Albert Dirisamer

Integrated contrast-enhanced diagnostic whole-body PET/CT as a first-line restaging modality in patients with suspected metastatic recurrence of breast cancer

OBJECTIVE(S) Only few information exist about the diagnostic accuracy of PET/CT for restaging patients with metastatic recurrence of breast carcinoma. Therefore, our study hypothesis was to perform diagnostic contrast enhanced CT (ce-CT) and FDG-PET in a one-step investigation, to prove sensitivity of each modality and to determine whether diagnostic PET/CT adds information over PET or contrast enhanced CT alone for restaging of patients with suspected recurrence of breast cancer. METHODS Fifty-two patients with suspected recurrence of breast cancer were included in our study. All of them were free of metastasis after the first line therapy. Indications for restaging were: Elevated tumor markers n=32, clinical deterioration n=16 and/or suspicious findings on other imaging studies n=48. Integrated PET/CT was performed using contrast-enhanced diagnostic CT for attenuation correction. RESULTS PET was correct in 44/52 patients (85%), ce-CT in 38/52 patients (73%) and PET/CT in 50/52 patients (96%). Sensitivity and specificity of lesion detection of PET, CT and PET/CT were 84%, 66% and 93%, and 100%, 92%, and 100%, respectively. DISCUSSION PET/CT can improve staging and alter therapeutic options in patients suspected to have breast cancer recurrence and distant metastatic disease, primarily by demonstrating local or distant nodal involvement occult at other imaging studies. The added value of FDG-PET/CT over other diagnostic modalities is mainly expressed by the fact that a noninvasive whole-body evaluation is possible in a single examination.

Detection of histologically proven peritoneal carcinomatosis with fused 18F-FDG-PET/MDCT

OBJECTIVE To evaluate peritoneal carcinomatosis in patients with gastrointestinal and gynecologic malignancies and to assess the diagnostic role for 18-FDG-PET and MDCT alone in comparison to the diagnostic accuracy of fused 18F-FDG-PET/MDCT by using surgical and histopathological findings as the standard of reference. METHODS AND SUBJECTS Sixty-two patients (13 males, 49 females; age range 43-81; mean age, 62 years with suspected peritoneal carcinomatosis were reviewed for the presence of peritoneal lesions on 18F-FDG-PET/MDCT scans (Discovery LS, GE Medical Systems). The results were compared with the histological findings at laparatomy. Thirty-one patients had peritoneal metastases, while 31 patients had negative histological findings at laparotomy. RESULTS CT detected peritoneal seeding in 26/31 patients, 18F-FDG-PET in 25/31 patients, and 18F-FDG-PET/MDCT in 30/31 patients, for a sensitivity of 88%, 88%, and 100%, respectively. False-positive findings were seen in MDCT in one patient, in 18F-FDG-PET in two patients, and in 18F-MDCT-PET/MDCT in one patient, for a specificity of 97%, 94%, and 97%, respectively. CONCLUSION Fused 18F-FDG-PET/MDCT is superior to MDCT and 18F-FDG-PET alone for the detection of peritoneal carcinomatosis especially in small lesions and it offers exact anatomic information for surgical treatment.

Performance of integrated FDG-PET/contrast-enhanced CT in the staging and restaging of colorectal cancer: Comparison with PET and enhanced CT

OBJECTIVE The purpose of this study was to assess the diagnostic value of PET/CT as a one step examination in patients with colorectal cancer. Therefore we proved whether diagnostic PET/CT adds information over PET or contrast-enhanced CT alone for staging or restaging of patients with colorectal cancer. METHODS Seventy-three patients (46 males and 27 females; age range: 50-81 years; mean age: 67 years) with known colorectal cancer underwent 18F-FDG-PET/CT for staging or restaging. RESULTS Of the 73 patients 26 patients underwent PET/CT for staging and 47 for restaging. 266 metastases could be detected in 60 patients. Contrast-enhanced PET/CT had a lesion-based sensitivity of 100%, contrast-enhanced CT of 91% and PET of 85%. PET/CT identified 2 lesions as false positive. PET/CT could also reach a patient-based sensitivity of 100%, which was superior to contrast-enhanced CT and PET. CONCLUSION Our study clearly demonstrated the added value of contrast-enhanced PET/CT in staging and restaging patients with colorectal cancer over CT and PET alone.

Feasibility of texture analysis for the assessment of biochemical changes in meniscal tissue on T1 maps calculated from delayed gadolinium-enhanced magnetic resonance imaging of cartilage data: comparison with conventional relaxation time measurements

