Clinical evaluation of a block sequential regularized expectation maximization reconstruction algorithm in 18F-FDG PET/CT studies.

PURPOSE: To investigate the clinical performance of a block sequential regularized expectation maximization (BSREM) penalized likelihood reconstruction algorithm in oncologic PET/computed tomography (CT) studies. METHODS: A total of 410 reconstructions of 41 fluorine-18 fluorodeoxyglucose-PET/CT studies of 41 patients with a total of 2010 lesions were analyzed by two experienced nuclear medicine physicians. Images were reconstructed with BSREM (with four different ß values) or ordered subset expectation maximization (OSEM) algorithm with/without time-of-flight (TOF/non-TOF) corrections. OSEM reconstruction postfiltering was 4.0 mm full-width at half-maximum; BSREM did not use postfiltering. Evaluation of general image quality was performed with a five-point scale using maximum intensity projections. Artifacts (category 1), image sharpness (category 2), noise (category 3), and lesion detectability (category 4) were analyzed using a four-point scale. Size and maximum standardized uptake value (SUVmax) of lesions were measured by a third reader not involved in the image evaluation. RESULTS: BSREM-TOF reconstructions showed the best results in all categories, independent of different body compartments. In all categories, BSREM non-TOF reconstructions were significantly better than OSEM non-TOF reconstructions (P<0.001). In almost all categories, BSREM non-TOF reconstruction was comparable to or better than the OSEM-TOF algorithm (P<0.001 for general image quality, image sharpness, noise, and P=1.0 for artifact). Only in lesion detectability was OSEM-TOF significantly better than BSREM non-TOF (P<0.001). Both BSREM-TOF and BSREM non-TOF showed a decreasing SUVmax with increasing ß values (P<0.001) and TOF reconstructions showed a significantly higher SUVmax than non-TOF reconstructions (P<0.001). CONCLUSION: The BSREM reconstruction algorithm showed a relevant improvement compared with OSEM reconstruction in PET/CT studies in all evaluated categories. BSREM might be used in clinical routine in conjunction with TOF to achieve better/higher image quality and lesion detectability or in PET/CT-systems without TOF-capability for enhancement of overall image quality as well.

TNM Staging of Non-Small Cell Lung Cancer: Comparison of PET/MR and PET/CT.

UNLABELLED: The purpose of this study was to compare the diagnostic accuracy of whole-body unenhanced PET/MR with that of PET/CT in determining the stage of non-small cell lung cancer. METHODS: This study was approved by the institutional review board and by national government authorities. Forty-two consecutive patients referred for the initial staging of non-small cell lung cancer underwent whole-body imaging with a sequential trimodality PET/CT/MR system. PET/MR and PET/CT datasets were evaluated separately, and a TNM stage was assigned on the basis of the image analysis. Nodal stations in the chest were identified according to the mapping system of the American Thoracic Society. The standard of reference was histopathology for the tumor stage in 20 subjects, for the nodal stage in 22 patients, and for extrathoracic metastases in 5 subjects. All other lesions were confirmed by at least 1 different imaging method. A Wilcoxon signed-ranks test was used for comparing PET/MR with PET/CT. RESULTS: PET/MR did not provide additional information compared with PET/CT. The diagnostic accuracy of both imaging modalities was equal (T staging, P = 0.177; N staging, P = 0.114; M staging, P = 0.465), however, with advantages for PET/CT by trend. In the subgroup with histopathologic confirmation of T and N stages, the situation was similar (T staging, P = 0.705; N staging, P = 0.334). CONCLUSION: This study indicates that PET/MR using a fast MR protocol does not improve the diagnostic accuracy of the staging of non-small cell lung cancer.

Combined PET/CT-perfusion in patients with head and neck cancers might predict failure after radio-chemotherapy: a proof of concept study.

BACKGROUND: [18F]FDG-PET/CT imaging is broadly used in head and neck cancer (HNSCC) patients. CT perfusion (CTP) is known to provide information about angiogenesis and blood-flow characteristics in tumors. The aim of this study was to evaluate the potential relationship of FDG-parameters and CTP-parameters in HNSCC preand post-therapy and the potential prognostic value of a combined PET/CT with CTP. METHODS: Thirteen patients with histologic proven HNSCC were prospectively included. All patients underwent a combined PET/CT with integrated CTP before and after therapy. Pre- and post-therapeutic data of CTP and PET of the tumors were compared. Differences were tested using Spearman's rho test and Pearson's correlation. A p-value of p <0.05 was considered statistically significant. Correlations were calculated using Pearson's correlation. Bootstrap confidence intervals were calculated to test for additive confidence intervals. RESULTS: Three patients died due to malignancy recurrence, ten patients were free of recurrence until the end of the follow-up period. Patients with recurrent disease had significantly higher initial CTP-values compared to the recurrence-free patients: BFpre 267.4 (171.2)ml/100 mg/min, BVpre 40.9 (8.4)ml/100 mg and MTTpre 8.2 (6.1)sec. No higher SUVs initially but significantly higher TLG compared to patients without recurrence were found. Post-therapeutic PET-values differed significantly between the two groups: SUVmaxpost 6.0 (3.2), SUVmeanpost 3.6 (2.0) and TLG 21751.7 (29794.0). CONCLUSION: In our proof of concept study, combined PET/CT with integrated CTP might show complementary prognostic data pre- and post chemo-radiotherapy. CTP may be used to predict local tumor recurrence, while FDGPET/CT is still needed for whole-body staging.

