Potential impact of (68)Ga-DOTATOC PET/CT on stereotactic radiotherapy planning of meningiomas

PURPOSE

Since meningiomas show a high expression of somatostatin receptor subtype 2, PET with (68)Ga-DOTATOC was proposed as an additional imaging modality beside CT and MRI for planning radiotherapy. We investigated the input of (68)Ga-DOTATOC-PET/CT on the definition of the "gross tumour volume" (GTV) in meningiomas, in order to assess the potential value of this method.

METHODS

Prior to radiotherapy, 42 patients with meningiomas (26 f, 16 m, mean age 55) underwent MRI and (68)Ga-DOTATOC-PET/CT examinations.

HISTORY

operated n = 24, radiotherapy n = 1, operation and radiotherapy n = 8, no treatment n = 9. PET/CT and MRI data were co-registered using a BrainLAB workstation. For comparison, the GTV was defined first under consideration of CT and MRI data, then using PET data.

RESULTS

3/42 patients were excluded from the analysis (two with negative PET results, one with an extensive tumour, not precisely delineable by MRI or PET/CT). The average GTV(CT/MRI) was 22(+/-19)cm(3); GTV(PET) was 23(+/-20)cm(3). Additional GTV, obtained as a result of PET was 9(+/-10)cm(3) and was observed in patients with osseous infiltration. In some pre-treated patients there were intratumoural areas (as identified in CT/MRI) without SR-expression (7(+/-11)cm(3)). Common GTV as obtained by both CT/MRI and PET was 15(+/-14)cm(3). The mean bi-directional difference between the GTV(CT/MRI) and GTV(PET) accounted to 16(+/-15)cm(3) (93%, p < 0.001). In a subgroup of seven patients with multiple meningiomas, PET showed a total of 19 lesions; nine of them were not recognizable by CT or MRI.

CONCLUSION

(68)Ga-DOTATOC-PET enables delineation of SR-positive meningiomas and delivers additional information to both CT and MRI regarding the planning of stereotactic radiotherapy. The acquisition on a PET/CT scanner helps to estimate the relation of PET findings to anatomical structures and is especially useful for detection of osseous infiltration. (68)Ga-DOTATOC-PET also allows detection of additional lesions in patients with multiple meningiomas.

Osteochondral defect repair after implantation of biodegradable scaffolds: indirect magnetic resonance arthrography and histopathologic correlation

BACKGROUND

Biodegradable scaffolds have become an important option in the treatment of osteochondral defects. Therefore, accurate and reproducible monitoring of scaffold repair tissue is crucial.

PURPOSE

To assess the feasibility of indirect magnetic resonance (MR) arthrography in determining the quality of osteochondral repair after scaffold implantation using an MR imaging (MRI) scoring and grading system with histology as reference.

MATERIAL AND METHODS

Osteochondral defects created at ovine condylar facets were treated with either a commercial poly (DL-lactide-co-glycolide) (PLG) scaffold or a modified softer one (n=6/group; 87% and 55% of the elastic modulus of ovine subchondral bone, respectively). Empty defects at the contralateral condyle served as control group. A 1.5T MRI scan was performed after 6 months with proton density (PD)-weighted (w) fat-saturated (fs) fast spin-echo (FSE), T1-w two-dimensional (2D), and 3D fs gradient echo (GE) sequences 30 min after intravenous Gd-DTPA administration and passive joint movement. Two independent radiologists evaluated the repair tissue. The MR findings were correlated with histological findings.

RESULTS

MRI and histological grading correlated well (10/12 cases). The stiff-scaffold group showed significantly superior repair in comparison to the control group (P<0.05). The 3D fs GE sequence proved to be most valuable in evaluating morphologic status. Complete defect filling and integration, intact surface and isointense signal to the adjacent native cartilage, subchondral incorporation with bone marrow edema, and graft plug enhancement were associated with a good histological outcome. Histologically, we found a smooth fibrocartilaginous layer and osseous replacement of the scaffold. Incomplete cartilage repair and irregular subchondral structures on the MRI correlated histologically with fibrocartilage-like repair and subchondral sclerosis, due to substantial degradation of the scaffold.

CONCLUSION

Indirect MR arthrography is an accurate, noninvasive monitoring tool in the follow-up of scaffold implants. The MRI scoring and grading system allows reliable assessment of normal and pathological repair, with high correlation to histological findings.

Early and late therapy response assessment with [18F]fluorodeoxyglucose positron emission tomography in pediatric Hodgkin's lymphoma: analysis of a prospective multicenter trial

PURPOSE

In adult Hodgkin's lymphoma (HL) risk stratification after early therapy response assessment with [(18)F]fluorodeoxyglucose (FDG) positron emission tomography (PET) seems to allow tailoring therapy with less toxicity for patients with adequate metabolic response. This study delivers the first prospective data on the potential of FDG-PET for response assessment in pediatric HL.

PATIENTS AND METHODS

FDG-PET was performed in 40 pediatric HL patients before polychemotherapy (PET-1), after two cycles of polychemotherapy (PET-2), and after completion of polychemotherapy (PET-3). Mean follow-up was 46 months (range, 26 to 72 months).

