(18)F]FDG in childhood lymphoma: clinical utility and impact on management

Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) is a very useful technique for the imaging of lymphomas in the adult population. It provides unique information about the behaviour of malignant cells and contributes to more accurate staging of the illness and better assessment of response to therapy. The purpose of this study was to evaluate the usefulness of FDG PET in childhood lymphoma compared with conventional imaging methods (CIMs) and clinical data. Between July 1998 and August 2001, 42 FDG PET examinations were performed using a dedicated PET system (27 examinations) or a hybrid coincidence PET system (15 examinations) for initial tumour staging ( n=7), restaging ( n=5) or assessment of response to therapy or residual masses ( n=30) in 27 children with Hodgkin's disease (HD) ( n=20) or non-Hodgkin's lymphoma (NHL) ( n=7). FDG PET results were compared with CIM findings and clinical data. Since 2000, a standardised questionnaire for evaluation of the clinical impact of FDG PET on both staging and therapy has been sent to the 16 referring physicians and 13 have replied. In all children, FDG PET was performed without any side-effects. FDG PET was found to be very sensitive (Se=12/12) for staging and restaging of the illness, showing more lesions than CIMs, with a 50% patient upstaging rate (6/12). It was very accurate for monitoring response to therapy and for characterisation of residual masses. False-positive results were observed in two NHL patients with thymic uptake and one false-negative result was obtained in a patient whose NHL relapsed 1 month after a negative FDG PET. The questionnaire emphasised the impact of FDG PET on clinical management, which was modified on the basis of the FDG PET results in 23% of patients. As previously demonstrated in the adult population, FDG PET appeared to be a very sensitive imaging technique for staging and restaging of lymphoma in children and was very useful for monitoring the response to therapy.     

Evaluation of tumour metabolism and multidrug resistance in patients with treated malignant lymphomas

The management of patients with treated malignant lymphomas requires functional methods to differentiate a residual soft tissue mass. Patients with treated Hodgkin's lymphoma (HL,n = 20, 68 malignant lesions, three benign lesions) or non-Hodgkin's lymphoma (NHL,n = 26, 46 malignant lesions, one benign lesion) were studied with positron emission tomography (PET) and fluorine-18 deoxyglucose (FDG). Oxygen-15 labelled water was used (n = 14, 25 lesions) in addition to FDG in order to obtain information on the tissue perfusion. Long-term follow-up studies with PET and FDG were performed in nine patients up to 511 days after the initiation of second-line therapy. Fourteen patients underwent single-photon emission tomography (SPET) with technetium-99m sestamibi immediately prior to the first PET examination. PET with FDG displays a high sensitivity for the detection of viable tumour tissue, all the malignant lesions being correctly classified in this study. The possible limitations are inflammatory processes, which may obscure tumour detection due to increased FDG uptake, and malignant lesions with low FDG uptake due to reduced perfusion. Difficulties exist in the prognosis of long-term response, since the change in FDG uptake may be variable. Long-term therapy outcome was correlated with the slope values obtained from the standardized integral uptake (SIU) data, which provides a new approach for the evaluation of PET follow-up studies.^99mTc-sestamibi, which should reflect the multidrug resistance, was evaluated with respect to therapy outcome. A high uptake of^99m-Tc-sestamibi was observed in patients with stable disease or better. The data support the hypothesis that sestamibi may reflect multidrug resistance. Due to technical limitations of the SPET technique, the use of a positron-labelled compound would be superior to SPET for clinical application.     

F-18 FDG PET/CT in the management of infected abdominal aortic aneurysm due to Salmonella

Mycotic aneurysm is a rare and life-threatening disorder. Computed tomography (CT) is considered to be the best diagnostic imaging modality that can detect an abdominal aortic aneurysm and changes in the surrounding structures. More recently, F-18 fluorodeoxyglucose (FDG) PET would seem to hold promise for the diagnosis of focal infection and during the follow-up after antibiotic treatment. We present a case of an infected abdominal aortic aneurysm due to Salmonella enteritidis. In this case, a combination of CT and FDG PET/CT provided accurate information for the diagnosis of the infected abdominal aortic aneurysm. Moreover, FDG PET/CT made an important contribution for monitoring response to antibiotic therapy.     

