Nuclear magnetic resonance is a noninvasive technique of imaging the brain using signals produced by magnetic fields and radiowaves. Sixteen patients with refractory temporal lobe epilepsy (TLE) had magnetic resonance imaging (MRI) during investigation for possible surgical management. These images plus those of 10 normal controls, were interpreted blind and the results from the TLE patients compared to the EEG and computerized tomographic (CT) scan findings. Fourteen patients compared with one normal control had one or more of the following: small temporal lobe, small mesial temporal structures, small hemisphere, and focal mesial temporal prolonged spin-spin relaxation time. These findings correlated with the electrographically determined seizure focus in 11 patients. Enlarged or asymmetrical temporal horns were seen with equal frequency in patients and controls and did not correlate with the seizure focus. CT scans were less likely to show these changes than MRI. Correlation of the MRI changes with histopathology of resected temporal lobes was poor. MRI reveals structural and possibly functional alterations which may aid in the localization of the seizure focus in the temporal lobes of patients with refractory complex partial seizures.

Contrary to common perception, the advent of third- and fourth-generation scanners has lead to a significant increase in radiation dose to the patient per computed tomography (CT) head scan. With that in mind, a pilot study was designed with the objective of assessing the effectiveness of a dental-style protective bib in reducing the dose to the radiosensitive organs of the neck and thorax. Radiation doses over the thyroid gland and breast were measured with thermoluminenscent dosemeters and an ionization chamber respectively in 110 patients undergoing routine head scans. Half the patients wore the protective bib and collar. With lead protection, the thyroid measurements were reduced by an average of 45 % and the breast measurements by an average of 76 %. Similar results were seen in phantom measurements.

Commercial phantoms designed for radiologists to practise the skills needed to biopsy lesions under ultrasound guidance can be prohibitively costly, and do not have an indefinite shelf-life. A gelatin-based in-house model has been developed to recreate the conditions found in human tissues, using materials which are cheap and in everyday use. This phantom remains useful for several weeks, although tears produced by the biopsy needle take progressively longer to bond when the reconstructed gelatin is older than a month. However, new phantoms can be built quickly and easily using fresh gelatin while recycling other components.

A computer-assisted mapping program was developed to determine changes of cerebral perfusion in normal and pathological aging using single photon emission computer tomography (SPECT) and 99mTc-hexamethylpropyleneamine oxime (HMPAO). The software program outlined the cortex on 14 adjacent brain slices, and superimposed a ring of 12 regions of interest on each slice. Regional/global and regional/cerebellar relative flow values were calculated in 27 patients with clinically diagnosed Alzheimer's disease (AD) (mean age 71 years, SD 7.6) and in 10 normal controls (mean age 73.7 years, SD 7.3). The Dementia Rating Scale (DRS) was used to assess mental status in all subjects. Multiple regression analysis demonstrated a significant correlation between relative flow values and the DRS score. Regional/cerebellar (R = 0.88, p < 0.0001) relative flow values were a better indicator of cortical impairment than regional/global relative flow values (R = 0.68, p = 0.003). Of the brain regions of interest, the left parietal flow values correlated best with the DRS score (r = 0.83, p < 0.0001), a cutoff value of 77 accurately classifying 80% of the normals and 100% of the patients diagnosed as having Alzheimer's disease. The data show that computer-assisted mapping of SPECT can provide semiquantitative flow values with high diagnostic accuracy.

Respiratory movement degrades magnetic resonance (MR) images of the chest and abdomen by increasing noise through the production of "ghost" artifacts and by decreasing edge sharpness in moving structures. Respiratory gating, which limits data acquisition to end-expiration, is successful in restoring edge sharpness and reducing ghosts but increases imaging time two to three times, which limits its use to sequences with short repetition times (TRs). To overcome this limitation, an alternative technique, respiratory triggering, was developed, which triggers the acquisition of an MR section at a fixed point on the respiratory cycle. This technique restores edge sharpness and reduces ghosts, but unlike gating, it can be used to produce an image at any phase of the respiratory cycle. Triggering requires long TRs since the TR is limited to the respiratory period (TP) or one-half of TP, depending on whether the same section is triggered once or twice during a single respiratory cycle. Gating and triggering were evaluated and compared for single-section and multi-section imaging of both volunteers and patients. The authors conclude that when a chest or abdominal survey is required, triggering takes less time than gating if TRs are required that exceed one-fifth of TP.

