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Medhat Osman

Publications and source records attributed to Medhat Osman.

12 recordsLinked to original sources
PubMed2006

Phase I single-dose study of intracavitary-administered iodine-131-TM-601 in adults with recurrent high-grade glioma.

PURPOSE: TM-601 binds to malignant brain tumor cells with high affinity and does not seem to bind to normal brain tissue. Preclinical studies suggest that iodine-131 (131I) -TM-601 may be an effective targeted therapy for the treatment of glioma. We evaluated the safety, biodistribution, and dosimetry of intracavitary-administered 131I-TM-601 in patients with recurrent glioma. PATIENTS AND METHODS: Eighteen adult patients (17 with glioblastoma multiforme and one with anaplastic astrocytoma) with histologically documented recurrent glioma and a Karnofsky performance status of > or = 60% who were eligible for cytoreductive craniotomy were enrolled. An intracavitary catheter with subcutaneous reservoir was placed in the tumor cavity during surgery. Two weeks after surgery, patients received a single dose of 131I-TM-601 from one of three dosing panels (0.25, 0.50, or 1.0 mg of TM-601), each labeled with 10 mCi of 131I. RESULTS: Intracavitary administration was well tolerated, with no dose-limiting toxicities observed. 131I-TM-601 bound to the tumor periphery and demonstrated long-term retention at the tumor with minimal uptake in any other organ system. Nonbound peptide was eliminated from the body within 24 to 48 hours. Only minor adverse events were reported during the 22 days after administration. At day 180, four patients had radiographic stable disease, and one had a partial response. Two of these patients further improved and were without evidence of disease for more than 30 months. CONCLUSION: A single dose of 10 mCi 131I-TM-601 was well tolerated for 0.25 to 1.0 mg TM-601 and may have an antitumoral effect. Dosimetry and biodistribution from this first trial suggest that phase II studies of 131I-TM-601 are indicated.

Adult↗
PubMed2004

PET/CT: artifacts caused by bowel motion.

BACKGROUND AND AIM: In a combined positron emission tomography (PET) and computed tomography (CT) system, the CT images can be used for attenuation correction as well as for image fusion. However, quantitative and qualitative differences have been reported between CT based attenuation corrected PET and conventional transmission scan corrected PET images. The purpose of this study was to investigate potential differences in PET/CT caused by attenuation differences in bowel due to motion. METHODS: Twelve patients had PET/CT scans performed using 68Ge transmission and CT attenuation correction methods. Three emission imaging datasets were generated including CT corrected PET, Ge corrected PET, and the difference images (CT corrected PET minus Ge corrected PET). PET difference images were used to identify regions of mismatch and to quantify possible discordance between images by using standardized uptake values (SUVs). Using the Ge corrected PET as the standard, differences in emission images were classified as an overestimation (pattern A) or an underestimation (pattern B) in these difference images. RESULTS: One hundred and twenty-three mismatched areas were identified. Among them, overestimated areas in CT corrected image were detected in 36 regions (pattern A), while underestimated areas were evaluated in the remaining 87 regions (pattern B). The mean value of the difference in pattern A (mean +/- standard deviation = 0.84 +/- 0.44) was slightly higher than that in pattern B (0.60 +/- 0.23), and statistically significant. Six of 36 regions in pattern A had an SUV of greater than 2.5 in CT corrected PET but less than 2.5 in Ge corrected PET; two of 87 regions with pattern B demonstrated an SUV greater than 2.5 in Ge corrected PET and less than 2.5 in CT corrected PET. CONCLUSION: Physiological bowel motion may result in attenuation differences and subsequent differences in SUVs. Overestimation of fluorodeoxyglucose uptake should not be misinterpreted as disease.

Abdominal Neoplasms↗
PubMed2004

Composite SISCOM images in mesial temporal lobe epilepsy: technique and illustration of regions of hyperperfusion.

