A new methodological approach for PET implementation in radiotherapy treatment planning

In this paper, a new methodological approach to using PET information in radiotherapy treatment planning has been discussed. Computed tomography (CT) represents the primary modality to plan personalized radiation treatment, because it provides the basic electron density map for correct dose calculation. If PET scanning is also performed it is typically coregistered with the CT study. This operation can be executed automatically by a hybrid PET/CT scanner or, if the PET and CT imaging sets have been acquired through different equipment, by a dedicated module of the radiotherapy treatment planning system. Both approaches have some disadvantages: in the first case, the bore of a PET/CT system generally used in clinical practice often does not allow the use of certain bulky devices for patient immobilization in radiotherapy, whereas in the second case the result could be affected by limitations in window/level visualization of two different image modalities, and the displayed PET volumes can appear not to be related to the actual uptake into the patient. To overcome these problems, at our centre a specific procedure has been studied and tested in 30 patients, allowing good results of precision in the target contouring to be obtained. The process consists of segmentation of the biological target volume by a dedicated PET/CT console and its export to a dedicated radiotherapy system, where an image registration between the CT images acquired by the PET/CT scanner and a large-bore CT is performed. The planning target volume is contoured only on the large-bore CT and is used for virtual simulation, to individuate permanent skin markers on the patient.     

Simple and effective immobilization for radiation treatment of choroidal melanoma

At our institution, patients diagnosed with choroidal melanoma requiring external beam radiation therapy are treated with two 6 MV volumetric-modulated arcs delivering 50 Gy over 5 daily fractions. The patient is immobilized using an Orfit head and neck mask and is directed to look at a light emitting diode (LED) during CT simulation and treatment to minimize eye movement. Patient positioning is checked with cone beam computed tomography (CBCT) daily. Translational and rotational displacements greater than 1 mm or 1° off the planned isocenter position are corrected using a Hexapod couch. The aim of this study is to verify that the mask system provides adequate immobilization and to verify our 2-mm planning target volume (PTV) margins are sufficient. Residual displacements provided by pretreatment verification and post-treatment CBCT data sets were used to assess the impact of patient mobility during treatment on the reconstructed delivered dose to the target and organs at risk. The PTV margin calculated using van Herk's method¹ was used to assess patient motion plus other factors that affect treatment position, such as kV-MV isocenter coincidence. Patient position variations were small and were shown to not cause significant dose variations between the planned and reconstructed dose to the target and organs at risk. The PTV margin analysis showed patient translational motion alone required a PTV margin of 1 mm. Given other factors that affect treatment delivery accuracy, a 2-mm PTV margin was shown to be sufficient for treatment of 95% of our patients with 100% of dose delivered to the GTV. The mask immobilization with LED focus is robust and we showed a 2-mm PTV margin is adequate with this technique.     

Prospective comparison of 18F-FDG PET with conventional imaging modalities (MRI, CT, and 67Ga scintigraphy) in assessment of combined intraarterial chemotherapy and radiotherapy for head and neck carcinoma.

