A comparison of 180 degrees and 360 degrees acquisition for attenuation-compensated thallium-201 SPECT images

This study compared attenuation compensated, myocardial SPECT images reconstructed from 180 degrees and 360 degrees data to determine if either data acquisition method might yield improved image quality. Specifically, this study analyzed how the use of either 180 degrees or 360 degrees data affects: (a) the relative count density distribution, (b) defect contrast and (c) level of statistical noise in the left ventricular (LV) wall in the reconstructed SPECT images. METHODS: Using the three-dimensional MCAT phantom simulating 201Tl uptake in the upper torso and the SIMSET Monte Carlo code, noise-free projection datasets for both 180 degrees (45 degrees LPO to 45 degrees RAO) and 360 degrees acquisition were generated with the effects of nonuniform attenuation, collimator-detector response and scatter. In addition, low-noise experimental phantom data were acquired over 180 degrees and 360 degrees. Assuming the same total acquisition time, four sets of noisy projection data were simulated from scaled noise-free, simulated data for the following acquisitions: (a) 180 degrees and (b) 360 degrees data acquired on a 90 degrees dual-detector system and (c) 180 degrees and (d) 360 degrees data acquired on a 120 degrees triple-detector system. For each of the four acquisition schemes, 400 realizations of noisy projection data were generated, and the normalized s.d. in the reconstructed images was calculated for five ROIs in the LV wall. Images were reconstructed with nonuniform attenuation compensation using ML-EM algorithm for 25, 50 and 75 iterations. RESULTS: Both the simulated noise-free and experimental low-noise images reconstructed from 180 degrees and 360 degrees data showed nearly identical count densities and defect contrasts in the LV wall. For the 90 degrees dual-detector system, 180 degrees images showed less noise, while for the 120 degrees triple-detector system, 360 degrees showed less noise; however, these differences in noise level were extremely small after a smoothing filter was applied. The 180 degrees images acquired with the 90 degrees dual-detector system showed the same noise level as the 360 degrees images acquired with the 120 degrees triple-detector system, so neither system geometry had an advantage with respect to reduced noise in the SPECT images. CONCLUSION: When nonuniform attenuation compensation is included in the reconstruction, the count density in the LV wall is nearly identical for 180 degrees and 360 degrees SPECT images, and the 90 degrees dual-detector and 120 degrees triple-detector SPECT systems produced similar SPECT images for the same total acquisition time.     

Genetic and developmental influences on infant mouse ultrasonic calling. II. Developmental patterns in the calls of mice 2-12 days of age

Both 360 degrees and 180 degrees rotation acquisition methods have been used in myocardial single photon emission tomography (SPET) studies. We compared both methods using 201Tl, 99Tcm and 123I radiopharmaceuticals with phantoms and clinical models. Myocardial phantom studies with anterior and inferior defects were performed using 201Tl, 99Tcm and 123I. Clinical models of 14 typical situations, including normal subjects, patients with anterior or inferior defects and a high right hemi-diaphragm, were studied. The radiopharmaceuticals were 201Tl, 99Tcm-sestamibi, 123I-BMIPP and 123I-MIBG. Four sets of 180 degrees anterior rotation data with starting angles of (A) posterior, (B) LPO 30 degrees, (C) LPO 60 degrees and (D) left lateral direction were generated and compared with 360 degrees rotation SPET. A polar map display was used for quantification. In phantom studies, the defect contrast on the map was higher in the anterior defect with 180 degrees rotation than with 360 degrees rotation. However, it was decreased in the inferior defect, particularly with 201Tl, because of decreased wall activity around the defect. In the patient model with anterior or inferior defects, the defect contrast was improved with 180 degrees SPET by up to 10%. A slight decrease in the normal region was also noted in the 180 degrees reconstruction. The effect of diffuse liver activity on the inferior region depended on the rotation range. A patient with a high right hemi-diaphragm showed a lower inferior count with 360 degrees SPET. In conclusion, the 360 degrees acquisition was superior to the 180 degrees acquisition in the phantom with defects. Clinically, the quantitative differences in radionuclide types (99Tcm, 123I or 201Tl) were not significant for quantifying a moderate degree (50-60% of peak count) of defect. However, we note quantitative variation depending on the rotation range in the 180 degrees method.     

