靶影象(target imaging)

CT在中枢神经系统应用中,一般层厚为5～10毫米,大的象素使空间分辨力不比目前应用的X线图象好。同时CT 分度范围为-1000～ 1000,高密度物质分辨力差,在骨骼系统诊断中有困难。为此减小象素以提高空间分辨力,考虑延长CT 值分度范围,以提高密度分辨力。在新的改良软件中加入高分解能力的演算方法,由于变调传导相关系数的改良使空间分辨力大幅度提高。     

Prostate cancer staging: should MR imaging be used?--A decision analytic approach

PURPOSE: To determine the appropriate use of magnetic resonance (MR) imaging for preoperative staging of prostate cancer. MATERIALS AND METHODS: Literature review was performed by using the principles of evidence-based medicine and medical technology assessment. A decision analytic model was used to compare (a) the strategy that radical prostatectomy is performed on the basis of clinical staging with (b) the strategy that extracapsular disease detected at MR imaging contraindicates radical prostatectomy in patients who were considered surgical candidates on the basis of clinical staging. RESULTS: After review of the literature, expert panel opinion did not recommend MR staging. No studies in which therapeutic efficacy was addressed were found. The decision analytic model indicated that the strategy including MR staging decreased costs (MR imaging, $10,568; radical prostatectomy, $11,669) and resulted in almost equal life expectancy (MR imaging, 12.59 years; radical prostatectomy, 12.60 years) and quality-adjusted life-years ([QALYs] MR imaging, 12.53; radical prostatectomy, 12.52). Results of sensitivity analyses demonstrated that the MR strategy was both more effective and less costly if the prior probability of extracapsular disease was at least 39% when considering QALY and 50% when considering unadjusted life expectancy. CONCLUSION: It is not yet conclusively determined whether preoperative MR staging is appropriate, but results of decision analysis suggest that MR staging is cost-effective for men with moderate or high prior probability of extracapsular disease.     

Is there an added role for diffusion weighted imaging in the staging of cervical carcinoma?

Objective

To assess the diagnostic accuracy of diffusion weighted imaging (DWI-MRI) being a non-contrast based MR sequence versus dynamic contrast enhanced MRI (DCE-MRI) in the preoperative loco-regional staging of the cervical carcinoma.

Emergency pediatric imaging: changes over the years (part I)

We have lived through an enormous era of technical advance and data acquisition and transfer. Radiology (imaging), has come out of this very strong and has spread to new endeavors and other disciplines. One of the major changes has been the enormous expansion of digital, cross-sectional, imaging. Just how this has affected pediatric radiology in terms of the skull and spine is the subject of this communication. The overall message is that we must keep a blend of plain films and digital cross-section studies and know what to keep and what to let go.Part II of this review article is available at     

High-resolution MR imaging for nodal staging in rectal cancer: are there any criteria in addition to the size?

PURPOSE: MR staging of nodal metastases in patients with rectal cancer using criteria based on size, shape and signal intensity can be difficult, because > or =50% of the nodes are less than 5 mm in size. Therefore new MR criteria were evaluated to see whether it can improve the MR assessment of nodal metastases in rectal cancer patients. MATERIALS AND METHODS: Ninety-nine patients with primary rectal carcinoma underwent 1.5 T high-resolution MRI with a quadrature phased array coil. Among them, 75 patients who had undergone total mesorectal excision were enrolled in this study. An MR radiologist, blinded for the histological results, randomly recorded the characteristics of each detectable node (LN); common criteria such as short-axis diameter, the ratio of long- to short-axis diameter, and signal intensity on each sequence; new criteria such as the margin (smooth, lobulated, spiculated, indistinct), a homogenous or mottled heterogeneous appearance, gross enhancement and its pattern, the venous encasement, and the dirty perirectal fat signal. RESULTS: Among 75 patients, 22 (29%) were node-positive. All patients who did not have detectable LN on MR were node-free (n = 15). Presence of LNs > 4 mm was significantly higher in the node-positive group. Presence of LNs > 8 mm was seen only in the node-positive group. Presence of a spiculated border and an indistinct border shows sensitivities of 45 and 36%, and specificities of 100 and 100%, respectively. Presence of a mottled heterogeneic pattern shows a sensitivity of 50%, a specificity of 95%. The presence of these three features were strongly correlated with LN positivity (P < 0.001, respectively). Presence of a venous encasement (n = 4) and dirty perirectal fat signal (n = 3) were also significantly (P < 0.05, respectively) correlated with LN positivity. CONCLUSION: In addition to size, new criteria such as a spiculated or indistinct border and a mottled heterogeneous appearance could be useful to predict regional lymph node involvement in patients with rectal cancer.     