RESULTS

At early and late response assessment, the proportion of PET-negative patients was significantly higher compared with those patients with negative findings in conventional imaging methods (CIMs; PET-2, 26 of 40 v CIM-2, one of 40; P < .001; PET-3, 21 of 29 v CIM-3, four of 29; P < .001). Sensitivity and negative predictive value were 100% for early and late therapy response assessment by PET. Both patients suffering a relapse during follow-up were identified by PET-2/3, whereas one of these patients was not detected by CIM-3. PET was superior to CIMs with regard to specificity in early and late therapy response assessment (68% v 3%, and 78% v 11%, respectively; both P < .001). Specificity of early therapy response assessment by PET was improved to 97% by quantitative analysis of maximal standardized uptake value reduction using a cutoff value of 58%.

CONCLUSION

Pediatric HL patients with a negative PET in response assessment have an excellent prognosis while PET-positive patients have an increased risk for relapse.

Multidetector computed tomography for preoperative assessment of hepatic vasculature and prediction of splenic artery steal syndrome in patients with liver cirrhosis before transplantation

The purpose of this study was to evaluate the accuracy of MDCT for preoperative assessment of hepatic vascular anatomy and the identification of liver-transplantation (OLT) patients at risk of developing subsequent splenic artery steal syndrome (SASS). A total of 145 patients with liver cirrhosis who had undergone OLT and had pre-operative three-phase MDCT (4- to 64-rows) within 100 days before OLT were enrolled retrospectively. MDCT and 3Ds were reviewed by two independent blinded observers (O1/O2). Pre-operative imaging findings were correlated with intra-operative results; findings indicative for SASS were correlated with clinical data and DSA. Among all 145 patients, 16 patients (11%) showed accessory hepatic arteries (accuracy O1/O2, 97%; with 3Ds, 100%); 32 (22%) patients had replaced hepatic arteries (accuracy O1, 97%; O2, 95%; with 3Ds, 100%; kappa = 0.87 and 0.89, P < 0.001). Among 119 patients, 12 patients developed SASS after OLT. The logistic regression model revealed the spleen volume (P = 0.0105) as a predictive factor of SASS. With spleen volumes >or=829 ml, an accuracy of 75% for prediction of SASS was obtained. MDCT with three-dimensional post-processing (3Ds) was highly accurate for pre-operative hepatic vessel evaluation in patients before OLT. In addition, spleen volume was a predictive factor for developing SASS after OLT.

18F-FET PET for planning of thermotherapy using magnetic nanoparticles in recurrent glioblastoma

PURPOSE

Thermotherapy using magnetic nanoparticles (nano cancer therapy) is a new concept of local tumour therapy, which is based on controlled heating of intra-tumoural injected magnetic nanoparticles. The aim of this study was to evaluate the usefulness of PET with a recently introduced amino acid tracer O-(2-[18F]fluoroethyl)-]L-tyrosine (FET) for targeting the nanoparticles implantation.

MATERIALS AND METHODS

Eleven patients with glioblastoma recurrences underwent MR and FET-PET imaging for planning of the nano cancer therapy. Thereafter, the gross tumour volumes (GTV) were defined, taking into consideration the results of both imaging tools.

RESULTS

The MRI-based mean GTV was 24.3 cm3 (range 2.5-59.7) and the PET-based mean GTV 31.9 cm3 (range 5.2-77.9). On the average the MRI identified an additional 8.9 +/- 4.7 cm3 and the FET-PET scan-an additional 16.5 +/- 15.2 cm3 outside of the common GTV (15.4 +/- 11.0 cm3). The mean final GTV accounted to 33.8 cm3 (range, 5.2-77.9). The additional information of FET-PET led to an increase in GTV by 22-286% in eight patients and to a decrease of 23% and 26%, respectively, in two patients. In one patient, the final GTV was defined on the basis of MRI data only.

CONCLUSIONS

FET-PET adds important information on the actual tumour volume in recurrent glioblastomas and is highly valuable for defining the target volume for the nano cancer therapy.

Modification of aminosilanized superparamagnetic nanoparticles: feasibility of multimodal detection using 3T MRI, small animal PET, and fluorescence imaging

PURPOSE

The aim of our study was to modify an aminosilane-coated superparamagnetic nanoparticle for cell labeling and subsequent multimodal imaging using magnetic resonance imaging (MRI), positron emission tomography (PET), and fluorescent imaging in vivo.

PROCEDURES

We covalently bound the transfection agent HIV-1 tat, the fluorescent dye fluorescein isothiocyanate, and the positron-emitting radionuclide gallium-68 to the particle and injected them intravenously into Wistar rats, followed by animal PET and MRI at 3.0 T. As a proof of principle hepatogenic HuH7 cells were labeled with the particles and observed for cell toxicity as well as detectability by MRI and biodistribution in vivo.

RESULTS

PET imaging and MRI revealed increasing hepatic and splenic accumulation of the particles over 24 h. Adjacent in vitro studies in hepatogenic HuH7 cells showed a rapid intracellular accumulation of the particles with high labeling efficiency and without any signs of toxicity. In vivo dissemination of the labeled cells could be followed by dynamic biodistribution studies.

