立体定向放射外科治疗癫痫的剂量-体积与脑水肿的相关性研究

目的 研究立体定向放射外科治疗低剂量照射癫痫灶引起的放射性脑水肿与治疗剂量和体积的相关性.方法 回顾性分析1999年10月-2005年5月山东万杰医院及重庆大坪医院γ刀中心治疗的各种类型难治性癫痫患者136例.对136例患者采用立体定向放射治疗的靶区体积和剂量进行对比分析,绘出散点图,并进行相关数据的Logistic回归性分析,得出一定剂量、体积范围内预测放射性脑水肿发生概率的方程.结果 立体定向放射外科的靶区中心剂量＞ 18 Gy或靶区体积＞ 30 cm3时,发生放射性脑水肿反应的可能性最大.回归性分析后得到预测方程,经验证该方程的正确率为94.7％.结论 利用靶区体积和剂量作为参数,通过相关性分析得到的方程,可以预测立体定向放射外科治疗癫痫患者后发生放射性脑水肿的概率,该方程有一定的临床参考价值.     

526例颅内功能性疾病立体定向放射外科治疗核磁影像定位的护理

目的：报道526例颅内功能性疾病在采用核磁1．5场强定位过程中,护理人员因人因病实施全方位的护理,使病人安全、顺利地完成影像定位,为立体定向放射外科治疗提供了可靠的保证。方法采取多方位按年龄、性别、根据病情的特殊性,选择合适的护理方式。结果通过护理技能,基本完成526例定位的护理工作,只有1名未能完成定位而放弃治疗,总体成功率为99．18％。结论以高度的责任心和事业心,娴熟的护理技术,为各类难治性颅脑疾病的病人带来了福音。     

机器人无框架立体定向仪在顽固性癫痫定位和治疗方面的应用

目的探讨机器人辅助无框架立体定向系统置入深部电极和射频热凝毁损的方法及效果。方法对7例额、颞发作间期存在痫样放电的顽固性癫痫患者,采用机器人辅助无框架立体定向系统经额向双侧颞叶内侧置入深部电极,记录深部电极脑电图。深部电极脑电图记录到颞叶内侧为临床发作或电发作起源灶者,遂行机器人立体定向系统经额入路射频热凝颞叶深部结构;并对6例同意进行神经干细胞移植者移植干细胞。结果术后24～52个月,7例随访按照Engel分级系统Ⅰ级4例(其中Ⅰa级3例、Ⅰd级1例),Ⅳa级2例、Ⅳc级1例。未有术后神经功能明显下降。结论机器人辅助立体定向系统置入深部电极、射频热凝毁损和移植神经干细胞安全、有效、方便、快捷,部分额、颞叶顽固性癫痫患者对立体定向射频热凝和神经干细胞移植治疗反应良好。     

机器人无框架立体定向仪在顽固性癫痫定位和 治疗方面的应用

目的探讨机器人辅助无框架立体定向系统置入深部电极和射频热凝毁损的方法及效果。方法对7例额、颞发作间期存在痫样放电的顽固性癫痫患者,采用机器人辅助无框架立体定向系统经额向双侧颞叶内侧置入深部电极,记录深部电极脑电图。深部电极脑电图记录到颞叶内侧为临床发作或电发作起源灶者,遂行机器人立体定向系统经额入路射频热凝颞叶深部结构;并对6例同意进行神经干细胞移植者移植干细胞。结果术后24～52个月,7例随访按照Engel分级系统Ⅰ级4例(其中Ⅰa级3例、Ⅰd级1例),Ⅳa级2例、Ⅳc级1例。未有术后神经功能明显下降。结论机器人辅助立体定向系统置入深部电极、射频热凝毁损和移植神经干细胞安全、有效、方便、快捷,部分额、颞叶顽固性癫痫患者对立体定向射频热凝和神经干细胞移植治疗反应良好。     

A hybrid method of attenuation correction for positron emission tomography brain studies

A hybrid method for attenuation correction (HAC) in positron emission tomography (PET) brain studies is proposed. The technique requires the acquisition of two short (1 min) transmission scans immediately before or after the emission study, with the patient and the head fixation system in place and after removing the patient from the scanner with the head fixation system alone. The method combines a uniform map of attenuation coefficients for the patient's head with measured attenuation coefficients for the head fixation system to generate a hybrid attenuation map. The HAC method was calibrated on 30 PET cerebral studies for comparison with the conventional measured attenuation correction method by ROI analysis. Average differences of less than 3% were found for cortical and subcortical regions. The HAC technique is particularly suitable in a PET clinical environment, allowing a reduction of the total study time, greater comfort for patients and an increase in patient throughput.     

