Head and neck cancer: detection of recurrence with three-dimensional principal components analysis at dynamic FDG PET

Monitoring and modelling the dynamics of the cellular glycolysis pathway: A review and future perspectives

BACKGROUND

The dynamics of the cellular glycolysis pathway underpin cellular function and dysfunction, and therefore ultimately health, disease, diagnostic and therapeutic strategies. Evolving our understanding of this fundamental process and its dynamics remains critical.

SCOPE OF REVIEW

This paper reviews the medical relevance of glycolytic pathway in depth and explores the current state of the art for monitoring and modelling the dynamics of the process. The future perspectives of label free, vibrational microspectroscopic techniques to overcome the limitations of the current approaches are considered.

MAJOR CONCLUSIONS

Vibrational microspectroscopic techniques can potentially operate in the niche area of limitations of other omics technologies for non-destructive, real-time, in vivo label-free monitoring of glycolysis dynamics at a cellular and subcellular level.

Zero-Extra-Dose PET Delayed Imaging with Data-Driven Attenuation Correction Estimation

PURPOSE

Delayed positron emission tomography (PET) imaging may improve sensitivity and specificity in lesion detection. We proposed a PET data-driven method to estimate the attenuation map (AM) for the delayed scan without an additional x-ray computed tomography (CT).

PROCEDURES

An emission-attenuation-scatter joint estimation framework was developed. Several practical issues for clinical datasets were addressed. Particularly, the unknown scatter correction was incorporated in the joint estimation algorithm. The scaling problem was solved using prior information from the early CT scan. Fourteen patient datasets were added to evaluate the method. These patients went through two separate PET/CT scans. The delayed CT-based AM served as ground truth for the delayed scan. Standard uptake values (SUVmean and SUVmax) of lesion and normal tissue regions of interests (ROIs) in the early and delayed phase and the respective %DSUV (percentage change of SUVmean at two different time points) were analyzed, all with estimated and the true AM. Three radiologists participated in lesion detection tasks with images reconstructed with both AMs and rated scores for detectability.

RESULTS

The mean relative difference of SUVmean in lesion and normal liver tissue were 3.30 and 6.69 %. The average lesion-to-background contrast (detectability) with delayed PET images using CT AM was 60 % higher than that of the earlier PET image, and was 64 % higher when using the data-based AM. %DSUV for lesions and liver backgrounds with CT-based AM were - 0.058 ± 0.25 and - 0.33 ± 0.08 while with data-based AM were - 0.00 ± 0.26 and - 0.28 ± 0.08. Only slight significance difference was found between using CT-based AM and using the data-based AM reconstruction delay phase on %DSUV of lesion. The scores associated with the two AMs matched well consistently.

CONCLUSIONS

Our method may be used in delayed PET imaging, which allows no secondary CT radiation in delayed phase. The quantitative analysis for lesion detection purpose could be ensured.

Dynamic whole-body PET imaging: principles, potentials and applications

PURPOSE

In this article, we discuss dynamic whole-body (DWB) positron emission tomography (PET) as an imaging tool with significant clinical potential, in relation to conventional standard uptake value (SUV) imaging.

BACKGROUND

DWB PET involves dynamic data acquisition over an extended axial range, capturing tracer kinetic information that is not available with conventional static acquisition protocols. The method can be performed within reasonable clinical imaging times, and enables generation of multiple types of PET images with complementary information in a single imaging session. Importantly, DWB PET can be used to produce multi-parametric images of (i) Patlak slope (influx rate) and (ii) intercept (referred to sometimes as "distribution volume"), while also providing (iii) a conventional 'SUV-equivalent' image for certain protocols.

RESULTS

We provide an overview of ongoing efforts (primarily focused on FDG PET) and discuss potential clinically relevant applications.

CONCLUSION

Overall, the framework of DWB imaging [applicable to both PET/CT(computed tomography) and PET/MRI (magnetic resonance imaging)] generates quantitative measures that may add significant value to conventional SUV image-derived measures, with limited pitfalls as we also discuss in this work.