CONCLUSIONS

We conclude that our modified superparamagnetic nanoparticles are stable under in vitro and in vivo conditions and are therefore applicable for efficient cell labeling and subsequent multimodal molecular imaging. Moreover, their multiple free amino groups suggest the possibility for further modifications and might provide interesting opportunities for various research fields.

Multislice computed tomography using a triple-phase contrast protocol for preoperative assessment of hepatic tumor load in patients with hepatocellular carcinoma before liver transplantation

For evaluation of triple-phase multislice computed tomography (CT) for assessment of hepatocellular carcinoma (HCC) before liver transplantation. All HCC patients who underwent liver transplantation at our institution between 2001 and 2006 and had contrast-enhanced abdominal 4-/16-slice CT [unenhanced, arterial (20 s delay), portal venous (40 s), and venous (80 s) scan] within 100 days before transplantation were enrolled retrospectively. CT data were reviewed by two observers. Results were correlated to histopathologic findings by means of a lesion-by-lesion evaluation. Thirty-two patients with 76 HCC-lesions were included. The lesion-based sensitivity of observer 1 and 2 was 78% (59/76) and 83% (63/76) (false positives, n = 6 and n = 10). The sensitivity of observer 1/2 was 89%/95% for lesions >20 mm (n = 37), 94% for lesions 11-20 mm (n = 18), and 43%/53% for lesions <10 mm (n = 21). The mean detection rates of unenhanced, arterial, portal venous, and venous phase scans were 30%, 74%, 59%, and 40%. All detected lesions were visible on arterial and/or portal venous scans (arterial only, 24%; portal venous only, 9%). Arterial and portal venous phase scans are the strongest contributors to the high detection rate of triple-phase multislice-CT in HCC. However, the detection of small HCC measuring <10 mm and false positive findings remains a challenge.

Sclerosing mesenteritis as a rare cause of upper abdominal pain and digestive disorders

Sclerosing mesenteritis is a rare inflammatory disease of the bowel mesentery of unknown etiology, which can be mistaken for malignancy. We report a case of a 60-year-old male patient with sclerosing mesenteritis as a rare cause of upper abdominal pain and digestive disorders, and present the corresponding magnetic resonance imaging (MRI) findings indicative of the underlying disease.

Use of positron emission tomography for staging, preoperative response assessment and posttherapeutic evaluation in children with Wilms tumour

PURPOSE

To evaluate FDG-PET for staging, grading, preoperative response assessment and posttherapeutic evaluation in children with Wilms tumour (WT).

METHODS

In this study, 23 FDG-PET examinations in 12 paediatric patients (female, n = 5; male, n = 7; age, 1-19 years) with WT (primary, n = 9; relapsed, n = 3) were analysed. All patients were examined with conventional imaging methods (CIM) according to the SIOP2001/GPOH trial protocol. Additionally, FDG-PET/PET-CT was performed for staging (n = 12), preoperative response assessment (n = 6) and posttherapeutic evaluation (n = 5). Imaging results of FDG-PET and CIM were analysed regarding the accuracy in tumour visualisation, impact on therapeutic management and preoperative response assessment, with clinical follow-up and histopathology as the standard of reference.

RESULTS

FDG-PET and CIM showed concordant results for staging of primary WT, whereas FDG-PET was superior in 1/3 cases with recurrent WT. Concerning histological differentiation, one case with anaplastic WT had an standard uptake value (SUV) of 12.3, which was remarkably higher than the average SUV in the eight cases with intermediate risk histology. No parameter analysed for PET or CIM was reliably predictive for histological regression or clinical outcome. After completion of therapy, FDG-PET was superior to CIM in 2/5 cases in detecting residual disease with therapeutic relevance.

CONCLUSION

FDG-PET does not provide additional information to the traditional imaging work-up for staging WT patients, preoperative response assessment and clinical outcome. FDG-PET was advantageous in ruling out residual disease after completion of first line treatment and in pretherapeutic staging of relapse patients. Furthermore, there seems to be a good correlation of initial SUV and histological differentiation.

Suspected chronic myocarditis at cardiac MR: diagnostic accuracy and association with immunohistologically detected inflammation and viral persistence

PURPOSE

To retrospectively compare the diagnostic accuracy of three cardiac magnetic resonance (MR) imaging approaches for the detection of histologic and immunohistologic criteria (reference standard) proved myocardial inflammation in patients clinically suspected of having chronic myocarditis (CMC).

MATERIALS AND METHODS

Cardiac MR imaging was performed in 83 consecutive patients (55 male, 28 female; mean age, 44.8 years +/- 17.7 [standard deviation]) clinically suspected of having CMC, after written informed consent was obtained according to guidelines of the local ethics committee, which approved the study. T2-weighted triple-inversion-recovery imaging to calculate the edema ratio (ER), T1-weighted imaging before and after contrast agent administration to calculate the myocardial global relative enhancement (gRE), and inversion-recovery gradient-echo imaging to evaluate areas of late gadolinium enhancement (LE) were performed. The MR results were correlated with the endomyocardial biopsy (EMB) findings to detect intramyocardial inflammation and cardiotropic viral genomes analyzed at polymerase chain reaction assay. For statistical analyses, receiver operating characteristic analysis and the Wilcoxon test for unpaired data were used because the Kolomogorov-Smirnov test revealed a distribution of data that was different from normality.

