PET/CT imaging: Effect of respiratory motion on apparent myocardial uptake

Background  Positron emission tomography (PET) attenuation correction (AC) using computed tomography (CT) can be affected by respiratory motion: hi-speed CT captures 1 point of the respiratory cycle while PET emission data averages many cycles. We quantified the changes in apparent myocardial uptake due to this respiratory-induced CT attenuation mismatch. as]Methods  Twenty-two patients undergoing fluorine-18 fluorodexyglucose (FDG) PET/CT received 3 sequential CT scans at normal resting end-inspiration (CT _INSPIR ), ending expiration (CT_EXPIR), and at midvolume between end-expiration and end-inspiration (CT _MIDVOL ). A pneumotachometer measured absolute changes in lung volume. Seven subjects also underwent a 3-minute transmission scan with a ⁶⁸Ge rotating rod source (RRS). The PET emission data set was reconstructed up to 4 times using CT _EXPIR , CT_INSPIR, CT _MIDVOL , and RRS AC maps. Relative heart position and cardiac uptake was measured for each CT attenuation correction. Results  Respiratory motion produced marked changes in global and regional myocardial uptake. Changes were large in the lateral and anterior regions at the lung-soft tissue interface (up to 30% using CT _INSPIR compared to CT _EXPIR for AC) and smaller in the septal region (10% or less). Data corrected with CT _EXPIR agreed best with the RRS. Conclusion  Respiratory effects can introduce large inhomogeneities in apparent myocardial uptake when CT is used for attenuation correction.     

Impact of metallic dental implants on CT-based attenuation correction in a combined PET/CT scanner

Our objective was to study the effect of metal-induced artifacts on the accuracy of the CT-based anatomic map as a prerequisite for attenuation correction of the positron emission tomography (PET) emission data. Twenty-seven oncology patients with dental metalwork were enrolled in the present study. Data acquisition was performed on a PET/CT in-line system (Discovery LS, GE Medical Systems, Milwaukee, Wis.). Attenuation correction of emission data was done twice, using an 80-mA CT scan (PET_CT80) and a ⁶⁸Ge transmission scan (PET_68Ge). Average count in kBq/cc was measured in regions with and without artifacts and compared for PET_CT80 and PET_68Ge. Data analysis of region of interests (ROIs) revealed that the ratio (ROIs PET_CT80/ROIs PET_68Ge) and the difference (ROIs PET_CT80 minus ROIs PET_68Ge) had a higher mean of values in regions with artifacts than in regions without artifacts (1.2±0.17 vs 1.06±0.06 and 0.68±0.67 vs 0.15±0.17 kBq/cc, respectively). For most of the studied artifactual ROIs, the PET_CT80 values were higher than those of the PET_68Ge. Attenuation correction of PET emission data using an artifactual CT map yields false values in regions nearby artifacts caused by dental metalwork. This may falsely estimate PET quantitative studies and may disturb the visual interpretation of PET scan. Electronic Publication     

Clinical evaluation of a breathing protocol for PET/CT

The aim of this study was to assess the frequency and severity of respiration-induced curvilinear respiration artifacts (RICA) on co-registered positron emission tomography/computed tomography (PET/CT) images acquired on a combined PET/CT scanner before and after modifying the respiration protocol for CT scanning, with retrospective analysis of two groups of 100 patients each, before and after implementing a respiration protocol with breath-hold (BH) in the normal expiration position for the acquisition of the CT images. The CT data were used as attenuation map and for image co-registration. A ranking of co-registered PET/CT and PET images (including maximum intensity projection) was done by two observers in consensus using a scale from 0 to 3. Zero indicated that no RICA was visible and 1, 2, and 3 described artifact with increasing severity. A significant difference in RICA occurrence was found between the two groups (p<0.0001). There was a 45% decrease of artifact frequency when using the normal expiration protocol and a 68% decrease of grade-2 and grade-3 artifacts (p=0.004). The results of this study suggest that BH during the normal expiration position for CT scanning can be recommended to reduce the occurrence and the severity of RICA on PET/CT.     

