Traumatic injuries of the alimentary tract in children.

Traumatic alimentary tract (AT) perforations in children secondary to instrumentation, though rare, can occur at any age, especially in neonates and young infants. Awareness of such a possibility is essential for prompt management to be initiated. Over a 10-year period (1986-1995), eight pediatric patients with AT perforations secondary to instrumentation were managed at the American University of Beirut Medical Center. Five had upper AT injuries that included three hypopharyngeal, one esophageal, and one gastric lesion. The remaining three patients had lower AT injuries involving the transverse colon in one and the rectum in two. All the patients but two (one with a hypopharyngeal and one with an esophageal injury) were managed surgically and all survived. These rare injuries are discussed in addition to the preventive measures to be taken.

Ipsilateral bronchial intubation in a neonate for expansion of post-operative unilateral atelectasis--case report.

Ipsilateral bronchial intubation was used for reexpansion of unilateral pulmonary atelectasis in a newborn, who developed postoperative right atelectasis following extrapleural repair of tracheoesophageal fistula.

Lateral electron equilibrium and electron contamination in measurements of head-scatter factors using miniphantoms and brass caps.

The head-scatter factor (Sh) can be measured with a narrow miniphantom or a metal cap provided it is completely covered by the photon beam and its lateral size is thick enough to prevent electron contamination contributions. The effects of lateral electron equilibrium (LEE) and electron contamination on the Sh values were studied. The EGS4 Monte Carlo technique was used to calculate the minimum beam radii (rLEE) required to achieve complete LEE for photon beams ranging from 60Co to 24 MV. The measurement shows that the error introduced to the Sh value due to lateral electron disequilibrium is negligible. The radii of the miniphantoms or the sidewall thicknesses of the caps can be reduced below rLEE provided they are thick enough to prevent the effect of electron contamination.

Beam characteristics of the therapax DXT300 orthovoltage therapy unit.

The operating performance and beam characteristics of a new orthovoltage unit, the Therapax DXT300, have been evaluated. Percentage depth-dose and backscatter tables are presented for several applicator sizes, at 30 cm and 50 cm focal skin distances (FSDS) and for multiple x-ray beam qualities with the tube operating between 100 and 300 kVp accelerating potential. The unit has been found to provide beam characteristics similar to those reported for other orthovoltage therapy machines. The linearity and short- and long-term stability/reproducibility of the unit's internal dosimetry system have also been studied, and results indicate a very stable beam output of better than 1% standard deviation. The data presented in this work should provide the basis for comparison with other units and act as a reference for clinics commissioning the Therapax DXT300 in the future.

Evaluation of a dual bias dual metal oxide-silicon semiconductor field effect transistor detector as radiation dosimeter.

A new type of direct reading semiconductor dosimeter has been investigated as a radiation detector for photon and electron therapy beams of various energies. The operation of this device is based on the measurement of the threshold voltage shift in a custom-built metal oxide-silicon semiconductor field effect transistor (MOSFET). This voltage is a linear function of absorbed dose. The extent of the linearity region is dependent on the voltage controlled operation during irradiation. Operating two MOSFETS at two different biases simultaneously during irradiation will result in sensitivity (V/Gy) reproducibility better than +/- 3% over a range in dose of 100 Gy and at a dose per fraction greater than 20 x 10(-2) Gy. The modes of operation give this device many advantages, such as continuous monitoring during irradiation, immediate reading, and permanent storage of total dose after irradiation. The availability and ease of use of these MOSFET detectors make them very promising in clinical dosimetry.

Sonographic diagnosis of a urachal cyst in utero.

With improvements in fetal screening techniques, urachal anomalies can now be detected antenatally. Characteristic sonographic features of a urachal cyst in utero are described.

Surgical presentation of Kawasaki disease (mucocutaneous lymph node syndrome).

Five patients with Kawasaki disease (mucocutaneous lymph node syndrome) are reported whose varied presentations included acute abdominal pain, peripheral arterial aneurysms, digital gangrene and sterile pyuria and whose presenting pathology ranged from hydrops of the gallbladder to enteric pseudo-obstruction. As the complications of the disease can usually be managed without resort to surgery, which is associated with a mortality rate of up to 25 per cent, the recognition of Kawasaki disease will prevent hazardous and unnecessary laparotomy.

Physical aspects of external beam radiotherapy for the treatment of malignant pleural mesothelioma.

The optimization of radiotherapy for the treatment of malignant mesothelioma highlights many of the currently outstanding problems in clinical radiation physics. The experimental investigation of an intuitively attractive irradiation technique with combined photon and electron beams using a specially constructed phantom has established that, due to the penetration in low density material of both primary electrons and those secondary to photon irradiation, the normal lung tissue is not spared to any significant degree by such a technique. Furthermore, great care needs to be exercised in the treatment planning calculations for this approach if absolute dosimetry errors as large as 50% are to be avoided.

Effects of gold and silver backings on the dose rate around an 125I seed.

Measurements of the effect of either gold or silver backing on the dose rate around an 125I seed were performed using a Therados RFA7 dosimetry system and a small diode detector which was 2.5 mm in diameter and 0.06 mm thick. It was found that the presence of the gold or silver backing modifies the diode response on the side of the 125I seed away from the backing. The effect depends on the backing material and the distance from the seed. There is a small increase close to the gold backing but a decrease further away. This decrease at distances greater than 10 mm from the seed is uniformly 10%, the same as found when the seed is backed by air. There is an increase of up to 25% observed with silver backing the seed and this increase remains significant more than 30 mm from the seed. When the response increases, the results are hard to interpret quantitatively because of variations in the diode response per unit dose with photon energy and extreme sensitivity to geometric changes. Nonetheless, except for the increase at close distances with the gold, the results are in agreement with EGS4 Monte Carlo photon transport simulations which are for a simplified geometry and account for x-ray fluorescence from the K-shell. Furthermore, the increase in the gold-backed case is qualitatively explained by Williamson's Monte Carlo calculations which take into account the L-shell fluorescent x-rays from gold.