To preserve the oral organs and functions in patients with head and neck carcinoma, accurate determination of the appropriate treatment after neoadjuvant chemotherapy and radiotherapy is of critical importance. We evaluated the diagnostic accuracy of (18)F-FDG PET relative to that of other conventional imaging modalities in the assessment of therapeutic response after combined intraarterial chemotherapy and radiotherapy as an organ preservation protocol. METHODS: The study was prospectively performed on 23 consecutive patients with head and neck squamous cell carcinoma who completed the treatment regimen and underwent 2 (18)F-FDG PET studies before and after neoadjuvant chemoradiotherapy. (67)Ga scintigraphy (only before therapy) as well as MRI and CT (both before and after therapy) were also performed. All images were blindly and independently interpreted without knowledge of histologic findings. The level of confidence in image interpretation was graded by means of a 5-point rating system (0 = definitely no tumor to 4 = definite tumor). RESULTS: Before treatment, (18)F-FDG PET detected primary tumors in all 23 patients and was more sensitive (100%) than MRI (18/23; 78.3%), CT (15/22; 68.2%), and (67)Ga scintigraphy (8/20; 40%), with a confidence level of 3 or 4 as a positive tumor finding. After chemoradiotherapy, residual tumors were histologically confirmed in 4 patients (pathologic complete response rate, 19/23; 82.6%). Although posttreatment (18)F-FDG PET showed almost equal sensitivity (4/4; 100%) compared with MRI (3/3; 100%) or CT (3/4; 75%), its specificity (17/19; 89.5%) was superior to MRI (7/17, 41.2%) and to CT (10/17; 58.8%) for primary lesions. Regarding metastases to neck lymph nodes, only specificity for posttreatment images was calculated because no metastasis was confirmed in any patients after treatment. Six subjects had (18)F-FDG PET-positive lymph nodes, which had pathologically no tumor cells and suggested an inflammatory reactive change after therapy. Therefore, the specificity of posttreatment (18)F-FDG PET (17/23; 73.9%) was almost identical to that of MRI (17/20; 85%) and CT (16/21; 76.2%) for neck metastasis. With combined chemoradiotherapy monitored with (18)F-FDG PET, 8 patients avoided surgery and the remaining 15 patients underwent a reduced form of surgery. CONCLUSION: (18)F-FDG PET facilitates differentiation of residual tumors from treatment-related changes after chemoradiotherapy, which may be occasionally difficult to characterize by anatomic images. (18)F-FDG PET has a clinical impact for the management of patients with head and neck cancers after neoadjuvant chemoradiotherapy by optimizing surgical treatment for each patient and contributes to the improvement of the patient's quality of life.     

PET, CT, and MRI in the evaluation of neuropsychiatric disorders: current applications

Positron emission tomography (PET) is emerging as a very useful clinical tool and is adding a great deal to our understanding of the pathophysiology of central nervous system (CNS) disorders. Although computed tomography (CT) and magnetic resonance imaging (MRI) have had a dramatic impact on patient management, there is often an important associated function abnormality which is best assessed by PET. In normal aging and in dementia, the CT and MRI brain changes of atrophy and white matter abnormalities are frequently nonspecific. PET has been more diagnostic, showing characteristic regional metabolic abnormalities. Evaluation of brain tumors such as astrocytomas with PET has demonstrated better correlation with histologic grade compared to CT. Unlike CT or MRI, PET can help to distinguish radiation necrosis from recurrent tumor, and can differentiate the extent of metabolically active tumor from surrounding edema. PET is useful in evaluating stroke patients, providing better prognostic information and demonstrating abnormalities sooner than CT. In epilepsy, PET appears to be superior to MRI in localizing seizure foci in patients with partial seizures. In head trauma patients, metabolic patterns are being described which will likely have an effect on patient management. The use of PET in schizophrenia has yielded very interesting results, with common patterns of metabolic abnormalities being demonstrated. CT and MRI in these patients have not been very useful. PET has also shown promise in movement disorders such as Huntington's disease. It is now clear that PET is already clinically useful and can provide valuable information unobtainable by CT and MRI. As new radioligands are developed, PET is certain to assume an even more important role in the future.     

Technical aspects of positron emission tomography/computed tomography fusion planning

Emerging technologies in radiation therapy computers and delivery systems allow surgically precise conformal radiation treatment that was not possible with previous generations of equipment. The newest treatment systems can compensate for tumor target motion as well as shape dose distributions to conform precisely to delineated target volumes. These sophisticated technologies now drive the development of imaging modalities able to generate equally high-resolution and lesion-specific roadmaps that are the foundation of these highly accurate radiation plans. Positron emission tomography/computed tomography (PET/CT) is currently becoming a routine imaging tool for radiation oncology because of its combined benefits of positron imaging and high-resolution anatomic display. The improved staging and lesion delineation provided by PET, combined with the 3D anatomic display provided by CT, now allows better treatment stratification and more precise targeting. Additionally, respiratory-gated 4D CT and 4D PET/CT have been used in the simulation process for respiratory-gated radiation therapy. Successful integration of PET/CT into the radiation therapy planning process requires an understanding of how therapy plans are derived and the process by which the patient receives therapy, because these dictate the method of image acquisition. The radiation oncologists, too, must understand the technology of positron imaging to adapt these functional images based on intensities rather than pixels to their targeting process. Modifications to the PET/CT scanner and room are necessary to image the patient in the reproducible position required for treatment planning. Although the impact of these efforts on patient outcome has yet to be determined, the benefit of better treatment choice, due to improved staging, and more precise targeting with less normal tissue exposure resulting in improved quality of life will likely promote PET/CT to the gold-standard for targeted therapies.     