Effects of selective head cooling on brain cell membrane activity during postischemic reperfusion

OBJECTIVE: To examine the effect of selective head cooling (SHC) on brain cell membrane activity involving ATPase, phospholipase A2, content of total membrane phospholipids during postischemic reperfusion, so as to elucidate the possible underlying mechanism on resuscitating effect of SHC. MATERIALS AND METHODS: Complete cerebral ischemia (CCI) was induced by the four-vessel model. 56 New Zealand rabbits were allocated randomly into two groups, non-ischemic control group had 30, 180 and 360 minutes reperfusion after CCI (n = 8); and SHC group with the same ischemic-reperfusion insult were all treated with SHC (28 degrees C, surface cooling method). Changes of Na+, K(+)-ATPase, Ca2+, Mg(2+)-ATPase, phospholipase A2, total phospholipids of brain cell membrane were observed. Comparison of data between two groups was made by Students' t test. RESULTS: Compared with non-ischemic controls following 30 minutes CCI, activities of Na+, K(+)-ATPase stepwisely decreased at 30, 180 and 360 minutes, Ca2+, Mg(2+)-ATPase dropped at 180 and 360 minutes, phospholipidase A2 increased markedly at 30, 180, 360 minutes, and total phospholipids decreased at 180 and 360 minutes reperfusion (P < 0.01). Selective head cooling inhibited all the above changes significantly (P < 0.01). CONCLUSION: The results suggest that selective head cooling initiated soon after reperfusion is beneficial for brain cell membrane function recruitment, which provides favourable effects on the damaged but still remediable brain cells for their resuscitation.     

Adenovirus-mediated gene transfer to liver grafts: an improved method to maximize infectivity

A patient motion-related artefact is one of the most important artefacts in single-photon emission tomography (SPET) imaging. This study evaluated the effect of the number and configuration of SPET detectors on motion artefacts. The following acquisition conditions were simulated based on original 360 degrees projection images: (1) single-detector 180 degrees rotation (S180), (2) a dual-detector rectangular (L-shaped) 180 degrees acquisition (D180L), (3) dual-detector cameras mounted opposite each other with 360 degrees acquisition (D360) and (4) triple-detector 360 degrees acquisition (T360). The motion artefacts were introduced using a syringe and a myocardial phantom. Clinical cases with technetium-99m methoxyisobutylisonitrile and thallium-201 studies were analysed to confirm the validity of this phantom simulation. The effect of continuous alternate rotation acquisition and summing the projections on the reduction of motion artefacts was investigated in each model. The effect of motion depended on the number and the configuration of the SPET detectors. A 1-pixel (6.4 mm) motion in the S180, D180L and D360 models generated only slight artefacts, and a 2-pixel motion led to an apparent decrease in activity or created hot areas in the myocardium. On the other hand, a T360 rotation created few artefacts even with a 2-pixel motion of the last quarter of the projections. Despite the difference in attenuation with 201Tl and 99mTc, similar artefact patterns were observed with both radionuclides in selected patient model studies. Continuous alternate rotation could reduce artefacts caused by less than a 2-pixel motion. In conclusion, calculating the average of the sum of the projections of triple-detector 360 degrees rotations with alternate rotation is the best method to minimize motion artefacts. This "averaging" effect of motion artefacts is a key to this simulation.     

