Temporal bone imaging

Ameliorated computed tomography techniques and new magnetic resonance sequences have led to an important improvement in temporal bone imaging. Computed tomography is still the method of choice for imaging of temporal bone fractures, middle ear disease, and conductive hearing loss, although magnetic imaging can add important information. Patients with lesions of the cerebellopontine angle; internal auditory canal; inner ear; and, in general, all patients with sensorineural hearing loss, vertigo, and tinnitus are best examined with magnetic resonance imaging. In some cases, however, such as congenital malformations and petrous apex lesions, magnetic resonance imaging and computed tomography are complementary. The value of both modalities is discussed.     

Neonatal seizures associated with cerebral lesions shown by magnetic resonance imaging

AIM: To determine the diagnostic potential of magnetic resonance imaging (MRI) in neonatal seizures; to elucidate the aetiology, timing, and prognosis of the cerebral lesions detected. METHODS: Thirty one term neonates with clinical seizures underwent ultrasonography between days 1-7 (mean 2.5 days) and a high field spin-echo MRI scan on days 1-30 (mean 8.1 days), both of which were repeated at 3 months of age. Routine investigation excluded, as far as possible, infection, haematological, and metabolic-toxic causes as causes of the neonatal seizures. RESULTS: Brain abnormality was demonstrated by MRI in 68% of infants and ultrasonographically in 10%. Diffuse brain lesions (present in 29%) were associated with high mortality (58%) and morbidity (42%), whatever the aetiology. In contrast to a better short term prognosis for neonates with focal lesions where no infants died, 33% had a handicap, and the rest were normal at a mean follow up age of 2 1/2 years. Cerebral lesions were presumed to have antepartum origin in 43% of cases. Seizure aetiology was considered to be hypoxic-ischaemic in 35%, haemorrhagic in 26%, metabolic disturbances and cerebral dysgenesis in 16% and unknown in 23%. CONCLUSIONS: MRI detected a remarkably high incidence of brain lesions in neonatal seizures. Almost half of these were of prenatal origin and pathogenesis may essentially be attributed to hypoxic and/or haemodynamic causes.     

Radionuclide bone imaging in pediatrics

Radionuclide imaging provides a functional as well as anatomic evaluation of bone and is particularly valuable in diagnosis, staging, and management of oncologic disorders, in differentiation of inflammatory conditions and trauma, and in hypovascular disorders of bone. The practitioner should be aware of those areas in which bone imaging is clinically effective for patient care. Radionuclide bone imaging is efficacious, delivers minimal radiation, and offers a functional method of evaluation for children with skeletal disorders.     

Obesity in childhood craniopharyngioma: relation to post-operative hypothalamic damage shown by magnetic resonance imaging

OBJECTIVE: To quantify the extent of hypothalamic damage after surgery for craniopharyngioma using magnetic resonance imaging (MRI) and to relate the findings to changes in body mass index (BMI). PATIENTS: Sixty-three survivors (36 males, 27 females) of childhood cramopharyngioma were treated surgically between 1973 and early 1994. METHODS: Cranial MRI was performed at a structured follow-up assessment 1.5-19.2 yr after the initial surgery. Hypothalamic damage was scored as 0 (no visible damage), 1 (intermediate), or 2 (severe). RESULTS: After surgery there was an increase in BMI standard deviation (SD) from diagnosis to study assessment in all but 7 patients. However, patients with MRI scores of 2 (n = 17) had a significantly greater increase in median BMI SD score at follow-up (+5.5 SD score), compared with +2.5 SD score and +1.1 SD score for patients with MRI scores of 1 or 0, respectively. Of the 17 cases with MRI scores of 2, 10 had a history of extreme weight loss or weight gain at presentation; preoperative neuroimaging demonstrated extensive hypothalamic infiltration by tumor in these cases. CONCLUSION: MRI gives sufficient anatomical definition to allow assessment of the extent of hypothalamic damage and, thereby, prediction of the patients most at risk for severe post-operative weight gain.     