Prospective feasibility trial of radiotherapy target definition for head and neck cancer using 3-dimensional PET and CT imaging.

The aim of this investigation was to evaluate the influence and accuracy of (18)F-FDG PET in target volume definition as a complementary modality to CT for patients with head and neck cancer (HNC) using dedicated PET and CT scanners. METHODS: Six HNC patients were custom fitted with head and neck and upper body immobilization devices, and conventional radiotherapy CT simulation was performed together with (18)F-FDG PET imaging. Gross target volume (GTV) and pathologic nodal volumes were first defined in the conventional manner based on CT. A segmentation and surface-rendering registration technique was then used to coregister the (18)F-FDG PET and CT planning image datasets. (18)F-FDG PET GTVs were determined and displayed simultaneously with the CT contours. CT GTVs were then modified based on the PET data to form final PET/CT treatment volumes. Five-field intensity-modulated radiation therapy (IMRT) was then used to demonstrate dose targeting to the CT GTV or the PET/CT GTV. RESULTS: One patient was PET-negative after induction chemotherapy. The CT GTV was modified in all remaining patients based on (18)F-FDG PET data. The resulting PET/CT GTV was larger than the original CT volume by an average of 15%. In 5 cases, (18)F-FDG PET identified active lymph nodes that corresponded to lymph nodes contoured on CT. The pathologically enlarged CT lymph nodes were modified to create final lymph node volumes in 3 of 5 cases. In 1 of 6 patients, (18)F-FDG-avid lymph nodes were not identified as pathologic on CT. In 2 of 6 patients, registration of the independently acquired PET and CT data using segmentation and surface rendering resulted in a suboptimal alignment and, therefore, had to be repeated. Radiotherapy planning using IMRT demonstrated the capability of this technique to target anatomic or anatomic/physiologic target volumes. In this manner, metabolically active sites can be intensified to greater daily doses. CONCLUSION: Inclusion of (18)F-FDG PET data resulted in modified target volumes in radiotherapy planning for HNC. PET and CT data acquired on separate, dedicated scanners may be coregistered for therapy planning; however, dual-acquisition PET/CT systems may be considered to reduce the need for reregistrations. It is possible to use IMRT to target dose to metabolically active sites based on coregistered PET/CT data.     

Comparison of CT and positron emission tomography/CT coregistered images in planning radical radiotherapy in patients with non-small-cell lung cancer

Imaging with F-18 fluorodeoxyglucose positron emission tomography (PET) significantly improves lung cancer staging, especially when PET and CT information are combined. We describe a method for obtaining CT and PET images at separate acquisitions, which allows coregistration and incorporation of PET information into the radiotherapy (RT) planning process for non-small-cell lung cancer. The influence of PET information on RT planning was analysed for 10 consecutive patients. Computed tomography and PET images were acquired with the patient in an immobilization device, in the treatment position. Using specially written software, PET and CT data were coregistered using fiducial markers and imported into our RT planning system (Cadplan version 6). Treatment plans were prepared with and without access to PET/CT coregistered images and then compared. PET influenced the treatment plan in all cases. In three cases, geographic misses (gross tumour outside planning target volume) would have occurred had PET not been used. In a further three cases, better planning target volume marginal coverage was achieved with PET. In four patients, three with atelectasis, there were significant reductions in V20 (percentage of the total lung volume receiving 20 Gy or more). Use of coregistered PET/CT images significantly altered treatment plans in a majority of cases. This method could be used in routine practice at centres without access to a combined PET/CT scanner .     

