Time to demand dosimetry for molecular radiotherapy?

Molecular radiotherapy (MRT) has been used clinically for around 75 years. Despite this long history of clinical use, there is no established dosimetry practice for calculating the absorbed dose delivered to tumour targets or to organs at risk. As a result, treatment protocols have often evolved based on experience with relatively small numbers of patients, each receiving a similar administered activity but, potentially, widely varying doses. This is in stark contrast to modern external-beam radiotherapy practice. This commentary describes some of the barriers to MRT dosimetry and gives some opinions on the way forward.

Head injury outcome prediction in the emergency department: a role for protein S-100B?

BACKGROUND: Biochemical markers released after head injury may reflect the degree of brain damage, which is related to subsequent disability. If the serum level of a marker were found to be related to outcome, then earlier identification and intervention would be possible. OBJECTIVE: To investigate the potential of the serum marker S-100B protein to predict the outcome after head injury. METHODS: Blood samples for S-100B concentrations were taken from 148 adults within six hours of a head injury (initial Glasgow coma score 4-15). Patients were recruited from the emergency departments of four hospitals in Greater Manchester, United Kingdom. Outcome was assessed in 119 patients (80%) at one month using the extended Glasgow outcome scale (GOSE). RESULTS: A significant inverse correlation between serum S-100B level and GOSE was found (Spearman's rho = -0.349, p < 0.0001). A serum S-100B concentration of > 0.32 micro g/l predicted severe disability (GOSE < 5) at one month with a sensitivity of 93% (95% confidence interval 68% to 100%), a specificity of 72% (54% to 79%), and a negative predictive value of 99% (93% to 100%). CONCLUSION: Serum S-100B concentration can be used in the emergency department to identify patients with head injury who are most likely to have a poor outcome at one month.

An automated technique for SPECT marker-based image registration in radionuclide therapy.

An automated technique for marker-based image registration in radionuclide therapy is described. This technique is based on localization of the centroids of external markers and on establishing correspondence between the individual markers of the two studies to be registered. Localization of the centroids of markers relies on segmenting the markers using iterative thresholding. Thresholding is locally adaptive in order to account for study-dependent conditions (e.g. crossover between adjacent markers and markers with varying radioactive concentrations). Following marker segmentation, the centroids of the markers are computed based on an intensity-weighted method. Finally, prior to the least-squares fit registration, the markers of the two sets are matched to achieve one-to-one correspondence. The technique was applied to both simulated and patient studies resulting in mean residual three-dimensional registration errors (+/- 1SD) of 1.7 +/- 0.1 mm and 3.5 +/- 0.3 mm respectively. The technique was compared with a semi-automated approach and no significant difference was found between the mean residual three-dimensional registration errors (t = 0.281. p = 0.8). This automated marker-based image registration technique provides robust and accurate registration. Although it was developed as part of a programme to generate three-dimensional dose distributions for radionuclide therapy, it could be useful for other clinical applications.

Automated CT marker segmentation for image registration in radionuclide therapy.

In this paper a novel, automated CT marker segmentation technique for image registration is described. The technique, which is based on analysing each CT slice contour individually, treats the cross sections of the external markers as protrusions of the slice contour. Knowledge-based criteria, using the shape and dimensions of the markers, are defined to enable marker identification and segmentation. Following segmentation, the three-dimensional (3D) markers' centroids are localized using an intensity-weighted algorithm. Finally, image registration is performed using a least-squares fit algorithm. The technique was applied to both simulated and patient studies. The patients were undergoing 131I-mIBG radionuclide therapy with each study comprising several 99mTc single photon emission computed tomography (SPECT) scans and one CT marker scan. The mean residual 3D registration errors (+/- 1 SD) computed for the simulated and patient studies were 1.8 +/- 0.3 mm and 4.3 +/- 0.5 mm respectively.

Femtosecond soliton generation in a praseodymium fluoride fiber laser.

We report what is to our knowledge the first femtosecond pulse generation at 1.3 micro m in a Pr 3(+)-doped fluoride fiber laser. After optimization of the cavity length and dispersion, the laser generated pulses as short as 620 fs. We also describe self-stabilization and self-organization of the output pulse train at repetition rates from the fundamental cavity frequency of 700 kHz up to 440 MHz and report on polarization effects.

Spontaneous spinal subdural haematoma during general anaesthesia.

Spontaneous spinal subdural haematoma causing acute spinal cord compression is a well recognized condition and often responds well to early surgical intervention. In the elderly, the haematoma usually occurs as a result of minor trauma or atherosclerosis with hypertension. We present in this report the history of a patient who became paraplegic during a general anaesthetic for an operation for removal of a ureteral calculus. Rupture of a spinal vascular malformation was found to be responsible for the subdural haematoma, which remained undiagnosed until surgical exploration.

Active transport of iron to mucosal surface of rat jejunum.

Estimations of steady-state fluxes of divalent Fe across rat intestinal segments in vitro provide evidence for two active transport mechanisms. Segments of the distal small intestine transport the mineral against electrochemical potential gradients from the serosal to the mucosal surface. Active transport in the reverse direction was confirmed with segments of proximal duodenum. The distal mechanism is dependent on cellular metabolism and is markedly decreased by metabolic inhibitors or in the absence of a metabolizable hexose. Cycloheximide, which inhibits protein biosynthesis, also blocks the active transport. Perfusion of jejunal and duodenal intestinal loops in situ in anesthetized rats provides evidence that endogenous Fe can be transferred to the lumen by a process otherthan shedding of mucosal cells. It is suggested that such transfer may occur via the active transport mechanism.