Assessment of tumor margins in head and neck cancer using a 3D-navigation system based on PET/CT image-fusion - A pilot study

OBJECTIVES

Determination of tumor margins in patients with squamous cell carcinoma of the head and neck (SCCHN) is mostly based on preoperative magnetic resonance imaging (MRI) or computed tomography scans (CT). Local recurrence of disease is often correlated with the presence of positive resection margins after surgical treatment. Positron emission tomography/computed tomography (PET/CT) imaging plays a crucial role in the assessment of patients with SCCHN. The purpose of this study was to determine whether PET/CT could predict tumor extension.

METHODS

In 12 patients who underwent surgical treatment of primary SCCHN (Stage III-IV) F18-FDG PET/CT image-fusion was performed on a 3D navigation-system based workstation. Image-guided needle biopsies were obtained from four different, color-coded metabolic areas within the tumor. The histopathological findings were correlated with findings on corresponding PET/CT scans.

RESULTS

81.3% of biopsies from the central area were positive. Specimens taken from the outer metabolic zone were positive in 66.7% of the patients. The highest incidence of positive biopsies was found in the zone adjacent to the outermost area. There was a statistically significant difference in positive tumor histopathology when comparing the various metabolic zones (p = 0.03).

CONCLUSION

Exact determination of tumor is an important research topic, although results remain controversial. The results of this study suggest that in some cases PET scans may overestimate tumor extension.

The 2D Hotelling filter - a quantitative noise-reducing principal-component filter for dynamic PET data, with applications in patient dose reduction

Background

In this paper we apply the principal-component analysis filter (Hotelling filter) to reduce noise from dynamic positron-emission tomography (PET) patient data, for a number of different radio-tracer molecules. We furthermore show how preprocessing images with this filter improves parametric images created from such dynamic sequence.

We use zero-mean unit variance normalization, prior to performing a Hotelling filter on the slices of a dynamic time-series. The Scree-plot technique was used to determine which principal components to be rejected in the filter process. This filter was applied to [¹¹C]-acetate on heart and head-neck tumors, [¹⁸F]-FDG on liver tumors and brain, and [¹¹C]-Raclopride on brain. Simulations of blood and tissue regions with noise properties matched to real PET data, was used to analyze how quantitation and resolution is affected by the Hotelling filter. Summing varying parts of a 90-frame [¹⁸F]-FDG brain scan, we created 9-frame dynamic scans with image statistics comparable to 20 MBq, 60 MBq and 200 MBq injected activity. Hotelling filter performed on slices (2D) and on volumes (3D) were compared.

Results

The 2D Hotelling filter reduces noise in the tissue uptake drastically, so that it becomes simple to manually pick out regions-of-interest from noisy data. 2D Hotelling filter introduces less bias than 3D Hotelling filter in focal Raclopride uptake. Simulations show that the Hotelling filter is sensitive to typical blood peak in PET prior to tissue uptake have commenced, introducing a negative bias in early tissue uptake. Quantitation on real dynamic data is reliable. Two examples clearly show that pre-filtering the dynamic sequence with the Hotelling filter prior to Patlak-slope calculations gives clearly improved parametric image quality. We also show that a dramatic dose reduction can be achieved for Patlak slope images without changing image quality or quantitation.

Conclusions

The 2D Hotelling-filtering of dynamic PET data is a computer-efficient method that gives visually improved differentiation of different tissues, which we have observed improve manual or automated region-of-interest delineation of dynamic data. Parametric Patlak images on Hotelling-filtered data display improved clarity, compared to non-filtered Patlak slope images without measurable loss of quantitation, and allow a dramatic decrease in patient injected dose.

The Potential Benefit by Application of Kinetic Analysis of PET in the Clinical Oncology

PET is an appropriate method to display the functional activities in target tissue using many types of traces. The visual assessment of PET images plus the semiquantitative parameter (SUV) are the main diagnostic standards considered in identifying the malignant lesion. However, these standards lack occasionally the proper specificity and/or sensitivity. That emphasizes the importance of considering supplemental diagnostic criteria such as the kinetic parameter. The latter gives the way to image the ongoing metabolic processes within the target tissue as well as to identify the alterations occurring at the microscale level before they become observable in the conventional PET-imaging. The importance of kinetic analysis of PET imaging has increased with newly developed PET devices that offer images of good quality and high spatial resolution. In this paper, we highlighted the potential contribution of kinetic analysis in improving the diagnostic accuracy in intracranial tumour, lung tumour, liver tumour, colorectal tumour, bone and soft tissue tumours, and prostate cancer. Moreover, we showed that the appropriate therapy monitoring can be best achieved after considering the kinetic parameters. These promising results indicate that the kinetic analysis of PET imaging may become an essential part in preclinical and clinical molecular imaging as well.

