Fat suppression in magnetic resonance imaging of the head and neck region: is the two-point DIXON technique superior to spectral fat suppression?

OBJECTIVE: The aim of our study was to systematically compare two-point Dixon fat suppression (FS) and spectral FS techniques in contrast enhanced imaging of the head and neck region. METHODS: Three independent readers analysed coronal T1 weighted images recorded after contrast medium injection with Dixon and spectral FS techniques with regard to FS homogeneity, motion artefacts, lesion contrast, image sharpness and overall image quality. RESULTS: 85 patients were prospectively enrolled in the study. Images generated with Dixon-FS technique were of higher overall image quality and had a more homogenous FS over the whole field of view compared with the standard spectral fat-suppressed images (p < 0.001). Concerning motion artefacts, flow artefacts, lesion contrast and image sharpness no statistically significant difference was observed. CONCLUSION: The Dixon-FS technique is superior to the spectral technique due to improved homogeneity of FS and overall image quality while maintaining lesion contrast. Advances in knowledge: T1 with Dixon FS technique offers, compared to spectral FS, significantly improved FS homogeneity and over all image quality in imaging of the head and neck region.

Contrast-enhanced ultrasonography as a new method for assessing autonomization of pedicled and microvascular free flaps in head and neck reconstructive surgery.

OBJECTIVE: Evaluating vascular autonomization of pedicled and microvascular free flaps for soft tissue reconstruction in the head and neck area by means of postoperative quantitative measurement of dynamic contrast values obtained with contrast-enhanced ultrasound. METHODS: 8/18 patients underwent lip reconstruction with a pedicle flap, 10 patients reconstruction of other parts of the head with a microvascular free transplant. Ultrasound examinations were conducted within the 1st postoperative week and 4 weeks after surgery. After the intravenous bolus of the ultrasound contrast agent, examinations were carried out for 30 sec without compression followed by 30 sec with compression of the vascular pedicle in bolus and flash kinetics. Digital cine loops were analyzed off-line with a quantification software (VueBox™) to determine the Rise Time (RT) between flap tissue with and without compression. RESULTS: Measurements showed increasing autonomous perfusion, independent of the vascular pedicle. No transplant was lost, but 4/10 patients with a microvascular flap and 1/8 patients with a pedicle flap developed postoperative complications. RT values for the pedicled and microvascular flaps obtained under compression differed significantly between the 1st and the 4th week (p = 0.025). CONCLUSIONS: Reliable neovascularization was achieved 4 weeks postoperatively. CEUS showed to be a useful method for assessing the degree of autonomization of pedicle and microvascular free flaps.

Diffusion-weighted imaging in oral squamous cell carcinoma using 3 Tesla MRI: is there a chance for preoperative discrimination between benign and malignant lymph nodes in daily clinical routine?

BACKGROUND: Preoperative staging of cervical lymph nodes is important to determine the extent of neck dissection in patients with oral squamous cell carcinoma (OSCC). PURPOSE: To evaluate whether a preoperative discrimination of benign and malignant cervical lymph nodes with diffusion-weighted imaging (DWI) (3T) is feasible for clinical application. MATERIAL AND METHODS: Forty-five patients with histological proven OSCC underwent preoperative 3T-MRI. DWI (b = 0, 500, and 1000 s/mm(2)) was added to the standard magnetic resonance imaging (MRI) protocol. Mean apparent diffusion coefficients (ADCmean) were measured for lymph nodes with 3 mm or more in short axis by two independent readers. Finally, these results were matched with histology. RESULTS: Mean ADC was significantly higher for malignant than for benign nodes (1.143 ± 0.188 * 10(-3) mm(2)/s vs. 0.987 ± 0.215 * 10(-3) mm(2)/s). Using an ADC value of 0.994 * 10(-3) mm(2)/s as threshold results in a sensitivity of 80%, specificity of 65%, positive predictive value of 31%, and negative predictive value of 93%. CONCLUSION: Due to a limited sensitivity and specificity DWI alone is not suitable to reliably discriminate benign from malignant cervical lymph nodes in daily clinical routine. Hence, the preoperative determination of the extent of neck dissection on the basis of ADC measurements is not meaningful.

