乏氧显像剂及乏氧显像的临床应用

肿瘤组织乏氧是恶性肿瘤的一个重要生物学特征,肿瘤中乏氧细胞存在于实体瘤中是常见现象。乏氧显像是检测肿瘤乏氧的非创伤的方法,本文简要介绍了乏氧显像剂研究现状及其在肿瘤放疗中的应用。     

肿瘤乏氧组织显像剂的研究进展

乏氧组织显像剂能选择性地滞留在乏氧组织或细胞中,通过无创性的核医学正电子发射体层摄影术/单光子发射计算机体层摄影术可评价实体肿瘤缺氧状态.一些显像剂适宜进行乏氧显像并能很好地反映肿瘤乏氧及其程度等情况,这些信息在肿瘤的临床诊断决策中起到重要作用.     

PET乏氧显像在预测肿瘤乏氧及指导临床治疗中的应用进展

放射性核素标记的乏氧显像是评估肿瘤乏氧程度的重要方法, 乏氧显像剂可以选择性地滞留于乏氧组织内, 直观反映乏氧的部位和乏氧的程度, 对肿瘤诊断、分期、疗效监测及预后评估等有指导意义, 同时也为临床选择及调整肿瘤治疗方案提供了客观依据。笔者主要对肿瘤乏氧PET显像近年来在临床研究中的进展及与肿瘤乏氧相关的治疗进展进行综述。     

乏氧组织显像剂研究最新进展

乏氧组织显像剂能选择性地滞留在乏氧组织或细胞中,并通过核医学显像探测组织缺氧及其程度。乏氧显像能直接提供任何器官中组织存活但有功能障碍的依据,这些信息在临床诊断决策中起到重要作用,尤其是在心、脑血管疾病和实体瘤的诊断方面。本文简要介绍乏氧组织显像剂与乏氧显像的特点及其研究的最新进展。     

18F-FMISO PET在肿瘤诊疗中的应用

肿瘤乏氧细胞的存在是影响肿瘤生物学特性的重要因素之一,它不仅使肿瘤本身更具侵袭性,而且能引起肿瘤细胞对放化疗的抗拒性。因此,在对肿瘤进行治疗前,有必要检测其乏氧程度。采用体外无创伤非侵入性方法评估肿瘤的乏氧性具有重要的临床意义,其中乏氧显像剂的测定在临床应用较广泛。乏氧显像剂大致可分为硝基咪唑类和非硝基咪唑类两大类,其中^18F-氟硝基咪唑（^18F-fluoromisonidazole,^18F-FMISO）已广泛用于临床研究,现就这方面工作简要综述如下。     

99mTc-HL91乏氧显像探测肿瘤乏氧状态的研究进展

乏氧显像剂99mTc-HL91能选择性地浓集于肿瘤的乏氧组织或细胞中,通过核医学显像探测肿瘤组织的乏氧,能直接提供肿瘤组织乏氧及其乏氧程度和分布的证据,不仅能用于恶性肿瘤的早期诊断,还能动态监测肿瘤组织乏氧状态,为临床诊断和治疗决策提供重要信息。     

肿瘤乏氧组织显像剂研究进展

用肿瘤乏氧组织显像剂检测肿瘤氧水平对肿瘤乏氧的诊断、指导治疗和疗效的评价具有很大的实用价值,并日益受到重视。尽管多年来已先后合成卤素元素(82Br、18F、131I、123I)和99mTc标记的硝基咪唑类化合物及非硝基咪唑化合物,但至今尚无一种理想的肿瘤乏氧组织显像剂,故新的显像剂的研制与开发是推动肿瘤乏氧组织显像技术发展的关键。     

肿瘤乏氧组织显像剂研究进展

用肿瘤乏氧组织显像剂检测肿瘤氧水平对肿瘤乏氧的诊断、治疗和疗效的评价具有很大的实用价值，并日益受到重视。尽管我年来已先后合成卤素元素（＾６２Ｂｒ、＾１８Ｆ、＾１３１Ｉ、＾１２２Ｉ）和＾９９ｍＴｃ档记的硝基咪唑类化合物及非硝基咪唑化合物，但至含尚无一种理想的肿瘤乏氧组织显像剂，故新的显像剂的研制与开发是推动肿瘤乏氧组织显像技术发展的关键。     

肿瘤乏氧放疗增敏剂研究进展

研究表明,肿瘤的生长是无序的生长,血管生成不充分,所以人体实体瘤大多存在氧缺乏区域,这一区域的肿瘤细胞抵抗电离辐射的能力超过含氧量正常的肿瘤细胞的2～3倍,其主要原因是减少了氧自由基对DNA增殖的损伤。实体瘤乏氧是放疗失败的主要原因,克服乏氧所导致的放疗抵抗是提高肿瘤治疗效果的一个重要途径。     

除FDG以外的用于肿瘤PET显像的18F标记物

综述了除FDG以外的用于肿瘤PET显像的18F标记物的研究和应用.这些18F标记物主要包括与相应受体结合的18F标记的蛋白质和多肽,18F标记的乏氧显像剂,用于评价基因治疗的18F标记物等.此外,还介绍了用于诊断不同恶性肿瘤的18F标记的组织特异性PET显像剂.     

