Voxel significance mapping using local image variances in subtraction ictal SPET.

Subtraction ictal SPET co-registered to MRI (SISCOM) has been shown to aid epileptogenic localization and improve surgical outcome in partial epilepsy patients. This paper reports a method of identifying significant areas of epileptogenic activation in the SISCOM subtraction image, taking into account normal variation between sequential 99Tcm-ethyl cysteinate diethylester SPET scans of single individuals, and attempts to assess the clinical value of statistical mapping in subtraction SPET. Non-linear inter-subject registration is used to combine a group of subtraction images into a common anatomical framework. A map of the pixel intensity standard deviation values in the subtraction images is created, and this map is non-linearly registered to a patient's SISCOM subtraction image. Pixels in the patient subtraction image were then evaluated based upon the statistical characteristics of corresponding pixels in the atlas. SISCOM images created with the voxel variance method were rated higher in quality than the conventional image variance method in 15 patients. No difference in localization rate was observed between the voxel variance mapping and image variance methods. The voxel significance mapping method was shown to improve the quality of clinical SISCOM images.

Biodistribution and radiation dosimetry of stabilized 99mTc-exametazine-labeled leukocytes in normal subjects.

UNLABELLED: Labeling leukocytes with 99mTc-exametazime is a validated technique for imaging infection and inflammation. A new radiolabeling technique has recently been described that enables leukocyte labeling with a more stable form of 99mTc-exametazime. A normal value study of stabilized 99mTc-exametazime-labeled leukocytes has been performed, including biodistribution and dosimetry estimates in normal subjects. METHODS: Ten volunteers were injected with stabilized 99mTc-exametazime-labeled autologous leukocytes to study labeled leukocyte kinetics and dosimetry in normal subjects. Serial whole-body imaging and blood sampling were performed up to 24 h after injection. Cell-labeling efficiency and in vivo viability, organ dosimetry, and clearance calculations were obtained from the blood samples and imaging data as well as urine and stool collection up to 36 h after injection. RESULTS: Cell-labeling efficiency of 87.5% +/- 5.1% was achieved, which is similar to or better than that reported with the standard preparation of 99mTc-exametazime. In vivo stability of the radiolabeled leukocytes was also similar to in vitro results with stabilized 99mTc-exametazime and better than previously reported in vivo stability for nonstabilized 99mTc-exametazime-labeled leukocytes. Organ dosimetry and radiation absorbed doses were similar with a whole-body absorbed dose of 1.3 x 10(-3) mGy/ MBq. Urinary and fecal excretion of activity was minimal, and visual assessment of the images showed little renal parenchymal activity and no bowel activity up to 2 h after injection. CONCLUSION: Cell labeling and in vivo stability appear improved compared with the leukocytes labeled with the nonstabilized preparation of 99mTc-exametazime. There are advantages in more cost-effective preparation of the stabilized 99mTc-exametazime and an extended window for clinical usage, with good visualization of abdominal structures on early images. No significant increase in specific organ and whole-body dosimetry estimates was noted compared with previous estimates using nonstabilized 99mTc-exametazime-labeled leukocytes.

Biliary sepsis as a cause of appearance of endoluminal Tc-99m HMPAO-labeled leukocytes: a case report.

A case is presented that shows the abnormal early appearance of Tc-99m HMPAO-labeled leukocytes within the small bowel lumen as a result of septic cholangitis. It is essential to perform early images with Tc-99m HMPAO-labeled leukocytes to differentiate between the appearance of abnormal uptake in the bowel and normal physiologic excretion, which occurs later in the renal and biliary tracts. Endoluminal radiolabeled leukocytes have been described in several clinical settings unrelated to bowel disease, such as swallowed activity from sinus or pulmonary infection, and it is important to differentiate this from primary gastrointestinal disease. To our knowledge, acute pyogenic cholangitis has not been shown previously as a cause of these appearances and should be included in the differential diagnosis for the early appearance of mobile radiolabeled leukocytes in the lumen of the gastrointestinal tract.

Clinical experience with radiolabelled monoclonal antibodies in the detection of colorectal and ovarian carcinoma recurrence and review of the literature.

A retrospective study was carried out to determine the diagnostic value of OncoScint CR/OV immunoscintigraphy in assessing patients with suspected recurrence of carcinoma of the colon and ovary. The scintigraphic results of 31 patients were compared with surgical and histopathological findings, conventional radiological examinations and clinical disease outcome over an average 3-year follow-up. Detected lesions were divided by location into hepatic or extrahepatic and the latter group was classified as local recurrence at the resection site, pelvic or abdominal regional lymph node involvement and distant metastatic disease. The combined sensitivity and accuracy of immunoscintigraphy in the detection of extra-hepatic disease was significantly higher than that of cross-sectional radiological imaging (87% and 83% vs 44% and 53% respectively) with equal specificity of 74%. Scintigraphy identified 14 (36%) of 39 extra-hepatic malignant lesions not diagnosed by conventional radiological techniques and influenced therapeutic planning in 8 (26%) of 31 patients studied. In the liver, conventional imaging had a significantly higher detection rate than immunoscintigraphy (sensitivity 93% vs 28%). In conclusion, these results show that OncoScint scintigraphy is a sensitive method for the detection of local recurrence and extra-hepatic metastases in colorectal and ovarian carcinoma and has an important role in the therapeutic decision-making process.

