Radiation dose to breast during digital mammography in Tanzania

The aim of this study was to evaluate the mean glandular dose (MGD), to assess the potential for optimization, and to propose diagnostic reference levels (DRLs). MGD was estimated from air kerma measurements and patient information collected during mammography examinations. The 75th percentile values were determined as the third quartile of the median MGD values for all hospitals, and DRLs set as 75th percentile of MGD values. The estimated median values of MGD ranged from 1.5 to 3.9 mGy for craniocaudal projection for median range of 15-59 mm compressed breast thickness (CBT). For a CBT range of 15-63 mm, the median MGD value was 1.5-5.1 mGy for medio-lateral oblique projection. Comparison with other studies showed that the MGD values obtained in this study were relatively high. The magnitude and wide variation of the exposure parameters suggest existing potential for optimization. The training of radiology staff was identified as a top priority.

Radiation exposure during CT procedures in Tanzania

The aim of this study was to evaluate optimisation status during common computed tomography (CT) procedures by determining values of volume computed tomography dose index (CTDIvol) and dose-length product (DLP) per examination. Patient and exposure data were collected from the CT console during various CT procedures. The results show that variations in CTDIvol and DLP values were mainly because of differences in the techniques used. The 75th percentile values were set as the third quartile of the median CTDIvol or DLP values for all hospitals. These values of 40.9, 9.0, 9.4 and 16.2 mGy for CTDIvol were determined for head, high-resolution chest, abdomen-pelvis and lumbar spine, respectively. The corresponding DLP values for the same sequence of CT procedures were 900, 360, 487 and 721 mGy.cm, respectively. The updated results provide a basis for optimising the procedures of CT in this country.

Agreement rates among single photon emission computed tomography using gallium-67, computed axial tomography and lymphangiography for Hodgkin disease and correlation of image findings with clinical outcome

BACKGROUND

This study was undertaken to systematically evaluate the agreement rates among single photon emission computed tomography using gallium-67 (Ga-67 SPECT), lymphangiography (LAG), and computed axial tomography (CT) scan findings for Hodgkin disease and to correlate radiologic findings with clinical outcome.

METHODS

One hundred three previously untreated patients with Hodgkin disease who had Ga-67 SPECT scan between August 1992 and December 1994 at our institution form the basis of this study. The agreement rates among Ga-67 SPECT, LAG, and CT scan findings were calculated by sites from the pretreatment evaluation throughout the courses of chemotherapy. The probabilities of recurrence or progression by sites were correlated with the radiologic findings.

RESULTS

The median follow-up was 3 years. The pretreatment agreement ranged from 75% to 100% between Ga-67 SPECT and CT scans, 85-100% between CT scan and LAG, and 74-99% between Ga-67 SPECT and LAG. A greater variation in agreement was observed once chemotherapy was started, the site with the least agreement being the mediastinum. The most common site of the recurrence or progression was also the mediastinum. When the CT scan showed persistent abnormality even after Ga-67 SPECT turned negative after chemotherapy, the chances of mediastinal recurrence or progression were 3 in 34 and 3 in 18 after 1-3 cycles and 4-6 cycles, respectively.

CONCLUSIONS

Although there was a relatively high correlation between Ga-67 SPECT and the other modalities, the intrinsic limitation of planar Ga-67 was still observed in Ga-67 SPECT especially in the mediastinum. There was still a moderate risk of mediastinal recurrence or progression even after residual CT scan abnormality lost gallium avidity from chemotherapy.