Dual-time point FDG PET imaging in the evaluation of pulmonary nodules with minimally increased metabolic activity

Diuretic 18F-FDG PET/CT imaging for detection and locoregional staging of urinary bladder cancer: prospective evaluation of a novel technique

PURPOSE

Positron emission tomography/computed tomography (PET/CT) with (18)F-fluorodeoxyglucose (FDG) has been used with limited success in the past in primary diagnosis and locoregional staging of urinary bladder cancer, mainly because of the pharmacokinetics of renal excretion of (18)F-FDG. In the present prospective study, we have evaluated the potential application of diuretic (18)F-FDG PET/CT in improving detection and locoregional staging of urinary bladder tumours.

METHODS

Twenty-five patients suspected of having primary carcinoma of the urinary bladder were evaluated prospectively for diagnosis and staging. All of these 25 patients underwent conventional contrast-enhanced computed tomography (CECT) of the abdomen/pelvis and whole-body diuretic (18)F-FDG PET/CT. In addition, pelvic PET/CT images were obtained using the special technique of forced diuresis using intravenous furosemide (20-40 mg). Of the 25 patients, 10 underwent radical cystectomy and 15 underwent transurethral resection of the bladder tumour (TURBT). Results of CECT and diuretic (18)F-FDG PET/CT were compared considering histopathology as a reference standard.

RESULTS

Of the 25 patients, CECT detected a primary tumour in 23 (sensitivity 92 %), while (18)F-FDG PET/CT was positive in 24 patients (sensitivity 96 %). Mean size and maximum standardized uptake value of the bladder tumours were 3.33 cm (range 1.6-6.2) and 5.3 (range 1.3-11.7), respectively. Of the 25 patients, only 10 patients underwent radical cystectomy based on disease status on TURBT. Among those ten patients, nine had locoregional metastases. Among the nine patients who had positive lymph nodes for metastasis on histopathology, CECT and PET/CT scan had a sensitivity of 44 and 78 %, respectively. (18)F-FDG PET/CT was found to be superior to CECT in the detection of the primary tumour and locoregional staging (p < 0.05).

CONCLUSION

Diuretic (18)F-FDG PET/CT is highly sensitive and specific and plays an important role in improving detection of the primary tumour and locoregional staging of urinary bladder tumours. Diuretic (18)F-FDG PET/CT demonstrated a higher diagnostic value when compared with CECT in these patients.

SUV on dual-phase FDG PET/CT correlates with the Ki-67 proliferation index in patients with newly diagnosed non-Hodgkin lymphoma

PURPOSE

PET using 18F-FDG integrated with CT is beneficial for staging patients with non-Hodgkin lymphoma (NHL). The Ki-67 index is used to assess the proliferation potential of tumor cells. The aim of this study was to evaluate the correlation of the Ki-67 index in tissue samples with the SUV at different sites on dual-phase FDG PET/CT of patients with newly diagnosed NHL.

MATERIALS AND METHODS

From September 2009 to March 2011, patients with newly diagnosed NHL who had received dual-phase FDG PET/CT for staging and biopsy samples that were evaluated for the Ki-67 expression were enrolled. The SUVmax of the biopsy site, the tumorous lesion sites, and 3 different bone marrow sites (right iliac crest, sternum, and L1) were measured. The SUVmean of the liver and spleen were also measured.

RESULTS

There were a total of 27 patients in this study. Significant correlations were observed between the Ki-67 index and the SUVmax of the right iliac crest in patients with early-stage disease (stage I and II) patients, the SUVmax of the biopsy and whole-body lesion sites in patients with late-stage disease (stage III and IV), and the retention index of SUVmax of the right iliac crest in patients whose bone marrow were involved by lymphoma cells.

CONCLUSIONS

For patients with newly diagnosed NHL, the significant correlation between the Ki-67 index and the SUV in this study suggests that dual-phase FDG PET/CT may be used as a noninvasive measurement of tumor proliferation.