MR-based attenuation correction for torso-PET/MR imaging: pitfalls in mapping MR to CT data

PURPOSE: MR-based attenuation correction (AC) will become an integral part of combined PET/MR systems. Here, we propose a toolbox to validate MR-AC of clinical PET/MRI data sets. METHODS: Torso scans of ten patients were acquired on a combined PET/CT and on a 1.5-T MRI system. MR-based attenuation data were derived from the CT following MR-CT image co-registration and subsequent histogram matching. PET images were reconstructed after CT- (PET(CT)) and MR-based AC (PET(MRI)). Lesion-to-background (L/B) ratios were estimated on PET(CT) and PET(MRI). RESULTS: MR-CT histogram matching leads to a mean voxel intensity difference in the CT- and MR-based attenuation images of 12% (max). Mean differences between PET(MRI) and PET(CT) were 19% (max). L/B ratios were similar except for the lung where local misregistration and intensity transformation leads to a biased PET(MRI). CONCLUSION: Our toolbox can be used to study pitfalls in MR-AC. We found that co-registration accuracy and pixel value transformation determine the accuracy of PET(MRI).     

Attenuation correction in cardiac PET/CT with three different CT protocols: a comparison with conventional PET

Purpose CT-based attenuation correction may influence cardiac PET owing to its higher susceptibility to misalignment compared with conventional ⁶⁸Ge transmission scans. The aims of this study were to evaluate whether CT attenuation correction leads to changes in tracer distribution compared with conventional cardiac PET and to determine a suitable CT protocol. Methods A total of 27 patients underwent PET/CT and subsequently a PET scan. Twenty patients received a low-dose CT (LDCT group; 120 kV, 26 mA, 8-s scan time), seven patients a slow CT (SCT group; 120 kV, 99 mA, 46-s scan time) and ten patients an ultra-low-dose CT (ULDCT group; 80 kV, 13 mA, 5-s scan time) as the transmission scan in PET/CT. Polar maps were divided into 17 segments and regression analysis was computed in every scan pair (CT attenuation corrected–⁶⁸Ge attenuation corrected). Correlation coefficient (r), the slope (s) and the offset (os) of the regression line were determined. Visual assessment of misalignment between the transmission and emission data was performed. The effective dose of the different transmission scans was calculated. Results Overall, there was a moderate correlation between the mean values measured in all segments on PET/CT and on PET when using LDCT (r=0.78, p<0.0001), SCT (r=0.79, p<0.0001) and ULDCT (r=0.82, p<0.0001). No differences were observed when comparing the scores assigned in the visual misalignment assessment in the three groups (p=0.12). The differences between the results from the regression analysis observed in the respective groups were not statistically significant (Kruskal-Wallis p=0.11 for r, p=0.67 for s and p=0.27 for os). The effective dose was lowest for the ULDCT. Conclusion Our study shows that CT-based attenuation correction is feasible for cardiac PET imaging. The results indicate that ultra-low-dose CT is the preferable choice for transmission scanning.     

Respiration artifacts in whole-body 18F-FDG PET/CT studies with combined PET/CT tomographs employing spiral CT technology with 1 to 16 detector rows

Purpose Co-registration accuracy in combined whole-body (WB) PET/CT imaging is impaired by respiration-induced mismatches between the CT and the PET. Furthermore, PET/CT misregistration may bias the PET tracer distribution following CT-based attenuation correction (CT-AC). With the introduction of multi-row CT technology of up to 16 detector rows into PET/CT designs, we investigated the incidence of respiration artifacts in WB PET/CT examinations of patients who were unable to follow any breath-hold instructions.Methods A total of 80 WB studies from six international sites operating PET/CT tomographs with 1-, 2-, 4-, 6-, 8-, and 16-row spiral CT were included. PET/CT examinations were acquired with the patients breathing normally during both the CT and the PET scan, and CT-AC was performed routinely. All studies were anonymized and reviewed independently by three radiologists and three nuclear medicine specialists. We report the frequency and severity of artifacts on CT and PET for the thorax and the abdomen.Results In WB PET/CT imaging of normally breathing patients, significant gains in diagnostic image quality can be expected from employing CT technology with six or more detector rows. In our study, fewer PET images appear distorted than corresponding CT images, which is due to the limited propagation of only mild CT image artifacts after the resampling of the CT-based attenuation map during CT-AC.Conclusion In whole-body PET/CT imaging of normally breathing patients, respiration-induced artifacts are reduced in both magnitude and prominence for PET/CT systems employing CT components of six or more detector rows.     