Application of intensity-modulated radiation therapy for pediatric malignancies

Novel radiation therapy delivery techniques have moved very slowly in the field of pediatric oncology. Some collaborative groups allow new radiation therapy delivery techniques in their trials. In many instances, the option of using these techniques is not addressed. These newer techniques of radiation delivery have the potential to reduce the probability of the common late effects of radiation and at the same time, potentially improve upon control and survival. The purpose of this study is to show the feasibility of IMRT in pediatric patients. No treatment results or toxicities will be presented. Five patients with a variety of pediatric malignancies received intensity-modulated radiation therapy (IMRT) at our institution as part of their disease management. A rigid immobilization device was developed for each patient and a computed tomography (CT) simulation was performed in the treatment position. In 3 of the patients, magnetic resonance imaging (MRI) scans were coregistered with the planning CT to facilitate target and critical structure delineation. In all but 1 patient, coplanar beam arrangements were used in the IMRT planning process. All IMRT plans exhibited a high degree of conformality. Dose homogeneity inside the tumor and rapid dose falloff outside the target volume is characteristic of IMRT plans, which allows for improved normal tissue sparing. Dose distributions were obtained for all plans, as well as dose and volume relationship histograms, to evaluate the fitness of the plans. IMRT is a viable alternative to conventional treatment techniques for pediatric cancer patients. The improved dose distributions coupled with the ease of delivery of the IMRT fields make this technique very attractive, especially in view of the potential to increase local control and possibly improve on survival.     

Application of intensity-modulated radiation therapy for pediatric malignancies

Novel radiation therapy delivery techniques have moved very slowly in the field of pediatric oncology. Some collaborative groups allow new radiation therapy delivery techniques in their trials. In many instances, the option of using these techniques is not addressed. These newer techniques of radiation delivery have the potential to reduce the probability of the common late effects of radiation and at the same time, potentially improve upon control and survival. The purpose of this study is to show the feasibility of IMRT in pediatric patients. No treatment results or toxicities will be presented. Five patients with a variety of pediatric malignancies received intensity-modulated radiation therapy (IMRT) at our institution as part of their disease management. A rigid immobilization device was developed for each patient and a computed tomography (CT) simulation was performed in the treatment position. In 3 of the patients, magnetic resonance imaging (MRI) scans were coregistered with the planning CT to facilitate target and critical structure delineation. In all but 1 patient, coplanar beam arrangements were used in the IMRT planning process. All IMRT plans exhibited a high degree of conformality. Dose homogeneity inside the tumor and rapid dose falloff outside the target volume is characteristic of IMRT plans, which allows for improved normal tissue sparing. Dose distributions were obtained for all plans, as well as dose and volume relationship histograms, to evaluate the fitness of the plans. IMRT is a viable alternative to conventional treatment techniques for pediatric cancer patients. The improved dose distributions coupled with the ease of delivery of the IMRT fields make this technique very attractive, especially in view of the potential to increase local control and possibly improve on survival.     

Anatomical adjustments in brain positron emission tomography using CT images

We have developed a method that allows us to place regions of interest on X-ray CT (XCT) images that are automatically adjusted to positron emission tomography (PET) images from the same patient. A face mask with landmarks was used during PET and XCT studies for matching slice positions between PET and XCT. Anatomical locations in different images of the same slice can be accurately adjusted using the landmarks and a video system. In our clinical experience misadjustments of the slice position are on the average less than 2 mm in axial distance and 1.0 degrees in slice angle. The method is easily applicable to any PET or XCT device.     