OBJECTIVE: To outline and validate a technique for subtraction ictal single photon emission tomography (SPET) co-registered to magnetic resonance imaging (MRI) (SISCOM), which allows non-linear co-registration of groups of subtraction SPET images to a single, template image. METHODS: In patients with mesial temporal lobe epilepsy, we used linear and non-linear transformation steps to co-register ictal and interictal images to a template SPET, then used the resultant ictal and interictal images to produce subtraction images. Statistical changes in subtraction SPET before and after the transformation steps in individual subjects were documented to validate the technique. Subtraction SPET images were thresholded to include pixel values 1 standard deviation (SD) above zero, and converted to binary. Images were combined by simple addition of images to form the final composite image. Final results were co-registered to a template MRI to demonstrate the regions most commonly hyperperfused in mesial temporal lobe epilepsy. RESULTS: Linear and non-linear transformation steps induced only small changes in standard deviations of subtraction SPET, typically approximately 1 pixel value. The final composite SISCOM images showed the anterior temporal lobe, insula and basal ganglia as the most commonly hyperperfused regions during mesial temporal lobe epileptic seizures. CONCLUSION: Our technique resulted in only small changes in statistical characteristics of individual subtraction SPET studies, and was acceptable for the purpose of creating composite SISCOM images.

Algorithms↗
PubMed2003

PET-CT: accuracy of PET and CT spatial registration of lung lesions.

PET-CT scanners offer the unique ability to acquire PET and CT data with rapid full body registration. The purpose of this study was to evaluate the accuracy of spatial registration between PET and CT data in patients with fluorine-18 fluoro-2-deoxy- D-glucose (FDG)-avid lung lesions. PET, CT and fused PET-CT images from 244 consecutive clinical patients undergoing whole-body FDG PET-CT imaging (GE Discovery LS, CT attenuation correction, OSEM reconstruction) were evaluated. Inclusion criteria for this analysis were lung lesions clearly defined on both PET and CT, lesion diameter less than 5 cm and clear borders. Patients were allowed to breathe freely during both PET and CT image acquisitions. The spatial coordinates of the visually estimated centers of the lesion were determined independently for PET and CT images and compared. Thirty-six patients (26 females, 10 males) with a total of 48 lesions were included (19 lung cancer patients with 26 lesions, 17 patients with 22 lung metastases). The average lung lesion diameter was 15.6+/-9 mm. The mean distance between the center of lesions independently determined for both PET and CT was 7.55+/-4.73 mm. Misregistration tended to be more pronounced in the lower lungs (10.2+/-6.55 mm) than in the upper lungs (6.67+/-4.28 mm) ( P=0.063). Misregistration also tended to be slightly more pronounced in the left lung (8.33+/-5.05 mm) than in the right lung (6.25+/-3.92 mm) ( P=0.059). In conclusion, with a dedicated PET-CT scanner and this clinically practical imaging algorithm, registration is usually accurate, but spatial misregistration of primary lung lesions does occur.

Female↗
PubMed2003

Accuracy of image fusion of normal upper abdominal organs visualized with PET/CT.

Although PET/CT scanners have the potential for precise fused registration of structures visualized on both PET and CT, physiological motion during the acquisition of both studies may alter the appearance of organ shape, size or location. The degree of possible mismatch in abdominal organ size and position between PET and CT has not been evaluated. The aim of this study was to assess the consistency in location and measured size of upper abdominal organs with PET and CT using a combined PET/CT system. Forty-six consecutive inpatients who underwent clinical PET/CT scans for suspected cancer were evaluated. CT and PET images attenuation corrected by both CT and germanium-68 transmission scans were obtained, and we separately determined the location of the top and bottom (height), anterior and posterior margins (thickness), and right and left margins (width) for each organ, including liver, spleen, and bilateral kidneys, using CT and both sets of PET images. Differences between the two modalities in terms of location and measured organ size were investigated. In the upper margin of the liver and lower margin of the spleen, more than 10% of the cases showed a larger discrepancy (>20 mm) between CT-based and Ge-corrected PET-based measurements, although the differences in the positions of the edges were less than 10 mm in most cases. The center of the liver tended to be located cephalad and to the right of the body, and that of the spleen tended to be cephalad and posterior on PET, as compared with CT. Moreover, the center of both kidneys tended to be seen cephalad, posterior, and to the right on PET. The liver appeared slightly larger on PET than CT in thickness (CT vs CT-corrected PET vs Ge-corrected PET = 156 mm vs 162 mm vs 162 mm) and width (186 mm vs 189 mm vs 188 mm). By contrast, the spleen appeared slightly smaller on PET than CT in height (84 mm vs 77 mm vs 80 mm) and width (85 mm vs 81 mm vs 80 mm). A similar tendency was observed in the left kidney (105 mm vs 100 mm vs 99 mm in height, and 64 mm vs 59 mm vs 58 mm in width) and the right kidney (99 mm vs 93 mm vs 93 mm in height, and 64 mm vs 59 mm vs 60 mm in width). These differences between the two modalities were statistically significant ( P<0.05). In conclusion, minor mismatches in location and organ size were found to exist between CT and PET images, in part due to physiological motion. Although these differences could potentially affect the quality of the image registrations, they were generally of a modest nature.