Respiratory motion artefact in the liver dome on FDG PET/CT: comparison of attenuation correction with CT and a caesium external source

Purpose Respiratory motion has been reported to be a potential cause of artefacts on PET/CT, and of errors in the quantification of lesion activity due to inaccurate attenuation correction. We examined FDG images corrected for attenuation with CT and a caesium external source in the same patients to study this artefact and to assess its impact on detection of lesions in the upper part of the liver.Methods A total of 122 patients underwent the examination using both attenuation correction techniques, with the Gemini PET/CT scanner. No breathing instructions were given. The images obtained were visually compared, and standardised uptake values (SUVs) in 35 lesions were measured (mean SUV/normal liver SUV) in 14 patients with lesions in the upper part of the liver (less than 5 cm from the upper border).Results CT-corrected images of the liver included an artefactual cold area in 84 patients (69%); this area was located in the posterior upper part of the liver (65 patients, 53%), included the top of the liver (ten patients, 8%) or affected both the top and the posterior part (nine patients, 8%). In lesions (and also in normal liver outside the artefactual area), SUVs obtained with CT correction were higher than those obtained with Cs correction (p<0.05), though this was usually without relevance for lesion detection. However, in patients with lesions situated inside the artefactual area, SUVs were lower with CT correction, and ability to detect two lesions (6%) was affected.Conclusion Failure to detect a liver lesion (especially in the superior and posterior parts) is a rare but possible pitfall when using only CT-corrected FDG images.     

Multiphase CT scanning and different intravenous contrast media concentrations in combined F-18-FDG PET/CT: Effect on quantitative and clinical assessment

Purpose

To evaluate the influence of multiphase CT scanning and different intravenous contrast media on contrast enhancement, attenuation correction and image quality in combined PET/CT.

Material and methods

140 patients were prospectively enrolled for F-18-FDG-PET/CT including a low-dose unenhanced, arterial and venous contrast enhanced CT. The first (second) 70 patients, received contrast medium with 370 (300) mg iodine/ml. The iodine delivery rate (1.3 mg/s) and total iodine load (44.4 g) were identical for both groups. Contrast enhancement and maximum and mean standardized FDG uptake values (SUVmax and SUVmean) were determined for the un-enhanced, arterial and venous PET/CT at multiple anatomic sites and PET reconstructions were visually evaluated.

Results

Arterial contrast enhancement was significantly higher for the 300 mg/ml contrast medium compared to 370 mg I/ml at all anatomic sites. Venous enhancement was not different between the two contrast media. SUVmean and SUVmax were significantly higher for the contrast enhanced compared to the non-enhanced PET/CT at all anatomic sites (all P < 0.001). Tracer uptake was significantly higher in the arterial than in the venous PET/CT in the arteries using both contrast media (all P < 0.001). No differences in tracer uptake were found between the contrast media (all P > 0.05). Visual assessment revealed no relevant differences between the different PET reconstructions.

Conclusions

There is no relevant qualitative influence on the PET scan from the use of different intravenous contrast media in its various phases in combined multiphase PET/CT. For quantitative analysis of tracer uptake it is required to use an identical PET/CT protocol.     

