Clinical positron imaging : official journal of the Institute for Clinical P.E.T最新文献

Purpose: The aim of this study was to evaluate the efficacy of FDG-CDET for the detection of recurrences of colorectal cancer, in occult disease or in doubtful cases at conventional imaging (CI). In all the evaluated cases, the result of FDG-CDET was compared with post surgical histology both on patient and on site bases.

Methods and patients: After fasting for 6h or more, 150-250 MBq of ¹⁸F-FDG were injected i.v. and 2D imaging (whole-body scan and at least a tomoscintigram) was started 45 min. later, using a PICKER CDET gamma camera. Among the 214 examinations (ex) performed for detection of recurrences of colorectal cancer between Jul 1997 and Feb 2000, we only considered the 58 cases with negative or questionable CI and a post surgical histologic proof.

Results: Patients were referred in three different contexts:

• 1.

  suspicion of recurrence (SR) due to raising CEA levels with normal CI i.e. occult disease (18 ex: 13 TP, 3 FN, 2 FP on patient basis, 17 TP, 9 FN, 4 FP on site basis)

• 2.

  SR due to equivocal image(s) at follow-up CI (25 ex: 18 TP, 5 FN, 2 TN on patient basis, 21 TP, 10 FN, 2 TN on site basis)

• 3.

  SR due to both raising CEA levels and equivocal CI (15 ex: 13 TP, 2 FN on patient basis, 16 TP, 8 FN, 3 TN, 1 FP on site basis).

• 4.

  The overall sensitivity was 44/54 = 81% on patient basis and 54/81 = 67% on site basis. Specificity could not be evaluated because of the very small number of patients re-operated in case of negative FDG-CDET.

• 5.

  Conclusion: When conventional imaging could not contribute, i.e. a sensitivity of zero by definition, FDG-CDET accurately diagnosed a recurrence in 81% of the patients and located 67% of all recurrent lesions. These results confirm, with post surgical histology as the only gold standard, that FDG-CDET is a powerful tool for diagnosis of recurrent colorectal cancer in difficult cases. It could be used as the first line examination as soon as a recurrence is suspected, in order to avoid less contributive imaging procedures.

Endostatin is a novel antiangiogenic agent currently in phase I trials. In the context of this trial, we are evaluating the use of non-invasive imaging with PET to determine the relationship between tumor blood flow and glucose metabolism in imaged tumors from treated patients.

Ten patients have been treated with escalating daily iv Endostatin doses of 30 to 180 mg/m². PET images were obtained before the start of therapy and again after 28 days of treatment. Each patient was scanned with Oxygen-15 labeled water for estimation of tumor blood flow and Flourine-18 labeled FDG to estimate tumor metabolic activity. In most cases, two distinct tumor-bearing sites were analyzed in each patient. Thus, a total of 19 tumors were imaged. Regional blood flow and standard uptake values (SUV) were computed at baseline and 28 days post treatment and the percentage change in blood flow and SUV plotted as a function of Endostatin dose.

Both blood flow and glucose metabolism in the imaged tumors were observed to increase in patients treated with ⩽60 mg/m²/d, but became uncoupled in the tumors imaged from patients treated at the 180 mg/m²/d dose level. Thus, in patients receiving Endostatin at a dose of 180 mg/m²/d, blood flow decreased but glucose metabolism increased. This relationship is displayed in Figure 1

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Figure 1.

Purpose: PET can be useful in determining the progression of malignant disease over time as well as the response to therapy. To achieve this, the physician must be able to unambiguously identify and characterize individual tumors among several different scans.

Methods: We have developed a coordinate system for identifying individual tumor sites on PET scans, selecting the carina on the transmission scan as a point of origin. Using this system, each tumor is given a set of spherical coordinates that identifies its position: a rho (ρ, displacement from carina), a theta (θ, angle between the A–P axis and the tumor), and a phi (φ, angle between the polar axis and the tumor). We tested this method on a patient with metastatic thyroid cancer, who underwent ¹⁸FDG and ¹²⁴I-Iodide PET scans in the same week. This sytem was also used on a patient with metastatic prostate cancer, who had two FDG scans done 7 weeks apart. The patient underwent chemotherapy treatment during this period, and the scans were performed to assess therapy response.