RESULTS

Intramyocardial inflammation and cardiotropic viral persistence were confirmed at immunohistologic analysis in 48 and 49 of the 83 patients, respectively. The sensitivity, specificity, and diagnostic accuracy of the MR parameters, as compared with the immunohistologic detection of inflammation, were, respectively, 62%, 86%, and 72% for gRE; 67%, 69%, and 68% for ER; and 27%, 80%, and 49% for LE. Cardiac MR-derived gRE, ER, and LE were not associated with polymerase chain reaction proof of viral genomes.

CONCLUSION

In patients clinically suspected of having CMC, increased gRE and ER indicating inflammation were common findings that could be confirmed at immunohistologic analysis, whereas LE had low sensitivity and accuracy. Cardiac MR imaging may be helpful in detecting intramyocardial inflammation noninvasively, but it fails to depict viral persistence.

Planning transarterial radioembolization of colorectal liver metastases with Yttrium 90 microspheres: evaluation of a sequential diagnostic approach using radiologic and nuclear medicine imaging techniques

The purpose of the study was to establish a diagnostic approach to the preparation of patients with colorectal liver metastases considered for transarterial radioembolization (RE). Twenty-two patients sequentially underwent computed tomography (CT; thorax/abdomen), magnetic resonance imaging (MRI; liver; hepatocyte-specific contrast), positron emission tomography (PET/PET-CT; F18-fluoro-desoxy-glucose), and angiography with perfusion scintigraphy [planar imaging; tomography with integrated CT (SPECT-CT)]. The algorithm was continued when no contraindication or alternative treatment option was found. The impact of each test on the therapy decision and RE management was recorded. Patient evaluation using CT revealed contraindications for RE in 4/22 patients (18%). Of the remaining 18 patients, 2 were excluded and 3 were assigned to locally ablative treatment based on MRI and PET results (28%). The remaining 13 patients entered the planning algorithm: SPECT-CT revealed gastrointestinal tracer accumulations in 4 (31%) patients [SPECT, 2 (15%)], making a modified application necessary. In five patients (38%), planar scintigraphy revealed relevant hepatopulmonary shunting. Therapy was finally administered to all 13 patients without therapy-related pulmonary or gastrointestinal morbidity. Each part of the diagnostic algorithm showed a relevant impact on patient management. The sequential approach appears to be suitable and keeps the number of unnecessary treatments and therapy risks to a minimum.

Brachytherapy of liver metastases

Brachytherapy for the treatment of liver metastases is a novel approach. In this procedure, techniques of locally ablative treatment in interventional radiology and radiation therapy are combined. After computed tomography (CT)-guided percutaneous implantation of catheters into the hepatic tumor, the irradiation is performed in an afterloading technique. This minimally invasive procedure offers circumscriptive high-dose rate irradiation of the lesion to treat in a single session, irrespective of breathing motion or potential cooling effects of neighboring vessels. Good local control rates have been achieved in several tumor entities, including both secondary and primary malignancies of the liver. This article gives an overview of the application technique, possible adverse events, and outcome with special attention to the pancreatic cancer scenario.

Incidental detection of breast cancer by 68Ga-DOTATOC-PET/CT in women suffering from neuroendocrine tumours

AIM

Somatostatin receptor (sstr) imaging using 68Ga-DOTATOC-PET/CT in neuroendocrine tumors (NET) is promising, suggesting a more sensitive detection of lesions with a low sstr-expression. This is also important for other sstr positive tumors, especially breast cancer whose incidence and age-range is similar to that of NET.

PATIENTS, METHODS

The PET/CT data of 33 consecutive women with NET (age: 33-78 years, mean 59) who underwent whole-body staging with 68Ga-DOTATOC was retrospectively analyzed for breast lesions. The data was read separately, side-by-side and as fused images. Focal tracer uptake in the breast was semiquantitatively analyzed by comparing the lesional SUVmax to normal breast tissue using Wilcoxon's rank sum test. Breast cancer lesions were compared visually to concomitant NET-lesions.

RESULTS

In six of 33 patients (18%) breast lesions were observed on the CT-scans and classified in four patients (12%) as suspicious. The same lesions also showed a pathological tracer uptake on the corresponding PET-scan, visually and semiquantitatively (p<0.01). Histological reevaluation of the suspicious lesions revealed two patients with NET metastases. Two patients had primary breast cancer with lower tracer uptake than concomitant abdominal NET-lesions. Breast cancer diagnosis resulted in a change of the therapeutic regimen.

CONCLUSION

68Ga-DOTATOC-PET/CT not only improves the staging of NET-patients, but also increases the chance to detect sstr-positive breast cancer. Although these lesions may show a lower tracer uptake than NET, they must not be overlooked or misinterpreted as metastases. Further imaging and clarification by histopathology is warranted, as the confirmation of a secondary malignoma has great impact on further therapeutic proceedings.