Modified Sugioka's osteotomy: more than 130 degrees posterior rotation for osteonecrosis of the femoral head with large lesion

High degree posterior rotational osteotomy was performed on 31 hips with extensive osteonecrosis that were outside of Sugioka's indication. Among them, 18 hips of 13 patients were reviewed at 24 to 94 months (mean, 42 months). The remaining 13 hips were excluded because the followup was less than 2 years. All hips had less than 1/3 of the posterior area intact preoperatively, which is out of the indication for traditional anterior rotational osteotomy. The posterior rotation applied to the femoral head was 130 degrees to 180 degrees (mean, 138 degrees ). Furthermore, 10 degrees to 25 degrees of intentional varus position was added to the rotation (mean, 15.8 degrees). The preoperative intact articular surface of the loaded portion of the femoral head was 0% to 40% (mean, 6.9%) on anteroposterior radiograph, and it was extended postoperatively to a mean of 80.3% (range, 53%-100%). Collapse was prevented in 17 hips that have remained pain free. The remaining 1 hip sustained secondary collapse and joint narrowing. Mean flexion was 105 degrees and abduction was 20 degrees. Postoperative angiography of 9 hips and bony scintigraphy of 17 hips indicated no findings implying impairment of blood supply. Despite a relatively short term experience, it is concluded that this technique was effective in the treatment of large necrotic lesions, especially for young patients.     

Partial nephrectomy in cancer of the upper pole of kidney. Anatomical bases

On the basis of their importance for nephron-sparing surgery in tumors of the superior pole of the kidney, we analyzed 3-dimensional endocasts of the intrarenal structures. In 86.6% the superior pole was related to 3 arteries involved in its resection. Management of the superior (apical) segmental artery is in general simple as well as the ligature of the artery related to the anterior surface of the upper infundibulum. Ligature of the branch of the posterior segmental artery, that is related to the upper infundibulum, is critical due to the risk of injuring this segmental artery with loss of a great portion of renal parenchyma. The posterior segmental artery (retropelvic artery) is involved and must be preserved in all cases of superior pole resection. A retropelvic vein with its upper dorsal plexus was present in 69% of the cases. This vein must be previously ligated to provided safe management of the arteries during superior pole resection.     

Transmission-based scatter correction of 180 degrees myocardial single-photon emission tomographic studies

Meaningful comparison of single-photon emission tomographic (SPET) reconstructions for data acquired over 180 degrees or 360 degrees can only be performed if both attenuation and scatter correction are applied. Convolution subtraction has appeal as a practical method for scatter correction; however, it is limited to data acquired over 360 degrees. A new algorithm is proposed which can be applied equally well to data acquired over 180 degrees or 360 degrees. The method involves estimating scatter based on knowledge of reconstructed transmission data in combination with a reconstructed estimate of the activity distribution, obtained using attenuation correction with broad beam attenuation coefficients. Processing is implemented for planes of activity parallel to the projection images for which a simplified model for the scatter distribution may be applied, based on the measured attenuation. The appropriate broad beam (effective) attenuation coefficients were determined by considering the scatter buildup equation. It was demonstrated that narrow beam attenuation coefficients should be scaled by 0.75 and 0.65 to provide broad beam attenuation coefficients for technetium-99m and thallium-201 respectively. Using a thorax phantom, quantitative accuracy of the new algorithm was compared with conventional transmission-based convolution subtraction (TDCS) for 360 degrees data. Similar heart to lung contrasts were achieved and correction of 180 degrees data yielded a 10.4% error for cardiac activity compared to 5.2% for TDCS. Contrast for myocardium to ventricular cavity was similarly good for scatter-corrected 180 degrees and 360 degrees data, in contrast to attenuation-corrected data, where contrast was significantly reduced. The new algorithm provides a practical method for correction of scatter applicable to 180 degrees myocardial SPET.     

Anterior cruciate ligament reconstruction. The effect of tibial tunnel placement on range of motion

In 111 patients who had anterior cruciate ligament reconstructions, postoperative radiographic measurements of anterior to posterior and medial to lateral location of the tibial tunnels were correlated with the final range of motion achieved. In the 25 patients with extension deficits of 10 degrees or more, placement of the tibial tunnel was more anterior (average, anterior 23% of the tibia) than in the remaining 86 patients with extension deficits of < 10 degrees (average, anterior 29% of tibia). This difference was statistically significant with P < 0.001. Logistic regression analysis revealed that the more anterior the placement of the tibial tunnel, the greater the loss of both flexion (P = 0.01) and extension (P = 0.002). In the 21 patients with full extension but flexion < 130 degrees, placement of the tibial tunnel tended to be more medial (average, medial 40% of the tibia) than in the 65 patients without flexion deficit (average, medial 45% of the tibia). We conclude that placement of the tibial tunnel in the "eccentric," anteromedial position may contribute to the development of flexion and extension deficits after anterior cruciate ligament reconstruction.     

