulsed field gradient NMR experiments on a variety of rock core samples are interpreted in the light of recent theoretical analysis of the effect of pore geometry and surface relaxation. This study is motivated by the need to test the applicability of that theory to real rock systems.

Dissecting and implementing STEAM spectroscopy

A rapid, simple method for constructing a site-specific STEAM sequence from a basic Hahn three-pulse sequence is presented. The method assures maximum signal available from the hardware.

Comparative imaging of the jaws

Explosive growth in high-technology imaging continues in dentistry as in all health sciences. Some new technology will find its way into general and some specialty dental practices; two examples, digital intraoral radiography and multimodality panoramic machines, are reviewed. New developments in the application of current imaging procedures (both conventional and "high tech") to diagnosis and management of diseases and injuries of the jaws, muscles of mastication, and salivary glands are presented. Recent information suggests that the risk of radiation-induced cancer in exposed populations may be greater than had been recognized. The impact of this data on both occupational and patient radiation exposure in dentistry is reviewed.

Removing effects of eddy currents in proton MR spectroscopy

The use of pulsed gradients to define a volume of interest for localized magnetic resonance spectroscopy produces magnetic field perturbations which distort both the free induction decay and the spectrum after Fourier transformation. A technique is presented that removes the artifacts from eddy currents from a sampled free induction decay. To linearize the phase, the nonlinear phase of a reference free induction decay is subtracted from the phase of a sample free induction decay. Next, to move the frequency to resonance and perform a zero-order phase correction, the line fit from a linear regression is subtracted from the phase. After reconstructing the free induction decay, the resulting frequency spectra are sorted into absorption mode and dispersion mode components.