Role of delayed imaging to differentiate intense physiological 18F FDG uptake from peritoneal deposits in patients presenting with intestinal obstruction

One of the main limitations of 18F-fluoro-2-deoxy-glucose positron emission tomography/computed tomography (FDG PET/CT) is false-positive tracer uptake by physiological and inflammatory conditions. Continuing FDG accumulation occurs in tumors, but not in inflammatory lesions, and dual time-point FDG PET can be useful for differentiating benign from malignant conditions. Experience is rather limited, and its application in the assessment of tumors inside peritoneal cavity has been rarely reported. We present 2 cases where dual time-point FDG PET imaging proved essential in differentiating intense physiological tracer uptake from peritoneal deposits in patients with intestinal obstruction.

Shorter-time dual-phase FDG PET/CT in characterizing solid or ground-glass nodules based on surgical results

OBJECTIVES

We compared the accuracy of shorter-time dual-phase (18)F-FDG PET/CT in evaluating 94 different lung nodules classified as solid or ground-glass nodules (GGNs).

MATERIALS AND METHODS

Early and delayed maximum standardized uptake values (SUV(max)) as well as the retention index (RI) of each nodule were determined in 75 solid nodules and 19 GGNs.

RESULTS

In solid nodules, early SUV(max), delayed SUV(max), and RI were higher in malignant than in benign lesions. In GGNs, these values were not significantly lower in the malignant than in the benign lesions.

CONCLUSION

In the patient group with solid nodules, shorter-time dual-phase (18)F-FDG PET/CT could significantly differentiate the malignant from the benign ones.

Diagnostic performance of dual-time 18F-FDG PET in the diagnosis of pulmonary nodules: a meta-analysis

RATIONALE AND OBJECTIVE

Perform a comprehensive meta-analysis evaluating the diagnostic performance of dual time point deoxy-2-[(18)F]fluoro-D-glucose positron emission tomography (FDG-PET) in the diagnosis of pulmonary nodules.

MATERIALS AND METHODS

MEDLINE, EMBASE, and PUBMED were queried between January 2000 and January 2011. Studies were included if they: 1) used dual time point FDG-PET as a diagnostic test for pulmonary nodules, 2) used pathology or clinical follow-up as the reference standard, and 3) reported absolute number of true-positive (TP), true-negative (TN), false-positive (FP), and false-negative (FN) results or stated sufficient data to derive these values. Summary sensitivity (SN), summary specificity (SP), positive and negative likelihood ratios (LR+) and (LR-), and diagnostic odds ratio were calculated. Heterogeneity of the results was assessed using Forest plots and the value of inconsistency index (I(2)).

RESULTS

Inclusion criteria were fulfilled by 10 articles with a total of 816 patients and 890 pulmonary nodules. The summary sensitivity was 85% (82%-89% at 95% confidence interval [CI]) and summary specificity was 77% (CI: 72%-81%), with a LR+ of 2.7 (CI: 1.4-5.2) and a LR- of 0.26 (CI: 0.14-0.49). Diagnostic odds ratio was 11 (CI: 3.8-32.2). Significant heterogeneity was found in the sensitivity (I(2) = 77%) and specificity (90.3%).

CONCLUSION

Dual time point FDG-PET demonstrates similar sensitivity and specificity to single time point FDG-PET in the diagnosis of pulmonary nodules. The additive value of the dual time point FDG-PET is questionable, primarily because of the significant overlap of benign and malignant nodule FDG-PET characteristics and lack of consensus criteria for quantitative thresholds to define nodules as malignant.

Impact of 18F-FDG PET scan on the prevalence of benign thoracic lesions at surgical resection