An orthotopic model of pancreatic somatostatin receptor (SSTR)-positive tumors allows bimodal imaging studies using 3T MRI and animal PET-based molecular imaging of SSTR expression

Somatostatin receptor (SSTR) scintigraphy is currently used as one standard imaging modality in neuroendocrine tumors (NETs). However, future optimization of NET imaging may be achieved with positron emission tomography based methods utilizing more sensitive and specific tracers in combination with computed tomography or magnetic resonance imaging. Here we established an orthotopic mouse model that reflects relevant aspects of human pancreatic NETs such as SSTR expression, dense vascularization and metastatic disease. This model was then utilized to test the feasibility of combined magnetic resonance imaging and animal positron emission tomography. Orthotopic implantation of amphicrine, SSTR-positive pancreatic AR42J cells resulted in rapidly growing tumors, with concomitant metastatic spread into abdominal lymph nodes and peritoneal cavity. Primary tumors as well as their metastases expressed the neuroendocrine markers chromogranin A and synaptophysin. For imaging experiments, the SSTR ligands (68)Ga-DOTATOC or (68)Ga-DOTANOC were injected intravenously, and animals were subsequently examined in an animal positron emission tomography scanner and a clinical 3T (tesla) magnetic resonance imager. All animals showed radionuclide accumulation in the primary tumor. Definite anatomical correlation was achieved using digital image fusion of the positron emission tomography and magnetic resonance imaging data. (68)Ga-DOTANOC strongly accumulated in the tumor tissue (mean 6.6-fold vs. control tissues) when compared to (68)Ga-DOTATOC, which showed a higher renal clearance. In good agreement with the biodistribution data, the kidney-to-tumor ratio was higher for (68)Ga-DOTATOC (2.43-fold vs. 1.75-fold). Consequently, (68)Ga-DOTANOC achieved better signal enhancement in the primary tumor and allowed for detection of metastatic lesions. In summary, we established a novel orthotopic pancreatic SSTR-positive tumor model and used this model to provide proof of principle for the diagnostic combination of SSTR-based molecular imaging and magnetic resonance imaging. Specifically, the animal model allowed the comparative evaluation of (68)Ga-DOTANOC and (68)Ga-DOTATOC, with (68)Ga-DOTANOC providing better tumor-specific accumulation and renal activity. We conclude that this animal model will be of innovative value for further investigation in the imaging of NETs.

Positron emission tomography for staging of pediatric sarcoma patients: results of a prospective multicenter trial

PURPOSE

The objective of this study was to evaluate the impact of positron emission tomography (PET) using fluorine-18-fluorodeoxyglucose (FDG) for initial staging and therapy planning in pediatric sarcoma patients.

PATIENTS AND METHODS

In this prospective multicenter study, 46 pediatric patients (females, n = 22; males, n = 24; age range, 1 to 18 years) with histologically proven sarcoma (Ewing sarcoma family tumors, n = 23; osteosarcoma, n = 11; rhabdomyosarcoma, n = 12) were examined with conventional imaging modalities (CIMs), including ultrasound, computed tomography (CT), magnetic resonance imaging, and bone scintigraphy according to the standardized algorithms of the international therapy optimization trials, and whole-body FDG-PET. A lesion- and patient-based analysis of PET alone and CIMs alone and a side-by-side (SBS) analysis of FDG-PET and CIMs were performed. The standard of reference consisted of all imaging material, follow-up data (mean follow-up time, 24 +/- 12 months), and histopathology and was determined by an interdisciplinary tumor board.

RESULTS

FDG-PET and CIMs were equally effective in the detection of primary tumors (accuracy, 100%). PET was superior to CIMs concerning the correct detection of lymph node involvement (sensitivity, 95% v 25%, respectively) and bone manifestations (sensitivity, 90% v 57%, respectively), whereas CT was more reliable than FDG-PET in depicting lung metastases (sensitivity, 100% v 25%, respectively). The patient-based analysis revealed the best results for SBS, with 91% correct therapy decisions. This was significantly superior to CIMs (59%; P < .001).

CONCLUSION

In staging pediatric sarcoma, subsidiary FDG-PET scanning depicts important additional information and has a relevant impact on therapy planning when analyzed side-by-side with CIMs.

Influence of attenuation correction by integrated low-dose CT on somatostatin receptor SPECT

AIM

Somatostatin receptor scintigraphy (SRS) is well-established in neuroendocrine tumour (NET) imaging. This study evaluated the impact of attenuation correction (AC) on SRS SPECT data in patients examined by SPECT-CT.

METHODS

Planar scintigraphy and SPECT-CT of 17 patients (10 men, seven women; age, 40-74 years; mean, 62 years) suffering from NET were included. For the visual assessment of AC, the intensity and contrast of foci classified as pathological were rated in both the non-attenuation corrected (NAC) and the attenuation corrected (AC) SPECT images using a 5-point score. The change in signal intensity after AC was semiquantified two-fold for each focus in both SPECT(AC) and SPECT(NAC): firstly by using tumour-to-background (TB) ratios (defined as T(max)/B(mean)) for the determination of a TB(AC)/TB(NAC) ratio. Secondly, by a T(max,AC)/T(max,NAC) ratio. Both ratios were correlated to the focus depth.

