Prospective comparison of 18F-NaF PET/CT versus 18F-FDG PET/CT imaging in mandibular extension of head and neck squamous cell carcinoma with dedicated analysis software and validation with surgical specimen. A preliminary study.

BACKGROUND: The aim of this study is to propose a new method to quantify radioactivity with PET/CT imaging in mandibular extension in head and neck squamous cell carcinoma (HNSCC), using innovative software, and to compare results with microscopic surgical specimens. PATIENTS AND METHODS: This prospective study enrolled 15 patients who underwent 18F-NaF and 18F-FDG PET/CT. We compared the delineations of bone invasions obtained with 18F-NaF PET/CT and 18F-FDG PET/CT with the results of histopathological analysis of mandibular resections (from right and left bone borders). A method for visualization and quantification of PET images was developed. RESULTS: For all patients, a significant difference (p = 0.032 for right limits and p = 0.011 for left limits) was observed between 18F-FDG PET/CT imaging and histopathology results, and no significant difference (p = 0.88 for right limits and p = 0.55 for left limits) was observed between 18F-NaF PET/CT imaging and histopathology results. The right limits were less than 10 mm in 93% of patients, and the left limits were less than 10 mm in 86% of patients. CONCLUSIONS: The dedicated software enabled the objective delineation of radioactivity within the bone. We can confirm that 18F-NaF is a precise and specific bone marker for the assessment of intraosseous mandibular extensions of head and neck cancers. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Evaluation of O-(2-[18F]-Fluoroethyl)-L-Tyrosine in the Diagnosis of Glioblastoma.

OBJECTIVE: To assess the feasibility of synthesis of O-(2-[(18)F]-fluoroethyl)-l-tyrosine (FET), a new positron emission tomographic (PET) tracer described in several studies but not yet considered standard in management of glioma, in routine practice and to determine FET uptake in a homogeneous group of patients with suspected high-grade glioma. DESIGN: Prospective nonrandomized trial. PATIENTS: Twelve patients with suspicion of high-grade glioma. RESULTS: The mean (SD) FET uptake ratio was 3.15 (0.72) for the 12 patients and 3.16 (0.75) for the 11 patients with glioblastoma. CONCLUSION: The initial results are promising and indicate that FET PET is a valuable and applicable tool for the imaging of high-grade glioma.

[Does tobacco smoking induce significant artificial irradiation?]. / Le tabagisme est-il la cause d'une irradiation artificielle significative?

Artificial irradiation due to tobacco smoking is a widely accepted phenomenon, but the possible health implications are controversial. The IAEA has estimated that smoking twenty cigarettes a day induces a total "radiation exposure" of 53 mSv, but several other authors have estimated that the effective dose is only about 0.4 mSv/year. The irradiation associated with smoking results from the use of fertilizers containing a emitters and from tobacco leaf fixation of radon 222 gas of telluric origin. Critical analysis of the literature suggests that irradiation due to smoking is much closer to 0.4 mSv/year than to 53 mSv/year. In order to avoid further confusion and controversy, human exposure to such radiation should be expressed as the annual effective dose.

Iterative three-dimensional expectation maximization restoration of single photon emission computed tomography images: application in striatal imaging.

Single photon emission computed tomography imaging suffers from poor spatial resolution and high statistical noise. Consequently, the contrast of small structures is reduced, the visual detection of defects is limited and precise quantification is difficult. To improve the contrast, it is possible to include the spatially variant point spread function of the detection system into the iterative reconstruction algorithm. This kind of method is well known to be effective, but time consuming. We have developed a faster method to account for the spatial resolution loss in three dimensions, based on a postreconstruction restoration method. The method uses two steps. First, a noncorrected iterative ordered subsets expectation maximization (OSEM) reconstruction is performed and, in the second step, a three-dimensional (3D) iterative maximum likelihood expectation maximization (ML-EM) a posteriori spatial restoration of the reconstructed volume is done. In this paper, we compare to the standard OSEM-3D method, in three studies (two in simulation and one from experimental data). In the two first studies, contrast, noise, and visual detection of defects are studied. In the third study, a quantitative analysis is performed from data obtained with an anthropomorphic striatal phantom filled with 123-I. From the simulations, we demonstrate that contrast as a function of noise and lesion detectability are very similar for both OSEM-3D and OSEM-R methods. In the experimental study, we obtained very similar values of activity-quantification ratios for different regions in the brain. The advantage of OSEM-R compared to OSEM-3D is a substantial gain of processing time. This gain depends on several factors. In a typical situation, for a 128 x 128 acquisition of 120 projections, OSEM-R is 13 or 25 times faster than OSEM-3D, depending on the calculation method used in the iterative restoration. In this paper, the OSEM-R method is tested with the approximation of depth independent resolution. For the striatum this approximation is appropriate, but for other clinical situations we will need to include a spatially varying response. Such a response is already included in OSEM-3D.

Multimodal image registration for localization of sentinel nodes in head and neck squamous cell carcinoma.

PURPOSE: The aim of this clinical study was to propose a new method of preoperative 3-dimensional localization of the neck sentinel node in clinically and radiographically N0 squamous cell carcinoma of the oral cavity. PATIENTS AND METHODS: This prospective study was carried out between August 2002 and August 2003. Ten patients with staged oral squamous cell cancer underwent this method of preoperative localization of the sentinel lymph node. At the present time, lymphoscintigraphy is recognized as the investigation of choice for the preoperative detection of sentinel nodes. Although we found it to be highly sensitive (100% in our study), it does not allow precise localization of the sentinel node in the anatomic context of the neck. To overcome this drawback, we used multimodal image registration applied to the cervical region in association with the imaging modalities of scintigraphy (single-photon emission computed tomography [SPECT] and gamma transmission) and computed tomography (CT). SPECT and gamma transmission (barium-133 sources) were carried out with a triple-head Philips-Marconi camera (Philips Medical System, Cleveland, OH), and CT was carried out with a General Electric console (GE Medical Systems, Milwaukee, WI). Gamma transmission was used to place the SPECT images in a reference cervical anatomic context (CT images). Registration involved the use of a manual method based on definition of homologous volume structures. RESULTS: Preoperative image registration effectively localized the cervical sentinel node in 9 of the 10 patients, enabling a guided surgical approach in 90% of cases. The sentinel node was localized and resected using a hand-held gamma probe. CONCLUSIONS: This original study adapts a new tool (multimodal image registration) to obtain precise preoperative localization of the cervical sentinel node in N0 oral squamous cell carcinoma. We confirmed the feasibility of this method in this indication. Although this method is a novel one, we believe that it will become extremely useful once a consensus has been reached on exclusive excision of the cervical sentinel node in oral cancers, as is the case for melanoma or breast cancer.