PET/CT在乳腺癌中的应用

乳腺癌是女性最常见的恶性肿瘤,如能得到早期诊断并早期治疗可明显地改善患者的预后情况甚至可以完全治愈。近年来正电子发射断层显像(PET)以及18F-FDG的广泛应用极大地改善了肿瘤患者的诊断和分期问题,及时改变了相应的治疗方法,而单纯的PET显像由于解剖定位欠清,有时正常生理性摄取与异常病理性摄取可能会难以鉴别,PET/CT的出现弥补了上述缺点,使FDGPET/CT在乳腺癌的分期与再分期、疗效监测、术前评估、原发病灶的诊断以及治疗方案的制订中都体现出自身独特的优势。     

Metallic artifacts caused by dental metal prostheses on PET images: a PET/CT phantom study using different PET/CT scanners

Objective  The objective of this study was to investigate the effects of computed tomography (CT) artifacts caused by dental metal prostheses on positron emission tomography (PET) images. Methods  A dental arch cast was fixed in a cylindrical water-bath phantom. A spherical phantom positioned in the vicinity of the dental arch cast was used to simulate a tumor. To simulate the tumor imaging, the ratio of the ¹⁸F-fluoro-deoxy-glucose radioactivity concentration of the spherical phantom to that of the water-bath phantom was set at 2.5. A dental bridge composed of a gold–silver–palladium alloy on the right mandibular side was prepared. A spherical phantom was set in the white artifact area on the CT images (site A), in a slightly remote area from the white artifact (site B), and in a black artifact area (site C). A PET/CT scan was performed with and without the metal bridge at each simulated tumor site, and the artifactual influence was evaluated on the axial attenuation-corrected (AC) PET images, in which the simulated tumor produced the strongest accumulation. Measurements were performed using three types of PET/CT scanners (scanners 1 and 2 with CT-based attenuation correction, and 3 with Cesium-137 (¹³⁷Cs)-based attenuation correction). The influence of the metal bridge was evaluated using the change rate of the SUVmean with and without the metal bridge. Results  At site A, an overestimation was shown (scanner 1: +5.0% and scanner 2: +2.5%), while scanner 3 showed an underestimation of −31.8%. At site B, an overestimation was shown (scanner 1: +2.1% and scanner 2: +2.0%), while scanner 3 showed an underestimation of −2.6%. However, at site C, an underestimation was shown (scanner 1: −25.0%, scanner 2: −32.4%, and scanner 3: −8.4%). Conclusions  When CT is used for attenuation correction in patients with dental metal prostheses, an underestimation of radioactivity of accumulated tracer is anticipated in the dark streak artifact area on the CT images. In this study, the dark streak artifacts of the CT caused by metallic dental prostheses may cause false negative finding of PET/CT in detecting small and/or low uptake tumor in the oral cavity.     

Correction of oral contrast artifacts in CT-based attenuation correction of PET images using an automated segmentation algorithm

Purpose  Oral contrast is usually administered in most X-ray computed tomography (CT) examinations of the abdomen and the pelvis as it allows more accurate identification of the bowel and facilitates the interpretation of abdominal and pelvic CT studies. However, the misclassification of contrast medium with high-density bone in CT-based attenuation correction (CTAC) is known to generate artifacts in the attenuation map (μmap), thus resulting in overcorrection for attenuation of positron emission tomography (PET) images. In this study, we developed an automated algorithm for segmentation and classification of regions containing oral contrast medium to correct for artifacts in CT-attenuation-corrected PET images using the segmented contrast correction (SCC) algorithm. Methods  The proposed algorithm consists of two steps: first, high CT number object segmentation using combined region- and boundary-based segmentation and second, object classification to bone and contrast agent using a knowledge-based nonlinear fuzzy classifier. Thereafter, the CT numbers of pixels belonging to the region classified as contrast medium are substituted with their equivalent effective bone CT numbers using the SCC algorithm. The generated CT images are then down-sampled followed by Gaussian smoothing to match the resolution of PET images. A piecewise calibration curve was then used to convert CT pixel values to linear attenuation coefficients at 511 keV. Results  The visual assessment of segmented regions performed by an experienced radiologist confirmed the accuracy of the segmentation and classification algorithms for delineation of contrast-enhanced regions in clinical CT images. The quantitative analysis of generated μmaps of 21 clinical CT colonoscopy datasets showed an overestimation ranging between 24.4% and 37.3% in the 3D-classified regions depending on their volume and the concentration of contrast medium. Two PET/CT studies known to be problematic demonstrated the applicability of the technique in clinical setting. More importantly, correction of oral contrast artifacts improved the readability and interpretation of the PET scan and showed substantial decrease of the SUV (104.3%) after correction. Conclusions  An automated segmentation algorithm for classification of irregular shapes of regions containing contrast medium was developed for wider applicability of the SCC algorithm for correction of oral contrast artifacts during the CTAC procedure. The algorithm is being refined and further validated in clinical setting.     

