Digital image fusion of CT and PET data sets--clinical value in abdominal/pelvic malignancies

Development and applications of a software for Functional Image Registration (FIRE)

Image registration with anatomical modalities, such as CT and MRI, facilitates the anatomical identification and localization in the interpretation of nuclear medicine images that lack anatomical information. The implementation of Functional Image Registration (FIRE), an operating system (OS) and platform independent multimodal image registration software is reported. In order to register the images without an operator's interaction, several automatic algorithms were implemented. These include principal axes matching and maximization of the mutual information methods. The user interface was designed to support the manual registration of the images. Fused images were composed by overlaying one image with the other one transparently, in which the opacity of the overlaid image was interactively controlled. FIRE was successfully applied to many clinical cases for which automatic and/or manual registration was required. An OS and platform independent program for image registration developed in this study will be useful for the clinical application of image registration techniques.

PET-CT in recurrent ovarian cancer: initial observations

Noninvasive diagnosis of early recurrence of ovarian cancer is challenging due to the small size of peritoneal metastases. Small-volume disease may not be evident at anatomic imaging in patients with elevated serum tumor markers. Functional imaging in the form of positron emission tomography (PET) can help identify patients with recurrent tumor. However, lesion localization for possible surgical treatment is difficult with PET alone. Combined functional-anatomic imaging with fused PET and computed tomographic (CT) scans is feasible and may improve disease detection by increasing radiologic sensitivity and specificity. PET and PET-CT have a potential role in evaluating patients for recurrent ovarian cancer, particularly those with negative CT or magnetic resonance imaging findings and rising tumor marker levels. Fused PET-CT scans obtained with combined scanners can help localize pathologic activity and differentiate this activity from physiologic radiotracer uptake. Combined functional-anatomic imaging can also increase diagnostic confidence at CT. Further study is needed to determine the possible benefits of lesion conspicuity at PET and anatomic localization at CT on fused PET-CT scans.

Preoperative Image Fusion of Fluoro-2-Deoxy-d-Glucose???Positron Emission Tomography and Computed Tomography Data Sets in Oral Maxillofacial Carcinoma

OBJECTIVE

The aim was to evaluate the clinical and therapeutic value of digital image fusion of 2-[18]-fluoro-2-deoxy-D-glucose (F18-FDG) positron emission tomography (PET) and computed tomography (CT) in patients suffering from an oral maxillofacial carcinoma.

METHODS

Seventeen patients (11 male, 6 female; age range: 45-89 years) suffering from an oral maxillofacial carcinoma underwent CT and F18-FDG-PET (333-370 MBq). The data of the 2 imaging modalities were fused on an image workstation. This image fusion was then visualized in the axial, coronal, and sagittal planes.

RESULTS

PET showed a high pathologic FDG uptake in the tumor in 17 of 17 patients. CT detected the tumor in 12 of 17 patients. The image fusion of FDG-PET and CT showed the tumor in 17 of 17 patients. The final diagnosis was carcinoma of the mandible in 9 of 17 patients, carcinoma of the mouth floor in 3 of 17 patients, carcinoma of the tongue in 3 of 17 patients, carcinoma of the roof of the mouth in 1 of 17 patients, and carcinoma of the parotis gland in 1 of 17 patients.

CONCLUSIONS

Preoperative image fusion of FDG-PET and CT data sets in oral maxillofacial carcinoma is possible in the clinical routine. Combined morphologic (CT) and functional (PET) imaging improves tumor localization even if the tumor is hardly visible on CT because of the artefacts of dental metallic implants (3/17 patients) or because of the small size of the tumor (2/17 patients). Image fusion is helpful for planning possible surgery (visual models) or radiotherapy (exact region of interest).

Image fusion of thallium-201 SPECT and MR imaging for the assessment of recurrent head and neck tumors following flap reconstructive surgery

The aim of this study was to assess the value of fused MR and Tl-201 single photon emission computed tomography (SPECT) images in the diagnosis of recurrent head and neck tumors in patients after flap reconstruction surgery. Twenty-four patients after resection of primary head and neck tumors with flap reconstruction were suspected of having recurrent tumor by follow-up MR examination. Both MR examination and Tl-201 SPECT were prospectively performed to produce fused images. For qualitative analysis, two independent readers separately evaluated the existence of tumor recurrence in the fused images. The Tl-201 uptake of the lesion (Tl index) was also quantitatively compared with that of the normal nuchal muscles. Eighteen patients were histologically proved as having recurrence. The remaining 6 patients, false positive on MRI alone, had non-recurrence. Using the fused images, false positive was found in 1 case for one reader and 2 cases for the other reader. The Tl index of recurrent tumors was significantly higher (p < 0.001) than that of non-recurrent mass lesions. In the assessment of recurrent tumors following flap reconstruction surgery in the head and neck, the use of fused MRI and Tl-201 SPECT images can reduce the number of false positives.