Repeated fluorodeoxyglucose positron emission tomography of the brain in infants with suspected hypoxic-ischaemic brain injury

Positron emission tomography (PET) permits the study of cerebral metabolism in vivo. We performed repeated PET studies with fluorine-18 fluorodeoxyglucose (FDG) as a tracer to measure cerebral glucose metabolism for estimation of neurological prognosis in infants with suspected hypoxic-ischaemic brain injury. Fourteen infants (gestational age 35.3 ± 4.67 weeks) were examined during the neonatal period (at age 38.4±2.7 weeks) and again at the age of 3.5±0.7 months; one further infant was studied only once at the age of 2.5 months. All children also underwent ultrasound examinations. Electroencephalography and computed tomography or magnetic resonance imaging were performed according to their clinical condition and their neurological development has been followed. FDG accumulated most actively in the subcortical areas (thalami, brainstem and cerebellum) and the sensorimotor cortex during the neonatal period. The repeated PET study showed that the uptake of FDG was markedly high and increased in all brain sections of infants with normal development (n=11), whereas those with delayed development (n=4) had significantly lower values (P0.005). Correspondence to: H. Suhonen-Polvi     

Delayed cerebral radionecrosis with a high uptake of 11C-methionine on positron emission tomography and 201Tl-chloride on single-photon emission computed tomography

A 47-year-old woman, who 2.5 years previously had undergone resection of a malignant astrocytoma of the left temporal lobe followed by radiotherapy, was found to have a mass in the left frontal lobe. This showed high uptake of thallium-201 (²⁰¹Tl) on single-photon emission computed tomography and ¹¹C-methionine on positron-emission tomography, suggesting recurrent tumour. Histological examination of the resected lesion, however, revealed it to be radionecrosis. This case thus illustrates a diagnostic pitfall in the use of these investigations for distinguishing radionecrosis from recurrent malignant glioma. Received: 19 September 1997 Accepted: 16 October 1997     

Proton therapy dosimetry using positron emission tomography

Protons deposit most of their kinetic energy at the end of their path with no energy deposition beyond the range, making proton therapy a valuable option for treating tumors while sparing surrounding tissues. It is imperative to know the location of the dose deposition to ensure the tumor, and not healthy tissue, is being irradiated. To be able to extract this information in a clinical situation, an accurate dosimetry measurement system is required. There are currently two in vivo methods that are being used for proton therapy dosimetry: (1) online or in-beam monitoring and (2) offline monitoring, both using positron emission tomography (PET) systems. The theory behind using PET is that protons experience inelastic collisions with atoms in tissues resulting in nuclear reactions creating positron emitters. By acquiring a PET image following treatment, the location of the positron emitters in the patient, and therefore the path of the proton beam, can be determined. Coupling the information from the PET image with the patient's anatomy, it is possible to monitor the location of the tumor and the location of the dose deposition. This review summarizes current research investigating both of these methods with promising results and reviews the limitations along with the advantages of each method.     

Fluorinated tracers for imaging cancer with positron emission tomography

2-[¹⁸F]fluoro-2-deoxy-d-glucose (FDG) is currently the only fluorinated tracer used in routine clinical positron emission tomography (PET). Fluorine-18 is considered the ideal radioisotope for PET imaging owing to the low positron energy (0.64 MeV), which not only limits the dose rate to the patient but also results in a relatively short range of emission in tissue, thereby providing high-resolution images. Further, the 110-min physical half-life allows for high-yield radiosynthesis, transport from the production site to the imaging site and imaging protocols that may span hours, which permits dynamic studies and assessment of potentially fairly slow metabolic processes. The synthesis of fluorinated tracers as an alternative to FDG was initially tested using nucleophilic fluorination of the molecule, as performed when radiolabelling with iodine-124 or bromide-76. However, in addition to being long, with multiple steps, this procedure is not recommended for bioactive molecules containing reactive groups such as amine or thiol groups. Radiochemical yields are also often low. More recently, radiosynthesis from prosthetic group precursors, which allows easier radiolabelling of biomolecules, has led to the development of numerous fluorinated tracers. Given the wide availability of ¹⁸F, such tracers may well develop into important routine tracers. This article is a review of the literature concerning fluorinated radiotracers recently developed and under investigation for possible PET imaging in cancer patients. Two groups can be distinguished. The first includes generalist tracers, i.e. tracers amenable to use in a wide variety of tumours and indications, very similar in this respect to FDG. These are tracers for non-specific cell metabolism, such as protein synthesis, amino acid transport, nucleic acid synthesis or membrane component synthesis. The second group consists of specific tracers for receptor expression (i.e. oestrogens or somatostatin), cell hypoxia or bone metabolism.     