Positron emission tomography in patients suffering from HIV-1 infection

This paper reviews currently available PET studies performed either to improve our understanding of the pathogenesis of HIV-1 infection or to assess the value of PET imaging in the clinical decision making of patients infected with HIV-1 presenting with AIDS-related opportunistic infections and malignancies. FDG PET has shown that HIV-1 infection progresses by distinct anatomical steps, with involvement of the upper torso preceding involvement of the lower part of the torso, and that the degree of FDG uptake relates to viral load. The former finding suggests that lymphoid tissues are engaged in a predictable sequence and that diffusible mediators of activation might be important targets for vaccine or therapeutic intervention strategies. In lipodystrophic HIV-infected patients, limited available data support the hypothesis that stavudine-related lipodystrophy is associated with increased glucose uptake by adipose tissue as a result of the metabolic stress of adipose tissue in response to highly active antiretroviral treatment (HAART). Finally, in early AIDS-related dementia complex (ADC), striatal hypermetabolism is observed, whereas progressive ADC is characterized by a decrease in subcortical and cortical metabolism. In the clinical setting, PET has been shown to allow the differentiation of AIDS-related opportunistic infections and malignancies, and to allow monitoring of side effects of HAART. However, in patients suffering from HIV infection and presenting with extracerebral lymphoma or other human malignancies, knowledge of viraemia is essential when interpreting FDG PET imaging.     

Use of 2-deoxy-2-[F-18]-fluoro-D-glucose positron emission tomography to monitor therapeutic response by rhabdomyosarcoma in children: report of a retrospective case study

PURPOSE: The purpose of this study was to study the use of 2-deoxy-2-[F-18]-fluoro-D-glucose positron emission tomography (F-18 FDG PET) for monitoring therapeutic response by rhabdomyosarcoma (RMSA) in children. PATIENTS AND METHODS: A retrospective case study was performed by searching a computer database for the patients with RMSA in whom F-18 FDG PET studies were performed pre- and posttreatment. The data of the PET studies from these patients were analyzed in conjunction with clinical treatment and other imaging studies to determine whether interval changes of F-18 FDG uptake by the RMSA reflect response of RMSA to treatment. RESULTS: Four patients with RMSA who received both pretreatment and posttreatment F-18 FDG PET studies were identified from the database and included in this study. A dramatic decrease of F-18 FDG uptake by the tumor was evident in the patients who had a favorable response to the therapy and prolonged remission of the disease. In contrast, persistent abnormal FDG uptake in one patient was associated with early relapse of the RMSA. CONCLUSIONS: F-18 FDG PET may be useful for monitoring therapeutic response by RMSA in children, which needs to be verified with a prospective study in a larger patient population.     

FDG PET findings of chronic myeloid leukemia in the chronic phase before and after treatment

We report 2 patients with chronic myeloid leukemia in the chronic phase showing diffusely increased F-18 fluorodeoxyglucose (FDG) uptake in the bone marrow before treatment. Follow-up FDG positron emission tomography (PET) scans were performed in a patient after cessation of treatment and in the other under treatment. Both FDG PET findings showed reduced FDG uptake in the bone marrow. A series of these FDG PET findings suggest the usefulness of FDG PET for the diagnosis and monitoring of chronic myeloid leukemia after treatment.     

Use of FDG PET/CT for investigation of febrile neutropenia: evaluation in high-risk cancer patients

Purpose

Febrile neutropenia (FNP) is a frequent complication of cancer care and evaluation often fails to identify a cause. [¹⁸?F]FDG PET/CT has the potential to identify inflammatory and infectious foci, but its potential role as an investigation for persistent FNP has not previously been explored. The aim of this study was to prospectively evaluate the clinical utility of FDG PET/CT in patients with cancer and severe neutropenia and five or more days of persistent fever despite antibiotic therapy.

Methods

Adult patients with a diagnosis of an underlying malignancy and persistent FNP (temperature ≥38°C and neutrophil count <500 cells/μl for 5?days) underwent FDG PET/CT as an adjunct to conventional evaluation and management.

Results

The study group comprised 20 patients with FNP who fulfilled the eligibility criteria and underwent FDG PET/CT in addition to conventional evaluation. The median neutrophil count on the day of the FDG PET/CT scan was 30 cells/μl (range 0–730 cells/μl). Conventional evaluation identified 14 distinct sites of infection, 13 (93?%) of which were also identified by FDG PET/CT, including all deep tissue infections. FDG PET/CT identified 9 additional likely infection sites, 8 of which were subsequently confirmed as “true positives” by further investigations. FDG PET/CT was deemed to be of ‘high’ clinical impact in 15 of the 20 patients (75?%).