Results: The patient with thyroid cancer had a total of 90 tumors, 82 of them identified in the ¹⁸FDG scan and 35 in the ¹²⁴I-Iodide scan, with 27 tumors identified in both. For ρ, θ, and φ among the 27 matching pairs of tumors, the mean differences were 6.80 ± 5 mm, 6.22 ± 4.54°, and 5.51 ± 5.81°, respectively. The disparity in coordinate values between corresponding tumors can be explained by the distinctive uptake patterns of the radiopharmaceuticals. The patient with prostate cancer had 9 tumors identifiable in both the pre- and post-therapy scans. The mean differences for ρ, θ, and φ among the 9 pairs of tumors were 1.93 ± 1.65 mm, 6.67 ± 5.53°, and 2.04 ± 2.02°, respectively. After thorough analysis, we have determined that corresponding tumors with ρ < 15 mm, θ and φ < 15° difference usually indicate a match.

Conclusion: This coordinate system facilitates the identification and characterization of individual tumors among multiple scans, thus aiding in both the assessment of diagnostic capabilities of different tracers, and the tracking of tumors following therapy.

Background: As the role of PET-FDG imaging is being established in the staging and monitoring of response to therapy in children with lymphoma, we encountered a case of an infection common in adolescence that may present with lymphoma-like signs and symptoms.

Methods: A 13-year-old previously healthy male presented with a left neck mass associated with weakness, fatigue, intermittent fevers and weight loss. He was then referred to the hematology/oncology department with a working diagnosis of lymphoma. The total wbc count was 5920/cu mm with 75% lymphocytosis without atypical lymphocytes. ESR was 20 mm. Serologic analysis for EBV, CMV, toxoplasmosis and hepatitis was also performed. The chest x-ray was normal. CT scan demonstrated multiple enlarged lymph nodes in both right and left jugulodigastric and spinal accessory chains; the largest mass within the left spinal accessory chain had focal necrosis within it. There were no enlarged mediastinal or axillary nodes. The spleen was massively enlarged and the splenic index was 924 (normal for age = 744).

Results: FDG imaging showed intense uptake in both cervical regions, the mediastinum and in the enlarged spleen. The results of the Monospot test and the EBV panel which were both positive, were available 3 & 5 days later. Based on these serologic results, the history, physical findings and the negative chest x-ray, the final diagnosis was infectious mononucleosis.

Conclusion: Despite availability, ease of performance and sensitivity of FDG imaging, this case illustrates the importance of clinical, hematologic and serologic assessment of disease prior to FDG imaging.

Purpose: The purpose of this investigation is to compare and explain discordant findings on high quality PET and CT where no corresponding CT abnormality is seen despite a significant appearing PET abnormality.

Methods: The methods involved the review of forty sequential oncologic cases. State-of-the-art helical post contrast CT scans and state-of the-art attenuated corrected and uncorrected PET images were examined. Discordant findings were classified as: Type A Obvious PET abnormalities fail to reveal CT anatomic abnormalities. Type B CT anatomic abnormalities show no PET abnormalities (usually benign disease). Only Type A discordance was evaluated and repeat CT scans were obtained if more than two weeks separated the exams.

Results: The results showed that there were four cases of Type A discordance. Case I showed a large PET abnormality with a negative CT. Repeat CT was again negative. The suspicion of a mis-registration artifact on PET due to motion was confirmed. Cases II, III, & IV had prominent PET abnormalities with normal CT scans within two to six weeks preceding the PET. Repeat CTs showed remarkable new findings corresponding exactly with the PET abnormalities.

Conclusion: In conclusion, when a conspicuous hypermetabolic focus has no corresponding CT anatomic structure on a high quality CT exam, extra evaluation is in order. Aside from technical artifacts, a relatively short time delay between CT and PET may account for development of new findings on CT in the face of aggressive disease.

