Evaluation of the postoperative spine: spinal instrumentation and fusion

Spinal instrumentation is used in a variety of clinical settings ranging from degenerative spine disease to tumors and infection. The primary goal is to provide internal fixation in a region of the spine to facilitate development of an osseous fusion. Hardware is often used to improve alignment and reduce deformities. It is selected based on the anatomic region, ease of implantation and postoperative care, and physician preference. This article will review the basic components of hardware used in the cervical, thoracic, and lumbar spine for anterior and/or posterior fusion. It will not review specific hardware in detail but will discuss general concepts applicable to the various types and strengths and weaknesses of the components. Evaluation of fusion mass will be considered, including some of the current controversies and the current accepted practices.     

SPECT和CT融合骨显像在小儿神经母细胞瘤中的应用

目的探讨SPECT和CT融合骨显像在探测小儿神经母细胞瘤（NB）转移性骨肿瘤中的临床价值。方法回顾性分析24例NB患儿,均行全身平面骨显像及局部SPECT和CT融合骨显像。将骨病灶显示的清晰度分为5级（不可见、模糊、可见、清晰、非常清晰）,良恶性诊断的确定性分为3级（不确定、可以确定、十分确定）,诊断效能指标包括灵敏度、特异性及准确性。对显像图像在骨病灶的清晰度显示、良恶性确定性诊断及探测恶性骨病灶的诊断效能方面进行分析,采用秩和检验及χ^2检验进行比较。结果24例NB患儿,全身平面骨显像发现骨病灶72个,有5个骨病灶未能显示,SPECT和CT融合显像和单独SPECT显像均分别发现骨病灶77个。对骨病灶的清晰度显示SPECT和CT融合显像,单独SPECT显像均优于平面显像（日值均为69．000,P均〈0．05）。平面显像和SPECT显像诊断恶性骨病灶的准确性分别为45．45％（35／77）和62．34％（48／77;χ^2=4．416,P〈0．05）,SPECT和CT融合诊断恶性骨病灶的灵敏度、特异性和准确性均较平面显像有提高,分别为82．35％（42／51）和53．19％（25／47）、88．46％（23／26）和40．00％（10／25）、84．42％（65／77）和45．45％（35／77）,χ^2=12．571,14．016和25．667,P均〈0．01。与SPECT显像的特异性（14／26,53．85％）和准确性（48／77,62．34％）相比,SPECT和cT融合诊断恶性骨病灶的特异性和准确性提高（χ^2=7．589,9．606,P均〈0．01）,两者间灵敏度差异无统计学意义（χ^2=2．942,P〉0．05）。SPECT和CT融合显像骨病灶良恶性的确定性诊断优于SPECT（H=28．000,P〈0．05）和平面显像（H=21．000,P〈0．05）。结论SPECT和CT融合骨显像能探测到NB患儿更多的骨病灶,是一种较好的探测NB患儿转移性骨肿瘤的显像方法。     

Anatomical accuracy of hybrid SPECT/spiral CT in the lower spine

AIM: The anatomical accuracy of hardware-based registration of skeletal single photon emission computed tomography (SPECT) and X-ray computerized tomography (CT) has as yet not been studied. The aim of this study was to evaluate this variable in the lower spine for a newly introduced hybrid SPECT/spiral-CT camera. METHODS: In 22 patients referred for degenerative joint disease or tumours, whole-body bone scintigraphy including hybrid SPECT/spiral CT of the lower spine was performed. Subsequent analyses were performed on these pairs of images as well as on data sets obtained after using a rigid automated fusion procedure in addition. Two observers independently measured the distances between the visually determined centres of gravity of the CT and SPECT representation of the fourth and fifth lumbar vertebral body in the X-, Y- and Z-directions (X-, Y- and Z-distances). RESULTS: The distances determined by the two observers for the two vertebral bodies correlated significantly and were averaged for further analysis. For hybrid SPECT/spiral CT without consecutive automated registration, the mean X-, Y- and Z-distances were 1.6+/-1.9 mm, 1.7+/-1.3 mm and 0.9+/-0.5 mm, respectively. Additional automated registration lowered these values to 1.2+/-0.9 mm, 1.1+/-0.7 mm and 0.8+/-0.4 mm, respectively. The difference for the Y-distance proved statistically significant (P<0.05). Additional automated registration significantly reduced the number of subjects in whom at least one of the distances determined was greater than the SPECT pixel size of 4.6 mm from 14% (n=3) to 0% (P<0.05). CONCLUSION: Hardware-based fusion between skeletal SPECT and CT offers a nearly perfect data match in the lower spine. The additional use of a tool for automated rigid registration has the potential to reduce the error of alignment even further and may be useful in patients with reduced compliance leading to movements between the two examinations.     

Bone SPECT of the spine: a comparison of attenuation correction techniques.