Conclusion

This study supports the utility of FDG PET/CT scanning in severely neutropenic patients with five or more days of fever. Further evaluation of the contribution of FDG PET/CT in the management of FNP across a range of underlying malignancies is required.     

Intraoperative radiation therapy in liver tissue in a pig model: monitoring with dual-modality PET/CT

PURPOSE: To assess, in a pig model, the value of dual-modality positron emission tomography (PET)/computed tomography (CT) for monitoring radiation therapy. MATERIALS AND METHODS: Central bile duct resection followed by creation of a biliodigestive anastomosis was performed in nine pigs. Six of these pigs were also treated with intraoperative radiation therapy (IORT) (20 Gy) in the area of the anastomosis. Two, 4, and 8 weeks postoperatively, contrast material-enhanced fluorine 18 fluorodeoxyglucose (FDG) PET/CT of the liver was performed in all of the animals. The radioactive tracer concentration in the region of the anastomosis was quantified, and the values were compared intraindividually with the values at the liver periphery. Histologic evaluation of the liver was performed 8 weeks postoperatively. The PET/CT images were assessed for changes in liver volume and bile duct diameter over time. RESULTS: In all nine pigs, the region of the anastomosis could be clearly defined on the fused PET/CT images. PET/CT revealed a decreased concentration of FDG in the irradiated field 2 and 4 weeks after IORT. At 8 weeks, however, the distribution of the tracer in the irradiated pigs did not differ from that in the nonirradiated pigs. Homogeneous tracer uptake in all liver regions was observed in the nonirradiated animals. The CT images showed an increase in liver volume in all pigs and bile duct dilatation that increased over time in the irradiated pigs. CONCLUSION: The morphologic and functional changes due to IORT in liver tissue can be accurately monitored with dual-modality PET/CT. By enabling the integration of functional and morphologic data, PET/CT may have an important role in monitoring radiation treatment.     

Impact of FDG PET on defining the extent of disease and on the treatment of patients with recurrent or metastatic breast cancer

OBJECTIVE: Our aim was to evaluate the impact of FDG PET on defining the extent of disease and on the treatment of patients with advanced breast cancer. MATERIALS AND METHODS: The medical records of 125 consecutive patients with recurrent or metastatic breast cancer referred for FDG PET from January 1998 through May 2002 were retrospectively reviewed. The rationale for FDG PET referral and the impact of FDG PET on subsequent treatment decisions for patients were determined by chart review. The impact of FDG PET on defining the extent of disease was determined by comparing the FDG PET interpretation at the time of the examination with findings from conventional imaging (CI) performed before FDG PET. FDG PET results were confirmed in nearly half (n = 61) of the patients by histopathology (n = 23) or follow-up imaging (n = 38; mean follow-up interval, 21.3 months). RESULTS: Patients were referred for FDG PET for the following reasons: evaluation of disease response or viability after therapy (n = 43 [35%]), local recurrence, with intent of aggressive local treatment (n = 39 [31%]), equivocal findings on CI (n = 25 [20%]), evaluation of disease extent in patients with known metastases (n = 13 [10%]), and elevated tumor markers with unknown disease site (n = 5 [4%]). Compared with CI findings, the extent of disease increased in 54 (43%), did not change in 41 (33%), and decreased in 30 (24%) of 125 patients using FDG PET. Results of FDG PET altered the therapeutic plan in 40 (32%), directly helped to support the therapeutic plan in 34 (27%), and did not change the plan devised before FDG PET in 51 (41%) of 125 patients. FDG PET altered therapy most frequently in the patients suspected of having locoregional recurrence and in those being evaluated for treatment response versus other referral categories (p = 0.04). For patients with confirmation of FDG PET findings, the sensitivity, specificity, and accuracy of FDG PET were 94%, 91%, and 92%, respectively. CONCLUSION: FDG PET contributes significantly to defining the extent of disease and deciding on treatment of patients with advanced breast cancer.     