Malignant tumors exhibit increased glucose metabolism which can be quantitated by SUV. SUV is criticized for its variability resulting from many factors including the method of drawing region of interest (ROI) over the tumor. The most common method manually draws or places ROI on various slices displaying highest FDG activity. This time consuming method is associated with significant individual variation. We describe a more reproducible, efficient spherical 3-D blob analysis method of SUV and tumor volume (TV) determination to evaluate CTA response. The spherical 3-D Blob analysis program is a completely automated method with data processing performed using IDL (RS Inc., Colorado). A threshold value is set for the ROI; all voxels above threshold are grouped by connectivity. Grouped voxels, called “blobs”, are displayed and statistics are calculated for each group. The threshold set for blob extraction and SUV determination is usually three times above background and is constant on repeat scans. Eight patients with metastatic carcinoma underwent PET/CT/MRI prior to and one week after chemotherapy. Three patients also had scans at one month. Maximum and average SUV's and TV were determined and appeared to be very reproducible when there was no clinical response or change on CT/MR. In these patients, repeat SUV's and volumes of the lesions (n = 38) varied by less than 20% of baseline. An increase/decrease in maximum SUV or TV correlated with a similar change in lesion size on CT/MR. The average SUV did not change. The spherical 3-D blob analysis program appears to be a reliable, efficient method of determining maximum SUV and volumetric measurements for following tumor response to CTA.

Purpose: The purpose of this study was to evaluate the diagnostic usefulness of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET).

Procedures: We performed FDG-PET in 22 patients with suspected primary or recurrent cancer (23 cases). The FDG-PET findings were compared with the final diagnosis, which was obtained by histological examination of resected, or biopsy specimens and the clinical course.

Results: In all patients, the sensitivity, specificity, and the accuracy of FDG-PET were 93.8%, 85.7%, 91.3%, respectively. In the patients with colo-rectal cancer, the sensitivity, specificity, and accuracy were 92.9%, 100%, 94.4%, respectively.

Conclusions: FDG-PET was considered to be clinically useful for the detection of primary or recurrent malignant tumors, and for differentiating recurrent tumors from inflammatory scars.

Purpose: With the increasing use of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) for scanning in oncology in our center, a radiation dose survey was performed to determine the impact on staff exposure. Conventional nuclear medicine procedures such as gallium scan, bone scans, and sestamibi cardiac scans are used for comparative purposes.

Procedure: Patients were measured using a hand-held radiation monitor (Victoreen 450-P) at various distances and times that replicate typical patient contact scenarios in the Diagnostic Imaging Department.

Results: We present our findings from the survey and the implications these have on staff radiation exposure. The data suggest that emerging oncologic techniques such as PET, high dose gallium-67, and high dose Tl-201 do not represent a significantly greater occupational radiation hazard than conventional nuclear medicine procedures.

Purpose: We reviewed ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) studies to determine the frequency of thymic visualization, to characterize this uptake to facilitate differentiation from disease, and to ascertain effects of therapy on visualization.

Methods: Hybrid positron emission tomography images performed on 14 patients with known or suspected malignancy before therapy, and on six of the patients after treatment, were reviewed. Mediastinal uptake was characterized by location, contour and intensity.

Results: Thymic uptake seen in five patients, 13–16-years-old, was characterized by an anterior midline location, regular contours, and a mean uptake ration of 2.5, and involved large glands. In five patients with mediastinal disease, 16–23-years-old, uptake was more posterior and eccentric in location with irregular borders and a mean uptake ratio of 4.3. One patient had anterior (thymic) and posterior (disease) mediastinal uptake. Three patients, 15–22-years-old, without disease and small thymus glands had no uptake. Five patients, including two with baseline uptake, showed no thymic uptake subsequently. One patient, negative initially, had thymic uptake five months after therapy.

Conclusions: Thymic ¹⁸F-FDG uptake occurs in younger patients, before or after treatment, and is associated with larger glands. Its midline anterior mediastinal location and mild intensity should facilitate discrimination from disease.

Purpose: Positron Emission Tomography (PET) with F18-fluorodeoxyglucose has been proven useful for staging non-small cell lung cancer. Bone scans are frequently performed for suspected skeletal metastases. The purpose of this study was to evaluate if bone scans compared to PET scans provide additional information that changes the stage of disease.

Procedures: Nineteen patients with non-small cell lung cancer had PET and bone scans done for staging of the malignancy. The results of both studies were compared.

Results: Bone and PET scans agreed on the presence or absence of skeletal metastases in all nineteen patients. The addition of a bone scan to a PET scan did not change the stage of the disease or the management in any of the patients. Bone scans allowed for more precise localization of the lesions in some patients.

Conclusions: Bone scans do not change the stage of disease when performed in addition to PET scans, but provide more precise localization of skeletal abnormalities.