RESULTS

A total of 46 pathological foci were found. Focus contrast and intensity significantly increased in 14/46 foci (30%) after AC (mean, 3.7-4.0) in the visual analysis (P<0.001). While TB ratios increased only in 24/46 foci after AC and no correlation between the T(BAC)/T(BNAC) ratio and focus depth (r=0.027; P=0.856) was found, T(max) was higher after AC in all foci and the T(max,AC)/T(max,NAC) ratio showed the expected correlation to focus depth (r=0.650; P<0.01), indicating the superiority of the Tmax approach for the demonstration of the effects of attenuation correction on focal uptake.

CONCLUSION

Attenuation correction of SRS SPECT data by SPECT-CT results in visually more clearly contrasted foci. Moreover, as focus intensity increases, especially in the more centrally localised foci, CT-based AC has a potential to further improve the sensitivity of SRS SPECT.

Assessment of local control after laser-induced thermotherapy of liver metastases from colorectal cancer: contribution of FDG-PET in patients with clinical suspicion of progressive disease

BACKGROUND

Management of patients after locally ablative treatment of liver metastases requires exact information about local control and systemic disease status. To fulfill these requirements, whole-body imaging using positron emission tomography with (18)F-fluorodeoxyglucose (FDG-PET) is a promising alternative to morphologic imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI).

PURPOSE

To evaluate FDG-PET for the assessment of local control and systemic disease in patients with clinical suspicion of tumor progression after laser-induced thermotherapy (LITT) of colorectal liver metastases.

MATERIAL AND METHODS

In 21 patients with suspicion of progressive disease after LITT, whole-body FDG-PET was performed. The presence of viable tumor within treated lesions, new liver metastases, and extrahepatic disease was evaluated visually and semiquantitatively (maximal standard uptake value [SUV(max)], tumor-to-normal ratio [T/N]). The standard of reference was histopathology (n = 25 lesions) and/or clinical follow-up (>12 months) including contrast-enhanced MRI of the liver.

RESULTS

Among 54 metastases treated with LITT, 29 had residual tumor. Receiver operating characteristic (ROC) analysis of SUV(max) (area under the curve (AUC) 0.990) and T/N (AUC 0.968) showed a significant discrimination level of negative or positive lesion status with an equal accuracy of 94% (51/54). The overall accuracy of visual FDG-PET was 96% (52/54), with one false-negative lesion among six examined within 3 days after LITT, and one false-positive lesion examined 54 days after LITT. In the detection of new intra- and extrahepatic lesions, FDG-PET resulted in correct alteration of treatment strategy in 43% of patients (P = 0.007).

CONCLUSION

FDG-PET is a promising tool for the assessment of local control and whole-body restaging in patients with clinical suspicion of tumor progression after locally ablative treatment of colorectal liver metastases with LITT.

123I-IMT SPECT for evaluation of the response to radiation therapy in high grade gliomas: a feasibility study

Assessing response to radiation therapy in patients with high grade gliomas is needed upon making decisions toward further therapy strategies. Currently used standard imaging tools such as CT and MRI are not sensitive enough to detect early therapy effects. We prospectively investigated if single photon emission computed tomography (SPECT) using radiolabelled amino acid derivate (123)I-methyltyrosine (IMT) would be useful for this aim. 10 patients with histologically proven high grade gliomas, who were candidates for radiation therapy, were enrolled in this investigation. All patients were examined by IMT SPECT before radiation therapy and 4 weeks after the initiation of the hypofractionated application of 40 Gy. Patients were followed up for 39 months; the tumours to background ratios (T/B) for IMT under/before radiation therapy were correlated to survival times. Initially, SPECT depicted an abnormal intratumoural IMT uptake in all patients (mean T/B ratios 1.37-1.87). In four out of 10 patients, the mean T/B ratios decreased by more than 10% under radiation therapy. In six other patients, the BQ decreased by less than 10% or increased. There were no significant correlations between the degree of changes in T/B and survival (r = -0.1, p = 0.973). Serial IMT SPECT measurements allow detection of changes in amino acid accumulation in high-grade gliomas under radiation therapy. However, these changes seem to possess no prognostic value in respect to survival prediction.

Living related liver transplantation: preoperative magnetic resonance imaging for assessment of hepatic vasculature of donor candidates

PURPOSE

To evaluate the accuracy of magnetic resonance angiography (MRA) for preoperative assessment of hepatic vascular anatomy in liver donors before living related liver transplantation.

MATERIAL AND METHODS

A total of 55 consecutive living liver donors (mean age 42 years, range 18-68 years) underwent multiphase contrast-enhanced MRA of the hepatic vessels. Two readers categorized vessel visualization on a five-point scale and recorded vascular anatomy or variations thereof for the arterial, portal venous and venous systems. All 55 living liver donors subsequently underwent right hemihepatectomy for hemiliver donation, and preoperative MRA results were correlated with surgical findings.