CT-MRI image fusion for delineation of volumes in three-dimensional conformal radiation therapy in the treatment of localized prostate cancer

The objective of this study was to assess the utility of CT-MRI image fusion software and compare both prostate volume and localization with CT and MRI studies. We evaluated the differences in clinical volumes in patients undergoing three-dimensional conformal radiation therapy for localized prostate cancer. After several tests performed to ensure the quality of image fusion software, eight patients suffering from prostate adenocarcinoma were submitted to CT and MRI studies in the treatment position within an immobilization device before the start of radiotherapy. The clinical target volume (CTV) (prostate plus seminal vesicles) was delineated on CT and MRI studies and image fusion was obtained from the superimposition of anatomical fiducial markers. A comparison of dose-volume histograms relative to CTV, rectum, bladder and femoral heads was performed for both studies. Image fusion showed a mean overestimation of CTV of 34% with CT compared with MRI. Along the anterior-posterior and superior-inferior direction, CTV was a mean 5 mm larger with CT study compared with MRI. The dose-volume histograms resulting from CT and MRI comparison showed that it is possible to spare a mean 10% of rectal volume and approximately 5% of bladder and femoral heads, respectively. This study confirmed an overestimation of CTV with CT images compared with MRI. Because this finding only allows a minimal sparing of organs at risk, considering the organ motion during each radiotherapy session and the excellent outcomes of prostate cancer treatment with CT based target identification, we are still reluctant to reduce the CTV to that identified by MRI.     

Practical 3-D radiotherapy planning of brain tumors.

In postoperative radiotherapy of brain tumors it is usually the case that preoperative imaging studies, either CT or MRI, were performed outside of the purview of the radiation therapy department. Thus the target volume is defined in an imaging study that does not lend itself readily for entry to a 3-D treatment planning system. A method is described that adjusts the patient structure defined by scan data to an appropriate position for radiotherapy. Software tools that are simple to use have been incorporated in a 3-D treatment planning program that allows oblique treatment planes to be defined. The program provides beam's-eye-view plots of the fields that are used to overlay simulation films and will automatically describe a field blocking outline that provides a prescribed margin on the target volume or other structures that have been defined. Finally, dose calculations in arbitrary planes through the head are made and isodose plots produced.     

Prospective study of bone marrow infiltration in aggressive lymphoma by three independent methods: whole-body MRI, PET/CT and bone marrow biopsy

PURPOSE: Initial lymphoma staging requires bone marrow assessment in aggressive lymphomas. Bone marrow lymphoma infiltration is routinely assessed by bone marrow biopsy (BMB), considered as the "gold standard". The aim of this study was to compare the performance of BMB, whole-body MRI and PET/CT for evaluation of BM infiltration. METHODS: Patients with newly diagnosed aggressive lymphoma were evaluated by BMB, MRI and PET/CT. Two radiologists, two nuclear medicine physicians and one pathologist independently assessed the results of the three modalities. Bone was considered as involved if BM was positive or if PET/CT or MRI was positive and if there was a resolution of the abnormal image shown on PET/CT or MRI halfway or at the end of therapy. RESULTS: Both MRI and PET/CT detected bone marrow lesions in the 9/43 patients, but two patients with multiple lesions had more lesions detected by PET/CT compared to MRI. Among these nine patients, two with an iliac crest lesion detected by both MRI and PET/CT had bone marrow involvement with large-cell lymphoma on histological examination. The other seven patients had focal MRI and PET/CT lesions in areas other than the iliac crest, where the blind BMB was done. The other patients had bone marrow without large-cell lymphoma involvement. In all cases, after lymphoma therapy bone marrow involvement regressed on histological examination, PET and MRI. CONCLUSION: These preliminary results suggest that non-invasive morphological procedures could be superior to BMB for bone marrow assessment in aggressive lymphomas. Ongoing study is underway to validate these results.     

Whole-body (18)F-FDG PET improves the management of patients with small cell lung cancer.

