Impact of metal implants on xSPECT/CT Bone reconstruction: the "shining metal artefact".

Novel reconstruction algorithms, such as xSPECT Bone, are gaining more and more importance in Nuclear Medicine. With xSPECT Bone, the reconstructed emission image is enhanced by the information obtained in the corresponding CT image. The CT defines tissue classes according to the Hounsfield units. In the iterative reconstruction, each tissue class is handled separately in the forward projection step, and all together in the back projection step. As a consequence, xSPECT Bone reconstruction generates images with improved boundary delineation and better anatomic representation of tracer activity. Applying this technique, however, showed that artefacts may occur, when no uptake regions, like metal implants, exhibit fictitious uniform tracer uptake. Due to limitations in spatial resolution in gamma cameras, the xSPECT Bone reconstructed image resulted in spill-out activity from surrounding high uptake region being uniformly distributed over the metal implants. This new technology of xSPECT Bone reconstruction in general enhances the image quality of SPECT/CT; however, the potential introduction of specific artefacts which inadvertently come along with this new technology and their frequency have not yet been addressed in the literature. Therefore, the purpose of this work was to identify and characterize these specific metal artefacts (the so-called shining metal artefact) in order to reduce false positives and avoid potentially misdiagnosing loosened or infected implants. In this work, we report five cases imaged with bone SPECT/CT of 5 anatomical regions (foot, elbow, spine, shoulder, ribs and knee). All cases demonstrated "shining metal artefacts" in xSPECT Bone reconstruction. While xSPECT Bone reconstruction algorithm significantly improves image quality for the diagnosis of bone and joint disorders with SPECT/CT, specific "shining metal artefacts" caused by the xSPECT Bone have to be recognized in order to avoid image misinterpretation suggesting metallic implant loosening or possible infection. The simultaneous analysis of conventionally reconstructed SPECT images (for Siemens the Flash3D reconstruction) helps to avoid misinterpretation of potential artefacts introduced by xSPECT Bone reconstruction

Neoadjuvant chemotherapy generates a significant tumor response in resectable pancreatic cancer without increasing morbidity: results of a prospective phase II trial

OBJECTIVE: To evaluate the morbidity of pancreaticoduodenectomy after neoadjuvant chemotherapy for resectable pancreatic cancer and to assess its histologic and metabolic response. BACKGROUND: Adjuvant chemotherapy improves the outcome of pancreatic cancer, but 25% of patients remain unfit after surgery. Neoadjuvant chemotherapy can be offered to all patients in a multimodality approach, but its efficacy and surgical morbidity are unknown. METHODS: Patients with resectable, cytologically proven adenocarcinoma of the pancreatic head received 4 bi-weekly cycles of gemcitabine (1000 mg/m(2)) and cisplatin (50 mg/m(2)) in this prospective phase II trial. Staging and restaging included chest x-ray, abdominal computed tomography (CT), positron emission tomography (PET)/CT, endoscopic ultrasound, and laparoscopy. Fluorodeoxyglucose uptake was quantified by the standard-uptake value (SUV) on baseline and restaging PET/CT. Immunohistochemistry for GLUT-1 and Ki-67 was performed. The histologic response, cytopathic effects, and surgical complications were graded by respective scores. RESULTS: Twenty-four of 28 patients had resection for histologically confirmed adenocarcinoma. The surgical morbidity was low without perioperative death and one pancreatic fistula. Histologic response was documented in 54% and cytopathic effects in 83% of the patients. A significant SUV decrease occurred during chemotherapy (P = 0.031), which correlated with the baseline SUV (P = 0.001), Ki-67 expression (P = 0.016), and histologic response (P = 0.01). Neither the metabolic nor the histologic response was predictive of the median disease-free (9.2 months) or overall survival (26.5 months). CONCLUSION: Neoadjuvant chemotherapy induced a significant metabolic and histologic response, which was best predicted by PET. Most importantly, surgery after neoadjuvant chemotherapy for pancreatic cancer was safe