Is (99m)Tc-labelled pamidronate a better agent than (99m)Tc-medronate for bone imaging?

OBJECTIVE: To evaluate the potential of (99m)Tc-pamidronate ((99m)Tc-APD) against (99m)Tc-medronate ((99m)Tc-MDP) as a new bone-seeking agent using intact bone and fractured femur in a rat model. METHODS: (99m)Tc-APD was prepared by the stannous reduction method. Scintigraphic images were obtained at 2 h and 24 h after intravenous injection of (99m)Tc-APD or (99m)Tc-MDP in rats, then they were culled to estimate activities in various organs. Bone uptake (as percent injected dose/gram weight) was estimated in an intact femur and in 1 week post-fracture model. The urinary excretion dose (as percent injected dose) was also estimated. RESULTS: The bone uptake of (99m)Tc-APD was significantly higher (P<0.05) than (99m)Tc-MDP at 2 h and 24 h post-injection studies. (99m)Tc-APD uptake was further increased (P<0.05) in the fracture model than the intact femur. (99m)Tc-APD uptake in the soft tissues including liver and the kidneys was lower than (99m)Tc-MDP. Renal excretion was faster and the ratios of bone to blood and bone to soft tissues were higher with APD than MDP. APD dose was selected at 1% of MDP, to obviate therapeutic effect, as the former compound is 100 times more potent than MDP. CONCLUSIONS: Our results suggest that (99m)Tc-APD uptake by intact bone and fractured bone was significantly higher than (99m)Tc-MDP. The renal clearance of (99m)Tc-APD was faster and soft tissue uptake was lower than (99m)Tc-MDP. These results suggest that APD has the potential to become an excellent bone-imaging agent.     

Can gemstone spectral imaging accurately determine iodine concentration? (a phantom study)

目的:利用CT能谱成像(GSI)技术测定不同浓度含碘溶液在静止及运动状态下的碘含量,分析GSI碘基图像上碘浓度的测量值与真实值之间的关系.方法:采用GE公司标准体模,其内放置有9种不同浓度的碘溶液试管,浓度依次为0.4、0.7、2.0、5.0、10.0、20.0、30.0、50.0和100.0 mg/ml.使用能谱CT GSI模式进行扫描,球管旋转一周时间分别为0.6、0.8及1.0 s/r.利用碘基图,选择相同层面、相同大小兴趣区,测量在静止及运动状态下(振幅为10 mm,频率为15 bpm)体模试管内碘含量,采用相关分析及配对t检验分析碘含量的测量值与真实值间的关系.结果:球管转速为0.8及1.0s时,无论是静止还是运动状态下,碘含量的测量值与真实值之间均具有明显的相关性(r=0.999,P＜0.001),且两者之间的差异无统计学意义(P＞0.05);而球管转速为0.6 s/r时,碘浓度测量值与真实值之间仅存在相关性(P＜0.001,r=0.999),两者数值之间差异有统计学意义(P＜0.05).结论:能谱CT在球管转速为0.8及1.0 s/r时能准确测量不同浓度溶液中的碘含量,即使在运动状态下亦可以用于定量分析,有望成为一种可靠的物质成分分析方法.     

Abdominal lymphoma staging: is MR imaging with T2-weighted turbo-spin-echo sequence a diagnostic alternative to contrast-enhanced spiral CT?