OBJECTIVE: The main utility of 18-fluorodeoxyglucose positron emission tomography (FDG-PET) lies in the staging of lung cancer. However, it can also be used to differentiate indeterminate pulmonary lesions, but its impact on the resection of benign lesions at surgery is unknown. The aim of this study was to compare the prevalence of benign lesions at thoracotomy carried out for suspected lung cancer, before and after the introduction of PET scanning in a large thoracic surgical centre. MATERIALS AND METHODS: We reviewed our prospectively recorded surgical database for all consecutive patients undergoing thoracotomy for suspected or proven lung cancer and compared the prevalence of benign lesions in 2 consecutive 2-year groups, before (group I) and after (group II) the introduction of FDG-PET scan respectively. RESULTS: Surgical resection was performed on 1233 patients during the study period. The prevalence of benign lesions at surgery in groups I and II was similar (44/626 and 41/607, both 7%), and also in group II between those who underwent FDG-PET scan and the remainder (21/301 and 20/306 respectively, both 7%). In group II, of the 21 patients with benign lesions, who underwent FDG-PET, 19 had a false positive scan (mean standardised uptake value 5.3 [range 2.6-12.7]). Of these, 13 and 4 patients respectively had non-diagnostic bronchoscopy and percutaneous transthoracic lung biopsy pre thoracotomy. There was no difference in the proportion of different benign lesions resected between group I and those with FDG-PET in group II. CONCLUSION: The introduction of FDG-PET scanning has not altered the proportion of patients undergoing thoracotomy for ultimately benign lesions, mainly due to the avidity for the isotope of some non-malignant lesions. Such false positive results need to be considered when patients with unconfirmed lung cancer are contemplated for surgical resection.

A black adrenal adenoma difficult to be differentiated from a malignant adrenal tumor by CT, MRI, scintigraphy and FDG PET/CT examinations

Black adrenal adenoma (BAA) is an adrenal adenoma which contains lipofuscin and has a black or brown appearance. Preoperative diagnosis of BAA is difficult because it is diagnosed by pathologic findings. We report a case of an incidentally discovered non-hyperfunctioning BAA in the left adrenal gland of a 58-year-old man. It showed an oval lipid-poor mass, 3 cm × 2 cm in size on computed tomography (CT) and magnetic resonance imaging (MRI), no avid uptake of (131)I-norcholesterol and (123)I-meta-iodobenzylguanidine (MIBG) on scintigraphy, and intense avid uptake of (18)F-fluorodeoxyglucose (FDG) on positron emission tomography-CT (PET/CT). FDG PET/CT showed that it was a hypermetabolic lesion, more intense than the activity of the liver, and the maximum standardized uptake value was 5.6 on 1-h early imaging and 8.3 on 2-h delayed imaging, suggesting a malignant tumor. BAA is a clinically rare benign adrenal adenoma, but it should be kept in mind that BAA may exhibit false-positive results for malignancy or inconclusive results for benignity with modern imaging modalities including CT, MRI, adrenal scintigraphy with radiolabelled cholesterol and radiolabelled MIBG, and FDG-PET like this case.

Clinical significance of primary lesion FDG uptake for choice between oesophagectomy and endoscopic submucosal dissection for resectable oesophageal squamous cell carcinomas

OBJECTIVES

To correlate primary oesophageal squamous cell carcinoma (SCC) (18)F-fluoro-deoxyglucose (FDG) uptake with pathological factors and examine its significance regarding choice of therapy.

METHODS

We retrospectively examined the factors affecting visible and non-visible FDG uptake in 37 primary lesions in 32 oesophageal SCC patients who underwent PET/CT before oesophagectomy or endoscopic submucosal dissection (ESD). We divided the lesions into pathological depth invasion ≥sm2 oesophagectomy (n = 18) and ≤sm1 ESD (n = 19) indicated groups and compared the diagnostic accuracy of FDG-PET with that of endoscopic ultrasound (EUS) performed for 23 superficial lesions to discriminate between these groups.

RESULTS

There were 17 visible and 20 non-visible lesions. The lesion visibility was significantly higher in the larger (≥40 mm), non-flat type, more deeply invaded, positive vascular invasion (P < 0.001 each), positive nodal metastasis (P = 0.04) and higher Glut-1 score (P = 0.005) tumour groups. When the visible and non-visible lesions indicated a need for oesophagectomy and ESD respectively, the sensitivity, specificity and accuracy of oesophagectomy were 94% (17/18), 100% (19/19) and 97% (36/37) and those of EUS were 75% (3/4), 79% (15/19) and 78% (18/23) respectively.