3.5D dynamic PET image reconstruction incorporating kinetics-based clusters

Standard 3D dynamic positron emission tomographic (PET) imaging consists of independent image reconstructions of individual frames followed by application of appropriate kinetic model to the time activity curves at the voxel or region-of-interest (ROI). The emerging field of 4D PET reconstruction, by contrast, seeks to move beyond this scheme and incorporate information from multiple frames within the image reconstruction task. Here we propose a novel reconstruction framework aiming to enhance quantitative accuracy of parametric images via introduction of priors based on voxel kinetics, as generated via clustering of preliminary reconstructed dynamic images to define clustered neighborhoods of voxels with similar kinetics. This is then followed by straightforward maximum a posteriori (MAP) 3D PET reconstruction as applied to individual frames; and as such the method is labeled '3.5D' image reconstruction. The use of cluster-based priors has the advantage of further enhancing quantitative performance in dynamic PET imaging, because: (a) there are typically more voxels in clusters than in conventional local neighborhoods, and (b) neighboring voxels with distinct kinetics are less likely to be clustered together. Using realistic simulated (11)C-raclopride dynamic PET data, the quantitative performance of the proposed method was investigated. Parametric distribution-volume (DV) and DV ratio (DVR) images were estimated from dynamic image reconstructions using (a) maximum-likelihood expectation maximization (MLEM), and MAP reconstructions using (b) the quadratic prior (QP-MAP), (c) the Green prior (GP-MAP) and (d, e) two proposed cluster-based priors (CP-U-MAP and CP-W-MAP), followed by graphical modeling, and were qualitatively and quantitatively compared for 11 ROIs. Overall, the proposed dynamic PET reconstruction methodology resulted in substantial visual as well as quantitative accuracy improvements (in terms of noise versus bias performance) for parametric DV and DVR images. The method was also tested on a 90 min (11)C-raclopride patient study performed on the high-resolution research tomography. The proposed method was shown to outperform the conventional method in visual as well as quantitative accuracy improvements (in terms of noise versus regional DVR value performance).

FDG PET/CT in carcinoma of unknown primary

Carcinoma of unknown primary (CUP) is a heterogeneous group of metastatic malignancies in which a primary tumor could not be detected despite thorough diagnostic evaluation. Because of its high sensitivity for the detection of lesions, combined ¹⁸F-fluoro-2-deoxyglucose positron emission tomography (FDG PET)/computed tomography (CT) may be an excellent alternative to CT alone and conventional magnetic resonance imaging in detecting the unknown primary tumor. This article will review the use, diagnostic performance, and utility of FDG PET/CT in CUP and will discuss challenges and future considerations in the diagnostic management of CUP.

Oral cavity cancer

The oral cavity is anterioly located and unique in the variety of tissues contained in this area. Although oral cancer screening may be done on clinical examination, imaging plays a critical role in staging and determination of deep margins for either tumor resectability or radiation planning. This article discusses the relevant anatomy on magnetic resonance imaging (MRI), including the lips and gingiva, floor of mouth, and oral tongue. This is followed by a discussion of standard MRI techniques, American Joint Committee on Cancer (AJCC) classification, and relevant MRI findings with discussion and imaging examples of carcinoma in major sites, including floor of mouth, oral tongue, buccal mucosa, bony upper alveolus, hard palate, and retromolar trigone. A brief summary of newer imaging techniques for evaluation of oral cancer is also presented.

Analysis and interpretation of dynamic FDG PET oncological studies using data reduction techniques

Background

Dynamic positron emission tomography studies produce a large amount of image data, from which clinically useful parametric information can be extracted using tracer kinetic methods. Data reduction methods can facilitate the initial interpretation and visual analysis of these large image sequences and at the same time can preserve important information and allow for basic feature characterization.

Methods

We have applied principal component analysis to provide high-contrast parametric image sets of lower dimensions than the original data set separating structures based on their kinetic characteristics. Our method has the potential to constitute an alternative quantification method, independent of any kinetic model, and is particularly useful when the retrieval of the arterial input function is complicated. In independent component analysis images, structures that have different kinetic characteristics are assigned opposite values, and are readily discriminated. Furthermore, novel similarity mapping techniques are proposed, which can summarize in a single image the temporal properties of the entire image sequence according to a reference region.