PET/CT of the abdomen: optimizing the patient breathing pattern

The aim of this study was to evaluate the respiration position, which is optimal for co-registration of abdominal CT images, and the corresponding positron emission tomography (PET) scan in a new combined PET/CT system. Ten patients (5 men, 5 women; age 57.7±15.3 years, age range 34–80 years) underwent imaging for tumor staging on a combined PET/CT scanner (Discovery LS, GE Medical Systems, Milwaukee, Wis.). The PET emission images were acquired during normal shallow breathing and during CT scanning the patients performed four different breathing tasks: free breathing (FB); maximum inspiration (MaxInsp); maximum expiration (MaxExp); and normal expiration (NormExp). NormExp was defined as the respiratory level that was reached when the patient first inhaled and then exhaled without forcing expiration, and then held the breath in this position. Movements of the spleen, liver, left and right kidney, and the bladder were measured by using the promontory of the sacrum as a reference point and measuring the distance from this point to the abdominal organs in the PET and CT images by two independent observers. Statistical comparison of the measured distances between the CT scans and the PET scan were made using a Wilcoxon signed-rank test with Bonferroni correction. Repeated-measures analysis of variance served for the assessment of intraobserver and interobserver agreement. There was no significant difference between NormExp and FB indicating that both respiration protocols are suitable for PET/CT image co-registration of abdominal studies. In contrast, the MaxExp and MaxInsp protocol are not suitable. The NormExp and FB respiration protocol are both suitable for the co-registration of abdominal PET/CT studies. In most patients the mismatch of abdominal organs will be lower than the resolution of the final co-registered PET/CT image. Electronic Publication     

Integrated PET/CT in the preoperative staging of lung cancer: A prospective comparison of CT,PET and integrated PET/CT

Purpose

The purpose of this study was to evaluate the role of integrated PET/CT in the staging of lung cancer compared with CT alone or PET alone.

Materials and methods

Thirty-three patients underwent integrated PET/CT for the staging of lung cancer. The tumor, node and metastasis (TNM) stages were assessed with CT, PET and integrated PET–CT and compared with the surgical and pathological staging.

Results

CT correctly evaluated the (T) status in (64%) of the patients, PET in (59%) and PET/CT in (86%). CT correctly evaluated the (N) status in (73%) of the patients, PET in (76%), and PET/CT (88%) with accuracy, sensitivity, specificity, PPV and NPV were 73%, 78%, 71%, 50% and 94% for CT, 76%, 67%, 79%, 55% and 95% for PET and 88%, 89%, 88%, 73% and 100% for PET/CT respectively, and for (M) status were 91%, 86%, 92%, 75% and 96% for CT, 88%, 71%, 92%, 71% and 92% for PET and 97%, 100%, 96%, 88% and 100% for PET/CT respectively. Regarding the overall TNM staging CT correctly staged 24 patients. PET correctly staged 23 cases while PET/CT correctly staged 30 cases. A significant difference in the accuracy of overall tumor staging between PET/CT and CT (P = 0.0412) or PET (P = 0.0233).

Conclusion

The integrated PET/CT is superior to either CT or PET in the staging of lung cancer which has an important impact on selection of the appropriate treatment regimen.     