Complex and lengthy interventional radiological techniques have resulted in a number of patients developing skin reactions in recent years. To safeguard against these side effects, we have investigated the degree to which entrance skin dose can be reduced by inserting 0.18 mm and 0.35 mm copper filtration in the incident beam. The potential reduction was measured on a 22 cm water phantom for each of eight models of a fluoroscopy unit. Using the catheter laboratory fluoroscopy unit on which radiofrequency ablations are routinely performed, we assessed the relative effectiveness of adding filtration and increasing the kV:mA ratio. Image quality was subjectively assessed for diagnostic and therapeutic acceptability in two groups of 10 patients undergoing radiofrequency ablations, pacemaker insertions or electrophysiology studies. One of the groups was screened with 0.35 mm copper filtration in place and the other group acted as the control. Maximum patient skin dose proved difficult to measure directly because of the unpredictable dose pattern. This pattern was studied in four patients using a film method in conjunction with thermoluminescent dosemeters. Copper filtration 0.35 mm thick inserted in the beams of the eight fluoroscopy units produced a mean reduction in entrance dose to the phantom of 58% with a mean increase in tube loading of 29%. At 100 kV the increased loading on the X-ray tube was equivalent to increasing the anteroposterior separation of the patient by 2 cm. Measurements on the catheter laboratory unit showed that the tube voltage would need to be raised above the normal diagnostic range to obtain an equivalent entrance dose reduction without the filter. The blackening of films under the patients showed complex patterns, but the estimated skin doses were consistent with those predicted by the phantom experiments. All six cardiologists considered there to be insignificant detriment to image quality in the procedures investigated.

Studies on a water phantom indicate that the insertion of extra tube filtration combined with the removal of the antiscatter grid can reduce the total energy imparted from paediatric fluoroscopy by a factor of more than four when automatic exposure control is used. The omission of the grid is responsible for up to 40% of the reduction while the addition of 0.7 mm steel filtration is found to account for a further reduction in energy imparted of between 57% and 70%, for depths of water simulating small patients of 6-16 cm thickness. For all contrast paediatric examinations the reduction in image quality was considered to be small and the diagnostic information unimpaired with the filter in place.

Mounting evidence indicates that scatter and attenuation are major confounds to objective diagnosis of brain disease by quantitative SPECT. There is considerable debate, however, as to the relative importance of scatter correction (SC) and attenuation correction (AC), and how they should be implemented. The efficacy of SC and AC for 99mTc brain SPECT was evaluated using a two-compartment fully tissue-equivalent anthropomorphic head phantom. Four correction schemes were implemented: uniform broad-beam AC, non-uniform broad-beam AC, uniform SC + AC, and non-uniform SC + AC. SC was based on non-stationary deconvolution scatter subtraction, modified to incorporate a priori knowledge of either the head contour (uniform SC) or transmission map (non-uniform SC). The quantitative accuracy of the correction schemes was evaluated in terms of contrast recovery, relative quantification (cortical:cerebellar activity), uniformity ((coefficient of variation of 230 macro-voxels) x 100%), and bias (relative to a calibration scan). Our results were: uniform broad-beam (mu = 0.12 cm(-1)) AC (the most popular correction): 71% contrast recovery, 112% relative quantification, 7.0% uniformity, +23% bias. Non-uniform broad-beam (soft tissue mu = 0.12 cm(-1)) AC: 73%, 114%, 6.0%, +21%, respectively. Uniform SC + AC: 90%, 99%, 4.9%, +12%, respectively. Non-uniform SC + AC: 93%, 101%, 4.0%, +10%, respectively. SC and AC achieved the best quantification; however, non-uniform corrections produce only small improvements over their uniform counterparts. SC + AC was found to be superior to AC; this advantage is distinct and consistent across all four quantification indices.