Accuracy of CT parameters for assessment of tumour size and aggressiveness in lung adenocarcinoma with bronchoalveolar elements

Accurate determination of tumour size in lung adenocarcinoma with bronchoalveolar features (BAC) is important for the determination of TNM (tumour, nodes, metastasis) scores used in staging, prognosis and therapy response assessment. However, tumour sizes derived using lung window (LW) CT or soft-tissue/mediastinal window (MW) CT often give different results. This study examines which measurement correlates best with actual tumour size and which best identifies advanced disease. This retrospective study included 43 BAC patients who underwent surgical resection with mediastinal lymphadenectomy <4 weeks post CT scan. The largest unidimensional tumour diameter on each CT window was compared with actual histopathological tumour size (HP). LW, MW and HP size measurements and a recently described CT parameter - the modified tumour shadow disappearance rate (mTDR) = (1 - [MW/LW]) - were then used to determine which parameter best discriminated between the presence or absence of advanced disease. There was no difference between HP and LW sizes, but MW significantly underestimated HP size (p<0.0001). Unlike MW (p = 0.01) and mTDR (p = 0.001), neither HP (p = 0.14) nor LW (p = 0.10) distinguished between patients with or without advanced disease. On receiver operating characteristic (ROC) analysis at a cut-off of ≤0.13, the sensitivity and specificity of mTDR for detecting advanced disease were 69% and 89%, respectively. In patients with tumours ≤3 cm, only mTDR remained a significant predictor of advanced disease (p = 0.017), with best cut-off at ≤0.20, giving a sensitivity and specificity of 71% and 94%, respectively. MW better predicts advanced disease than LW and might also need to be recorded for RECIST (response evaluation criteria in solid tumours) assessment for T staging of BAC; however, mTDR appears to be an even better predictor and should also be used

Contrast-enhanced 18F-FDG PET/CT: 1-stop-shop imaging for assessing the resectability of pancreatic cancer

Patients with pancreatic cancer continue to have a poor prognosis, with a 5-y survival rate of less than 5%. Surgery is the only treatment that offers a potential cure. Determining resectability is the principal goal of staging in pancreatic cancer patients. Our objective was to evaluate the value of combined contrast-enhanced (18)F-FDG PET/CT in assessing the resectability of pancreatic cancer and to compare enhanced PET/CT with the performance of PET alone and unenhanced PET/CT. METHODS: Fifty patients (25 women and 25 men; mean age, 64.3 y; range, 39-84 y) with biopsy-proven pancreatic adenocarcinoma underwent enhanced (18)F-FDG PET/CT for the evaluation of resectability. Criteria for unresectability were distant metastases, peritoneal carcinomatosis, arterial infiltration, or invasion of neighboring organs other than the duodenum. The performance of enhanced PET/CT regarding resectability was compared with that of PET alone and unenhanced PET/CT. Histology, intraoperative findings, and follow-up CT with clinical investigations were used as the reference standard. RESULTS: According to the reference standard, 27 patients had disease that was not resectable because of distant metastases (n=17), peritoneal carcinomatosis (n=5), or local infiltration (n=5). In the assessment of resectability, PET alone had a sensitivity of 100%, specificity of 44%, accuracy of 70%, positive predictive value of 61%, and negative predictive value of 100%; unenhanced PET/CT had respective values of 100%, 56%, 76%, 66%, and 100%; and enhanced PET/CT, 96%, 82%, 88%, 82%, and 96%. In 5 patients, unresectability was missed by all imaging methods and was diagnosed intraoperatively. Enhanced PET/CT was significantly superior to PET alone (P=0.035), and there was a trend for enhanced PET/CT to be superior to unenhanced PET/CT (P=0.070). CONCLUSION: The use of enhanced PET/CT as a 1-stop-shop imaging protocol for assessing the resectability of pancreatic cancer is feasible and accurate. Enhanced PET/CT is significantly superior to PET alone