CONCLUSIONS

Primary lesion FDG visibility can be one of the indicators for choosing between oesophagectomy and ESD for resectable oesophageal SCCs.

The role of dual time point FDG PET imaging in the evaluation of solitary pulmonary nodules with an initial standard uptake value less than 2.5

AIM

To evaluate the accuracy of dual time point 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography (PET) imaging in the evaluation of the mildly metabolic solitary pulmonary nodule (SPN) and to assess whether accuracy could be improved by delaying second image acquisition to 180 minutes.

MATERIALS AND METHODS

Fifty-four patients were included in the study. Thirty-six had an SUV(max) <2.5 at 60 min. For these patients, two methods of interpreting the subsequent delayed FDG PET imaging at 180 min were investigated. The first method analysed the SUV(max) of SPNs on delayed imaging, in which an SUV(max) of 2.5 or more was regarded as a criterion for malignancy. The second method was retention index (RI) analysis, in which an increase of 10% or more in SUV(max) between the initial and delayed images, was regarded as an indication of malignancy.

RESULTS

For the group as a whole (n=54), the sensitivity, specificity and accuracy of using an SUV(max) of 2.5 or more as an indication of malignancy at the time of initial image acquisition (60 min) was 58, 89, and 74%, respectively. For SPNs that had an initial SUV(max) <2.5 (n=36), the sensitivity, specificity, and accuracy of using an SUV(max) of 2.5 or more as a criterion for malignancy on the delayed image acquisition (180 min), was 36, 96, and 78% respectively. However, if an RI of >10% was used as a criterion for malignancy between the initial and delayed images, the sensitivity, specificity, and accuracy was 73, 80, and 78%, respectively. These results are similar to a recent paper, where image acquisition occurred at 60 and 120 min post-tracer injection.

CONCLUSION

Dual time point FDG PET imaging with RI analysis, is a useful technique in evaluating SPN with an initial SUV(max) <2.5. Prolonging second image acquisition from 120 to 180 min does not appear to improve the accuracy of this technique. However, given that maximal FDG uptake by lung carcinomas is thought to be in the region of 5h, it may be that improving the accuracy of dual time point FDG PET imaging requires a more significant delay in second image acquisition in this specific subgroup.

[What is the role of FDG-PET in thoracic oncology in 2010?]

18F-Fluorodeoxyglucose-Positron Emission Tomography (FGD-PET) has been considered to have a major impact on the management of lung malignancies since the beginning of this century. Its value has been demonstrated by many publications, meta-analysis and European/American/Japanese recommendations. PET combined with computed tomography has provided useful information regarding the diagnosis and staging of lung cancer and allows for the delivery of adaptive radiotherapy. In its more common uses, PET has been shown to be cost-effective. With the widespread use of new radiotracers, PET will play an increasing role in the evaluation of response to treatment.

[PET-CT for evaluation of the solitary pulmonary nodule: an update]

INTRODUCTION

Positron emission tomography (PET) with 18F-FDG has become an important tool for the characterization of solitary pulmonary nodules (SPN).

BACKGROUND

The results of the main meta-analyses show that the sensitivity and specificity of 18F-FDG PET for determining malignancy of SPN are close to 95% and 80% respectively. The limits of the technology are now well known. False negative results are mainly due to certain histological types with low metabolic activity (such as bronchiolo-alveolar carcinoma and typical carcinoid), or small size (nodules less than 8 mm). False positives are mainly represented by granulomatous and infectious processes.

VIEWPOINTS

A gain in accuracy occurred with the advent of hybrid PET/CT machines that combine the functional data from 18FDG-PET and the morphological data of computed tomography. Improved imaging protocols (eg. injection of iodinated contrast media) could further enhance the performance of PET-CT. Further improvements will rely on respiratory synchronization protocols and on the advent of new PET tracers.

CONCLUSION

18F-FDG PET-CT should be performed for any nodule over 8 mm in size when the pre-test probability of malignancy is not deemed negligible.