Abdomen↗
PubMed2003

Prevalence and patterns of bone metastases detected with positron emission tomography using F-18 FDG.

PURPOSE: The aim of this retrospective study was to report the prevalence and imaging characteristics of bone metastases detected with F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) and, when possible, compare these findings with the performance of bone scans in the same patients. METHODS: The reports of 403 patients with histologically proved malignant disease who underwent a PET scan for initial or post-therapeutic staging were reviewed for the presence of possible bone metastases. Based on the final diagnosis confirmed by histopathologic analysis or clinical follow-up, the PET findings of patients with positive bone metastases were evaluated in terms of location, intensity, and patterns. When the PET scan was positive, the PET results were compared with the findings of available bone scans. RESULTS: PET studies suggested the presence of bone metastases in 38 patients (9%). No follow-up data were available for 9 patients, and the remaining 29 were evaluated further. Of these patients, 6 had false-positive findings, whereas bone metastatic involvement was clinically confirmed in 23 patients. The primary malignant findings included lung cancer (n = 9), esophageal cancer (n = 3), lymphoma (n = 2), melanoma (n = 2), thyroid cancer (n = 2), breast cancer (n = 1), colon cancer (n = 1), prostate cancer (n = 1), testicular cancer (n = 1), and nasopharyngeal cancer (n = 1). On PET, 5 patients had a solitary metastatic focus (22%), and the remaining 18 patients had multiple lesions (78%). The vertebrae were the most frequently involved bones (74%), followed by pelvic bones (70%), ribs (65%), upper extremities including the scapula (48%), sternum (43%), and lower extremities (43%). The patterns of abnormal uptake were classified into three groups: focal (15 patients, 65%), diffuse (2 patients, 9%), and a mixed pattern (6 patients, 26%). Most of the lesions showed intense abnormal uptake (18 patients, 78%); 5 patients had both intense and moderate FDG uptake. Thirteen of the 23 patients with confirmed bone metastases also had a bone scan, which revealed positive bone disease in all of these patients. However, PET consistently revealed more metastatic foci than did the bone scan on a lesion basis. CONCLUSIONS: The most frequent pattern of detectable bone metastases with FDG-PET imaging was multiple foci of intense uptake. PET revealed more lesions than did bone scanning, independent of the type of cancer or location of bone involvement, in patients who were accurately diagnosed by FDG-PET imaging.

Adolescent↗
PubMed2003

Uptake in supraclavicular area fat ("USA-Fat"): description on 18F-FDG PET/CT.

UNLABELLED: The supraclavicular region is a common site for lymph node metastases. A commonly reported type of nonmalignant (18)F-FDG uptake on PET imaging in the supraclavicular region is "muscle uptake" purportedly due to muscle contraction in tense patients during the (18)F-FDG uptake phase. PET/CT offers the unique opportunity to correlate PET findings with CT anatomy in the supraclavicular region. METHODS: Images from the first 359 consecutive clinical whole-body studies (in 347 patients) using (18)F-FDG and a PET/CT scanner (with CT attenuation correction and ordered-subsets expectation maximization [OSEM] reconstruction) were retrospectively reviewed. The supraclavicular region was evaluated for the presence of abnormal uptake on PET images, and the corresponding CT findings were assessed. Three distinct patterns of abnormal (18)F-FDG uptake were noted: pattern A (uptake localizing to supraclavicular area fat [USA-fat], i.e., without corresponding lymph node or muscle uptake on CT), pattern B (uptake localizing to muscle on CT), and pattern C (uptake localizing to lymph nodes or soft-tissue masses on CT). RESULTS: Forty-nine patients (14.1%) (32 female, 17 male; mean age, 51.4 +/- 15.6 y; age range, 12-77 y) showed abnormal (18)F-FDG uptake in the supraclavicular region. Twenty patients (5.8%) had muscle uptake (group B); 15 (4.3%) had definite abnormal lymph nodes (group C). However, 14 patients (4.0%) had USA-fat (group A) and foci of very low Hounsfield units on CT. These foci were also present on (68)Ge attenuation-corrected images (when obtained) and non-attenuation-corrected images. Uptake in USA-fat was typically bilateral and symmetric, intense, more often multifocal than linear, and located in fat on PET/CT. Age was not significantly different for group C versus the 2 other groups. Intensity; mean standardized uptake value, lean (SUV(L MEAN)); or maximum standardized uptake value, lean (SUV(L MAX)), did not allow differentiation between patterns A and C (P > 0.05). Standardized uptake values (SUV(L MAX), 3.1; SUV(L MEAN), 2.1) were significantly lower in group B than in the 2 other groups (P < 0.005). CONCLUSION: So-called muscle uptake in the supraclavicular region may be caused in a significant proportion of cases by an unrelated process we call the USA-fat finding, with (18)F-FDG uptake in tissues of low-Hounsfield (fat) density. This finding most likely reflects an underlying nonpathologic process that we hypothesize to be in foci of brown fat. This intense supraclavicular uptake should be recognized and should not be misinterpreted as a malignant metastatic process or as muscle uptake.

