Diagnostic value of retrospective PET-MRI fusion in head-and-neck cancer.

BACKGROUND: To assess the diagnostic value of retrospective PET-MRI fusion and to compare the results with side-by-side analysis and single modality use of PET and of MRI alone for locoregional tumour and nodal staging of head-and-neck cancer. METHODS: Thirty-three patients with head-and-neck cancer underwent preoperative contrast-enhanced MRI and PET/CT for staging. The diagnostic data of MRI, PET, side-by-side analysis of MRI and PET images and retrospective PET-MRI fusion were systematically analysed for tumour and lymph node staging using receiver operating characteristic (ROC) analysis. The results were correlated to the histopathological evaluation. RESULTS: The overall sensitivity/specificity for tumour staging for MRI, PET, side-by-side analysis and retrospective PET-MRI fusion was 79%/66%, 82%/100%, 86%/100% and 89%/100%, respectively. The overall sensitivity/specificity for nodal staging on a patient basis for MRI, PET, side-by-side analysis and PET-MRI fusion was 94%/64%, 94%/91%, 94%/82% and 94%/82%, respectively. MRI, PET, side-by-side analysis and retrospective image fusion were associated with correct diagnosis/over-staging/under-staging of N-staging in 70.4%/18.5%/11.1%, 81.5%/7.4%/11.1%, 81.5%/11.1%/7.4% and 81.5%/11.1%/7.4%, respectively.ROC analysis showed no significant differences in tumor detection between the investigated methods. The Area Under the Curve (AUC) for MRI, PET, side-by-side analysis and retrospective PET-MRI fusion were 0.667/0.667/0.702/0.708 (p > 0.05). The most reliable technique in detection of cervical lymph node metastases was PET imaging (AUC: 0.95), followed by side-by-side analysis and retrospective image fusion technique (AUC: 0.941), which however, was not significantly better then the MRI (AUC 0.935; p > 0.05). CONCLUSIONS: We found a beneficial use of multimodal imaging, compared with MRI or PET imaging alone, particular in individual cases of recurrent tumour disease. Side-by-side analysis and retrospective image fusion analysis did not perform significantly differently.

PET-MRI fusion in head-and-neck oncology: current status and implications for hybrid PET/MRI.

PURPOSE: To review the current status and clinical effect of PET-MRI image fusion in the staging of head-and-neck cancer and to show its implications for imaging with future hybrid PET/MRI scanners. MATERIALS AND METHODS: We reviewed the current literature in order to provide an overview of the potential of the combination of the anatomic and functional imaging capabilities of magnetic resonance imaging (MRI) and of the potential for molecular and metabolic imaging with Positron emission tomography (PET). The research question was whether these image devices might be of synergistic value. RESULTS: PET with [18F]-fluorodeoxyglucose has shown promising results for the assessment of lymph node involvement in cancer, the identification of distant metastasis and synchronous and metachronous tumors, and the evaluation of tumor recurrence or carcinoma of an unknown primary. For morphologic imaging, MRI has several advantages compared with computed tomography in the head-and-neck area. This is mainly because of the superior soft tissue contrast and fewer artifacts from dental implants. Moreover, MRI allows functional imaging, such as the assessment of perfusion with dynamic contrast-enhanced MRI. The published data indicate that image fusion should be beneficial in the case of the recurrence of oromaxillofacial cancer and in the evaluation of potential metastatic lymph nodes. However, retrospective image fusion is technically demanding in the head-and-neck area, mainly because of the varied patient positions used for the various scanners and the anatomic complexity of this region. CONCLUSIONS: Combined PET/MRI scanners might overcome the above-named problems. Both sequential and fully integrated PET/MRI scanners are now available in selected departments, and future studies will show whether hybrid PET/MRI is of greater clinical value than PET/CT and retrospective image fusion techniques.

Semiautomatic algorithm for lymph node analysis corrected for partial volume effects in combined positron emission tomography-computed tomography.

Positron emission tomography-computed tomography (PET-CT) is superior compared to stand-alone PET in evaluation of malignancies. Few studies have employed high-resolution structural information to correct PET. We designed a semiautomatic algorithm using CT and PET to obtain a partial volume corrected (PVC) standardized uptake value (SUV) and a combined morphologic and functional parameter (multimodal SUV) for lymph node assessment. Lesions were segmented by a semiautomatic algorithm in CT images. Lesion volume was used for PVC and for calculating the multimodal SUV. The method was applied to 47 lymph nodes (30 patients) characterized as suspicious in 18F-fluorodeoxyglucose-PET-CT. In phantoms, PVC improved significantly the measured uptake of the lesion. In patients, 36 lymph nodes could be segmented without problems; in 11 lesions, a manual interaction was necessary. SUVs before PVC (mean 1.29) increased significantly (p < .0005) after PVC (mean 2.8). If SUV 2.5 was used as a threshold value to distinguish between benign and malignant lesions, 11 of the 47 lesions changed from benign to malignant after the PVC. The mean multimodal SUV was 0.39 mL for the benign lesions and 4.47 mL for the malignant lesions. In this work we presented a method for quantitative analysis of lymph nodes in PET-CT. PVC leads to significant differences in SUV.

Voxel-based reproducibility of T2 relaxation time in patellar cartilage at 1.5 T with a new validated 3D rigid registration algorithm.