Results

Using our new cubed sum coefficient similarity measure, we have shown that structures with similar time activity curves can be identified, thus facilitating the detection of lesions that are not easily discriminated using the conventional method employing standardized uptake values.

Is PET-based treatment planning the new standard in modern radiotherapy? The head and neck paradigm

The use of positron-emission tomography (PET) in the treatment planning process has become more and more popular over the years, although important questions such as how, when, and for which clinical benefit have never been answered. In this framework, the objective of this article is to review the evidence supporting the use of PET in radiotherapy treatment planning, with special emphasis on its application for head and neck tumors. The use of positron-labeled fluorodeoxyglucose for target volume selection should be discussed in terms of sensitivity and specificity in comparison with typical anatomic imaging modalities. It will not be of similar utility across all tumor sites. The use of PET for target volume delineation requires specific tuning of parameters such as image acquisition, processing, and segmentation, and this may vary from one tumor site to another. Molecular imaging with other tracers and "theragnostic" are in the pipeline, but how much the patient will gain from it and how these advances should be implemented in routine clinical practice are unresolved questions. Therefore, although integration of PET images into the radiotherapy process seems promising, for the moment it should remain in the research arena.

Impact of the type of imaging modality on target volumes delineation and dose distribution in pharyngo-laryngeal squamous cell carcinoma: comparison between pre- and per-treatment studies

BACKGROUND AND PURPOSE

It has been shown that the use of pre-treatment FDG-PET impacted on the GTV delineation of pharyngo-laryngeal tumors. The goals of this study were to evaluate (1) the impact of FDG-PET GTV on dose distribution, and (2) the impact of per-treatment re-imaging on target volume delineation and dose distribution.

MATERIALS AND METHODS

Eighteen patients with squamous cell carcinoma of the oropharynx or larynx/hypopharynx were treated with curative intent by forward planning IMRT. Prior to treatment and on average after a dose of 46 Gy, all patients underwent contrast-enhanced CT, MRI and FDG-PET. After coregistration, GTVs were delineated manually on CT and MRI and automatically on FDG-PET. From these volumes, CTVs and PTVs were derived using consistent guidelines. Planning was performed using conformal radiotherapy.

RESULTS

GTVs, CTVs and PTVs based on pre-treatment FDG-PET were significantly smaller than those based on pre-treatment CT. Such difference in target volumes (TV) translated into a significant reduction in the irradiated volumes (reduction of 13 and 18% of the V50 and V95, respectively), Dmean to ipsilateral parotids (30.7 and 38.6% for FDG-PET and CT based plans, respectively) and to controlateral parotids (11.2 and 14.4% for FDG-PET and CT based plans, respectively). TVs based on per-treatment CT or MRI were also significantly smaller compared to those delineated from pre-treatment CT. Volumes delineated with MRI were significantly smaller than those delineated with CT. Due to radiotherapy-induced peri-tumoral inflammation, automatic delineation of FDG-PET GTV could not be performed. Such reductions in TVs translated into a reduction of the irradiated volumes compared to pre-treatment CT planning (reduction for V50 of 19 and 32%, and for V95 of 22 and 40%, for CT and MRI, respectively); Dmean to the ipsilateral parotids were also reduced (ipsilateral parotid Dmean of 20.4% for CT and of 20.1% for MRI compared to 24.7% for pre-treatment CT).

CONCLUSIONS

The use of pre-treatment FDG-PET and per-treatment CT or MRI significantly impacts on the delineation of TVs in pharyngo-laryngeal SCC, translating into more normal tissue sparing after conformal radiotherapy planning.

Rational Diagnosis of Squamous Cell Carcinoma of the Head and Neck Region: Comparative Evaluation of CT, MRI, and18FDG PET

OBJECTIVE

We sought to evaluate the efficiency of (18)FDG PET, CT, and MRI for the preoperative staging of squamous cell carcinoma (SCC) of the head and neck region.

CONCLUSION

MRI is recommended as the method of choice in the preoperative evaluation of SCC of the oral cavity and the oropharynx. PET can provide relevant diagnostic information in case of equivocal findings by MRI or CT. Routine use of PET, however, does not appear to be necessary if optimized MRI is available.