The effect of femoral tunnel position and graft tensioning technique on posterior laxity of the posterior cruciate ligament-reconstructed knee

We report the effects of femoral tunnel position and graft tensioning technique on posterior laxity of the posterior cruciate ligament-reconstructed knee. An isometric femoral tunnel site was located using a specially designed alignment jig. Additional femoral tunnel positions were located 5 mm proximal and distal to the isometric femoral tunnel. With the graft in the proximal femoral tunnel, graft tension decreased as the knee flexed; with the graft in the distal femoral tunnel, graft tension increased as the knee flexed. When the graft was placed in the isometric femoral tunnel, a nearly isometric graft tension was maintained between 0 degrees and 90 degrees of knee flexion. One technique tested was tensioning the graft at 90 degrees of knee flexion while applying an anterior drawer force of 156 N to the tibia. This technique restored statistically normal posterior stability to the posterior cruciate ligament-deficient knee between 0 degrees and 90 degrees for the distal femoral tunnel position, between 0 degrees and 75 degrees for the isometric tunnel position, and between 0 degrees and 45 degrees for the proximal tunnel position. When the graft was tensioned with the knee in full extension and without the application of an anterior drawer force, posterior translation of the reconstructed knee was significantly different from that of the intact knee between 15 degrees and 90 degrees for all femoral tunnel positions.     

In vivo anteroposterior femorotibial translation of total knee arthroplasty: a multicenter analysis

A study was conducted to determine in vivo femorotibial contact patterns for subjects having a posterior cruciate retaining or posterior cruciate substituting total knee arthroplasty. Femorotibial contact of 72 subjects implanted with a total knee replacement, performed by five surgeons, was analyzed using video fluoroscopy. Thirty-one subjects were implanted with a posterior cruciate retaining total knee replacement with a flat polyethylene posterior lipped insert, 12 with a posterior cruciate retaining total knee replacement with a curved insert, and 29 with a posterior cruciate substituting total knee replacement. Each subject performed successive deep knee bends to maximum flexion. Video images at 0 degree, 30 degrees, 60 degrees, and 90 degrees flexion were downloaded onto a workstation computer. Femorotibial contact paths were determined for the medial and lateral condyles using an interactive model fitting technique. Femorotibial contact anterior to the tibial midline in the sagittal plane was denoted as positive and contact posterior was denoted as negative. Analysis of average femorotibial contact pathways of both posterior cruciate retaining designs revealed posterior femorotibial contact in full extension with anterior translation of femorotibial contact commonly observed in midflexion and terminal flexion. In posterior cruciate substituting designs, anterior femoral translation was seen medially at 30 degrees to 60 degrees flexion but rarely was observed laterally. Posterior femoral rollback laterally from full extension to 90 degrees flexion was seen in 100% of subjects implanted with a posterior cruciate substituting total knee replacement, versus 51.6% (posterior lipped polyethylene insert) and 58.3% (curved insert) of those with a posterior cruciate retaining total knee replacement. Data from this multicenter study are remarkably similar to previous fluoroscopy data from a single surgeon series, showing a lack of customary posterior femoral rollback in both posterior cruciate retaining designs, and conversely showing an average anterior femoral translation with knee flexion. Posterior femoral rollback, less than in normal knees, routinely was observed in posterior cruciate substituting total knee arthroplasty, attributed to engagement of the femoral component cam with the tibial post. The abnormal anterior femoral translation observed in posterior cruciate retaining total knee arthroplasty may be a factor in premature polyethylene wear observed in retrieval studies.     

