Radiation exposure during fluoroscopy: should we be protecting our thyroids?

BACKGROUND: Recent reports on thyroid cancer among Australian orthopaedic surgeons prompted the present study which sought to evaluate the effectiveness of lead shielding in reducing radiation exposure (RE) to the thyroid region during endo-urological procedures. METHODS: Radiation exposure to the thyroid region of the surgeon and scrubbed nurse was monitored for 20 consecutive operations over a 6-week period by thermoluminescent dosimeters (TLD). A TLD was placed over and underneath a thyroid shield of 0.5 min lead equivalent thickness to monitor the effect of shielding. RESULTS: Eight percutaneous nephrolithotomies, seven retrograde pyelograms and ureteric stentings and five ureteroscopies for calculous disease were monitored. Total exposure time was 63.1 min. For the surgeon, the total cumulative RE over and under the lead shield was 0.46 and 0.02 mSv, respectively, equating to a 23-times reduction in RE if shielding was used. This effectively reduced RE to almost background levels, which was represented by the control TLD exposure (0.01 mSv). CONCLUSION: Although RE without thyroid shields did not exceed current standards set by radiation safety authorities, no threshold level has been set below which thyroid carcinogenesis is unlikely to occur. Because lead shields are easy to wear and can effectively reduce RE to the thyroid region to near-background levels, they should be made easily available and used by all surgeons to avoid the harmful effects of radiation on the thyroid.

Increased pertechnegas lung clearance in interstitial lung disease.

BACKGROUND: Interstitial lung disease (ILD) is characterized by inflammation within the alveolar walls and interstitium of the lungs. This causes increased alveolar-capillary membrane permeability. The diagnosis is made by clinical features, chest roentgenography, lung function tests, and high-resolution CT, and it is confirmed by lung biopsy. Radionuclide aerosol tracers such as Tc-99m DTPA show increased lung clearance in ILD. The clearance rate of microaerosol pertechnegas (modified Technegas) from the lungs in the assessment of ILD was evaluated. METHODS: Thirty-two patients (22 with ILD and 10 with non-ILD) were evaluated with pertechnegas. Pertechnegas is formed by adding 3% oxygen to technegas, a microaerosol ventilation agent. Regions of interest were then drawn around the lungs, and clearance rates were determined from the best exponential fit. RESULTS: The mean clearance rate of pertechnegas was significantly increased in ILD and measured 5.78 +/- 2.2 minutes compared with non-ILD, which measured 8.53 +/- 2.42 minutes (P < 0.001). The sensitivity and specificity rates of pertechnegas clearance (less than 8 minutes) in ILD were 90% and 60%, respectively. When combined with chest roentgenography, the sensitivity and specificity rates increased to 100% and 90%, respectively. CONCLUSIONS: Pertechnegas is highly effective in determining the presence of active ILD. It differentiates between active ILD and non-ILD, and it is highly sensitive and specific when combined with chest roentgenography. Its potential role in the management of ILD merits further investigation.

Assessment of inflammatory bowel disease activity by technetium 99m phagocyte scanning.

Autologous technetium 99m-labeled phagocyte scanning has been used to assess disease activity in inflammatory bowel disease in 51 consecutive patients. Strong correlations were found between the 24-h fecal excretion of isotope and the histologic score of mucosal biopsy specimens (rS = 0.84, p less than 0.001, where rS is Spearman's rank correlation coefficient), and between the 24-h fecal excretion of isotope and a clinical inflammatory bowel disease activity index based on the Crohn's disease activity index (rS = 0.87, p less than 0.001). To develop a clinically useful and objective measure of inflammatory bowel disease activity that did not require a 24-h stool collection, the intensity of bowel uptake on scanning was graded visually from 0 to 4, a ratio of count rates for the region of interest to the iliac crest reference region was calculated, and the rapidity of labeled phagocyte uptake into inflamed bowel was measured as the peak uptake time. Visual grading of disease activity on the scans was validated by comparing it with the ratio of count rates from inflamed bowel regions of interest and those from the iliac crest reference region. The ratio of count rates showed a significant correlation with the clinical disease activity index (r = 0.75, p less than 0.001). The visual scan grade also correlated well with the clinical activity index (r = 0.87, p less than 0.001). Count rates from hourly scans were also used to calculate the time of peak uptake of counts for a given region of interest. There was a strong negative correlation between this peak uptake time and the fecal excretion of isotope (rS = -0.81, p less than 0.001), a clinical activity index (r = -0.60, p less than 0.001), and the histologic score of the mucosal biopsy specimens (r = -0.84, p less than 0.001). These results indicate that the technetium 99m-labeled phagocyte scan provides an objective assessment of disease activity in inflammatory bowel disease using the visual scan grade, ratio of count rates for the region of inflamed bowel, or by the peak uptake time, thereby avoiding the problems associated with fecal collections. This scanning test may prove to be of significant value in clinical management and in the assessment of treatment response.