Cerebral glucose utilization in pediatric neurological disorders determined by positron emission tomography

We measured local cerebral glucose utilization in 19 patients with Lennox-Gastaut syndrome (LG), partial seizures (PS), atypical and classical phenylketonuria (PKU), Leigh disease, and subacute sclerosing panencephalitis (SSPE), using positron emission tomography (PET). The mean values of regional glucose utilization in interictal scans of LG were significantly reduced in all brain regions when compared with that of PS (P<0.005). PET studies of glucose utilization in LG revealed more widespread hypometabolism than in PS. Two siblings with dihydropteridine reductase deficiency, a patient with classical PKU, and a boy with cytochrome c oxidase deficiency showed reduced glucose utilization in the caudate and putamen. A marked decrease in glucose utilization was found in the cortical gray matter of a patient with rapidly progressive SSPE, despite relatively preserved utilization in the caudate and putamen. The PET study of a patient with slowly progressive SSPE revealed patterns and values of glucose utilization similar to those of the control. Thus, PET provided a useful clue toward understanding brain dysfunction in LG, PS, PKU, Leigh disease, and SSPE.     

Alternative positron emission tomography with non-conventional positron emitters: effects of their physical properties on image quality and potential clinical applications

The increasing amount of clinically relevant information obtained by positron emission tomography (PET), primarily with fluorine-18 labelled 2-deoxy-2-fluoro-d-glucose, has generated a demand for new routes for the widespread and cost-efficient use of positron-emitting radiopharmaceuticals. New dual-head single-photon emission tomography (SPET) cameras are being developed which offer coincidence detection with camera heads lacking a collimator or SPET imaging with specially designed collimators and additional photon shielding. Thus, not only satellite PET imaging units but also nuclear medicine units investing in these new SPET/PET systems need to examine all available alternatives for rational radionuclide supplies from host cyclotrons. This article examines 25 ”alternative” positron-emitting radionuclides, discusses the impact of their decay properties on image quality and reviews methods for their production as well as for their application in imaging techniques.     

Measurement of absolute bone blood flow by positron emission tomography

A method of measuring bone blood flow has been developed using ¹⁸F sodium fluoride and positron emission tomography. The blood flow levels are in line with those obtained experimentally from microsphere embolisation. This investigative method could be applied to elucidate a number of clinical questions involving bone perfusion.     

MRI and 18F-fluorodeoxyglucose positron emission tomography in hemimegalencephaly

We report hemimegalencephaly in a 44-year-old woman with mental retardation, epilepsy and a mild hemiparesis. In addition to typical findings on MRI, 2-deoxy-2[¹⁸F]fluorodeoxyglucose positron-emission tomography (PET) demonstrated glucose hypometabolism of the affected hemisphere. The results of PET have been coregistered with morphological information from the MRI studies by image fusion. Received: 14 December 1999/Accepted: 15 February 2000     

Feasibility of imaging photodynamic injury to tumours by high-resolution positron emission tomography

One early effect of the treatment of tumours by the new modality photodynamic therapy (PDT) is a reduction in tumour glucose levels. We have employed the widely used positron-emitting glucose analogue flurorine-18 fluoro-2-deoxy-d-glucose ([¹⁸F]-FDG), to determine whether, in principle, PDT-induced injury might be delineated non-invasively and quantitatively by positron emission tomography (PET). The scanner was of the high-density avalanche-chamber (HIDAC) type with a resolution of 2.6 mm. Subcutaneous T50/80 mouse mammary tumours, sensitised by haematoporphyrin ester, were illuminated by graded doses of interstitial 630 nm light. Thirty hours later, any remaining viable tumour was detected (a) by region-of-interest analysis of the PET images and (b) by gamma counting the excised tumour. PET measurements of % uptake of [¹⁸F]-FDG into tumour correlated closely with ex vivo gamma counting (slope=0.976, r²⁼0.995), validating the in situ method. Uptake into untreated, control tumours was 3.8%±1.1% of the injected activity. Uptake of [¹⁸F]-FDG into treated tumours decreased by 0.7% for every 100 mm³ reduction in remaining viable histological volume. Outcome was further compared with that measured by (a) T2-weighted proton imaging on a 4.7-T magnetic resonance imaging (MRI) system and (b) histological analysis of subsequently sectioned tumours. PET using [¹⁸F]-FDG described the absolute volume of surviving tumour histological mass to the same degree as high-resolution MRI. The conclusion of these initial studies is that PET with [¹⁸F]-FDG, although non-specific, quantitatively described at early times the extent of tumour destruction by PDT. Received 1 April and in revised form 9 May 1998