Dual time point C-11 acetate PET imaging can potentially distinguish focal nodular hyperplasia from primary hepatocellular carcinoma

C-11 acetate positron emission tomography (PET) is known to have high sensitivity in detecting hepatocellular carcinoma. However, one of the shortcomings of C-11 acetate PET in the diagnosis of hepatocellular carcinoma is that C-11 acetate also accumulates in focal nodular hyperplasia, which makes it challenging to distinguish hepatocellular carcinoma form focal nodular hyperplasia when a conventional single time point PET imaging method is used. Two patients with suspected hepatocellular carcinoma and negative fluoro-deoxy-glucose PET scans underwent C-11 acetate PET dual time imaging in which both early and delayed images were acquired. One patient was subsequently confirmed having hepatocellular carcinoma while the other had focal nodular hyperplasia. C-11 acetate imaging was positive in both patients. Interestingly, in hepatocellular carcinoma the C-11 acetate activity in the delayed images is higher than in the early images while in focal nodular hyperplasia, the C-11 acetate activity decreased in the delayed image when compared with early images. Our findings suggest that dual time point imaging has potential to improve the diagnostic accuracy of C-11 acetate PET in the diagnosis of hepatocellular carcinoma.

Evaluation of pulmonary nodules and lung cancer with one-inch crystal gamma coincidence positron emission tomography/CT versus dedicated positron emission tomography/CT

Dedicated positron emission tomography (PET)/CT scanners using BGO and related detectors (d-PET) have become standard imaging instruments in many malignancies. Hybrid gamma camera systems using NaI detectors in coincidence mode (g-PET) have been compared to d-PET but reported usefulness has been variable when gamma cameras with half-inch to three-fourth-inch thick crystals have been used without CT. Our aim was to compare g-PET with a 1-in.-thick crystal and inbuilt CT for lesion localization and attenuation correction (g-PET/CT) and d-PET/CT in patients presenting with potential and confirmed lung malignancies. One hour after (18)F-fluorodeoxyglucose (FDG), patients underwent BGO d-PET/CT from jaw to proximal thigh. This was followed by one to two bed position g-PET/CT 194 +/- 27 min after FDG. Each study pair was independently analysed with concurrent CT. d-PET/CT was interpreted by a radiologist experienced in both PET and CT, and g-PET/CT by consensus reading of an experienced PET physician and an experienced CT radiologist. A TNM score was assigned and studies were then unblinded and compared. Fifty-seven patients underwent 58 scan pairs over 2 years. Eighty-nine per cent concordance was shown between g-PET/CT and d-PET/CT for the assessment of intrapulmonary lesions, with 100% concordance for intrapulmonary lesions >10 mm (36 of 36). Eighty-eight per cent (51 of 58) concordance was shown between g-PET/CT and d-PET/CT for TNM staging. Coincidence imaging using an optimized dual-head 1-in.-thick crystal gamma camera with inbuilt CT compares reasonably well with dedicated PET/CT for evaluation of indeterminate pulmonary lesions and staging of pulmonary malignancies and may be of some value when d-PET/CT is not readily available.

FDG PET and PET/CT in the Management of Pediatric Lymphoma Patients

Fluorodeoxyglucose (FDG) PET has an ever-increasing role in the management of Hodgkin's and non-Hodgkin's lymphomas, which has been demonstrated in numerous studies in the adult population. In children and adolescents, however, only a limited number of studies have investigated the role of FDG PET in lymphoma. This article reviews the currently available literature on the clinical application of FDG PET in the management of childhood lymphoma. The authors believe that FDG PET (and especially PET/CT) is a valuable imaging modality in the initial diagnosis, response assessment, and post-therapy residual evaluation of Hodgkin's and FDG-avid non-Hodgkin's lymphomas in children and adolescents, and will have a significant impact on the clinical management of pediatric lymphoma.