Tumor Volume in Pharyngolaryngeal Squamous Cell Carcinoma: Comparison at CT, MR Imaging, and FDG PET and Validation with Surgical Specimen

PURPOSE

To compare computed tomography (CT), magnetic resonance (MR) imaging, and fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) for delineation of gross tumor volume (GTV) in pharyngolaryngeal squamous cell carcinoma and to validate results with the macroscopic surgical specimen when available.

MATERIALS AND METHODS

Twenty-nine patients with stages II-IV squamous cell carcinoma treated with radiation therapy or chemotherapy and radiation therapy (n = 20) or with total laryngectomy (n = 9) were enrolled. Ten patients had oropharyngeal, 13 had laryngeal, and six had hypopharyngeal tumors. CT, MR imaging, and PET were performed with patients immobilized in a customized thermoplastic mask, and images were coregistered. GTVs obtained with the three modalities were compared quantitatively and qualitatively. If patients underwent total laryngectomy, images were validated with the surgical specimen after three-dimensional coregistration. The effect of each modality was estimated with linear mixed-effects models. Adjustments for multiple comparisons were made with the Bonferonni or Sidak method.

RESULTS

For oropharyngeal tumors and for laryngeal or hypopharyngeal tumors, no significant difference (P >.99) was observed between average GTVs delineated at CT (32.0 and 21.4 cm(3), respectively) or MR imaging (27.9 and 21.4 cm(3), respectively), whereas average GTVs at PET were smaller (20.3 [P </=.10] and 16.4 cm(3) [P </=.01], respectively). GTVs from surgical specimens were significantly smaller (12.6 cm(3), P </=.06). In nine patients for whom a surgical specimen was available, no modality adequately depicted superficial tumor extension; this was due to limitations in spatial resolution. In addition, false-positive results were seen for cartilage, extralaryngeal, and preepiglottic extensions.

CONCLUSION

Compared with GTVs at CT and MR imaging, GTVs at FDG PET were smaller. In nine patients for whom a surgical specimen was available, PET was found to be the most accurate modality. However, no modality managed to depict superficial tumor extension.

Role of 11-C-methionine positron emission tomography for the delineation of the tumor volume in pharyngo-laryngeal squamous cell carcinoma: comparison with FDG-PET and CT

BACKGROUND AND PURPOSE

Although computed tomography (CT) remains the imaging modality of reference in head and neck squamous cell carcinoma (HNSCC) for the three-dimensional (3D) conformal radiotherapy, its poor soft tissue contrast can hamper precisely delineate the tumor volume. Besides anatomical imaging, 2-[18F] fluoro-2-deoxy-d-glucose-positron emission tomography (FDG-PET) has been shown to enhance the accuracy of the tumor delineation but l-methyl [11C]-methionine-positron emission tomography (MET-PET) has never been tested for this purpose. This study was undertaken to determine the potential added value of MET-PET for the delineation of gross target volume (GTV) in HNSCC, as compared to CT and FDG-PET.

PATIENTS AND METHODS

Twenty-three patients (10 oropharynx, 8 larynx and 5 hypopharynx) presenting with stage II-IV HNSCC were prospectively enrolled. They were treated by primary radiotherapy or by total laryngectomy. Images (CT, FDG-PET and MET-PET) were acquired with a thermoplastic mask and after coregistration, tumor volumes were delineated on CT and using an adaptative threshold-based automatic method on FDG- and MET-PET. Absolute volumes as well as the mismatch between modalities were compared.

RESULTS

For oropharyngeal lesions, FDG volumes were significantly smaller (19.43 ml+/-21.36) than CT (29.04 ml+/-30.97) (P=0.013). On the other hand, MET volumes (24.36 ml+/-20.59) were not different from CT volumes. Similar results were found for laryngeal and hypopharyngeal tumors, with volume of 24.93 ml+/-19.02 for CT, 21.84 ml+/-15.32 for MET-PET and 14.49 ml+/-11.3 for FDG-PET (P=0.003). Large mismatches were observed between modalities, in particular between CT and PET.

CONCLUSIONS

Our study confirms that the use of FDG-PET may result in a significant reduction of GTV's as compared to CT. On the contrary, MET-PET does not have any additional value since MET volumes are not different from CT volumes, probably because of the high uptake of MET by the normal mucosa and salivary glands surrounding the tumor.