Usefulness of color kinesis imaging for evaluation of regional right ventricular wall motion in patients with surgically repaired tetralogy of Fallot

We evaluated regional right ventricular wall motion during systole in patients with surgically repaired tetralogy of Fallot (TOF) using color kinesis imaging. Color kinesis images were obtained in a subcostal sagittal view from 19 patients with repaired TOF (TOF group), aged 3 to 5 years, and 20 age-matched normal subjects (control group). For regional wall motion analysis, the endocardial motion distance and the fractional area change (FAC) were calculated for 6 segments obtained from color kinesis images. The endocardial inward excursion distances and the FACs in the upper, middle, and lower posterior segments of the TOF group were significantly greater than those of the control group (p <0.01 for each segment). The upper anterior segment showed significantly reduced inward excursion distance and FAC in the TOF group than in the control group (p <0.01, both). The dyskinetic outward excursion distances of the middle and lower posterior segments were significantly lower in the TOF group than in the control group (p <0.01, both). In the upper and middle anterior segments, the endocardial outward excursion distances were significantly higher in the TOF group than in the control group (p <0.01 and 0.05). Correlation between right ventriculographic and color kinesis measurements was excellent (y = 1.14x - 1.30, r = 0.87 for the endocardial inward excursion, and y = 1.03x +/- 0.56, r = 0.91 for the FAC). In conclusion, color kinesis is a useful method for assessing regional right ventricular wall motion. Segmental analysis of color kinesis images provides accurate, automated, and quantitative diagnosis of regional right ventricular wall motion abnormalities in patients with surgically repaired TOF.     

Isolation and characterization of mitochondria from turkey spermatozoa

The purpose of the present investigation was to evaluate 99Tcm-labelled alpha-D-glucose 1-phosphate (GP) aerosols for single photon emission computed tomographic (SPECT) ventilation lung imaging in comparison to 99Tcm-diethylenetriaminepentaacetate (DTPA) aerosols. Ten normal nonsmoking male volunteers (aged 20-30 years) were included in this study after obtaining their informed consent. 99Tcm-GP, 30 mCi, in 2 ml was placed in the nebulizer (Venticis II) and inhalation continued for 5 min of normal breathing with oxygen flowing through. In 10 subjects dynamic images were obtained from the posterior position for 90 min with 45 frames on a 64 x 64 matrix by the use of a gamma camera. At the end of the dynamic study planar images of the lung (anterior, posterior and laterals) were recorded. Decay corrected clearance curves and kep values were obtained by the pulmonary epithelial programme and T1/2 values were calculated. The same procedure was followed by the use of 99Tcm-DTPA in the same subjects 2 weeks later. SPECT studies of the lung were performed in five subjects after inhalation of 99Tcm-GP aerosols. Clearance curves were monoexponential. The difference in T1/2 values between the right and left lungs was statistically insignificant (P > 0.10). The mean T1/2 values were 316.5 +/- 44.7 and 80.8 +/- 13.4 min for 99Tcm-GP and 99Tcm-DTPA, respectively. The difference was significant (P < 0.0005). On scintigraphic images 99Tcm-GP showed high alveolar deposition and low adhesion to major airways like 99Tcm-DTPA. However, it is preferred to 99Tcm-DTPA for SPECT studies because of its prolonged pulmonary clearance.     