Craniocaudal motion velocity in the cervical spinal cord in degenerative disease as shown by MR imaging

PURPOSE: To investigate, by means of MR phase imaging, the effects of compression on the velocity of craniocaudal motion in the spinal cord. MATERIAL AND METHODS: Spin-echo pulse sequences with velocity encoding gradients were used to examine 12 patients with cervical spondylosis and 6 normal volunteers. Oblique-axial phase images at 3 levels (cranial, middle and caudal), were obtained with prospective electrocardiogram gating. The middle level was set at the site where the spinal cord was most severely compressed, and the cranial and caudal sections were set where it was not compressed. Time-velocity curves were generated at these 3 levels and focal velocity change was correlated with motor function in the lower extremities. RESULTS AND CONCLUSION: The cord showed a higher motion velocity at the compression level than at noncompression levels. This paradoxical increase in velocity was observed in 7 out of 8 patients whose lower extremity motor function was impaired. Four patients with normal lower extremity motor function did not demonstrate this increase in velocity. An increase in motion velocity was therefore found to correlate with impaired lower extremity motor function.     

Trabecular bone morphology from micro-magnetic resonance imaging

The effect of intraseptal microinfusions of the GABA-A agonist muscimol on spontaneously occurring or hypothalamically induced hippocampal formation (HPC) theta field activity and the simultaneously occurring discharge properties of CA1 pyramidal and dentate granule layer phasic theta-ON cells, was investigated in urethane-anesthetized rats. The microinfusion of 5.0-12.5 nmol of muscimol into the medical septum/vertical limb of the diagonal band of Broca (MS/vDBB) resulted in a progressive reduction (beginning 5 min postinfusion) in the power (amplitude) and finally the total loss of theta field activity. In contrast, theta field frequency remained unaffected during the entire postinfusion period that theta field activity was present. In the time immediately following the first 1-min intraseptal microinfusion of 5 nmol muscimol, (before changes in theta amplitude occurred) a brief period of increased phasic theta-ON cell excitability was noted. This was manifested as an increase in the number of discharges per rhythmic burst. Associated with the progressive reduction of the amplitude of theta field activity, phasic theta-ON cell discharge rates progressively decreased for a period beginning 5 min postinfusion of 5 nmol muscimol. Despite the progressive decrease in the number of discharges and a noticeable reduction in the degree of rhythmicity, phasic theta-ON cells maintained their preferred timing of discharges in relation to the phase of theta field activity, while the latter was present. Just prior to the complete abolishment of theta field activity, phasic theta-ON cells ceased discharging. During the period when theta field activity was replaced on low amplitude asynchronous activity, phasic theta-ON cells discharged in bursts correlated with every occurrence of sharp wave field activity. The results support the following conclusions: (1) the brief excitatory effect on HPC theta-ON cell discharges may be correlated pharmacologically with an initial brief increase in HPC ACh turnover. The reduction of phasic theta-ON cell discharges and theta field activity may be correlated with the longer lasting reduction of HPC ACh turnover, controlled by MS/vDBB GABA-A inputs to MS/vDBB cholinergic septohippocampal neurons, possibly along with a direct inhibition of the GABAergic septohippocampal projection; (2) the primary contribution of the MS/vDBB nuclei, as a nodal point in the ascending brainstem HPC synchronizing system, is the modulation of the amplitude of HPC formation theta field activity and secondarily to relay frequency-coded inputs from the posterior hypothalamic region (posterior and supramammillary nuclei); (3) HPC theta and sharp wave field activity represent functionally distinct neural inputs to the same population of phasic theta-ON cells located in both the CA1 pyramidal and dentate granule cell layers.     

Maxillary alveolar bone imaging. Wiener filter design

Optimal digital filter design is essential for noise suppression in the detection of subtle radiographic bony changes. The purpose of this study was to determine the signal (Ps) and noise (Pn) power spectra of sampled maxillary alveolar bone, to derive the optimal Wiener filter transfer function, H, from sets of Ps and Pn, and to quantify noise suppression through application of this filter. Sixteen standardized radiographs were made of five interproximal bony areas, each area from a separate dry human maxilla. The radiographs were digitized (0.02 mm/pixel resolution) and identical profiles (scan lines) generated between lead markers for each set of films. Ps was calculated from the averaged scan line of each set, Pn was calculated from the difference between the noisy images and the averaged scan line for each set, and an average maxillary H was calculated from the sets of Ps and Pn. Filtering of the 80 noisy sample radiographic profiles with H resulted in a 39% reduction in noise. Application of this digital filter should significantly improve detection of radiographic bony changes in the maxilla.     