RESULTS

Overall vessel visualization assessment demonstrated good or very good ratings for the majority of patients. For hepatic arteries, the mean score was 4.4+/-0.8 (mean+/-standard deviation), and for the portal venous and venous systems it was 4.6+/-0.7 and 4.3+/-0.8, respectively. Among all 55 donors, 16 (29%) demonstrated accessory or replaced hepatic arteries, and seven (13%) and 20 (36%) donors had surgically relevant portal vein (trifurcation or early right posterolateral branching types) and hepatic vein variations, respectively. Correlation coefficients between MRA and surgery were 0.94, 1.00 and 0.91 for hepatic arteries, portal veins and hepatic veins, respectively.

CONCLUSION

In the preoperative evaluation before living related liver donation, contrast-enhanced MR angiography was a highly accurate, noninvasive tool for visualizing the hepatic vasculature and variations thereof in liver donor candidates.

Multislice Computed Tomographic Angiography for Preinterventional Planning of Port Placement for Intra-Arterial Hepatic Infusion Chemotherapy

PURPOSE

To determine the impact of preinterventional multislice computed tomographic angiography (MSCTA) on the interventional management of patients scheduled for hepatic port placement.

METHODS

A total of 21 patients with metastatic colorectal cancer confined to the liver were referred for interventional placement of an intra-arterial hepatic port system and underwent triphasic MSCT of the abdomen. The arterial phase images were processed to reveal the arterial anatomy, to identify anomalies, and to prospectively plan the interventional management. Ten anatomical characteristics of the liver blood supply, which were considered to be crucial for the interventional procedure, were analyzed per patient (presence, origin, and configuration of liver arteries, angles, and distances to connected vessels). Based on these data, 6 predictions on the interventional procedure were made, including final catheter position, catheter type, the necessity for guiding catheter, expenditure of time, and the need for changing the standard implantation procedure. All findings were correlated with catheter angiography during the port placement.

RESULTS

Normal vascular anatomy of the hepatic arteries was seen in 43% of the patients. As vascular variants, most frequently, we found an accessory right artery (19%), a replaced right artery arising from the superior mesenteric artery (14%), or a left hepatic artery, fed by the left gastric artery, in combination with a middle hepatic artery arising from the right hepatic artery (10%). The correct detailed anatomical description compared with angiographic findings was provided by an MSCTA image analysis in 20 of 21 patients (sensitivity = 0.98, specificity = 0.99; chi2 = 1.024, P = 0.311; 95% confidence interval (CI) = 95.24; 76.18-99.88). The prospective planning of the angiographic management, including the appropriate choice of the port catheter based on MSCTA, was correct in 17 of 21 patients (sensitivity = 0.71, specificity = 0.76; chi2 = 2.487, P = 0.115; 95% CI = 80.95; 58.09-94.55).

CONCLUSIONS

The MSCTA is effective for planning interventional port implantation in patients considered for hepatic arterial infusion chemotherapy.

Impact of image fusion and attenuation correction by SPECT-CT on the scintigraphic detection of parathyroid adenomas

AIM

In addition to planar parathyroid scintigraphy, SPECT and image fusion with CT/MR improve adenoma detection in primary hyperparathyroidism (pHPT). This study evaluated the use of a hybrid SPECT-CT device concerning image fusion and attenuation correction (AC).

PATIENTS, METHODS

The data of 26 patients with pHPT, preoperatively examined by (99m)Tc-sestamibi dual-phase scintigraphy plus SPECT-CT (low-dose CT), was retrospectively evaluated by two observers in a consensus reading. The images of planar scintigraphy, non-attenuation corrected SPECT (SPECT(NAC)), attenuation corrected SPECT (SPECT(AC)) and SPECT(AC)-CT were interpreted and compared to the results of surgery. The effect of AC on focus intensity was semiquantified by determination of the tumor-to-background (TB) ratio for SPECT(AC) and SPECT(NAC). Finally, the TB(AC)/TB(NAC)-ratio was calculated for each focus and correlated to the distance of a focus from the body surface.

RESULTS

20/26 (77%) patients were positive in planar scintigraphy. One focus was detected by SPECT only. AC of SPECT-data increased image contrast but had no impact on the detection rate. Additional SPECT(AC)-CT image fusion facilitated the localization of three mediastinal foci. In the semiquantitative analysis an increase in TB after AC was observed, although there was no strong correlation between depth of the focus (16-60 mm) and the TB(AC)/TB(NAC)-ratio (r = 0.213, p = 0.353).

CONCLUSION

The detection rate of planar scintigraphy is only slightly improved by SPECT imaging. Due to the low spatial resolution of the CT component, the benefit of image fusion is limited to mediastinal foci. However, as TB and image contrast is measurably improved after AC there is a potential to improve the sensitivity of parathyroid SPECT.

Impact of FDG-PET/MRI image fusion on the detection of pancreatic cancer

BACKGROUND

This study assessed the value of image fusion with (18)F-fluorodeoxyglucose-positron emission tomography (FDG-PET) and magnetic resonance imaging (MRI) in patients suspected of having pancreatic cancer.