Diagnostic accuracy of 2-[fluorine-18]fluro-2-deoxy-D-glucose positron emission tomography imaging in nonsquamous tumors of the head and neck

PURPOSE

To evaluate the diagnostic accuracy of 2-[fluorine-18]fluro-2-deoxy-D-glucose positron emission tomography (FDG-PET) for detecting nonsquamous tumors of the extracranial head and neck (NSTHN).

MATERIALS AND METHODS

The records of all patients with suspected or proven NSTHN undergoing PET imaging in our institution over a 12-year period were reviewed. Forty-four patients (24 males and 20 females; age range, 6-81 years; mean age, 51.2 years) were classified into 3 main groups: thyroid tumors (n = 19), salivary gland tumors (n = 7), and miscellaneous lesions (n = 18). The PET findings for each individual group with respect to the primary site, cervical nodal and distant metastases, were correlated with histopathology or follow-up (2-year minimum)

RESULTS

The overall diagnostic accuracy of FDG-PET for all NSTHN was 86%, However, the diagnostic accuracy varied for the histologic subtype (thyroid, salivary, miscellaneous) and the area being evaluated (primary site, nodal metastases, distant metastases).

CONCLUSION

There is variable diagnostic accuracy of FDG-PET in detecting different histologic subtypes of NSTHN. This information should be taken into consideration when considering PET for evaluation of NSTHN.

Performance evaluation of principal component analysis in dynamic FDG-PET studies of recurrent colorectal cancer

Performance evaluation of principal component analysis (PCA) of dynamic F-18-FDG-PET studies of patients with recurrent colorectal cancer. Principal component images (PCI) of 17 iteratively reconstructed data sets were visually and quantitatively evaluated. The F-18-FDG compartment model parameters were estimated using polynomial regression. All structures were present in PCI1. PCI2 was correlated with the vascular component and PCI3 with the tumor. The vessel density in the tumor was estimated with a correlation coefficient equal to 0.834. PCA supports the visual interpretation of dynamic F-18-FDG-PET studies, facilitates the application of compartment modeling and is a promising quantification technique.

Use of positron emission tomography in anticancer drug development

Positron emission tomography (PET) is increasingly being used in anticancer drug development. The technique is applicable to studies of drug delivery, and where specific probes are available, to provide pharmacodynamic readouts noninvasively in patients. Mathematical modeling of the imaging data enhances the quality of information that is obtained from such studies. This section provides a review of the PET methodologies that have been used for the development of new cancer therapies. Other than imaging of radiolabeled drugs, PET modeling has found extensive application in studies with 2-[11C]thymidine, [18F]fluorodeoxyglucose, H2(15)O, C15O, and receptor ligands.

A shifting landscape: what will be next FDG in PET oncology?

The tumor-seeking agent most widely used in positron emission tomography (PET) is 2-(18)F-fluorodeoxy-D-glucose (FDG). The clinical usefulness of FDG PET has already been proved in detecting, staging and restaging various kinds of malignant tumors, but nuclear medicine physicians suffer from a "diagnostic dilemma," in which a relatively high false positive ratio of FDG PET in diagnosing malignant tumors prevails. To increase more specific tumor uptake or more specific tumor characterization, numerous PET radiopharmaceuticals have been developed, and some of them are being tested in clinical trials. This review will briefly survey the tumor uptake mechanism and clinical significance of representative non-FDG PET radiopharmaceuticals used in clinical trials for patients with cancers.

Positron emission tomography in the evaluation of stage III and IV head and neck cancer

BACKGROUND

Detection of metastatic disease in head and neck cancer patients is critical to preoperative planning, because patients with distant metastasis will not benefit from surgical therapy. Conventional radiographic modalities, such as CT and MR, give excellent anatomic detail but poorly identify unenlarged lymph nodes harboring metastatic disease.

OBJECTIVE

A pilot study was conducted to evaluate the usefulness of 18-fluorodeoxyglucose positron emission tomography (FDG-PET) detection of metastatic disease in patients with advanced-stage head and neck cancer.