Image artifacts from variable self-attenuation are recognized as major sources of diagnostic uncertainty in SPECT. For myocardial perfusion studies, an attenuation map is often obtained from a separate transmission study. However, for many applications such as bone SPECT, it has been believed to be unnecessary to obtain a transmission study to correct for the effects of attenuation. We have had significant success in clinical management of lower spine pain using bone SPECT. This success has led us to consider SPECT for the management of cervical spine pain. Cervical spine reconstructions without attenuation correction are difficult to interpret, because the high attenuation in the mandible and skull tends to decrease estimates of activity of the upper cervical spine, and the lower cervical/upper thoracic vertebrae are obscured by the shoulders. We present a technique that uses downscatter to provide attenuation correction for these acquisitions and compare it with other recognized attenuation correction techniques. METHODS: An emission study is acquired using two windows: one for obtaining the photopeak data and another for obtaining the downscattered photons. A body outline is estimated from these datasets using a projection data thresholding method. From this outline, a uniform attenuation map is created using attenuation coefficients appropriate for 99mTc in water (0.154 cm(-1)). These maps are used in SPECT reconstruction using ordered-subset expectation maximization (OSEM). This method is compared with (a) no attenuation correction (NC), (b) conventional Chang attenuation correction based on the interactive determination of the body outline from the 99mTc emission photopeak data (ChangAC) and (c) OSEM correction using attenuation maps estimated with a line source and fanbeam collimators (transAC). RESULTS: Patient studies using scatterAC demonstrated a significant improvement in the uniformity of estimated cervical spine uptake in normal patients, compared with either NC or ChangAC. Results using scatterAC were similar to those of transAC. We also observed significant improvement in uniformity using scatterAC in SPECT of the lower back in obese patients, as well as the relative limitations of scatterAC versus nonuniform, transmission-based attenuation correction. CONCLUSION: Comparisons with reconstructions using transmission data for estimating attenuation demonstrate that reasonable quantitative accuracy can be obtained in SPECT of the cervical spine using this simple attenuation estimate. Both scatterAC and transAC appear to provide consistent and expected uniform spine uptake in the cervical spines of normal patients.     

SPECT／CT对脊柱病变鉴别诊断的价值

目的评价SPECT／CT显像在脊柱病变鉴别诊断中的应用价值。方法对53例^99Tc^m-MDP全身骨显像脊柱呈放射性浓聚患者进行SPECT／CT显像,获得SPECT、CT及两者的融合图像。所有病灶均以病理学诊断及6个月以上的影像学随访为最终诊断结果,计算SPECT／CT融合图像的诊断效能。结果SPECT／CT骨显像诊断骨转移肿瘤的灵敏度为96．00％（24／25）,特异性为96．43％（27／28）,准确性为96．23％（51／53）,假阳性率为3．57％（1／28）,假阴性率为4．00％（1／25）,阳性预测值为96．00％（24／25）,阴性预测值为96．43％（27／28）。对脊柱浓聚灶诊断非转移性骨病变的灵敏度为96．43％（27／28）,特异性为96．00％（24／25）,准确性为96．23％（51／53）,假阳性率为4．00％（1／25）,假阴性率为3．57％（1／28）,阳性预测值为96．43％（27／28）,阴性预测值为96．00％（24／25）。结论SPECT／CT同机融合显像结合了CT的解剖定位功能与^99Tc^m-MDP骨显像的高灵敏度,可提高诊断的特异性和准确性,有助于对脊柱病变的鉴别诊断。     

Bone invasion in patients with oral cavity cancer: comparison of conventional CT with PET/CT and SPECT/CT

PURPOSE: To prospectively compare the accuracy of helical contrast material-enhanced computed tomography (CT) with that of CT and positron emission tomography (PET) combined and CT and single photon emission CT (SPECT) combined in the detection of bone invasion in patients scheduled to undergo surgery for clinically suspected oral cavity carcinoma with possible bone invasion, with surgical results as the reference standard. MATERIALS AND METHODS: This study had local ethical committee approval, and all patients gave written informed consent. Thirty-four consecutive patients (17 men, 17 women; mean age, 64.2 years; age range, 46.0-84.6 years) who were clinically suspected of having bone invasion from oral cavity carcinoma prospectively underwent helical contrast-enhanced CT, coregistered PET/CT, and coregistered SPECT/CT. Two radiologists assessed the contrast-enhanced CT images and two nuclear medicine physicians separately assessed the PET/CT and SPECT/CT images in consensus and without knowledge of the results of other imaging tests. The presence of bone involvement as suggested with an imaging modality was compared with histologic findings in the surgical specimen. RESULTS: With histologic findings as the standard of reference, the accuracy of SPECT/CT (88% [30 of 34 patients]) was lower than that of PET/CT and contrast-enhanced CT (94% [32 of 34 patients] and 97% [33 of 34 patients], respectively). Sensitivity was highest with PET/CT (100% [12 of 12 patients]), and specificity was highest with contrast-enhanced CT (100% [22 of 22 patients]). Fluorine 18 fluorodeoxyglucose (FDG) uptake seen on two sides of the same cortical bone was not a helpful imaging pattern for better identifying bone invasion in patients without evident cortical erosion on CT scans. CONCLUSION: The assessment of cortical erosion with contrast-enhanced CT and the CT information from PET/CT are the most reliable methods for detecting bone invasion in patients with oral cavity carcinoma. FDG uptake seen on PET/CT images does not improve identification of bone infiltration.     