FDG avidity and PET/CT patterns in primary gastric lymphoma

PURPOSE: The use of 18F-fluoro-deoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in primary gastric lymphoma (PGL) is challenging due to physiologic FDG activity in the stomach and variability in the degree of uptake in various histologic subtypes. This study assesses FDG avidity and PET/CT patterns in newly diagnosed PGL. METHODS: Sixty-two PET/CT studies of newly diagnosed PGL were reviewed (24 low-grade mucosa-associated lymphoid tissue [MALT], 38 aggressive non-Hodgkin's lymphoma [AGNHL]). FDG avidity, patterns (focal/diffuse), and intensity (visually vs. the liver and SUVmax) were assessed and compared to 27 controls. Gastric CT abnormalities and extragastric sites were recorded. RESULTS: Gastric FDG uptake was found in 55/62 (89%) PGL (71% MALT vs. 100% AGNHL, p < 0.001) and 63% controls. A diffuse pattern was found in 60% PGL (76% MALT vs. 53% AGNHL, p = NS) and 47% controls. FDG uptake higher than liver was found in 82% PGL (58% MALT vs. 97% AGNHL, p < 0.05) and 63% controls. SUVmax in FDG-avid PGLs was 15.3 +/- 11.7 (5.4 +/- 2.9 MALT vs. 19.7 +/- 11.5 AGNHL, p < 0.001) and 4.6 +/- 1.4 in controls. CT abnormalities were found in 79% PGL (thickening, n = 49; ulcerations, n = 22). Extra-gastric FDG-avid sites were seen in none of MALT, but 61% of AGNHL (nodal, n = 18; nodal and extranodal, n = 5). CONCLUSIONS: FDG avidity was present in 89% of PGLs, including all patients with AGNHL but only 71% of MALT. FDG uptake can be differentiated, in particular in AGNHL-PGL, from physiologic tracer activity by intensity but not by pattern. Extragastric foci on PET and structural CT abnormalities are additional parameters that can improve PET/CT assessment of PGL. Defining FDG avidity and PET/CT patterns in AGNHL and a subgroup of MALT-PGL before treatment may be important for further monitoring therapy response.     

FDG positron emission tomography for differentiation of degenerative and infectious endplate abnormalities in the lumbar spine detected on MR imaging

OBJECTIVE: The objective of our study was to evaluate the usefulness of FDG positron emission tomography (PET) for the differentiation of degenerative and infectious endplate abnormalities in the lumbar spine that were detected on MR imaging. SUBJECTS AND METHODS: FDG PET was performed prospectively in 30 consecutive patients with substantial endplate abnormalities (craniocaudal diameter of bone marrow abnormalities, > or = 25% of vertebral height) found during MR imaging of the lumbar spine. Both the MR and PET images were evaluated by two experienced musculoskeletal radiologists and two experienced nuclear physicians. The diagnosis of either degeneration with different types of endplate abnormalities or disk-space infection was determined. Clinical follow-up and, in selected cases, bone biopsies with cultures were used as the standard of reference. RESULTS: On the MR images, 25 of the 38 degenerated levels were classified as Modic type I, 13 levels as type II, and none as type III. Five disk-space infections were diagnosed in four patients. MR imaging findings were false-positive at one disk level with type I abnormalities and false-negative at two levels with infection. PET did not show FDG uptake in the intervertebral spaces of any patient with degenerative disease. FDG PET findings were true-positive in all five levels with disk-space infection. The sensitivity and specificity for MR imaging in detecting disk-space infection were 50% and 96%, and were 100% and 100% for FDG PET, respectively (not significant, McNemar test, p = 0.5). CONCLUSION: Our findings suggest that FDG PET may prove useful for differentiation of degenerative and infectious endplate abnormalities detected on MR imaging. Even in active (Modic type I) degenerative endplate abnormalities in our series, PET did not show increased FDG uptake.     

Rapid detection of human infections with fluorine-18 fluorodeoxyglucose and positron emission tomography: preliminary results