Ultrasonographic cross-sectional characteristics of muscles of the head and neck

OBJECTIVE: Computed tomography and magnetic resonance imaging are the common techniques for evaluating cross-sectional areas and volumes of human jaw muscles. Because computed tomography has the disadvantage of showing cumulative biological effects and because MRI poses a problem in terms of clinical availability and cost, the purpose of this study was to determine whether ultrasonography could be used to measure local linear cross-sectional dimensions of muscles of the head and neck. STUDY DESIGN: In 46 patients with signs and symptoms of temporomandibular disorders, the anterior temporalis, anterior masseter, deep masseter, anterior digastric, posterior digastric, and sternocleidomastoid muscles were measured bilaterally by ultrasonography to assess linear local cross-sectional dimensions. Measurements were made in 2 sessions with a time interval of at least 5 minutes. Data were analyzed for reliability and variability through use of the intraclass correlation coefficient (ICC) and the repeatability coefficient (RC). To assess local muscle asymmetry patterns, the absolute asymmetry index was used, with the mean maximum muscle diameters of the respective right and left sides calculated from 3 consecutive measurements. RESULTS: Satisfactory visualization of muscles was obtained in 93.8% of 1104 imaging procedures. For the ultrasound measurements there was a significant difference in local cross-sectional dimensions between the first and second sessions for the anterior temporalis muscle only (P < .01). Acceptable intrarater reliabilities were obtained for the deep masseter (ICC = 0.92), anterior digastric (ICC = 0.91), and sternocleidomastoid (ICC = 0.86) muscles, whereas evaluation of the posterior digastric (ICC = 0.74), anterior masseter (ICC = 0.72), and anterior temporalis (ICC = 0.70) muscles was associated with moderate reliability. Variability of repeated measurements was found to be acceptable for the anterior temporalis (RC = 0.32 mm) and posterior digastric (RC = 0.48 mm) muscles. Analysis of muscle site-related local cross-sectional dimensions showed a significant difference between the right and left sides for the deep masseter muscle only (P < .05). The study population investigated revealed mean asymmetry indices ranging from 5.3% for the anterior digastric muscle to 8.7% for the deep masseter muscle. CONCLUSIONS: Ultrasonography may prove to be a reliable diagnostic technique for the evaluation of cross-sectional dimensions and areas of muscles of the head and neck.     

A method of correlating and merging cerebral morphology and function by a special head holder

A method is introduced which records and correlates topographically identical morphological and functional image data by means of a special head holder system which is adaptable to different modalities (MRI, PET, SPECT). It is based on a commercially available thermoplastic headmask. A thermoplastic form is used to mold an individual headmask (time required: 7 min) for all modalities providing a fixation of the patient during acquisition. This method guarantees an exact repositioning and therefore the same slice orientation of the images. The in-plane correlation is performed by adapting standard offset parameters determined with a homogeneous head phantom. By fusion (merging) of the brain outline contours or images themselves the accuracy was tested in MRI vs. PET resp. SPECT (transaxial accuracy: < or = 2.0 mm, axial: < or = 3.0 mm in patients with MRI-slice thickness of 6.0 mm).     

201Tl myocardial SPECT. First experiences with a simultaneous transmission-emission acquisition protocol for patient-specific attenuated correction

AIM: In this study our first clinical experiences with simultaneous transmission and emission acquisition in 201 TI myocardial SPECT (T/E-SPECT) are discussed. METHODS: The non-uniform attenuation (AK) was carried out with a triple-head camera (PRISM 3000, Picker Inc.) correction equipped with fanbeam collimators. A line source of 750 MBq 99mTc was used to construct the transmission profile. Prior to investigation patients got 80-120 MBq 201TI-chloride intravenously injected. RESULTS: The study comprises the evaluation of 40 patients, derived from the clinical routine. The investigation followed an usual one day protocol. Our results using T/E-SPECT reveal an almost equilibrated activity distribution between anterior and posterior myocardial wall. CONCLUSION: For this reason it is to be expected that T/E-SPECT provides more reliable information about the posterior myocardial wall, than the usual SPECT technique without attenuation correction.     