Adipose Tissue↗
PubMed2003

Initial experience with oral contrast in PET/CT: phantom and clinical studies.

UNLABELLED: The aims of the study were to evaluate the effects of oral contrast on apparent tracer activity measured with PET/CT when using CT attenuation correction and to report our initial experience in the use of oral contrast with PET/CT. METHODS: Phantom studies with (18)F activity and saline bags or syringes filled with barium or gastrografin of varying densities were performed using a PET/CT scanner (CT attenuation correction). In the study, 91 clinical patients received dilute oral contrast and were evaluated by whole-body (18)F-FDG PET. RESULTS: A phantom experiment with CT contrast (1.3% weight/volume [w/v] barium) showed a "cold" area in the cold stomach whereas a phantom with high-density barium (98% w/v) showed an artifactual focus of intense "activity" in the cold stomach. In clinical studies, stomach and right colon were opacified by CT contrast. Maximal measured contrast density was 239 Hounsfield units. CONCLUSION: High-density barium causes overestimation of tissue (18)F-FDG concentration. Low-density barium does not cause significant artifacts and appears suitable for clinical use.

Administration, Oral↗
PubMed2003

Direct comparison of (18)F-FDG PET and PET/CT in patients with colorectal carcinoma.

UNLABELLED: The purpose of this study was to compare (18)F-FDG PET and PET/CT in a population of patients with colorectal cancer. METHODS: PET and PET/CT images from 45 patients (17 women, 28 men; mean age +/- SD, 60.8 +/- 11.1 y) with known colorectal cancer referred for PET from June to November 2001 were retrospectively reviewed. Images were acquired with a PET/CT scanner, and (68)Ge attenuation correction was applied. PET images and fused (68)Ge attenuation-corrected PET and CT images were independently and separately interpreted by a moderately experienced reader unaware of the clinical information. Certainty of lesion characterization was scored on a 5-point scale (0 = definitely benign, 1 = probably benign, 2 = equivocal, 3 = probably malignant, 4 = definitely malignant). Lesion location was scored on a 3-point scale (0 = uncertain, 1 = probable, 2 = definite). The presence or absence of tumor was subsequently assessed using all available clinical, pathologic, and follow-up information. Analysis was provided for lesions detected by both PET and PET/CT. RESULTS: The frequency of equivocal and probable lesion characterization was reduced by 50% (50 to 25) with PET/CT, in comparison with PET. The frequency of definite lesion characterization was increased by 30% (84 to 109) with PET/CT. The number of definite locations was increased by 25% (92 to 115) with PET/CT. Overall correct staging increased from 78% to 89% with PET/CT on a patient-by-patient analysis. CONCLUSION: PET/CT imaging increases the accuracy and certainty of locating lesions in colorectal cancer. More definitely normal and definitely abnormal lesions (and fewer probable and equivocal lesions) were identified with PET/CT than with PET alone. Staging and restaging accuracy improved from 78% to 89%.

Adult↗
PubMed2002

Quantitative evaluation of 2-deoxy-2-[18F] fluoro-D-glucose uptake in hepatic metastases with combined PET-CT: iterative reconstruction with CT attenuation correction versus filtered back projection with 68Germanium attenuation correction.