The aim of this study was to evaluate the impact of whole-body (18)F-FDG PET on staging and managing patients with small cell lung cancer (SCLC). METHODS: The treatment records of 42 consecutive patients (27 men, 15 women; mean age, 62 y; age range, 45-83 y) with SCLC were reviewed. Whole-body (18)F-FDG PET was performed for initial staging in 24 patients and for restaging after chemotherapy or radiation treatment in 20 patients. Two patients of the initial staging group were restaged with PET after therapy. PET findings were correlated with clinical and radiologic findings (CT of the chest and abdomen, bone scan, and CT or MRI of the brain). The impact of PET on staging and management decisions was determined. RESULTS: For 12 of 42 patients (29%), PET results changed the patient's management. In 8 patients (19%), PET resulted in a change of radiation therapy because of the detection of previously unknown tumor foci. Adjuvant radiation therapy was cancelled in 3 patients. A change of radiation field and volume was necessary in 5 patients. In 1 patient, PET results excluded extensive disease, which permitted surgical resection of the tumor. Chemotherapy was discontinued in 2 patients and restarted in 1 patient on the basis of the PET findings. In 5 patients (12%), PET excluded malignancy as the suspicious lesions found with conventional cross-sectional imaging did not take up (18)F-FDG. CONCLUSION: The results of this study show that (18)F-FDG PET has a major impact on the management of patients with SCLC, influencing both the stage and the management in 29% of patients. PET is a highly valuable tool for accurate target definition of radiation treatment by reducing the probability of overlooking involved areas.     

Simulator Verification of the Accuracy of Patient Repositioning after Virtual Simulation

PURPOSE: To evaluate the frequency and amount of displacements after repositioning a patient on the physical simulator following virtual simulation. MATERIAL AND METHODS: After laser marking at the CT scanner and virtual simulation, patients were repositioned on the simulator. The isocenter obtained from the calculated table movements was checked by fluoroscopically measuring the distances to standardized anatomic landmarks and comparing them to the treatment plan. RESULTS: In 86% of patients, displacements were < or = 0.5 cm. There was no significant difference between the supine and prone position, diagnosis categories or CT reconstruction indices. The use of immobilization devices and cranial versus body stem localization did make a significant difference. Rates of exact repositioning were high in brain and head and neck patients and comparatively low in abdominal tumors and breast cancer. CONCLUSIONS: Immobilization devices play an important role for the precision of radiotherapy. Whenever precise positioning is possible (e. g. with a head mask), virtual simulation alone might be sufficient. Patients with abdominal and breast tumors, were repositioning precision is often suboptimal, might profit from an additional physical simulation.     

20. The Case for PET/CT. Experience at the University of Pittsburgh

Purpose: Whole-body positron emission tomography (PET) with [F-18]fluorodeoxyglucose (FDG) is an important tool in the management of patients with cancer. While the sensitivity of FDG PET for tumor localization is most often reported to be >/= 85%, the specificity is frequently found to be lower. One limitation of whole-body PET imaging is the confounding effect of normal physiologic FDG accumulation in kidneys, ureters, bladder, stomach and bowel. Also, highly metabolically active tissues such as brain and muscle can mask detection of adjacent abnormalities. Interpretation of functional PET images can be improved by correlation with anatomic imaging, e.g. CT or MRI. The utility of both visual comparison and retrospective fusion of PET with previously acquired morphologic studies may be, however, limited by the time interval between image acquisition and patient positioning differences.Results: In our experience with over 150 examinations using a unique combined PET/CT scanner, we have frequently found that the direct registered images were critical to correct study interpretation. In this work, we review the beneficial results of a combined PET/CT tomograph for diagnosis/staging and localization of malignancy. We will further present specific examples of clinical questions uniquely addressed by PET/CT, and their impact on patient management.Conclusion: Acquisition of co-registered PET and CT images in the same scanning session may enable physicians to more precisely discriminate physiologic uptake and tumor. Our initial experience suggests that this combined PET/CT device may improve the accuracy of PET, and in so doing, enhance the value of diagnostic PET in oncologic applications.     