Subclavian arterio-esophageal fistula secondary to fish bone impaction: report of a case

A 48-year-old Indian man swallowed a fish bone and presented 1 week later with dysphagia, following a single episode of fresh hematemesis. A barium swallow demonstrated a horizontal mucosal tear at the level of the aortic arch, and computed tomography (CT) showed mediastinal emphysema and a bleeding point medial to the left subclavian artery which appeared to be contained by a surrounding hematoma. Subsequently, he developed sudden massive hematemesis and collapsed. Despite emergency surgery, the patient died. At the postmortem examination, a 1.2-cm fistula tract was found connecting the esophagus to the left subclavian artery. This case report emphasizes that a diagnosis of arterio-esophageal fistula should be considered if a patient presents with fresh hematemesis and a recent history of foreign body ingestion.     

Magnetic resonance imaging in patients with bone marrow disorders

Magnetic resonance imaging (MRI) provides a non-invasive means to evaluate a large fraction of marrow in less than one hour. Marrow disorders produce non-specific changes in marrow signal intensities which primarily reflect changes in proportions of fat and cellular elements. The pattern of these signal changes narrows the differential diagnosis, and the combination of these features with the clinical context allows interpretations which are clinically useful in many ways. These include: 1) the diagnosis of avascular necrosis (and its distinction from other causes of joint pain), 2) detection of osteomyelitis, 3) differential diagnosis of hypoplastic disorders, 4) staging of lymphomas and myeloma, 5) selection of patients for autologous bone marrow transplant, 6) objective measures of marrow response to therapy, 7) detection of leukemic transformation, and 8) improved detection of marrow disease (primary or secondary) in patients with otherwise unexplained bone pain.     

Magnetic resonance imaging of the bone marrow in hematological malignancies

The objective of this study was to determine the feasibility of using a fast (short-duration) transmission computed tomogram (TCT), acquired immediately before or after the emission CT, to correct for photon attenuation in cardiac SPECT. METHODS: The asymmetric fanbeam geometry with a 99mTc line source was used to acquire TCTs after conventional cardiac emission CT imaging on a triple-head SPECT system. The TCTs were reconstructed to generate patient-specific attenuation maps, which were used with an iterative maximum likelihood algorithm to reconstruct attenuation-corrected cardiac SPECT studies. The results of attenuation correction based on TCTs as short as 1 min were compared with long-duration transmission imaging for a phantom and several human studies. RESULTS: Attenuation correction based on asymmetric fanbeam TCT significantly improves the uniformity of images of a uniform tracer distribution in a cardiac-thorax phantom configured to simulate a large patient. By using a high-activity line source and a rapid camera rotation, a suitable attenuation map for this phantom can be obtained from a 4-min TCT. A similar result is obtained for patients with thorax widths of <40 cm. CONCLUSION: A sequential imaging protocol for acquiring a fast TCT can be used for attenuation correction of cardiac SPECT imaging. The sequential TCT can be acquired without significantly extending the duration of the imaging study. This method provides a way to perform attenuation correction on existing triple-head SPECT systems without extensively modifying the system.     

Cranial bone flap fixation clamps: compatibility at MR imaging

To evaluate the compatibility of a commercially pure titanium aneurysm clip associated with magnetic resonance (MR) imaging at 1.5 T. Artifacts of the Spetzler titanium aneurysm clip were compared with those produced by six different nonferromagnetic aneurysm clips. With the titanium clip, no magnetic attraction was present, heating was minor, and the artifacts involved a small signal void. With the six other aneurysm clips, artifacts were larger. The presence of Spetzler titanium aneurysm clips is safe at MR imaging at 1.5 T or less.     