METHODS

Total body FDG-PET imaging was performed in a prospective manner on 12 consecutive patients with a new diagnosis of stage III or IV mucosal squamous cell carcinoma of the head and neck. Chest CT was also performed on all 12 patients. Patients found to have metastatic disease on either CT or PET imaging underwent procedures to obtain histopathologic confirmation of disease.

RESULTS

Three patients (25%) had FDG-PET scans demonstrating metastatic disease. Two of these patients had no evidence of disease on chest radiograph or chest CT but were noted to have positive FDG-PET imaging within the mediastinal lymphatics. Mediastinoscopy was performed confirming metastatic disease in these patients. The third patient had a peripheral lung lesion detected on chest radiograph, CT, and FDG-PET. This nodule was diagnosed by CT-guided biopsy as squamous cell carcinoma.

CONCLUSION

FDG-PET scanning detected mediastinal disease in two patients (17%) with advanced-stage head and neck squamous cell carcinoma that was not identified with conventional imaging techniques. PET imaging seems to have significant potential in the detection of occult metastatic disease, particularly in the mediastinal lymphatics.

Alzheimer's disease versus dementia with Lewy bodies: cerebral metabolic distinction with autopsy confirmation

Seeking antemortem markers to distinguish Dementia with Lewy bodies (DLB) and Alzheimer's disease (AD), we examined brain glucose metabolism of DLB and AD. Eleven DLB patients (7 Lewy body variant of AD [LBVAD] and 4 pure diffuse Lewy body disease [DLBD]) who had antemortem position emission tomography imaging and autopsy confirmation were compared to 10 autopsy-confirmed pure AD patients. In addition, 53 patients with clinically-diagnosed probable AD, 13 of whom later fulfilled clinical diagnoses of DLB, were examined. Autopsy-confirmed AD and DLB patients showed significant metabolic reductions involving parietotemporal association, posterior cingulate, and frontal association cortices. Only DLB patients showed significant metabolic reductions in the occipital cortex, particularly in the primary visual cortex (LBVAD -23% and DLBD -29% vs AD -8%), which distinguished DLB versus AD with 90% sensitivity and 80% specificity. Multivariate analysis revealed that occipital metabolic changes in DLB were independent from those in the adjacent parietotemporal cortices. Analysis of clinically diagnosed probable AD patients showed a significantly higher frequency of primary visual metabolic reduction among patients who fulfilled later dinical criteria for DLB. In these patients, occipital hypometabolism preceded some clinical features of DLB. Occipital hypometabolism is a potential antemortem marker to distinguish DLB versus AD.

Lymphoscintigraphy for interpretation of changes of cervical lymph node function in patients with oral malignant tumors: comparison of Tc-99m-Re and Tc-99m-HSA-D

OBJECTIVE

The purpose of this study is to compare the usefulness of technetium-99m-rhenium colloid (Tc-99m-Re) and technetium-99m-human serum albumin diethylene-triamine-pentaacetic acid (Tc-99m-HSA-D) as lymphoscintigraphic agents and to discuss the significance of lymphoscintigraphy in comparison with computed tomography (CT), magnetic resonance imaging (MRI), and ultrasonography (US).

STUDY DESIGN

Dynamic and static lymphoscintigraphies were performed with Tc-99m-Re and Tc-99m-HSA-D. The usefulness of the 2 agents was evaluated statistically in comparison with pathologic findings and palpation. The significance of lymphoscintigraphy is discussed in comparison with CT, MRI, and US (by the literature of CT, MRI, and US).

RESULTS

Lymphoscintigraphy was superior to palpation, and Tc-99m-Re was superior to Tc-99m-HSA-D in accuracy, specificity, and the incidence of true-positive and false-positive. Statistical significance was shown between the static lymphoscintigraphy with Tc-99m-Re and palpation. The reliability of lymphoscintigraphy seemed to be slightly inferior to CT and MRI in specificity and accuracy. However, lymphoscintigraphy had some advantages that CT and MRI lacked; for example, it showed very high sensitivity (100%) and no false-negative (0%). It also showed changes of lymph node function, showed all levels of neck nodes at one time, and showed a possibility of detecting small lymph node metastases.

CONCLUSION

Lymphoscintigraphy was more useful than palpation in detecting lymph node metastases, and Tc-99m-Re was superior to Tc-99m-HSA-D as an agent. Lymphoscintigraphy is significant when it is performed as a preliminary examination before CT or MRI.