The purpose of this study was to evaluate the feasibility of 2-[fluorine-18]fluoro-2-deoxy-d-glucose (FDG) and positron emission tomography (PET) for rapid detection of human infections. Eleven patients who were known or suspected to be harboring various infections were studied with FDG-PET. Dynamic scans over the putative infection sites were performed immediately after FDG (370 MBq) injection through 60 min, and static images including multiple projection images were then obtained. FDG uptake was assessed visually into four grades (0, normal; 1, probably normal; 2, probably abnormal; 3, definitely abnormal). For the semiquantitative index of FDG uptake in infections, the standardized uptake value of FDG normalized to the predicted lean body mass (SUV-lean, SUL) was determined from the images obtained at 50–60 min after FDG injection. PET results were compared with final clinical diagnoses. Eleven lesions in eight patients, which were interpreted as grade 2 or 3 by FDG-PET, were all concordant with active infectious foci. The SUL values of infections ranged from 0.97 to 6.69. In two patients, FDG-PET correctly showed no active infection. In one patient, it was difficult to detect infectious foci by FDG-PET due to substantial normal background uptake of FDG. In total, FDG-PET correctly diagnosed the presence or absence of active infection in 10 of 11 patients. Fusion images of PET with computed tomography showed the most intense FDG uptake to be within an abscess wall. In conclusion, FDG-PET appears to be a promising modality for rapid imaging of active human infections. More extensive clinical evaluation is warranted to determine the accuracy of this method. Received 5 March and in revised form 20 May 1998     

兔VX2移植瘤氩氦刀治疗前后^18F-FDG PET／CT显像及病理学变化

目的研究兔VX2移植瘤氩氦靶向冷冻治疗系统（简称氩氦刀）治疗后PET／CT显像及病理学的变化,观察治疗后肿瘤组织的演化过程,探索氩氦刀治疗后疗效评价的方法。方法36只日本大白兔在兔VX2肿瘤种植后第4周,进行^18F-脱氧葡萄糖（FDG）PET／CT显像;显像后进行氩氦刀治疗。术后按随机数字表将兔完全随机分为6组,每组6只。分别在氩氦刀治疗后第1,3,7,14,30和60天进行PET／CT显像;分析PET／CT图像,观察标准摄取值（SUV）的变化;第2次PET／CT显像（术后显像）后处死大白兔,取出原肿瘤组织,进行病理学检查和免疫组织化学检测,比较病理学和免疫组织化学的变化。统计软件为SPSS16．0,组间比较采用配对资料的t检验和双变量相关分析,P〈0．05为差异有统计学意义。结果氩氦刀治疗后病理学检查提示,治疗区呈现坏死-炎性反应-机化过程。CT表现：肿瘤区域术后第3天至第14天有一短暂性增大,然后呈缩小的趋势;最大SUV（SUVmax）术后第1天即出现明显下降（由治疗前2．54±1．12下降至0．67±0．12）,第3天轻度升高（1．71±0．82）,然后逐渐减低（治疗后第60天为0．51±0．32）,治疗前后SUVmax变化差异有统计学意义（t=5．471,8．716,11．388,5．713,7．144和7．213,P均〈0．05）。治疗前后靶区面积变化与SUVmax变化相关性不明显（r=0．259,P=0．675）。治疗前后肿瘤微血管密度变化与SUVmax变化密切相关（r=0．865,P=0．032）。结论PET／CT显像可真实反映肿瘤组织氩氦刀治疗后的变化过程,是评价氩氦冷冻治疗疗效较理想的方法。     

The influence of I-131 therapy on FDG uptake in differentiated thyroid cancer

OBJECTIVE: 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) [or PET/computed tomography (CT)] is more likely to show false-negative results when it is performed shortly after chemotherapy and/or radiotherapy because of "metabolic stunning". The present study aimed to evaluate the influence of I-131 therapy on FDG uptake and the detection of recurrence or metastasis of differentiated thyroid cancer (DTC). METHODS: We retrospectively enrolled 16 consecutive FDG-PET/CT studies which had been performed in patients with DTC with elevated thyroglobulin (TG) but negative I-131 whole-body scan. All studies were performed under L: -thyroxine suppression. The patients were divided into groups A and B for PET/CT performed within 4 months of I-131 therapy or no such therapy, respectively. Each lesion identified on PET/CT was characterized using a 5-point scale by visual analysis: 0 = definitely benign, 1 = probably benign, 2 = equivocal, 3 = probably malignant, and 4 = definitely malignant. The maximum standardized uptake value (SUV max) in each lesion was also measured for semiquantitative analysis. We compared the visual grading and SUV max of the lesion of highest FDG uptake between groups A and B. RESULTS: For visual analysis, group B had significantly more patients with an uptake score of 3 or 4 than group A (80% vs. 17%, P = 0.01). In addition, there were significantly more equivocal results from group A than from group B (67% vs. 10%, P = 0.02). If the patients with the highest uptake scores of 2, 3, and 4 were considered to be positive for local recurrence or metastasis, there would be no significant difference between the positive rates of groups A and B (83% vs. 90%, P = 0.7). However, the mean SUV max of positive results was significantly lower for group A than for group B (3.1 +/- 0.9 and 6.6 +/- 3.5, respectively, P = 0.02). CONCLUSIONS: The preliminary results suggested that FDG uptake in DTC may be negatively influenced by I-131 therapy within 4 months, resulting in lower FDG uptake and more equivocal results. Further studies are necessary to determine whether it is secondary to "metabolic stunning" caused by I-131 therapy.     