MR imaging of edema accompanying benign and malignant bone tumors

To evaluate the incidence, quantity, and presentation of intra- and extraosseous edema accompanying benign and malignant primary bone lesions, the magnetic resonance (MR) studies of 63 consecutive patients with histologically proven primary bone tumors were reviewed. MR scans were assessed for the presence and quantity of marrow and soft tissue edema and correlated with peroperative findings, resected specimens and follow-up data. The signal intensity and enhancement of tumor and edema prior to and after intravenous administration (if any) of gadolinium-labeled diethylene triamine pentaacetate (Gd-DTPA) was analyzed. Marrow edema was encountered adjacent to 8 of 39 malignant tumors and 14 of 24 benign lesions. Soft tissue edema was found accompanying 28 of 39 malignancies and 10 of 24 benign disorders. On unenhanced T1-weighted MR images tumor and edema were difficult to differentiate. Tumor inhomogeneity made this differentiation easier on T2-weighted sequences. In 36 patients the contrast medium Gd-DTPA was used. Edema was present in 27 of these patients and the respective enhancement of tumor and edema could be compared. Edema always enhanced homogeneously, and in most cases it enhanced to a similar degree as or more than tumor. Marrow and, more specifically, soft tissue edema is a frequent finding adjacent to primary bone tumors. The mere presence and quantity of marrow and soft tissue edema are unreliable indicators of the biologic potential of a lesion. Unenhanced MR scans cannot always differentiate between tumor and edema, but the administration of Gd-DTPA is of assistance in differentiating tumor from edema.(ABSTRACT TRUNCATED AT 250 WORDS)     

交锁髓内钉治疗胫腓骨骨折及骨不连的疗效观察

目的:探讨交锁髓内钉治疗胫腓骨骨折和骨不连的临床疗效.方法:选取我院2006年7月～2009年8月收治的60例胫腓骨骨折、骨不连患者的临床资料,所有患者均通过交锁髓内钉进行治疗,随访9～24个月,观察患者的临床疗效,并总结治疗经验.结果:患者经过交锁髓内钉治疗后,60例患者对位良好,未发生感染、畸形愈合、主钉未发生弯曲或者折断.所有患者经过功能锻炼和康复治疗、负重练习,所有患者均达到骨性愈合.结论:交锁髓内钉治疗胫腓骨骨折、骨不连,手术创伤损伤小,固定牢靠,骨折愈合率高,术后并发症少,临床疗效满意,值得在临床推广.     

Xenogeneic rejection mechanisms shown by intravital microscopy

The importance of this model is that it showed exactly where in the organ the xenogeneic damage occurred. The liver received the blood mainly via portal veins, which merge with the pulsatile arterioles in the Disse spaces. This periportal area is followed by the sinusoids and ends in the central or postsinusoidal vein. IVM enables us to differentiate between perfused and unperfused sinusoids and to calculate the ratio. Not all sinusoids are perfused at any time. It appears that 5% to 10% are unperfused. During xenoperfusion, only 65% of sinusoids show blood flow after a perfusion of 12 minutes. This is less than in hemorrhagic shock. Only the combined platelet inhibitors and apheresis resulted in remarkable improvement. The calculation of an index indicates the improvement of acinar perfusion. Thrombocytes and leukocytes remain, however, in the liver. In conclusion, the model used to analyze the dynamics of microvascular liver perfusion and sinusoidal perfusion is suitable for such investigations in a xenogeneic model. It has no major side effects, either on the perfusing blood or on the liver, as proved in the isogeneic control group. The important finding in our eyes is that the perfusion failure begins in the periportal fields, where the blood enters the foreign microvasculature and where the leukocytes first come in contact with the foreign endothelium. All previous manipulations had only a minor impact on this contact of cells with the foreign endothelium. The study indicates that the early events of xenogeneic hyperacute rejection are of unspecific character and involve leukocytes and thrombocytes to a major degree, thus being responsible for the dramatic decrease in the microcirculation in xenogeneic livers.     

Quantitative assessment of bone marrow hematopoiesis using parametric magnetic resonance imaging

Spatial maps of the percentage cellularity in pelvic bone marrow were calculated at a resolution of 15.6 mm3 from six volunteers and 10 patients treated for documented hematologic disease using a three-point Dixon MRI pulse sequence. The percentage cellularity calculation was aided by analyzing a two-dimensional feature space consisting of the apparent water fraction (Wa), and the T2 relaxation time of water (T2w). An extracellular water fraction was assigned to each voxel on the basis of a two-component T2w algorithm. In six cases, the method was compared to results obtained from core biopsies or aspirates of the posterior iliac crest. The results indicate that segmentation schemes that combine high-quality phase-contrast imaging with nuclear relaxation time measurements can potentially identify the true fractional marrow volume occupied by hematopoietic elements in a variety of clinical situations.