Body surface area adapted iopromide 300 mg/ml versus 370 mg/ml contrast medium injection protocol: Influence on quantitative and clinical assessment in combined PET/CT

Purpose

To investigate the quantitative and qualitative differences between combined positron emission tomography and computed X-ray tomography (PET/CT) enhanced with contrast medium with either an iodine concentration 300 mg/ml or 370 mg/ml.

Materials and methods

120 consecutive patients scheduled for F-18-Fluorodeoxyglucose (FDG) PET/CT were included. The first (second) 60 patients received contrast medium with 300 (370) mg iodine/ml. Intravenous injection protocols were adapted for an identical iodine delivery rate (1.3 mg/s) and body surface area (BSA) adapted iodine dose (22.26 g I/m²). Maximum and mean standardized uptake values (SUV_max; SUV_mean) and contrast enhancement (HU) were determined in the ascending aorta, the abdominal aorta, the inferior vena cava, the portal vein, the liver and the right kidney in the venous contrast medium phase. PET data were evaluated visually for the presence of malignancy and image quality.

Results

Both media caused significantly higher values for HU, SUV_mean and SUV_max for the enhanced PET/CT than the non-enhanced one (all p < 0.01). There were no significant differences in the degree of increase of HU, SUV_mean and SUV_max between the two contrast media at any anatomic site (all p > 0.05). Visual evaluation of lesions showed no differences between contrast and non-contrast PET/CT or between the two different contrast media (p = 0.77).

Conclusion

When using a constant iodine delivery rate and total iodine dose in a BSA adapted injection protocol, there are no quantitative or qualitative differences in either CT or PET between contrast media with an iodine concentration of 300 mg/ml and 370 mg/ml, respectively.     

PET/CT对肿瘤放疗策略的影响

目的：探讨PET／CT对肿瘤放疗策略的影响。方法：对189例恶性肿瘤进行放疗前^18F-FDG全身PET／CT检查,应用标准摄取值（SUV）进行评价,病灶区SUV≥2．5为阳性。结果：PET／CT检查后,56例放射策略发生变化,其中14例（25．0％）改行其他治疗,12例（21．4％）将根治性放疗改为姑息性放疗,18例（32．1％）改变了照射靶区,12例（21．4％）调整了放疗剂量。结论：PET／CT为恶性肿瘤放疗前的全面评估和决策提供了更多更有效的临床信息,其功能显影和解剖影像同机融合的突出优势,明显提高了治疗效果,减少或减轻了并发症的发生。     

PET/CT中CT仿真人体模型的图像质量与辐射剂量关系的研究

目的 以仿真人体模型为实验对象,研究PET/CT中CT图像质量与辐射剂量的关系,为保证图像质量同时降低受检者的辐射剂量提供数据依据。方法 用美国GE Discovery ST型 PET/CT,对仿真人体模型（Model RS-550）进行扫描。CT采集条件：管电压120 kV,管电流30~250 mA范围内11种固定值及自动管电流,螺距（pitch）分别为0.938、1.375、1.75,模拟临床PET/CT的全身扫描方式对仿真人体模型进行扫描。对图像进行分析,计算腹部主要器官的噪声、信噪比及质量因数。结果 噪声随有效剂量的增加而降低,有效剂量<15 mSv时,噪声变化幅度较大;>15 mSv时,噪声变化缓慢。信噪比、对比信噪比随有效剂量增加而增加。相同的有效剂量时,质量因数与扫描方案相关。自动管电流模式下的所有指标,均优于固定管电流采集模式。结论在CT图像质量达到一定程度后,进一步增加有效剂量,图像质量提高有限。根据不同的临床需求在保证一定图像质量的前提下,选择适当的CT扫描方案,降低受检者的有效剂量。     

Modification of [18F]-FDG PET/CT imaging protocols in obese oncology patients: A nationwide survey