Evaluation of pelvic ring injuries using SPECT/CT.

OBJECTIVE: The incidence of pelvic fractures is relatively low compared with other fracture locations. The low incidence is in great contrast to the high morbidity and mortality. Particularly in the elderly, with apparently isolated fractures of the pubic rami, these observations are believed to be due to additional occult lesions of the posterior pelvic ring. In these cases diagnosis cannot be established by conventional imaging alone and SPECT/CT is considered as a diagnostic adjunct. The aim of this study was to assess concomitant bony or soft tissue lesions within the pelvic ring in a population of patients with fractures of the anterior elements. MATERIALS AND METHODS: In all patients with no obvious lesions of the posterior pelvic ring on X-rays and CT or with suspicious but inconclusive findings on CT an additional SPECT/CT was carried out in a non-acute setting within 3 days of the trauma. RESULTS: In all cases additional lesions within the pelvic ring were found. Most lesions were vertical sacral fractures, followed by transverse fractures, one non-dislocated fracture of the acetabulum on the side of the pubic rami fracture, and one post-traumatic dilatation of the sacroiliac joint with increased tracer uptake. CONCLUSION: According to our results after SPECT/CT all patients with pubic rami fracture suffered additional lesions, none detectable previously by X-ray or CT, within the pelvic ring. In this context SPECT/CT has proved to be very helpful in the clinical routine to visualize occult fractures and instability within the sacroiliac joint.

Whole-body nonenhanced PET/MR versus PET/CT in the staging and restaging of cancers: preliminary observations.

PURPOSE: To assess the diagnostic performance of whole-body non-contrast material-enhanced positron emission tomography (PET)/magnetic resonance (MR) imaging and PET/computed tomography (CT) for staging and restaging of cancers and provide guidance for modality and sequence selection. MATERIALS AND METHODS: This study was approved by the institutional review board and national government authorities. One hundred six consecutive patients (median age, 68 years; 46 female and 60 male patients) referred for staging or restaging of oncologic malignancies underwent whole-body imaging with a sequential trimodality PET/CT/MR system. The MR protocol included short inversion time inversion-recovery ( STIR short inversion time inversion-recovery ), Dixon-type liver accelerated volume acquisition ( LAVA liver accelerated volume acquisition ; GE Healthcare, Waukesha, Wis), and respiratory-gated periodically rotated overlapping parallel lines with enhanced reconstruction ( PROPELLER periodically rotated overlapping parallel lines with enhanced reconstruction ; GE Healthcare) sequences. Primary tumors (n = 43), local lymph node metastases (n = 74), and distant metastases (n = 66) were evaluated for conspicuity (scored 0-4), artifacts (scored 0-2), and reader confidence on PET/CT and PET/MR images. Subanalysis for lung lesions (n = 46) was also performed. Relevant incidental findings with both modalities were compared. Interreader agreement was analyzed with intraclass correlation coefficients and κ statistics. Lesion conspicuity, image artifacts, and incidental findings were analyzed with nonparametric tests. RESULTS: Primary tumors were less conspicuous on STIR short inversion time inversion-recovery (3.08, P = .016) and LAVA liver accelerated volume acquisition (2.64, P = .002) images than on CT images (3.49), while findings with the PROPELLER periodically rotated overlapping parallel lines with enhanced reconstruction sequence (3.70, P = .436) were comparable to those at CT. In distant metastases, the PROPELLER periodically rotated overlapping parallel lines with enhanced reconstruction sequence (3.84) yielded better results than CT (2.88, P < .001). Subanalysis for lung lesions yielded similar results (primary lung tumors: CT, 3.71; STIR short inversion time inversion-recovery , 3.32 [P = .014]; LAVA liver accelerated volume acquisition , 2.52 [P = .002]; PROPELLER periodically rotated overlapping parallel lines with enhanced reconstruction , 3.64 [P = .546]). Readers classified lesions more confidently with PET/MR than PET/CT. However, PET/CT showed more incidental findings than PET/MR (P = .039), especially in the lung (P < .001). MR images had more artifacts than CT images. CONCLUSION: PET/MR performs comparably to PET/CT in whole-body oncology and neoplastic lung disease, with the use of appropriate sequences. Further studies are needed to define regionalized PET/MR protocols with sequences tailored to specific tumor entities.