Objectives:To (1) establish the feasibility of texture analysis for the in vivo assessment of biochemical changes in meniscal tissue on delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC), and (2) compare textural with conventional T1 relaxation time measurements calculated from dGEMRIC data (“T1(Gd) relaxation times”). Materials and Methods:We enrolled 10 asymptomatic volunteers (7 men and 3 women; mean age, 27.2 ± 4.5 years), without a history of meniscus damage, in our study. MRI of the right knee was performed at 3.0 T. An isotropic, 3-dimensional (3D), double-echo steady-state sequences was used for morphologic evaluation, and a dual flip angle 3D gradient echo sequence was used for T1(Gd) mapping. All MRI scans were performed 90 minutes after injection of 0.2 mmol/kg of Gd-diethylenetriamine pentaacetic acid (DTPA)2−, and subsequently, during application of a compressive force (50% of the body weight) in the axial direction. Regions of interest, covering the central portions of the posterior horn of the medial meniscus, were defined on 3 adjacent sagittal sections. Based on the relaxation time maps, mean T1(Gd), as well as the T1(Gd) texture features derived from the co-occurrence matrix (COC: Angular Second Moment, Entropy, Inverse Difference Moment) and wavelet transform (WAV: WavEnLL, WavEnHL, WavEnHH, WavEnLH), were calculated. Paired t tests were used to assess differences between baseline and compression, and intraclass correlation coefficients (ICC) were calculated to establish the intrarater reliability of the measurements. Results:Mean T1(Gd) (−67.3 ms, P = 0.011), Angular Second Moment (−0.0002, P = 0.009), Entropy (+0.033, P = 0.025), WavEnLL (+1011.16, P = 0.002), WavEnHL (+18.64, P = 0.012), and WavEnLH (+72.74, P = 0.035) differed significantly between baseline and compression. Intrarater reliability was substantial for mean T1(Gd) relaxation times (ICC = 0.99–1.0), and also for T1(Gd) co-occurrence matrix (ICC = 0.63–0.92) and WAV (ICC = 0.86–0.98) features. Conclusions:Texture features extracted from T1 maps calculated from dGEMRIC data are feasible for the in vivo assessment of biochemical changes in the menisci, such as might be induced by mechanical loading. Thus, T1(Gd) texture features complement conventional relaxation time measurements. Further studies are necessary to determine whether the mechanical compression, or a prolonged Gd-DTPA2− uptake, or both, are responsible for the observed decrease in mean T1(Gd) relaxation times in the menisci.

Effects of magnetic resonance image interpolation on the results of texture-based pattern classification: a phantom study.

Objectives:To (1) determine whether magnetic resonance (MR) image interpolation at the pixel or k-space level can improve the results of texture-based pattern classification, and (2) compare the effects of image interpolation on texture features of different categories, with regard to their ability to distinguish between different patterns. Materials and Methods:We obtained T2-weighted, multislice multiecho MR images of 2 sets of each 3 polystyrene spheres and agar gel (PSAG) phantoms with different nodular patterns (sphere diameter: PSAG-1, 0.8-1.25 mm; PSAG-2, 1.25-2.0 mm; PSAG-3, 2.0-3.15 mm), using a 3.0 Tesla scanner equipped with a dedicated microimaging gradient insert. Image datasets, which consisted of 20 consecutive axial slices each, were obtained with a constant field of view (30 × 30 mm2), but with variations of matrix size (MTX): 16 × 16; 32 × 32; 64 × 64; 128 × 128; and 256 × 256. Original images were interpolated to higher matrix sizes (up to 256 × 256) by means of linear and cubic B-spline (pixel level) as well as zero-fill (k-space level) interpolation. For both original and interpolated image datasets, texture features derived from the co-occurrence (COC) and run-length matrix (RUN), absolute gradient (GRA), autoregressive model, and wavelet transform (WAV) were calculated independently. Based on the 3 best texture features of each category, as determined by calculation of Fisher coefficients using images from the first set of PSAG phantoms (training dataset), k-means clustering was performed to separate PSAG-1, PSAG-2, and PSAG-3 images belonging to the second set of phantoms (test dataset). This was done independently for all original and interpolated image datasets. Rates of misclassified data vectors were used as primary outcome measures. Results:For images based on a very low original resolution (MTX = 16 × 16), misclassification rates remained high, despite the use of interpolation. For higher resolution images (MTX = 32 × 32 and 64 × 64), interpolation enhanced the ability of texture features, in all categories except WAV, to discriminate between the 3 phantoms. This positive effect was particularly pronounced for COC and RUN features, and to a lesser degree, also GRA features. No consistent improvements, and even some negative effects, were observed for WAV features, after interpolation. Although there was no clear superiority of any single interpolation techniques at very low resolution (MTX = 16 × 16), zero-fill interpolation outperformed the two pixel interpolation techniques, for images based on higher original resolutions (MTX = 32 × 32 and 64 × 64). We observed the most considerable improvements after interpolation by a factor of 2 or 4. Conclusions:MR image interpolation has the potential to improve the results of pattern classification, based on COC, RUN, and GRA features. Unless spatial resolution is very poor, zero-filling is the interpolation technique of choice, with a recommended maximum interpolation factor of 4.

Interstitial Lung Diseases

The term interstitial lung disease (ILD) comprises a diverse group of diseases that lead to inflammation and fibrosis of the alveoli, distal airways, and septal interstitium of the lungs. The ILDs consist of disorders of known cause (e.g., collagen vascular diseases, drug-related diseases) as well as disorders of unknown etiology. The latter include idiopathic interstitial pneumonias (IIPs), sarcoidosis and a group of miscellaneous, rare, but nonetheless interesting, diseases. In patients with ILD, MDCT enriches the diagnostic armamentarium by allowing volumetric high resolution scanning, i.e., continuous data acquisition with thin collimation and a high spatial frequency reconstruction algorithm. CT is a key method in the identification and management of patients with ILD. It not only improves the detection and characterization of parenchymal abnormalities, but also increases the accuracy of diagnosis. The spectrum of morphologic characteristics that are indicative of interstitial lung disease is relatively limited and includes a reticular pattern (with or without traction bronchiectasis), thickening of interlobular septa, honeycombing, nodules, and ground-glass opacities. In the correct clinical context, some patterns or combination of patterns, together with the anatomic distribution of the abnormality, i.e., from the lung apex to the base, or peripheral subpleural versus central bronchovascular, can lead the interpreter to a specific diagnosis. However, due to an overlap of the CT morphology between the various entities, complementary lung biopsy is recommended in virtually all cases of ILDs.