Diagnostic radiation for immediate post-surgical assessment of osseointegrated dental implants has been discouraged, due to the possibility of detrimental effects of ionizing radiation on healing and remodeling of bone. To assess this possibility, we investigated the effects of ionizing radiation on proliferation and differentiation of osteoblasts using osteoblast-like cells isolated from the calvariae of newborn rats (ROB) and a clonal osteoblastic cell line (MC3T3-E1). The cells were exposed on day 3 to a single dose of x-rays at either 40, 100, 400, or 4000 mGy, respectively, from a linear accelerator radiotherapeutic machine (Linac) or a 40-mGy dose from a diagnostic chest x-ray machine. The effects of radiation on cell growth and alkaline-phosphatase-specific (ALP) activity were evaluated at three-day intervals after irradiation up to day 12 in ROB cells, and evaluated at day 12 in MC3T3-E1 cells. At the culture end-point, the effects on formation of bone-like nodules were also evaluated in both ROB and MC3T3-E1 cells. Exposure of 4000 mGy differentially affected the two cell types. It inhibited cell growth and alkaline phosphatase activity, and inhibited DNA content in MC3T3-E1 cells. This irradiation also strongly inhibited the formation of bone-like nodules in ROB cells. On the other hand, exposure of 40-, 100-, and 400-mGy (Linac) and 40-mGy (diagnostic quality) irradiation induced no significant changes in cell growth, alkaline phosphatase activity, and formation of bone-like nodules in ROB cells. These doses also induced no significant changes in DNA content and ALP activity in MC3T3-E1 cells. These results indicate that ionizing radiation at a single dose of up to 400 mGy induces no significant changes in cell growth and differentiation of osteoblast-like cells, at least in vitro. Higher radiation doses (4000 mGy) may exert different effects on cell proliferation and cell differentiation of osteoblasts, depending on the cell types affected. Thus, diagnostic radiation seems to have less effect on proliferation and differentiation of osteoblasts.

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Pulmonary veno-occlusive disease is a rare form of primary pulmonary hypertension of unknown aetiology. Four On clinical examination he was a healthy boy without cyanosis who had neither tachycardia nor tachypnoea at rest. He was hypertensive with a blood pressure of 150/80 mm Hg. A right ventricular heave was present. Cardiac auscultation showed an accentuated pulmonary component of the second heart sound but no murmurs, and normal breath sounds were heard on auscultation of his chest. Chest radiography showed a normal cardiac outline but pulmonary changes were consistent with acute pulmonary oedema (fig 1).The patient underwent cardiac catheterisation. These original records were not available for review, but the haemodynamic findings were interpreted as being 'consistent with a left atrial lesion', whereas angiography showed normal cardiac anatomy. As a result of these apparent inconsistencies, surgical exploration of the right and left atria was performed. This showed the presence of four normal pulmonary veins and confirmed normal cardiac anatomy. During the operation the pulmonary artery peak systolic pressure was 50 mm Hg and the mean pulmonary

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Sensitivity was found to be 26%, specificity to be 81% and overall accuracy 69%--too low to justify the diagnosis of N2 disease on size of 1.5 cm or larger. CT is not a valid means of diagnosing malignant involvement of mediastinal nodes.