SPECT/CT for imaging of the spine and pelvis in clinical routine: a physician's perspective of the adoption of SPECT/CT in a clinical setting with a focus on trauma surgery.

Injuries of the axial skeleton are an important field of work within orthopaedic surgery and traumatology. Most lesions following trauma may be diagnosed by means of conventional plain radiography, computed tomography or magnetic resonance imaging. However, for some aspects SPECT/ CT can be helpful even in a trauma setting. In particular, the combination of highly sensitive but nonspecific scintigraphy with nonsensitive but highly specific computed tomography makes it particularly useful in anatomically complex regions such as the pelvis and spine. From a trauma surgeon's point of view, the four main indications for nuclear medicine imaging are the detection of (occult) fractures, and the imaging of inflammatory bone and joint diseases, chronic diseases and postoperative complications such as instability of instrumentation or implants. The aim of the present review was to give an overview of the adoption of SPECT/CT in a clinical setting.

Image quality and radiation dose comparison of prospectively triggered low-dose CCTA: 128-slice dual-source high-pitch spiral versus 64-slice single-source sequential acquisition.

Currently 64-multislice computed tomography (MSCT) scanners are the most widely used devices allowing low radiation dose coronary CT angiography (CCTA) with prospective ECG triggering. Latest 128-slice dual-source CT (DSCT) scanners offer prospective high-pitch spiral acquisition covering the heart during one single beat. We compared radiation dose and image quality from prospective 64-MSCT versus high-pitch spiral 128-slice DSCT scanning, as such data is lacking. CCTA of 50 consecutive patients undergoing 128-DSCT (2 × 64 × 0.6 mm collimation, 0.28 s rotation time, 3.4 pitch, 100-120 kV tube voltage and 320 mAs tube current-time product) were compared to CCTA of 50 heart rate (HR) and BMI matched patients undergoing 64-MSCT (64 × 0.625 mm collimation, 0.35 s rotation time, 100-120 kV tube voltage and 400-650 mA tube current). Image quality was rated on a 4-point scale by two independent cardiac imaging physicians (1 = excellent to 4 = non-diagnostic). Of 710 coronary segments assessed on 128-DSCT, 216 (30.4%) achieved an image quality score 1 excellent, 400 (56.3%) score 2, 76 (10.7%) score 3 and 18 (2.6%) score 4 (non-diagnostic). Of 737 coronary segments evaluated on 64-MSCT 271 (36.8%) had an image quality score of 1, 327 (44.4%) 2, 110 (14.9%) score 3, and 29 (3.9%) segments score 4. Average image quality score for both scanners was similar (P = 0.641). The mean heart rate during scanning was 58.7 ± 5.6 bpm on 128-DSCT and 59.0 ± 5.6 bpm on 64-MSCT, respectively. Mean effective radiation dose was 1.0 ± 0.2 mSv for 128-DSCT and 1.7 ± 0.6 mSv for 64-MSCT (P < 0.001). 128-DSCT with high-pitch spiral mode allows CCTA acquisition with reduced radiation dose at maintained image quality compared to 64-MSCT.

Detection of primary choriocarcinoma in the mediastinum by F-18 FDG positron emission tomography.

A 31-year-old woman with a history of infection with human papilloma virus was found to have an elevated human chorionic gonadotropin level (beta-HCG) of more than 9000 IU/L in January 2006. The patient reported an irregular menstrual cycle. Extensive clinical work-up including gynecologic examinations with laparoscopy, hysteroscopy, and curettage were performed but no pathologic explanation of this elevated beta-HCG could be found. In the initial computed tomography (CT) of the abdomen and the thorax, a tumor could not be detected. Based on a clinical decision, chemotherapy with methotrexate in a dose of 1 mg/kg body weight was started. Four months after beginning of the chemotherapy the beta-HCG level dropped to 3048 IU/L. At this time a first F-18 FDG PET was performed and the findings were negative. After completion of 7 cycles of chemotherapy the beta-HCG level rose again. In a second F-18 FDG PET in August 2006 focal, intense and pathologic F-18 FDG accumulation with a SUV max. of 5.4 was seen in the mediastinum in the region of the thymus. At this time the beta-HCG level was 7000 IU/L. In a subsequent CT of the chest a retrosternal mass of 4 x 1.7 cm was detected with contrast enhancement. Resection of the tumor and thymus gland demonstrated a choriocarcinoma in part adjacent to the thymus and in part in the thymus. Postoperative beta-HCG levels dropped to 105 IU/L.