Limitations of dual time point PET in the assessment of lung nodules with low FDG avidity

FDG PET has long shown efficacy in the evaluation of indeterminate pulmonary nodules. More recently, the use of dual time point imaging has been looked at as a means for improving sensitivity and accuracy. While initial reports were very promising, more recent results looking specifically at pulmonary lesions with low levels of FDG avidity demonstrated limitations. These lesions (initial maximum standard uptake value of less than 2.5) are of particular interest due to the fact that well-differentiated adenocarcinomas, broncheoaveolar carcinoma and carcinoid may have low FDG avidity on standard PET imaging, leading to false-negative exams. Our study retrospectively reviewed the accuracy of dual time point (DTP) FDG PET imaging to determine if it aided in the identification of malignant pulmonary nodules when initial time point imaging showed a maximum SUV of less than 2.5. 113 patients had undergone a total of 130 DTP PET/CT with 152 lesions assessed. 67 lesions were subsequently definitively diagnosed as benign or malignant based upon biopsy or imaging follow-up. Utilizing a maximum SUV increase of 10%, which optimizes our sensitivity and specificity; our results demonstrate a sensitivity of 63% and a specificity of 59%, similar to other investigators evaluating lesions with low FDG avidity. Increasing or decreasing this threshold did not improve our results, nor did the addition of lesions with maximum SUV's of 2.5 or greater on initial imaging. Specifically in nodules with low FDG avidity (max SUV<2.5), the sensitivity was 61%, specificity 58%, and accuracy was 60%. Our findings suggest that DTP FDG PET may not be of benefit in the assessment of pulmonary nodules with maximum SUV of less than 2.5 on initial imaging.

Dual-time point 18F-FDG PET/CT scan for differentiation between 18F-FDG-avid non-small cell lung cancer and benign lesions

OBJECTIVE

The aim of this study is to clarify the difference of F-18 FDG uptake kinetics between FDG-avid non-small-cell lung cancer (NSCLC) and benign lesions associated with various etiologies on dual-time point PET/CT scan, and to determine the optimal parameter for differentiation.

MATERIALS AND METHODS

The materials were 76 FDG-avid solitary NSCLC in 76 patients and 57 FDG-avid solitary benign lesions associated with various etiologies in 61 patients. FDG PET/CT scan was performed at 60 and 120 min after intravenous injection of 4.4 MBq/kg F-18 FDG. The maximum standardized uptake value (SUVmax) on early and delayed scans and the percent change of SUVmax (%DeltaSUVmax) between the two time points were measured. The optimal differential parameter was determined by receiver-operating characteristic curve analysis and evaluation of diagnostic accuracy.

RESULTS

The mean +/- SD of early SUV max, delayed SUVmax and %DeltaSUVmax were 8.3 +/- 5.2, and 10.2 +/- 6.5, and 21.9% +/- 18.9 in FDG-avid NSCLC, and 3.8 +/- 3.2, 4.0 +/- 3.7, and 11.3% +/- 26.0 in FDG-avid benign lesions, respectively. Delayed SUVmax in NSCLC was significantly higher than early SUVmax (P < 0.0001); while not different in benign lesions. Percent change of SUVmax in NSCLC was also significantly higher than that in benign lesions (P < 0.01). The optimal parameter for the differentiation was delayed SUVmax > 5.5 and yielded sensitivity of 77.6%, specificity of 80.7% and accuracy of 78.9%, which provided better differentiation than the use of %DeltaSUVmax or the traditional parameter of early SUVmax > 2.5. However, 11 (19.2%) benign lesions were indistinguishable from NSCLC.

CONCLUSION

Although delayed PET/CT scan enhances the difference of FDG uptake between FDG-avid NSCLC and benign lesions, and the use of delayed SUVmax > 5.5 appears to improve the differentiation of these hypermetabolic lesions compared with an early scan, careful interpretation and management for correct differentiation are still required.

Dual-time point PET/CT with F-18 FDG for the differentiation of malignant and benign bone lesions

PURPOSE

The purpose of the present study was to evaluate whether 2-fluoro[fluorine-18]-2-deoxy-D: -glucose (F-18 FDG) positron emission tomography (PET) could differentiate malignant and benign bone lesions and whether obtaining delayed F-18 FDG PET images could improve the accuracy of the technique.