PURPOSE: To evaluate the diagnostic value of MR imaging in abdominal lymphoma staging, in comparison with that of the established spiral CT, within the context of a prospective study. METHODS: 50 patients with non-Hodgkin (n = 27) and Hodgkin lymphoma (n = 23) were examined with a plain T2-weighted TSE sequence (parameters: TE 90 ms, TR >2.500 ms, slice thickness 8 mm, slice interval 0.8 mm, ETL 20, NEX 4), and with spiral CT following oral and intravenous administration of contrast agent. RESULTS: Both CT and MR imaging agreed in showing abdominal lymphomas in 34/50 cases. The size of the detected lymphomas was between 1.5-9 cm (mean: 4.3 +/-2.2 cm). In the analysis of the individual lymph node sites, CT showed involvement of the paraaortic lymph nodes in 29/50 patients, compared with 28/50 in MRI, and involvement of the portal lymph nodes in 15/50, compared with 12/50. Both techniques showed the iliac lymph nodes in 21/50 patients, the inguinal lymph nodes in 10/50, and the mesenteric lymph nodes in 11/50. Both techniques also showed focal organ lesions in 12/50 cases. CONCLUSIONS: In the staging of abdominal lymphomas, MR imaging with a T2-weighted TSE sequence can be regarded as equal to spiral CT in the detection of lymph adenopathy and the demonstration of focal organ lesions. In addition to the absence of ionizing radiation, the advantage of MR imaging is that there is no necessity for oral or intravenous administration of contrast agent.     

Delayed gadolinium‐enhanced magnetic resonance imaging (dGEMRIC) of hip joint cartilage in femoroacetabular impingement (FAI): Are pre‐ and postcontrast imaging both necessary?

The purpose of this study was to assess if delayed gadolinium MRI of cartilage using postcontrast T₁ (T_1Gd) is sufficient for evaluating cartilage damage in femoroacetabular impingement without using noncontrast values (T₁₀). T_1Gd and ΔR₁ (1/T_1Gd ? 1/T₁₀) that include noncontrast T₁ measurements were studied in two grades of osteoarthritis and in a control group of asymptomatic young‐adult volunteers. Differences between T_1Gd and ΔR₁ values for femoroacetabular impingement patients and volunteers were compared. There was a very high correlation between T_1Gd and ΔR₁ in all study groups. In the study cohort with Tonnis grade 0, correlation (r) was ?0.95 and ?0.89 with Tonnis grade 1 and ?0.88 in asymptomatic volunteers, being statistically significant (P < 0.001) for all groups. For both T_1Gd and ΔR₁, a statistically significant difference was noted between patients and control group. Significant difference was also noted for both T_1Gd and ΔR₁ between the patients with Tonnis grade 0 osteoarthritis and those with grade 1 changes. Our results prove a linear correlation between T_1Gd and ΔR₁, suggesting that T_1Gd assessment is sufficient for the clinical utility of delayed gadolinium MRI of cartilage in this setting and additional time‐consuming T₁₀ evaluation may not be needed. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Diffusion-weighted imaging as part of hybrid PET/MRI protocols for whole-body cancer staging: Does it benefit lesion detection?

Purpose

Positron emission tomography/magnetic resonance imaging (PET/MRI) requires efficient scan protocols for whole-body cancer staging. The aim of this study was to evaluate if the application of diffusion-weighted MR imaging (DWI) results in a diagnostic benefit for lesion detection in oncologic patients if added to a whole-body [18F]-fluorodesoxyglucose ([18F]-FDG) PET/MRI protocol.

Methods

25 consecutive oncologic patients (16 men, 9 women; age 57 ± 12 years) prospectively underwent whole-body [18F]-FDG-PET/MRI including DWI on a hybrid PET/MRI scanner. A team of two readers assessed [18F]-FDG PET/MRI without DWI for primary tumors and metastases. In a second session, now considering DWI, readers reassessed [18F]-FDG PET/MRI accordingly. Additionally, the lesion-to-background contrast on [18F]-FDG PET and DWI was rated qualitatively (0, invisible; 1, low; 2, intermediate; 3, high). Wilcoxon's signed-rank test was performed to test for differences in the lesion-to-background contrast.