Catheter-related focal FDG activity on whole body PET imaging

INTRODUCTION: Whole body FDG positron emission tomography (PET) scan is increasingly being used in the management of a variety of cancers and infections. Cancer patients and other very sick patients have central venous catheters, which could be associated with common complications like thrombosis and infections. We describe catheter-related focal FDG uptake on whole body FDG PET scans in 4 patients. MATERIALS AND METHODS: Four patients underwent whole body FDG-PET scanning 60 minutes after intravenous injection of F18-FDG (2 for localization of site of infection, 1 for primary cancer site localization, and 1 for restaging of colon cancer). The whole body PET images were compared and correlated with the patients' history, radiology and laboratory tests. RESULTS: Focal and intense FDG activity is seen in all 4 patients at the distal end of the intravenous catheter. The average SUV of this activity was 6.3 (n = 3). Catheter-related thrombosis was identified as the cause of FDG activity in 3 patients, whereas catheter-related infection was considered in one patient. CONCLUSION: Focal and intense FDG activity, in relation to the distal end of a central venous catheter, has a benign etiology, usually seen with catheter-related venous thrombosis and can be seen with catheter related infection.     

Changes in 18F-fluorothymidine and 18F-fluorodeoxyglucose positron emission tomography imaging in patients with head and neck cancer treated with chemoradiotherapy

Objective

This study compared change of ¹⁸F-fluorothymidine (FLT) uptake with that of ¹⁸F-fluorodeoxyglucose (FDG) in head and neck squamous cell cancer (HNSCC) patients during and after treatment and evaluated the utility for early monitoring of response to chemoradiotherapy.

Methods

Thirty patients with newly diagnosed HNSCCs treated with concurrent chemoradiotherapy underwent FLT and FDG PET in pre-treatment (PET1), mid-treatment (PET2) and post-treatment (PET3) stages. The PET images were evaluated quantitatively using maximum standardized uptake values (SUVs). Ratios between SUVs at PET2 and PET3 were also calculated.

Results

According to the SUVs, no significant differences were found with primary site location, cellular differentiation and T category in all PET scans. About a 78 % median decrease in FLT SUV was observed at the total dose (TD) of 30 Gy and no apparent change was observed thereafter. About a 40 % decrease in FDG SUV was observed at TD 30 Gy and significant decreases were then found at the 4- and 6-week time points after the therapy. FLT PET demonstrated no recurrence regions in patients with a PET3/PET2 ratio of <1.5. In comparison, FLT SUVs in PET3 with recurrence were increased more than three times. However, no significant difference was found between the values with recurrence and those with no recurrence in FDG PET.

Conclusion

FLT PET signal change preceded FDG PET change and the increase of FLT uptake after the therapy can imply recurrence or a residual tumor. FLT PET seems promising for early evaluation of chemoradiation effects in HNSCCs.     

11C-choline PET for the detection of bone and soft tissue tumours in comparison with FDG PET

We assessed and compared the usefulness of C-choline positron emission tomography (PET) with that of 2-[ F]fluoro-2-deoxy-D-glucose (FDG) PET for the differentiation between benign and malignant bone and soft tissue tumours. A total of 43 patients with 45 lesions were included. C-choline PET and FDG PET were performed from 5 and 40 min, respectively, after injection of 275-370 MBq tracer. PET data were evaluated by using the standardized uptake value (SUV) and were analysed according to the pathological data. C-choline uptake in malignancies was 4.9+/-2.1 (n=14), which was significantly higher than that in benign lesions (2.5+/-1.7, n=31) (P <0.0001). The sensitivity, specificity and accuracy of C-choline PET were 100%, 64.5% and 75.6%, respectively, when 2.59 of the SUV was used as the cut-off value. The FDG uptake in malignancies was 5.1+/-4.2 (n=14) and was also significantly larger than that in benign lesions 2.9+/-2.9 (n=31) (P<0.003). The sensitivity, specificity and accuracy of FDG PET were 85.7%, 41.9% and 55.6%, respectively (cut-off=1.83). The C-choline uptake in the lesions correlated with FDG uptake ( r=0.61, P<0.003). In receiver operating characteristic (ROC) analysis, the area under the ROC curve for C-choline PET (area=0.847) was higher than that for FDG PET (area=0.717). This study showed that C-choline PET was superior to FDG PET in differentiation between malignant and benign lesion in bone and soft tissue tumours. C-choline PET might be useful as a screening method for malignant bone and soft tissue tumours.     