Codes for sound-source location in nontonotopic auditory cortex

We evaluated two hypothetical codes for sound-source location in the auditory cortex. The topographical code assumed that single neurons are selective for particular locations and that sound-source locations are coded by the cortical location of small populations of maximally activated neurons. The distributed code assumed that the responses of individual neurons can carry information about locations throughout 360 degrees of azimuth and that accurate sound localization derives from information that is distributed across large populations of such panoramic neurons. We recorded from single units in the anterior ectosylvian sulcus area (area AES) and in area A2 of alpha-chloralose-anesthetized cats. Results obtained in the two areas were essentially equivalent. Noise bursts were presented from loudspeakers spaced in 20 degrees intervals of azimuth throughout 360 degrees of the horizontal plane. Spike counts of the majority of units were modulated >50% by changes in sound-source azimuth. Nevertheless, sound-source locations that produced greater than half-maximal spike counts often spanned >180 degrees of azimuth. The spatial selectivity of units tended to broaden and, often, to shift in azimuth as sound pressure levels (SPLs) were increased to a moderate level. We sometimes saw systematic changes in spatial tuning along segments of electrode tracks as long as 1.5 mm but such progressions were not evident at higher sound levels. Moderate-level sounds presented anywhere in the contralateral hemifield produced greater than half-maximal activation of nearly all units. These results are not consistent with the hypothesis of a topographic code. We used an artificial-neural-network algorithm to recognize spike patterns and, thereby, infer the locations of sound sources. Network input consisted of spike density functions formed by averages of responses to eight stimulus repetitions. Information carried in the responses of single units permitted reasonable estimates of sound-source locations throughout 360 degrees of azimuth. The most accurate units exhibited median errors in localization of <25 degrees, meaning that the network output fell within 25 degrees of the correct location on half of the trials. Spike patterns tended to vary with stimulus SPL, but level-invariant features of patterns permitted estimates of locations of sound sources that varied through 20-dB ranges. Sound localization based on spike patterns that preserved details of spike timing consistently was more accurate than localization based on spike counts alone. These results support the hypothesis that sound-source locations are represented by a distributed code and that individual neurons are, in effect, panoramic localizers.     

Automatic three-dimensional matching of CT-SPECT and CT-CT to localize lung damage after radiotherapy

The aim of this study was to develop a fast and clinically robust automatic method to register SPECT and CT scans of the lungs. METHODS: CT and SPECT scans were acquired in the supine position from 20 patients with healthy lungs. After partial irradiation of the lungs by radiotherapy, the scans were repeated. Two matching methods were compared: a conventional method with external skin markers and a new method using chamfer matching of the lung contours. In the latter method, a unique value for the SPECT threshold, needed for segmentation of the SPECT lungs, was determined by iteratively applying the chamfer matching algorithm. RESULTS: The new technique for CT-SPECT matching could be implemented in a fully automatic manner and required less than 2 min. No large systematic shifts or rotations were present between the matches obtained with the marker method and the lung contour method for healthy or partially irradiated lungs. For healthy lungs, the number of ventilation SPECT counts outside the CT-defined lung was taken as a measure for a good match. This number of outside counts was slightly lower for the new method than for the conventional method, which indicates that the accuracy of the new method is at least comparable to the conventional method. For ventilation, a systematic difference between the results of the matching methods, a small translation in the anterior --> posterior direction, could be attributed to an inconsistency of the marker positions (2 mm). For perfusion, a somewhat larger anterior --> posterior shift was found, which was attributed to the gravity force. CT-CT correlation on the lung contours using chamfer matching was tested with the same dataset. For accurate matching, the CT slices encompassing the diaphragm had to be deleted. CONCLUSION: The new method based on lung contour matching is a fast, automatic procedure and allows accurate clinical follow-up.     

Pain-pressure threshold in the head and neck region of episodic tension-type headache patients

Pain-pressure thresholds of the head and neck region of 31 female patients (aged 13 to 50 years; mean, 28.4 +/- 9.6 years) suffering from episodic tension-type headache and 32 female control subjects (aged 15 to 46 years; mean, 26.6 +/- 8.6 years) were recorded with an electronic algometer by the same blinded observer. The multivariate analysis of variance revealed that the algometer values obtained from different age groups of patients and control subjects were statistically different, but the values for the right-side muscles were not statistically different from the corresponding values for the left-side muscles. The pain-pressure thresholds of the patient group were lower than those of the control group for the superior sternocleidomastoid muscles, middle sternocleidomastoid muscles, and trapezius insertion muscles (P < .01) but were not statistically different for the anterior temporal, middle temporal, posterior temporal, deep masseter, anterior masseter, inferior masseter, medial pterygoid, posterior digastric, splenius capitis, and upper trapezius muscles (P > .01). The results may indicate that pain-pressure thresholds of the head and neck region should be considered in the diagnosis of episodic tension-type headache. The results may also propose that the increased pain sensitivity of the head and, especially, the neck region, may be included in the pathogenetic mechanism in episodic tension-type headache.     