IntroductionThe use of medical imaging for diagnosis, staging and follow-up in Oncology context is incredibly important, being the use of [18F]-FDG PET/CT particularly advantageous in specific contexts like the case of obese patients. However, imaging the latter can be challenging sometimes, since their own body size may affect overall image quality and adds technical difficulties for the operator(s) performing the examination.MethodsThis research project was developed with the aim of analysing the current personal practices of Portuguese Nuclear Medicine Technologists (NMTs) in the adaptation of ¹⁸F-FDG PET/CT oncological protocols for obese patients and comparing the results with parameters referenced in literature. A non-experimental research study was conducted using a survey delivered online to NMTs through social media platforms (Facebook® and LinkedIn®) and by sending the link directly to contacts within the research team professional and personal networks.ResultsAnswers from a total of 26 participants were obtained, with 88.5% of participants admitting modifying technical protocols in examinations for obese patients. Changes in PET protocols included an increase in the administered activity (60.9%), an increase in scan time per individual bed position (69.6%) and the use of Time-of-Flight (TOF) technology whenever available. Protocol changes in CT included increasing the mA (82.6%), raising the KVp (47.8%), the application of iterative reconstruction (69.6%) and the use of automatic exposure control (AEC) (52.2%). The remaining parameters (pitch, algorithm, slice thickness, display FOV, gantry rotation time and energy acceptance window) were claimed not to be modified by around 90% of professionals.ConclusionPortuguese NMTs tend to change the [18F]-FDG PET/CT protocols for obese patients. However, while some of the parameters appear to be contradictory or redundant, others require further optimisation, especially in the CT component.Implications for practiceEfforts should be made to optimize acquisition protocols used in [18F]-FDG PET/CT scans for obese patients.     

PET and PET/CT in endocrine tumours

Functional information provided by PET tracers together with the superior image quality and the better data quantification by PET technology had a changing effect on the significance of nuclear medicine in medical issues. Recently introduced hybrid PET/CT systems together with the introduction of novel PET radiopharmaceuticals have contributed to the fact that nuclear medicine has become a growing diagnostic impact on endocrinology. In this review imaging strategies, different radiopharmaceuticals including the basic mechanism of their cell uptake, and the diagnostic value of PET and PET/CT in endocrine tumours except differentiated thyroid carcinomas will be discussed.     

PET/CT在恶性肿瘤诊断与治疗中的应用

1 PET/CT的基本原理和技术特点PET(Positron Emission Tomography)是正电子发射断层显像是一种利用放射性核素示踪技术分析组织生物化学即器官功能、血流和代谢变化情况的影像技术,其利用回旋加速器产生正电子核素11C1、3N1、5O1、8F通过化学合成的显像剂如18F-FDG1、3N-NH3等注入人体进行检测,得到靶器官的断层和三维图像,因其对于功能代谢和受体分布等的显示具有优势,故被称为“分子成像”或“生化显像”〔1〕,在肿瘤、心血管、神经等疾病中具有广泛的应用,不足之处是对病灶的解剖定位差,检查花费时间稍长。CT(Computed Tomogr…     

^18氟-脱氧葡萄糖PET/CT显像在原发性肝细胞癌中的应用研究

目的评价18氟-脱氧葡萄糖(18FDG)PET/CT在原发性肝细胞癌中的应用价值.材料和方法28例患者被分成3组.第一组为未经相关治疗的HCC组,共13例;第二组为肝脏良性病变组,共9例;第三组为HCC治疗后疗效观察组,共6例.18FDG PET/CT影像学表现结合手术病理及临床随访,计算18FDG PET/CT对HCC诊断的敏感性,并分析标准摄取值(SUV)的影响因素.结果第一组患者Ⅰ型表现7例,Ⅱ型表现5例,Ⅲ型表现1例;第二组患者Ⅰ型表现0例,Ⅱ型表现4例,Ⅲ型表现5例;18FDG PET/CT对HCC诊断的灵敏度为53.8%,其SUV值的大小和肿瘤的生物学行为有关.第三组患者Ⅰ型表现5例,Ⅱ型表现0例,Ⅲ型表现1例,其SUV值的大小与肿瘤残留有关.结论18FDG PET/CT显像在HCC生物学特性评估及HCC治疗后疗效监测方面有明显优势.