Katsumi Hayakawa

In situ tissue engineering for tracheal reconstruction using a luminar remodeling type of artificial trachea.

BACKGROUNDnAfter successful trials of tracheal reconstruction using mesh-type prostheses in canine models, the technique has been applied clinically to human patients since 2002. To enhance tissue regeneration, we have applied a new tissue engineering approach to this mesh-type prosthesis.nnnMETHODSnThe prosthesis consists of a polypropylene mesh tube reinforced with a polypropylene spiral and atelocollagen layer. The cervical tracheas of 18 beagle dogs were replaced with the prosthesis. The collagen layer was soaked with peripheral blood in 6 of the dogs, with bone marrow aspirate in another 6, and with autologous multipotential bone marrow-derived cells (mesenchymal stem cells) in another 6. The dogs were humanely killed at 1 to 12 months after the operation.nnnRESULTSnAll 18 dogs survived the postoperative period. Bronchoscopically, 3 of 4 dogs in the peripheral blood group showed stenosis, whereas no stenosis was evident in all 8 of the dogs in the bone marrow and mesenchymal stem cell groups 6 months after the operation. Faster epithelialization and fewer complications, such as mesh exposure and luminal stenosis, were observed in these two groups than in the peripheral blood group. Histologically, the cells from autologous bone marrow were found to proliferate into the tracheal tissue during the first month. Cilial movement in these two groups was faster than that in the peripheral blood group and recovered to 80% to 90% of the normal level.nnnCONCLUSIONSnBone marrow aspirate and mesenchymal stem cells enhance the regeneration of the tracheal mucosa on this prosthesis. This in situ tissue engineering approach may facilitate tracheal reconstruction in the clinical setting.

Superior sagittal sinus thrombosis in neonates

Three neonatal patients with superior sagittal sinus thrombosis are reported. The neurologic signs were bulging of the anterior fontanel and clonic hemi-convulsions. Neonatal polycythemia was believed to be an etiologic factor in two patients. Computed tomography revealed massive edema with slit-like ventricles in two patients. Increased density of the torcular Herophili and straight sinus also were demonstrated in two patients. The diagnosis of superior sagittal sinus thrombosis was confirmed by cerebral angiography in one patient and by digital subtraction angiography in the other two patients. Digital subtraction angiography appears to offer a definite advantage in the diagnosis of cerebral sinus thrombosis in the neonatal period.

Mechanism of burn injury during magnetic resonance imaging (MRI)--simple loops can induce heat injury.

To determine the mechanism of burn injury associated with magnetic resonance imaging (MRI), the induced current in the loops of a conductive lead was measured. Seven types of loops with effective areas within the range from 100 to 12 000 cm2 were made and then each loop was placed in the bore of a whole-body MR system at 0.5 T and MRI was carried out. During radio frequency (RF) irradiation, an induced voltage was observed in loops that were placed with their axes parallel to the linearly polarized transmitting RF field. The voltage had a sincfunction characteristic and was within the range 55-235 V at the RF pulse sequence for usual MR imaging. When the axis was vertical, negligible current was observed. A resistor inserted into the circuit of a 30 x 40 cm loop sparked and burned out. Simple loops of conductive material may result in the induction of a large and potentially hazardous voltage in the imaging system. Self-resonance of such a loop may add greatly to hazards by increasing the effective coupling to the RF transmitter. Also, impedance matching of the inserted resistor with the impedance of the loop increases the dissipated power at the resistor.

A quantitative assessment of scintigraphy of the legs using 201Tl

Abstract201Tl perfusion scintigraphy of the legs was evaluated to define intermittent claudication quantitatively, based on Sapirsteins indicator fractionation principle. After intravenous injection of 201Tl with or without exercise, the distribution of the radiotracer throughout the body was obtained using the whole body scanner. Regional blood flow of cardiac output for three segments of the leg was estimated as a regional fractional uptake (rFU) distributed in these segments compared with the whole body distribution. The validity of the principle was confirmed by a comparative study with 99mTc-MAA (r=0.979). Normal rFUs (%) for each section at rest and after stress, respectively, were 5.49±0.69 and 19.40±2.04 (whole leg); 3.57±0.49 and 12.26±1.91 (thigh); 1.59±0.34 and 6.58±0.61 (calf). The rates of rFU change from the state of rest to stress (ΔrFU) in normals were 3.41±0.45 (whole leg), 3.44±0.61 (thigh), and 4.30±1.03 (calf). Although rFU was within normal limits in patients with arteriosclerosis obliterans (ASO) and thromboangitis obliterans (TAO), ΔrFU of the whole leg was significantly decreased from the normal value of 3.41±0.45 to 1.95±0.40 for ASO (P(0.001) and 1.82±0.47 for TAO (P(0.001). A defect or decreased activity on the stress scintigraph was well correlated with the angiographic findings.

Periventricular hyperintensity detected by magnetic resonance imaging in infancy

Twenty-one infants younger than 12 months of age were diagnosed as having periventricular hyperintensity (PVH) on T2-weighted magnetic resonance imaging. Ten infants had experienced neonatal asphyxia, 6 intracranial hemorrhage, 2 bacterial meningitis, and 3 apnea. PVH was classified according to its extent. Round foci of PVH surrounding the frontal and occipital horns of the lateral ventricles were observed in 4 infants (PVH pattern I). Continuous PVH was observed in 17 infants (PVH patterns II and III). Fourteen infants with continuous PVH had spastic diplegia or quadriplegia. Developmental delay was demonstrated in 15 infants with continuous PVH. No PVH pattern I infants had cerebral palsy; only 1 such infant had mild developmental delay. Our study suggests that the extent of PVH reflects the severity of brain damage in neonates with cerebral injuries.

MR imaging of myopathy

Magnetic resonance imaging was performed in 8 patients with muscle disease and 6 normal controls. High intensity areas of varying dimensions were found in thigh muscles of the patients with progressive muscular dystrophy (PMD) and congenital myopathy. Shortened T1 and prolonged T2 values with disease progression were characteristic. The T1 values were variable and prolonged, T2 values were more characteristic of progressive muscular degeneration. The T1 value may help to detect the early stage of PMD. Magnetic resonance imaging is useful in detecting the muscle lesions in PMD and essential for selection of a biopsy site.

Magnetic resonance imaging in preterm infants

Magnetic resonance imaging was performed in 9 preterm infants at 37-43 weeks postmenstrual age. They all were born at 26-35 weeks gestation. Myelination was graded according to its most cephalic location. Myelination pattern 2 (myelination observed in the posterior limb of the internal capsule and adjacent structures of the thalamus and lenticular nucleus) was demonstrated in 2 infants, pattern 3 (myelination of the corona radiata) in 3 infants, and pattern 4 (myelination of the centrum semiovale) in 4 infants. Bilateral low intensity areas were found on T1-weighted images in 7 infants and a ribbon-like, high intensity was observed in 5. These findings revealed a wide variety of magnetic resonance imaging appearance in apparently normal preterm infants. Caution is needed in interpreting the pathologic nature of such features in preterm infants during the perinatal period.