Evaluation of intraoperative radiation therapy for unresectable pancreatic cancer with FDG PET.

This investigation was undertaken to evaluate 18F-labeled fluorodeoxyglucose (FDG) PET in monitoring patients after intraoperative radiotherapy (IORT) for unresectable pancreatic cancer and to compare its usefulness with CT. METHODS: FDG PET was performed in 12 consecutive unresectable ductal adenocarcinoma patients before (n = 12) and after IORT (0.7-11.9 mo, n = 14). In the follow-up period, FDG PET results after IORT were divided into three groups: early (0-2.0 mo after IORT, n = 7), intermediate (2.1-4.0 mo, n = 5) and delayed period (4.1 mo or later, n = 2). FDG uptake at 60 min after injection of 185 MBq FDG under fasting conditions was analyzed with standardized uptake value (SUV). Three parameters, the highest SUV in the tumor, the area of tumor showing SUV of more than 2.0 and the average SUV in the tumor area were calculated. Ratios of each parameter after IORT to that before IORT were defined as residual uptake ratio (RUR)-1, -2 and -3, respectively. Tumor regression after IORT was evaluated with CT as tumor size ratio (TSR) every 2 mo. RESULTS: Results of RUR-1 and -3 were consistent with tumor size measured by CT. They decreased in 10 patients with partial response and increased in 2 patients with no change, although these 2 patients had abscesses. RUR-3 decreased consistently as 0.65+/-0.33 in 2 mo, 0.51+/-0.39 in 4 mo and 0.24 in 4 mo or later after IORT, respectively. RUR-1 decreased in early period, but demonstrated no change through the remaining periods. There were discrepancies between the results of RUR-2 and those of the other RURs. CT results revealed a slow decrease in tumor size, because TSR was 0.91 +/-0.10, 0.76+/-0.11 and 0.70+/-0.18 in 2, 4 and 6 mo after IORT, respectively. RUR-3 was smaller than TSR at 2 mo (P < 0.05) and 4 mo (P = 0.056). These results indicate that the measurement of the average SUV in the tumor area with FDG PET could evaluate the local response of pancreatic cancer after IORT earlier and more markedly than with CT. CONCLUSION: FDG PET was useful in monitoring patients after IORT, because the decrease of metabolism in pancreatic tumor could be detected earlier than the decrease in tumor size.     

F-18 FDG PET/CT evaluation of radiotherapy response in rare case of mucosa-associated lymphoid tissue lymphoma

We experienced two cases of mucosa-associated lymphoid tissue (MALT) lymphoma arising at unusual locations and used F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) to evaluate their response to radiation therapy (RT). A 62-year-old male with proven prostatic MALT lymphoma and a 43-year-old woman with proven duodenal MALT lymphoma had diffuse FDG uptake in the lesion. Both cases were treated with RT; following FDG, PET/CT showed decreased FDG uptake in each lesion. Neither patient had evidence of recurrence at more than 18 months after RT. FDG PET/CT is useful for indicating the treatment site in MALT lymphoma and in evaluation of therapeutic response following RT.     

F-18 FDG PET Images of the Cervix at Various Time Points after the Loop Electrosurgical Excision Procedure

F-18 FDG PET is useful for monitoring residual or recurrent tumors after surgical resection. We describe five F-18 FDG PET images of three patients who had cervical carcinoma and then underwent a loop electrosurgical excision procedure (LEEP). Two of the images were taken within 15 days and three at least 2 months after LEEP. The earlier F-18 FDG PET images revealed linear hypermetabolic lesions in the cervix that were produced by inflammation. This was confirmed by pathological analysis. The later F-18 FDG PET images did not reveal any remarkable hypermetabolism in the cervix without any treatment. These observations suggest that, to determine the response to LEEP therapy, F-18 FDG PET should not be performed within 15 days of the procedure.