METHODS

In a prospective study, 67 patients with bone lesions detected by computed tomography (CT) or magnetic resonance imaging were included. Whole body PET/CT imaging was performed at 1 h (early) after the F-18 FDG injection and delayed imaging at 2 h post injection was performed only in the abnormal region. Semiquantitative analysis was performed using maximum standardized uptake value (SUV(max)), obtained from early and delayed images (SUV(maxE) and SUV(maxD), respectively). The retention index (RI) was calculated according to the equation: RI = (SUV(maxD) - SUV(maxE)) x 100/SUV(maxE.) Histopathology of surgical specimens and follow-up data were used as reference criteria. The SUV(maxE) and RI were compared between benign and malignant lesions.

RESULTS

The final diagnoses revealed 53 malignant bone lesions in 37 patients and 45 benign lesions in 30 patients. There were statistically significant differences in the SUV(maxE) between the malignant and benign lesions (P = 0.03). The mean SUV(maxE) was 6.8 +/- 4.7 for malignant lesions and 4.5 +/- 3.3 for benign lesions. However, a considerable overlap in the SUV(maxE) was observed between some benign and malignant tumors. With a cutoff value of 2.5 for the SUV(maxE), the sensitivity, specificity, and accuracy were 96.0%, 44.0%, and 72.4%, respectively. The positive predictive value (PPV) and negative predictive value (NPV) were 67.1% and 90.9%, respectively. There were significant differences in the RI between the malignant and benign lesions (P = 0.004). But there was overlap between the two groups. The mean RI was 7 +/- 11 for the benign lesions and 18 +/- 11 for the malignant lesions. When an RI of 10 was used as the cutoff point, the sensitivity, specificity, and accuracy were 90.6%, 76.0%, and 83.7.0%, respectively. The PPV and NPV were 81.4% and 87.1%, respectively.

CONCLUSIONS

The results of this study indicate that dual-time point F-18 FDG PET may provide more help in the differentiation of malignant tumors from benign ones.

Best practices in PET/CT: consensus on performance of positron emission tomography-computed tomography

Positron emission tomography-computed tomography (PET-CT) using the glucose metabolism tracer 2-deoxy-2-[F-18]fluoro-D-glucose (FDG) has become a widespread and preferred imaging modality for evaluating most cancers. Since commercial PET-CT scanners became available in 2001, there has been rapid dissemination of this hybrid imaging modality and PET-CT scanners have largely replaced stand-alone PET scanners. How PET-CT scans are performed and applied to cancer management has varied considerably, in part reflecting the varied background of the practice settings and training experience of the physicians performing and interpreting the PET-CT studies. Combined PET/CT with FDG has become the gold standard in oncologic imaging by accurately defining anatomy and function of many tumors. From April 2-4, 2008, a focus group composed of physicians and technologists from different practice settings and training backgrounds entitled "Best Practices in PET/CT Symposium" was held in Sonoma, California. The symposium focused on optimization of PET-CT protocols but also included other pertinent topics related to PET-CT imaging in oncology. This article summarizes areas of consensus reached by the group regarding many of the discussion topics. The summary consensus covered in this article is meant to provide direction for future discussions on how to improve the application of this hybrid modality to patient care.

Role of modern imaging techniques for diagnosis of infection in the era of 18F-fluorodeoxyglucose positron emission tomography

During the past several years, it has become quite evident that positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) imaging can play a major role in the management of patients with suspected infection. Particularly, several groups have demonstrated that this powerful imaging methodology is very effective in the evaluation of osteomyelitis, infected prostheses, fever of unknown origin, and AIDS. In view of its extraordinary sensitivity in detecting disease activity and the ability to quantitate the degree of FDG uptake, PET might prove to be an appropriate modality for monitoring disease activity and evaluating response to therapy. FDG-PET has many advantages over existing imaging techniques for the diagnosis of infectious diseases. These include feasibility of securing diagnostic results within 1.5 to 2 h, excellent spatial resolution, and accurate anatomical localization of sites of abnormality. The availability of PET/computed tomography as a practical tool has further enhanced the role of metabolic imaging in many settings. In the future, this modality is very likely to be employed on a routine basis for detecting, characterizing, and monitoring patients with suspected and proven infection.