3-D MRI/CT fusion imaging of the lumbar spine

Objective  

The objective was to demonstrate the feasibility of MRI/CT fusion in demonstrating lumbar nerve root compromise.     

Thoracic and lumbar spine fusion: postoperative radiologic evaluation

A retrospective review of 206 consecutive thoracic and lumbar fusions revealed a variety of surgical procedures performed for instability and malalignment after severe trauma. Stabilization procedures included insertion of 103 Harrington distraction and 15 Harrington compression rods, 84 Weiss spings, six Luque rods, and 10 miscellaneous plates and wires as single or multiple devices in combination with anterior and/or posterior fusions. Complications of surgical fusion included nine unhooked rods, six fatigue fractures of rods and springs, five overdistractions of vertebrae, four cases of severe kyphosis, and two failures of reduction. A meaningful postoperative radiologic evaluation can be accomplished only when indications for surgical techniques, their radiologic appearance, and possible complications are known.     

SPECT/CT融合显像对可疑骨转移灶的诊断效能

目的：评价SPECT/CT融合显像对可疑骨转移灶的诊断效能。方法回顾性分析64例恶性肿瘤患者经全身骨显像发现的96个可疑骨转移病灶,对可疑病灶行同机SPECT/CT融合显像,由两名核医学医师分别对SPECT、CT及SPECT/CT融合显像进行分析并评分,以病理学结果或6个月以上复查影像学及临床随访结果作为最终确诊依据。SPECT/CT融合显像对可疑病灶的诊断效能通过受试者工作特征曲线（ROC曲线）进行评价。结果 SPECT/CT显像诊断可疑骨转移灶的灵敏度、特异度、准确率、阳性预测值和阴性预测值分别为93．1%、86．8%、90．6%、91．5%和89．2%;ROC曲线下面积：SPECT/CT融合图像为0．956,CT图像为0．897,SPECT图像为0．710。结论 SPECT/CT融合显像较SPECT及CT显像具有较高的诊断效能。     

Small-animal SPECT and SPECT/CT: application in cardiovascular research

Preclinical cardiovascular research using noninvasive radionuclide and hybrid imaging systems has been extensively developed in recent years. Single photon emission computed tomography (SPECT) is based on the molecular tracer principle and is an established tool in noninvasive imaging. SPECT uses gamma cameras and collimators to form projection data that are used to estimate (dynamic) 3-D tracer distributions in vivo. Recent developments in multipinhole collimation and advanced image reconstruction have led to sub-millimetre and sub-half-millimetre resolution SPECT in rats and mice, respectively. In this article we review applications of microSPECT in cardiovascular research in which information about the function and pathology of the myocardium, vessels and neurons is obtained. We give examples on how diagnostic tracers, new therapeutic interventions, pre- and postcardiovascular event prognosis, and functional and pathophysiological heart conditions can be explored by microSPECT, using small-animal models of cardiovascular disease.     

Impact of 111In-DTPA-octreotide SPECT/CT fusion images in the management of neuroendocrine tumours

Purpose  Somatostatin receptor scintigraphy with [¹¹¹In]-diethylene triamine pentaacetate acid (DTPA)-octreotide is an accurate method for detecting neuroendocrine tumours (NETs) but often does not provide clear anatomical localisation of lesions. The aim of this study was to assess the clinical usefulness of anatomical-functional image fusion. Materials and methods  Fifty-four patients with known or suspected NET were included in the study. Planar and single-photon-emission computed tomography (SPECT) imaging was performed using a dual-head gamma camera equipped with an integrated X-ray transmission system, and the images were first interpreted alone by two nuclear medicine physicians and then compared with SPECT/CT fusion images together with a radiologist. The improvement provided by SPECT/CT in the interpretation of SPECT data alone and any modification in patientmanagement were recorded. Results  Fusion images improved SPECT interpretation in 23 cases, providing precise anatomical localisation of increased tracer uptake in 20 cases and disease exclusion in sites of physiological uptake in 5. In 10 patients, SPECT/CT allowed definition of the functional significance of lesions detected by diagnostic CT. SPECT/CT data modified clinical management in 14 cases by changing the diagnostic approach in 8 and the therapeutic modality in 6. Conclusions  Our study demonstrates that image fusion is clearly superior to SPECT alone, allowing precise localisation of lesions and reducing false-positive results.