Stress MR imaging for evaluation of popliteal artery entrapment

The popliteal artery entrapment (PAE) syndrome has been recognized as a cause of arterial occlusion in young people. It is the result of an anomaly of the relationship between the popliteal artery and the gastrocnemius muscle. Eight young healthy volunteers (16 legs) and six patients (10 legs) with suspected PAE underwent magnetic resonance (MR) imaging. Gradient-echo images were obtained in axial planes with the leg at rest and during active plantar flexion against resistance. Imaging at rest allowed identification of PAE signs in only one leg, which had an anomalous medial course of the popliteal artery. In the other cases, only the stress technique was able to show signal loss in the popliteal artery due to muscular compression (two legs) or the presence of accessory muscle slip around the vessel (two legs), as confirmed at surgery. MR imaging is therefore a useful technique for the diagnosis of PAE because of its capability of combining information obtainable with other modalities.     

MR imaging of muscle and tender points in fibromyalgia

Fibromyalgia is a syndrome manifested by chronic, diffuse muscu-loskeletal aching and soreness, palpable muscle tender points, and other symptoms. Standardized clinical diagnostic criteria have recently been developed. Skeletal muscle has been postulated as the end organ in this disease. Biochemical, histologic, electromyographic, and conventional radiographic studies have demonstrated no definitive abnormality. This study sought to establish whether magnetic resonance (MR) imaging could demonstrate any abnormality in these patients. Eighteen patients were entered in the study, 14 of whom were able to complete their examinations. T1 -weighted, T2-weighted, gradient-echo, and STIR (short-tau inversion-recovery) sequences were performed in all patients, with selected patients examined with T1weighted, gadopentetate dimeglu-mine-enhanced sequences. The trapezius and suboccipital regions were imaged in patients who, clinically, had active fibro-myalgia. No abnormalities could be detected. The authors conclude that the conventional MR imaging used in this study was unable to depict any primary skeletal muscle abnormality in fibromyalgia.     

Uterine contractions: Possible diagnostic pitfall at MR imaging

A total of 206 nongravid patients with various gynecologic problems underwent pelvic magnetic resonance (MR) examinations that included both sagittal T2-weighted and contrast agent–enhanced T1-weighted images. MR images were retrospectively reviewed to identify changes in endometrial configuration on serial images obtained during the same MR examination. In 20 MR examinations (all in women of reproductive age), endometrial distortion due to myometrial bulging was noted on T2-weighted or contrast-enhanced T1-weighted images. It was absent on other MR images obtained at different times. Myometrial bulging exhibited low signal intensity in 18 examinations. The finding resembled adenomyosis or leiomyoma on T2-weighted or contrast-enhanced T1-weighted images. These results evidence the presence of transient myometrial bulging and transient low-intensity myometrium in the nongravid uterus. This phenomenon is thought to represent uterine contraction. Clinicians should be aware of the potential presence of transient low-signal-intensity myometrial bulging that could present diagnostic problems in the normal uterus.     

Controversies in cervical spine imaging in trauma patients

No area of emergency radiology has generated as much discussion in recent years as the subject of cervical spine imaging for trauma patients. This review will be in three parts. The first will examine the indications for cervical imaging and will focus on those factors that make patients at high risk or low risk for cervical injury. The second part will discuss the merits of radiography and computed tomography as the main screening diagnostic examination. In addition to the roles of each modality in the evaluation process, such factors as efficacy of diagnosis, time (duration) of study, and cost will be discussed. Finally, the third part will explore the methods currently employed to clear the cervical spine in comatose patients.Presented at the Annual Meeting of the American Society of Emergency Radiology, Las Vegas, Nevada, 22–25 October, 2003     

Brodie Abscess: MR imaging appearance in 10 patients

The magnetic resonance (MR) imaging features of Brodie abscess have not yet been fully evaluated. Ten patients with Brodie abscess, eight of long bone and two of vertebra, were studied with MR imaging. Long bone abscess had a characteristic “target” appearance with four layers: (a) a center with low signal intensity on T1-weighted images and high signal intensity on T2-weighted and STIR (short-inversion-time inversion recovery) images, (b) an inner ring isointense to muscle on T1-weighted images and with high signal intensity on T2-weighted and STIR images, (c) an outer ring hypoin-tense on all images, and (d) a peripheral halo hypointense on T1-weighted images. In six of eight cases, a soft-tissue mass was found. The two vertebral abscesses had a less specific appearance, with low signal intensity on T1-weighted images and high signal intensity on T2-weighted and STIR images. Only the peripheral halo was clearly identified in both cases.     