Rotational deformation of the canine left ventricle measured by magnetic resonance tagging: effects of catecholamines, ischaemia, and pacing

OBJECTIVE: The aim was to investigate the generation of rotation of the left ventricular apex with respect to the base by magnetic resonance tagging, a non-invasive method of labelling the myocardium, in a canine model. METHODS: 18 dogs were imaged at baseline and during: (1) inotropic stimulation with dobutamine; (2) chronotropic stimulation with atrial pacing; (3) anterior wall ischaemia; (4) posterior wall ischaemia; and (5) varying left ventricular activation site; six dogs underwent each intervention. Apical rotation of the apex (torsion) was quantified. The epicardium and the endocardium were considered separately, as were the anterior and posterior walls. RESULTS: Mean torsion of the epicardium [anterior 3.1(SEM 1.2) degrees, posterior 9.9(1.0) degrees] was less than that of the endocardium [anterior 8.1(2.6) degrees, posterior 14.9(2.0) degrees, p < 0.05 for both]. Anterior torsion was less than posterior torsion for both the epicardium, p < 0.05, and the endocardium, p < 0.05. Dobutamine increased torsion of both the epicardium [anterior 13.3(2.2) degrees, posterior 12.6(1.7) degrees, p < 0.05 for both] and the endocardium [anterior 24.6(2.3) degrees, posterior 16.5(2.1) degrees, p < 0.05 for both]. Atrial pacing at 160% baseline rate increased torsion of both the anterior wall [epicardium 6.6(1.0) degrees, endocardium 11.3(1.2) degrees, p < 0.05] and the posterior wall [epicardium 13.0(1.3) degrees, endocardium 19.4(1.9) degrees, p < 0.05]. Anterior wall ischaemia reduced torsion of the anterior wall only [epicardium -2.0(1.0) degrees, endocardium 6.7(2.3) degrees, both p < 0.05]. Posterior wall ischaemia reduced torsion of the posterior wall of the epicardium only [7.1(1.2) degrees, p < 0.05] but also reduced torsion of the anterior wall [epicardium 0.7(1.0) degrees, endocardium 2.4(1.6) degrees, p < 0.05 for both]. Altering the pattern of left ventricular activation by atrioventricular pacing reduced torsion of the posterior wall of the epicardium [6.6(1.2) degrees, p < 0.05] and of the anterior [3.6(1.9) degrees, p < 0.05] and posterior [7.1(1.6) degrees, p < 0.05] walls of the endocardium. CONCLUSIONS: Rotational deformation of the left ventricle is dependent on the pattern of left ventricular activation and the contractile state. That a decrease in the contractile state in one area (by ischaemia) can cause a decrease in rotation in another suggests that this rotation depends on the complex fiber arrangement of the whole ventricle.     

Directional masking of phase locking in the amphibian auditory nerve

Directional masking in the amphibian auditory periphery was investigated by presenting frogs with a continuous tone from above and a continuous broadband noise from four different horizontal directions. This paradigm mimics the natural situation in which frogs are located in three-dimensional space and interference can and does arise from any direction. Intracellular recordings were made from single auditory-nerve fibers of the anesthetized adult leopard frogs using a dorsal approach. Vector strength (VS) and the mean preferred firing phase (MP) were measured for 94 low-frequency fibers. Thirty-six percent of the fibers demonstrated direction sensitivity of noise masking of VS. Most fibers exhibited a maximum decrease in VS at 90 degrees or 270 degrees noise incident angle and a minimum decrease in VS at 0 degrees or 180 degrees noise incident angle, suggesting higher noise susceptibility to the lateral fields than to the anterior or posterior field. Forty-nine percent of the fibers demonstrated direction sensitivity of noise masking of MP. Maximum shift in MP occurred most often at 90 degrees or 180 degrees noise incident angle, whereas minimum shift in MP occurred most frequently at 0 degrees or 270 degrees noise incident angle, suggesting higher noise susceptibility to the ipsilateral or posterior field than to the contralateral or anterior field. The difference in the directionality patterns of VS and MP suggests different mechanisms underlying noise masking of these two measures of phase locking in the amphibian auditory nerve.