Usefulness of FDG PET for assessment of early recurrent epithelial ovarian cancer

OBJECTIVE

The purpose of our study was to evaluate the diagnostic accuracy of FDG positron emission tomography (PET) in comparison with CT in detecting recurrent ovarian carcinoma and its ability to reveal small tumor recurrence.

MATERIALS AND METHODS

We reviewed the records of 31 consecutive patients with pathologically proven epithelial carcinoma who underwent FDG PET 1 month before second-look surgery to assess recurrent tumor. Of these 31 patients, 21 patients also underwent CT 1 month before second-look surgery. The diagnostic accuracies of FDG PET (n = 31), CT (n = 21), and combined FDG PET and CT (n = 21) in detecting recurrent tumor were calculated and compared with each other using the Bennett's test in 21 patients who underwent both imaging studies. Detection rates of individual tumors relative to their sizes were compared between FDG PET and CT using the McNemar test.

RESULTS

The sensitivity, specificity, and accuracy of FDG PET, CT, and combined FDG PET and CT for revealing recurrent ovarian cancer were 45.3%, 99.7%, 91.0%; 54.5%, 99.6%, 91.7%; 58.2%, 99.6%, 92.4%, respectively. We found no statistically significant difference in the diagnostic accuracy of FDG PET, CT, and combined FDG PET and CT (chi(2) < 5.991). Detection rates of tumor nodules found on CT were significantly greater than those on FDG PET when nodule size was 0.3-0.7 cm (p < 0.05).

CONCLUSION

FDG PET did not improve the overall diagnostic accuracy in detecting recurrent ovarian carcinoma compared with CT. Rather, FDG PET was inferior to CT in its ability to reveal small-tumor recurrence.

PET-CT-guided percutaneous puncture of an infected cyst in autosomal dominant polycystic kidney disease: case report

An infected cyst in autosomal dominant polycystic kidney disease was identified with a combined positron emission tomographic (PET) and computed tomographic (CT) system, an experimental setup mimicking an integrated CT-PET scanner. Image fusion of fluorine 18 fluorodeoxyglucose PET and CT images allowed exact localization of the infected cyst among many cysts identified on previous CT and magnetic resonance images. Confirmation was obtained instantly, followed by CT-guided percutaneous puncture. Integrated imaging systems hold promise for direct PET-guided puncture of areas of increased fluorodeoxyglucose uptake by using the anatomic accuracy of CT.

[Physical and methodological aspects of multimodality imaging and principles of treatment planning in 3D conformal radiotherapy]

The recent evolutions of the imaging modalities, the dose calculation models, the linear accelerators and the portal imaging permit to improve the quality of the conformal radiation therapy treatment planning. With DICOM protocols, the acquired imaging data coming from different modalities are treated by performant image fusion algorithms and yield more precise target volumes and organs at risk. The transformation of the clinical target volumes (CTV) to planning target volumes (PTV) can be realised using advanced probabilistic techniques based on clinical experience. The treatment plans evaluation is based on the dose volume histograms. Their precision and clinical relevance are improved by the multi-modality imaging and the advanced dose calculation models. The introduction of the inverse planning systems permitting to realise modulated intensity radiation therapy generates highly conformal dose distributions. All the previously cited complex techniques require the application of rigorous quality assurance programs.

The fusion of anatomic and physiologic imaging in the management of patients with cancer

Imaging is of major clinical importance in the noninvasive evaluation and management of patients with cancer. Computed tomography (CT) and other anatomic imaging modalities, such as magnetic resonance imaging (MRI) or ultrasound, have a high diagnostic ability by visualizing lesion morphology and by providing the exact localization of malignant sites. Nuclear medicine provides information on the function and metabolism of cancer. Over the last decade, there have been numerous attempts to combine data obtained from different imaging techniques. Fused images of nuclear medicine and CT (or to a lesser extent, MRI) overcome the inherent limitations of both modalities. Valuable physiologic information benefits from a precise topographic localization. Coregistered data have been shown to be useful in the evaluation of patients with cancer at diagnosis and staging, in monitoring the response to treatment, and during follow up, for early detection of recurrence. Time-consuming and difficult realignment and computation for fusion of independent studies have, until now, limited the use of registration techniques to pilot studies performed in a small number of patients. The development of the new technology of single photon emission computed tomography/CT and positron emission tomography/CT that allows for combined functional and anatomic data acquisition has the potential to make fusion an everyday clinical tool.