Dynamic contrast-enhanced MR imaging assessment of vascularized free fibular grafts

Magnetic resonance (MR) imaging may be a noninvasive method for assessing perfusion of vascularized bone grafts placed for treatment of avascular necrosis. One proximal femur of seven beagles was devascularized, with insertion of a vascularized fibular graft. MR imaging at 1 week (seven dogs) and 6 weeks (five dogs) after surgery included pre- and postcontrast spin-echo sequences, unenhanced twodimensional time-of-flight (TOF) vascular imaging, and dynamic gradient-echo imaging during infusion of gadolinium. Relative signal intensity values of selected regions obtained from the dynamic gradientecho images were plotted as percent enhancement versus time. In the operated hip, MR imaging did not show enhancement in six of seven femoral heads and greater trochanters at 1 week after surgery, with similar results after 6 weeks. MR imaging of fibular grafts 6 weeks after surgery showed an initial rapid increase in enhancement and a subsequent slower increase in five of five dogs, although no enhancement was seen in six of seven dogs at 1 week. These findings contrasted with a rapid initial increase in enhancement followed by slow decline in non-operated hips. Two-dimensional TOP imaging did not show the vascular pedicle of the graft in any dog. Findings of radionuclide bone scanning performed 1 week after surgery were consistent with devascularization of the operated femur and fibular graft. However, tetracycline distribution and histologic findings confirmed the viability of five of five grafts within the devascularized femurs 6 weeks after surgery. Thus, dynamic contrast-enhanced MR imaging at 6 weeks after surgery is valuable for assessing vascular bone graft perfusion, while similar imaging at 1 week may suggest otherwise.     

Right-side aortic arch with aneurysm of aberrant left subclavian artery: MR imaging appearance.

Reports of aneurysms of the subclavian artery in both normal and anomalous aortic arches have been rare. The authors describe a patient with a right-side aortic arch and an aneurysm of the aberrant left subclavian artery, which, to the authors' knowledge, is a previously unreported association. At presentation, the aneurysm appeared as a calcified left superior mediastinal mass. Magnetic resonance imaging enabled preoperative diagnosis and guided surgical planning.     

MR angiography of congenital heart disease: Value of segmented two-dimensional inflow technique and maximum-intensity-projection display

Magnetic resonance (MR) angiography of the cardiovascular system was evaluated in 41 patients with congenital heart disease by using a two-dimensional (2D) inflow technique based on a magnetization-prepared gradient-echo pulse sequence with segmented k-space data acquisition and electrocardiographic gating at 0.5 T. Inversion and saturation prepulses were used to suppress stationary tissue and enhance intravascular signal. Presaturation slabs were applied where certain vascular structures had to be suppressed. Sequence parameters were optimized by evaluating signal intensity and contrast characteristics for various flip angles and inversion and saturation delay times. The heart and intrathoracic vasculature were encompassed with 40–50 overlapping sections. Both 2D angiograms and maximum-intensity-projection images were evaluated. Combining data sets acquired in the sagittal and transverse orientations provided the most satisfactory information about the pulmonary arteries. The highest signal-to-noise ratios were obtained with a flip angle of 65° and short prepulse delay times. Two-dimensional MR angiography can provide useful diagnostic information but requires a thorough understanding of in-plane and hemodynamically induced signal intensity changes.     

Adrenal tissue characterization with 0.5-T MR imaging: Value of T2*-weighted images

The authors investigated the value of magnetic resonance (MR) imaging at 0.5 T for distinguishing adrenal adenomas from adrenal metastases. The series included 23 adrenal adenomas (18 nonhyperfunctioning, five hyperfunctioning) and 23 adrenal metastases from various organs. Adrenal tumor–liver signal intensity ratios on T1-, T2-, and T2*-weighted images were calculated for adrenal tissue characterization. Adrenal adenomas were more precisely distinguished from adrenal metastases on T2*-weighted images (21 of 23, 91%) than on T2-weighted images (15 of 23, 65%). T1-weighted images were not useful for this distinction. In conclusion, T2*-weighted images were better than routine T2-weighted images for distinguishing adrenal adenomas from adrenal metastases. It can be postulated that the total signal intensity of adrenal adenomas, which contain some fat components, decreased on T2*-weighted images because of an out-of-phase effect.