PURPOSE: Iterative reconstruction (IR) is a statistical reconstruction method that may be influenced by high background activity such as in the liver. Recently developed combined positron emission tomography (PET) and computerized tomography (CT) instrumentation utilizes CT attenuation correction that may also differ compared to 68Germanium (68Ge) segmented attenuation correction (IR SAC). Quantitative differences could affect the clinical interpretation of metastatic foci and subsequent response to therapy. The purpose of this study is to characterize potential quantitative differences specifically in hepatic metastases. PROCEDURES: Thirty-three metastatic liver lesions in 23 patients were evaluated. Whole-body 2-deoxy-2[18F]fluoro-D-glucose(FDG) PET images were obtained on a dedicated PET-CT device and reconstructed with IR and CT measured attenuation correction (IR CT MAC), IR and 68Ge segmented attenuation correction, and also with filtered back-projection and segmented attenuation correction (FBP SAC). Regions of interest over the liver lesions (L) and liver background (B) were drawn on FBP SAC images and superimposed on the co-registered IR CT MAC and IR SAC images for comparison. To identify the individual effects of IR and CT attenuation correction, IR SAC was first compared to FBP SAC, followed by a comparison of IR CT MAC and IR SAC. Differences were expressed as bias (%) and compared to FBP SAC. RESULTS: Compared to FBP SAC, IR SAC showed significantly lower liver lesion (mean bias -7.1%; P < 0.00001), significantly higher liver background (mean bias -3.5%; P = 0.005), and significantly lower L/B ratio (mean bias -10.1%; P < 0.00001). Compared to IR SAC, the IR CT MAC showed small but not statistically significant increases in liver lesion (mean bias 3.0%; P = 0.1) and liver background (mean bias 4.3%; P = 0.09), and no significant difference in L/B ratio (mean bias -1.3%; P = 0.5). The overall effect of IR CT MAC compared to FBP SAC was a significant decrease in liver lesion (mean bias -4.2%; P = 0.002), significant increase in liver background (mean bias 8.7%; P = 0.002), and significantly lower L/B (mean bias -11.1%; P < 0.00001) compared to FBP SAC. CONCLUSION: Compared to FBP, IR resulted in significantly lower mean hepatic tumor activity, higher mean liver background activity, and lower L/B activity, but these differences were modest. These differences were similarly seen in the CT corrected IR CT MAC when compared to FBP SAC. CT attenuation correction did not result in significant differences when compared to 68Ge correction. Although the differences in IR CT MAC were modest, consistent reconstruction methods are important to decrease the measurement variability and improve reproducibility.

Journal Article↗
PubMed2002

PET/CT: comparison of quantitative tracer uptake between germanium and CT transmission attenuation-corrected images.

UNLABELLED: In PET, transmission scanning for attenuation correction has most commonly been performed with an external positron-emitting radionuclide source, such as (68)Ge. More recently, combined PET/CT scanners have been developed in which the CT data can be used for both anatometabolic image formation and attenuation correction of the PET data. The purpose of this study was to assess the quantitative differences between CT-based and germanium-based attenuation-corrected PET images. METHODS: Twenty-eight patients with known or suspected cancer underwent whole-body (18)F-FDG PET/CT scanning for clinical diagnostic purposes. For each patient, attenuation maps were obtained from both the CT scan and the (68)Ge transmission data, and 2 different attenuation-corrected emission datasets were produced. Measured activity concentrations (both mean and maximum) from identical regions of interest in representative normal organs and in 36 pathologic foci of uptake were compared. RESULTS: CT-corrected emission images generally showed slightly higher radioactive concentration values than did germanium-corrected images (P < 0.01) for all lesions and all normal organs except the lung. Mean and maximum radioactivity concentrations were 4.3%-15.2% higher for CT-corrected images than for germanium-corrected images. Calculated radioactivity concentrations were significantly greater in osseous lesions than in nonosseous lesions (11.0% vs. 2.3%, P < 0.05, for mean value; 11.1% vs. 2.1%, P < 0.01, for maximum value). A weak positive correlation was observed between the CT Hounsfield units within the regions of interest and the percentage difference in apparent tracer activity in the CT-corrected images. CONCLUSION: Although quantitative radioactivity values are generally comparable between CT- and germanium-corrected emission PET images, CT-based attenuation correction produced radioactivity concentration values significantly higher than the germanium-based corrected values. These effects, especially in radiodense tissues, should be noted when using and comparing quantitative PET analyses from PET and PET/CT systems.

Algorithms↗