OBJECT: T2 relaxation time is a promising MRI parameter for the early diagnosis and follow-up of osteoarthritis. Assessing the evolution of osteoarthritis needs exact comparison of datasets acquired at different times and knowledge of the T2 reproducibility. The aims of this work were to establish a method for voxel-wise comparison of T2 datasets and to assess voxel-based T2 reproducibility in healthy patellar cartilage. MATERIALS AND METHODS: A new rigid 3D-registration algorithm was developed. The precision of the registration algorithm was calculated with numerical simulations and in vitro measurements. In vivo T2 reproducibility was assessed in six volunteers measured at seven different times. The voxel-based reproducibility was characterized with the coefficient of variation (CV) of T2, and its regional variations were analyzed. RESULTS: The registration algorithm showed an average registration precision lower than 25% of the voxel size. In vivo voxel-based T2 reproducibility exhibited a median CV of 10.1%. Reproducibility showed significant regional differences. Largest CVs (15.4%) were found near the articular surface. The central regions showed the lowest CVs (7.2%) and the lateral regions intermediate CVs (11.2%). CONCLUSION: Using a rigid 3D-registration algorithm provides voxel-based T2 reproducibility errors comparable to former, 2D region-based approaches, thus opening the possibility of voxel-based monitoring of cartilage degradation in osteoarthritis.

Textural Parameters of Tumor Heterogeneity in ¹8F-FDG PET/CT for Therapy Response Assessment and Prognosis in Patients with Locally Advanced Rectal Cancer.

UNLABELLED: (18)F-FDG PET/CT is effective in the assessment of therapy response. Changes in glucose uptake or tumor size are used as a measure. Tumor heterogeneity was found to be a promising predictive and prognostic factor. We investigated textural parameters for their predictive and prognostic capability in patients with rectal cancer using histopathology as the gold standard. In addition, a comparison to clinical outcome was performed. METHODS: Twenty-seven patients with rectal cancer underwent (18)F-FDG PET/CT before, 2 wk after the start, and 4 wk after the completion of neoadjuvant chemoradiotherapy. In all PET/CT scans, conventional parameters (tumor volume, diameter, maximum and mean standardized uptake values, and total lesion glycolysis [TLG]) and textural parameters (coefficient of variation [COV], skewness, and kurtosis) were determined to assess tumor heterogeneity. Values on pretherapeutic PET/CT as well as changes early in the course of therapy and after therapy were compared with histopathologic response. In addition, the prognostic value was assessed by correlation with time to progression and survival time. RESULTS: The COV showed a statistically significant capability to assess histopathologic response early in therapy (sensitivity, 68%; specificity, 88%) and after therapy (79% and 88%, respectively). Thereby, the COV had a higher area under the curve in receiver-operating-characteristic analysis than did any analyzed conventional parameter for early and late response assessment. The COV showed a statistically significant capability to evaluate disease progression and to predict survival, although the latter was not statistically significant. CONCLUSION: Tumor heterogeneity assessed by the COV, being superior to the investigated conventional parameters, is an important predictive factor in patients with rectal cancer. Furthermore, it can provide prognostic information. Therefore, its application is an important step for personalized treatment of rectal cancer.

Clinical Impact of Cardiac-Gated PET Imaging.

Electrocardiogram-gated cardiac positron emission tomography is a valuable addition to the armamentarium of clinical positron emission tomography. It provides incremental diagnostic information and can be conveniently embedded into clinical protocols. In the same way electrocardiogram gating was added to myocardial perfusion single photon emission computed tomography, it can be expected that this approach will be a standard component in the future.

Motion Artifacts in Oncological and Cardiac PET Imaging.

Image quality in PET examinations is influenced by several factors. Patient motion during PET data acquisition is a substantial problem that potentially leads to smearing artifacts, resulting in the loss of diagnostic accuracy both in visual and quantitative image analyses. In hybrid imaging, coregistration of functional (PET) and morphologic (CT or MR imaging) data can be hampered by patient movement between the acquisitions, resulting in additional sources of error. This article describes the artifacts due to patient movement.

PET-CT based automated lung nodule detection.

An automatic method is presented in order to detect lung nodules in PET-CT studies. Using the foreground and background mean ratio independently in every nodule, we can detect the region of the nodules properly. The size and intensity of the lesions do not affect the result of the algorithm, although size constraints are present in the final classification step. The CT image is also used to classify the found lesions built on lung segmentation. We also deal with those cases when nearby and similar nodules are merged into one by a split-up post-processing step. With our method the time of the localization can be decreased from more than one hour to maximum five minutes. The method had been implemented and validated on real clinical cases in Interview Fusion clinical evaluation software (Mediso). Results indicate that our approach is very effective in detecting lung nodules and can be a valuable aid for physicians working in the daily routine of oncology.

Sclerosing angiomatoid nodular transformation of the spleen presenting as a rapidly growing tumour in a patient with rectal cancer.

A patient with rectal cancer developed a rapidly growing splenic mass 2 years after cancer treatment. Since a metastatic process could not be ruled out, splenectomy was performed, and the tumour emerged as a sclerosing angiomatoid nodular transformation (SANT) of the spleen. SANT is a rare, recently recognised, non-neoplastic vascular lesion of the spleen that radiologically may be difficult to distinguish from vascular splenic lesions such as splenic hamartoma, haemangioma or littoral cell angioma. However, morphologically and immunohistochemically it is separated from those tumours by its unique nodular angiomatoid proliferation pattern. SANT is considered to be a benign lesion. This case is reported because of its important clinical impact for the differential diagnosis of splenic masses. Data regarding growth rates of these lesions are scarce and a growth progression as in this case, that finally led to the indication for splenectomy due to lingering suspicion of malignancy, is novel.