Chemotherapy response assessment in stage IV melanoma patients—comparison of <Superscript>18</Superscript>F-FDG-PET/CT,CT, brain MRI,and tumormarker S-100B

PURPOSE: This study aims to compare the use of 18F-FDG-PET/CT, CT, brain MRI, and tumormarker S-100B in chemotherapy response assessment of stage IV melanoma patients. METHODS: In 25 patients with stage IV melanoma, FDG-PET/CT and S-100B after 2-3 months (three cycles) of chemotherapy was compared with baseline PET/CT and baseline S-100B. Retrospectively, the response was correlated with the outcome. In patients with clinical suspicion for brain metastases, MRI or CCT was performed. RESULTS: There was agreement between FDG-PET/CT and CT regarding response to chemotherapy in all patients. There was a clear trend to a longer OS of PET/CT responders (n=10) compared with PET/CT non-responders (n=15; p=0.072) with remarkably better 1-year OS of 80% compared to 40% (p=0.048). There was a significant longer PFS of PET/CT responders compared with PET/CT non-responders (p=0.002). S-100B was normal at baseline in eight of 22 patients where it was available. Chemotherapy response assessment with S-100B failed to show correlation with OS or PFS. Eleven patients developed brain metastases during treatment, first detected by PET/CT in two and by MRI or CCT in nine of 11 patients. Appearance of brain metastases was associated with a poor survival. CONCLUSIONS: 18F-FDG-PET/CT and CT alone are equally suitable for chemotherapy response assessment in melanoma patients and clearly superior to S-100B. PET/CT responders have better early survival, but this is shortlived due to late therapy failure--often with brain recurrence. Additional brain MRI for therapy response assessment in such high-risk patients is mandatory to detect brain metastases missed by PET/CT.     

全身MRI与PET/CT在淋巴瘤骨髓浸润诊断及预后中的作用

淋巴瘤是一种血液系统恶性肿瘤。淋巴瘤骨髓浸润(BMI)使疾病分期上升至IV期, 是疾病进展、预后较差的标志。常规部位的骨髓活检(BMB)具有创伤性, 且检出率低。PET/CT与全身MRI的出现, 丰富了BMI的检测手段。PET/CT与全身MRI对于淋巴瘤, 尤其是侵袭性淋巴瘤BMI均具有较高的检出率, 二者孰高孰低, 尚未定论。对于红骨髓、良性骨髓病变(炎症等)、淋巴瘤BMI病灶以及肿瘤治疗后骨髓的变化与骨髓残留或复发病灶, 全身MRI很难区分, 而PET/CT却可以很好地鉴别这些病灶。但是, PET/CT存在电离辐射; 对于惰性淋巴瘤的BMI, 超出PET/CT分辨率的病灶, 可能出现假阴性; 某些情况会限制PET/CT的使用, 包括18F-FDG生理性摄取量可能发生改变的正常组织、18F-FDG摄取相关性炎症、高血糖或高胰岛素血症导致的18F-FDG分布的改变、肿瘤患者治疗后出现的骨髓活化等。然而, 这些情况可以使用全身MRI。因此, 全身MRI和PET/CT相辅相成, 优势互补, 但二者均不能代替BMB。对于常规BMB阴性, 但影像学提示阳性的患者, 在影像学引导下进行BMB, 可以提高BMI的检出率。另外, 全身MRI阳性的淋巴瘤BMI患者与全身MRI阴性的淋巴瘤BMI患者相比, 前者预后可能较差。     

Radiological diagnosis of Klatskin's tumour

Patients with Klatskin's tumour present clinically unspecific symptoms such as painless jaundice and cholangitic discomfort. The only curative treatment is R0 resection of the tumour. To allow stage-specific therapy, accurate tumour staging is indispensable, the first step of which is abdominal sonography. If there is a suspect finding, cross-sectional imaging techniques like MRI or MDR-CT are used to clarify or stage the lesion, respectively. To estimate resectability, MRI together with MRC and MRI angiography are superior to MDR-CT. Biopsy using ERC is required before starting any specific treatment. If therapeutically relevant peritoneal carcinosis is clinically suspected although not radiologically confirmed, PET should also be performed. The value of PET/CT has to be evaluated in further studies. For optimal treatment, close cooperation between clinicians and radiologists is necessary.