Results

49 lesions were detected in 16 patients (5 primaries, 44 metastases). All 49 lesions were concordantly detected by [18F]-FDG PET/MRI alone and [18F]-FDG PET/MRI with DWI. The lesion-to-background contrast on DWI compared to [18F]-FDG PET was rated lower in 22 (44.9%) of 49 detected lesions resulting in a significantly higher lesion-to-background contrast on [18F]-FDG PET compared to DWI (P = 0.001).

Conclusions

DWI as part of whole-body [18F]-FDG PET/MRI does not benefit lesion detection. Given the necessity to optimize imaging protocols with regard to patient comfort and efficacy, DWI has to be questioned as a standard tool for whole-body staging in oncologic PET/MRI.     

Ionising radiation exposure from medical imaging – A review of Patient's (un) awareness

IntroductionMedical imaging is the main source of artificial radiation exposure. Evidence, however, suggests that patients are poorly informed about radiation exposure when attending diagnostic scans. This review provides an overview of published literature with a focus on nuclear medicine patients on the level of awareness of radiation exposure from diagnostic imaging.MethodsA review of available literature on awareness, knowledge and perception of ionising radiation in medical imaging was conducted. Articles that met the inclusion criteria were subjected to critical appraisal using the Mixed Methods Appraisal Tool.Results140 articles identified and screened for eligibility, 24 critically assessed and 4 studies included in synthesis. All studies demonstrated that patients were generally lacking awareness about radiation exposure and highlighted a lack of communication between healthcare professionals and patients with respect to radiation exposure.ConclusionStudies demonstrate a need to better inform patients about their radiation exposure, and further studies focusing on nuclear medicine patients are particularly warranted.Implications for practiceAdequate and accurate information is crucial to ensure the principle of informed consent is present.     

Synthesis and evaluation of radioiodinated (S,S)-2-(α-(2-iodophenoxy)benzyl)morpholine for imaging brain norepinephrine transporter

Purpose Abnormality of the brain norepinephrine transporter (NET) has been reported in several psychiatric and neuronal disorders. Since NET is an important target for the diagnosis of these diseases, the development of radiopharmaceuticals for imaging of brain NET has been eagerly awaited. In this study, we synthesized (S,S)-2-(α-(2-iodophenoxy)benzyl)morpholine [(S,S)-IPBM], a derivative of reboxetine iodinated at position 2 of the phenoxy ring, and evaluated its potential as a radiopharmaceutical for imaging brain NET using SPECT.Methods (S,S)-^123/125I-IPBM was synthesized in a halogen exchange reaction. The affinity and selectivity of (S,S)-IPBM for NET was measured by assaying the displacement of ³H-nisoxetine and (S,S)-¹²⁵I-IPBM from the binding site in rat brain membrane, respectively. The biodistribution of (S,S)-¹²⁵I-IPBM was also determined in rats. Furthermore, SPECT studies with (S,S)-¹²³I-IPBM were carried out in the common marmoset.Results (S,S)-¹²⁵I-IPBM was prepared with high radiochemical yields (65%) and high radiochemical purity (>98%). (S,S)-IPBM showed high affinity and selectivity for NET in the binding assay experiments. In biodistribution experiments, (S,S)-¹²⁵I-IPBM showed rapid uptake in the brain, and the regional cerebral distribution was consistent with the density of NET. The administration of nisoxetine, a selective NET-binding agent, decreased the accumulation of (S,S)-¹²⁵I-IPBM in the brain, but the administration of selective serotonin transporter and dopamine transporter binding agents caused no significant changes in the accumulation. Moreover, (S,S)-¹²³I-IPBM allowed brain NET imaging in the common marmoset with SPECT.Conclusion These results suggest that (S,S)-¹²³I-IPBM is a potential SPECT radiopharmaceutical for imaging brain NET.     

Therapy-induced bone changes in oncology imaging with 18F-sodium fluoride (NaF) PET–CT

Annals of Nuclear Medicine - 18F-Sodium fluoride (18F-NaF) is a PET tracer that is mostly used in the evaluation of bone metastasis in oncology cases. Recently, 18F-NaF PET/CT is gaining wide...