The evaluation and calibration of fan-beam collimators.

The aims of this study were (a) to determine the true focal length of a fan-beam collimator and (b) to calibrate image size (mm/pixel) for each collimator to permit inter-comparison of image data acquired on different gamma camera systems. A total of six fan-beam collimators on three dual-head gamma camera systems were evaluated using a set of four cobalt-57 point source markers. The markers were arranged in a line in the transverse plane with a known separation between them. Tomographic images were obtained at three radii of rotation. From reconstructed transaxial images the distance between markers was measured in pixels and used to determine pixel size in mm/pixel. The system value for the focal length of the collimator was modified by up to +/-100 mm and transaxial images were again reconstructed. To standardize pixel size between systems, the apparent radius of rotation during a single-photon emission tomography (SPET) acquisition was modified by changes to the effective collimator thickness. SPET images of a 3D brain phantom were acquired on each system and reconstructed using both the original and the modified values of collimator focal length and thickness. Co-registration and subtraction of the reconstructed transaxial images was used to evaluate the effects of changes in collimator parameters. Pixel size in the reconstructed image was found to be a function of both the radius of rotation and the focal length. At the correct focal length, pixel size was essentially independent of the radius of rotation. For all six collimators, true focal length differed from the original focal length by up to 26 mm. These differences in focal length resulted in up to 6% variation in pixel size between systems. Pixel size between the three systems was standardized by altering the value for collimator thickness. Subtraction of the co-registered SPET images of the 3D brain phantom was significantly improved after optimization of collimator parameters, with a 35%-50% reduction in the standard deviation of residual counts in the subtraction images. In conclusion, we have described a simple method for measurement of the focal length of a fan-beam collimator. This is an important parameter on multidetector systems for optimum image quality and where accurate co-registration of SPET to SPET and SPET to MRI studies is required.

Short duration therapy for Helicobacter pylori in Western Australia: the impact of metronidazole resistance.

BACKGROUND: Limited Australian data are available on either short duration therapy for Helicobacter pylori infection, or the impact of metronidazole resistance on the outcome of treatment. AIM: To compare the efficacy of two treatment regimens and determine the influence metronidazole resistance has on clearing H. pylori infection. METHODS: Eighty patients with H. pylori infection proven at upper gastrointestinal endoscopy, none of whom had previously received therapy for H. pylori, were randomised to one week therapy with either bismuth subcitrate one tablet qid, tetracycline 500 mg qid and metronidazole 400 mg tds (BTM), or lansoprazole 30 mg bd, amoxycillin 500 mg qid and metronidazole 400 mg tds (LAM). Effectiveness of therapy was measured by C14-urea breath test at six weeks. RESULTS: On an intention-to-treat basis, clearance of infection was achieved in 17 of 32 (53%; 95% CI: 35-71%) evaluable patients receiving BTM and 32 of 46 (70%, 54-82%) patients receiving LAM (p = 0.16). Metronidazole resistance was found in 32 of 65 (49%) patients in whom H. pylori was isolated by culture. On a per-protocol basis, of patients who had metronidazole sensitive strains of H. pylori 23 of 24 (96%) cleared infection after therapy with either BTM or LAM, compared with 14 of 24 (58%) who were metronidazole resistant (p = 0.004). Clarithromycin resistance was not found in 45 patients tested. CONCLUSIONS: In Western Australia clearance rates of H. pylori infection, after one week of BTM or LAM, are lower than in other published series. The high incidence of metronidazole resistance is the main determinant of our relatively poor eradication rates.

Isolated torsion of the fallopian tube in a premenarchal girl : Case report and review of the literature.

A case is reported of an isolated torsion of the left fallopian tube in a 12-year-old premenarchal girl, and the relevant literature is reviewed. This would seem to be an infrequent cause of acute abdominal pain in girls, and is rarely diagnosed preoperatively. The correct treatment is detorsion of a viable tube, or salpingectomy if ischaemia and necrosis have occurred.

Systemic lupus erythematosus serositis.

The imaging appearances of a case of systemic lupus erythematosus, which manifested initially as a serositis, is described. Barium small bowel study showed segments of spiculation with tethering, angulation, and obstruction. On computed tomography there was ascites and segments of asymmetrical thickening of small bowel wall were observed. Laparotomy revealed extensive patchy serosal and peritoneal plaques but biopsy of these lesions did not lead to a definitive diagnosis. The diagnosis was made on the basis of marked elevation of antinuclear and anti-double stranded DNA antibodies.