Tumour volume delineation in prostate cancer assessed by [11C]choline PET/CT: validation with surgical specimens.

PURPOSE: PET has been proven to be helpful in the delineation of gross tumour volume (GTV) for external radiation therapy in several tumour entities. The aim of this study was to determine if [(11)C]choline PET could be used to localize the carcinomatous tissue within the prostate in order to specifically target this area for example with high-precision radiation therapy. METHODS: Included in this prospective study were 20 patients with histological proven prostate carcinoma who underwent [(11)C]choline PET/CT before radical prostatectomy. After surgical resection, specimens were fixed and cut into 5-mm step sections. In each section the area of the carcinoma was delineated manually by an experienced pathologist and digitalized, and the histopathological tumour volume was calculated. Shrinkage due to resection and fixation was corrected using in-vivo and ex-vivo CT data of the prostate. Histopathological tumour location and size were compared with the choline PET data. Different segmentation algorithms were applied to the PET data to segment the intraprostatic lesion volume. RESULTS: A total of 28 carcinomatous lesions were identified on histopathology. Only 13 (46 %) of these lesions had corresponding focal choline uptake. In the remaining lesions, no PET uptake (2 lesions) or diffuse uptake not corresponding to the area of the carcinoma (13 lesions) was found. In the patients with corresponding PET lesions, no suitable SUV threshold (neither absolute nor relative) was found for GTV segmentation to fit the volume to the histological tumour volume. CONCLUSION: The choline uptake pattern corresponded to the histological localization of prostate cancer in fewer than 50 % of lesions. Even when corresponding visual choline uptake was found, this uptake was highly variable between patients. Therefore SUV thresholding with standard algorithms did not lead to satisfying results with respect to defining tumour tissue in the prostate.

Mandibular reconstruction with microvascular re-anastomosed fibular free flaps - two complementary methods of postoperative transplant monitoring.

PURPOSE: Evaluation of two complementary methods, i.e. luminescence ratiometric oxygen imaging (LROI) and contrast-enhanced ultrasound (CEUS) for postoperative evaluation of the perfusion of osseocutaneous fibular free flaps used for mandibular reconstructions. PATIENTS AND METHODS: 15 patients with microvascular re-anastomosed osseocutaneous fibular flaps were included in this trial. Perfusion of the cutaneous part of the flap was determined by measuring a fluorescent oxygen sensor foil covering the flap's skin surface with a handheld fluorescence-microscope. The sensor contains a reservoir of oxygen that is consumed by the tissue, which corresponds to the perfusion status of a flap. Measurements were done before explantation, after successful anastomosis and 1 day after surgery. Additionally, flap perfusion was qualitatively evaluated by contrast-enhanced ultrasound (CEUS) in 13 out of 15 patients. Ultrasound examinations were carried out with a high resolution linear probe after an intravenous bolus injection of 2.4 ml SonoVue® within the first 14 days after surgery. RESULTS: Out of the 15 harvested and transplanted flaps, 3 showed microcirculatory problems on the first postoperative day. All complications were detected by LROI prior to clinical signs. For LROI, we were able to confirm the threshold slope value of 0.3 for differentiating between well perfused and compromised flaps as suggested in our previous study. CEUS showed qualitatively detectable bone perfusion in the 13 measured flaps. 2 flaps that were lost on the second and third postoperative day were also lost for CEUS control. The flap survival rate was 87%, and the complication rate was 33%. CONCLUSION: LROI has been proven to deliver reproducible objective results for monitoring cutaneous flaps. In addition, CEUS is a promising method for evaluating the microcirculation of the deeper parts (such as bone) of osseocutaneous flaps. Both methods supplement each other, thus allowing the monitoring of all levels of osseocutaneous flaps.