METHODS

32 patients (12 women, 20 men; age 24-79 years; mean 56.6 years) were included. All patients underwent whole-body FDG-PET examinations and contrast-enhanced MRI. Image fusion used a semiautomatic voxel-based algorithm. Separate reading, side-by-side analysis and evaluation of fused PET/MRI images were performed. Results were correlated to histopathology (n = 30), or clinical follow-up (n = 2).

RESULTS

15/32 patients had pancreas cancer and 17/32 patients benign disease. The sensitivity and specificity for cancer detection by FDG-PET were 93 and 41% for visual and 86 and 58% for semiquantitative analysis whereas MRI achieved 100 and 76% respectively. Topographical assignment of PET foci by image fusion was superior to side-by-side analysis in 11/39 (28%) foci (in 8/32 patients). However, a true impact on therapeutic strategy was observed only in 1/8 patients as the presence of multiple metastases, irresectable primaries or medical reasons for inoperability prevented a curative setting.

CONCLUSION

Compared to side-by-side analysis, PET/MRI image fusion improves the anatomical assignment and interpretation of FDG foci. The therapeutic benefit for the patient however is limited in patients with multiple lesions or incurable primaries.

Impact of whole-body MRI and FDG-PET on staging and assessment of therapy response in a patient with Ewing sarcoma

In patients with Ewing sarcoma, precise staging is not only crucial for the therapeutic regimen but also for a reliable evaluation of response to therapy. We report on a 15-year-old girl with metastatic spread of a Ewing sarcoma who, apart from conventional staging by bone scan, chest X-ray and CT, was subsidiary examined by FDG-PET and whole-body MRI before and after chemotherapy. Both modalities detected more bone lesions than the bone scan, which led to an altered strategy for radiotherapy. Both examinations might be a great asset to stage-adjusted therapy regimens, ultimately influencing patient outcome.

Long-lasting remission of pulmonary metastases of renal cell cancer under IFN-beta therapy in a patient with multiple sclerosis

BACKGROUND

Immunomodulary therapy based on interferon (IFN)-a has been shown to be effective in a subset of patients with advanced renal cell carcinoma (RCC). IFN-Beta has occasionally been reported to induce remissions in RCC, but is well established in the treatment of multiple sclerosis (MS). There is an ongoing debate whether hyperactivation of the immune system may convey protection against the development of cancer in MS patients.

PATIENTS AND METHODS

A 54-year-old female MS patient underwent tumor nephrectomy for RCC in 1994. 1 year later, several bilateral pulmonary metastases were documented by computed tomography and were histologically confirmed thereafter. Therapy with IFN-Beta was started.

RESULTS

Soon after initiation of IFN-Beta treatment, the patient achieved an almost complete remission which is still ongoing after 10 years of IFN-Beta therapy.

CONCLUSION

To our knowledge, this is the longest remission under IFN-Beta treatment ever reported in an RCC patient. We conclude that IFN-Beta should be particularly considered as a therapeutic option in the rare occasion of metastatic RCC in patients with MS.

Correlative imaging strategies implementing CT, MRI, and PET for staging of childhood Hodgkin disease

BACKGROUND

The value of different correlative imaging strategies with F18-fluorodeoxyglucose positron emission tomography (FDG-PET) and conventional imaging modalities (CIM) for initial staging of pediatric Hodgkin disease (HD) was assessed.

METHODS

Thirty-three patients (age, 4 to 18 y) with histologically proven HD underwent initial staging with computed tomography (thorax), magnetic resonance imaging (neck, abdomen, pelvis), and FDG-PET in a prospective study. Image fusion (PET-CIM) was performed using a semiautomatic voxel-based algorithm. Analysis of separate, side-by-side (SBS) and fused PET and CIM was performed evaluating 21 nodal and 6 extranodal regions per patient for presence of lymphoma, applying a 5-point confidence scale. The reference data was clinical follow-up (>12 mo).

RESULTS

Concerning lymph node regions above and below the diaphragm the accuracy of CIM, PET, SBS, and image fusion was 86%, 89%, 94%, 97%, and 94%, 94%, 97%, 98%. In extranodal regions, the accuracy was 96%, 96%, 100%, and 100%. The reviewers' confidence was improved significantly by image fusion. Staging and therapy assignment on the basis of CIM was correctly modified by SBS in 5 and 4, by image fusion in 7 and 5 patients.

CONCLUSIONS

Combined reading of FDG-PET and CIM is crucial for accurate staging in pediatric HD. Image fusion improves the observers' confidence and has impact on the therapeutic management.

Hepatocellular carcinoma in association with hepatic focal nodular hyperplasia

PURPOSE

To report the association between hepatocellular carcinoma (HCC) and hepatic focal nodular hyperplasia (FNH) and the possible impact on clinical decision-making with regard to resective approaches in patients with FNH.

MATERIAL AND METHODS

We retrospectively analyzed the findings in 77 adult patients who underwent liver resections for FNH between October 1989 and September 2001 at our center. HCC within the confines of FNH was found in two patients. We demonstrate the magnetic resonance imaging (MRI) and macroscopic and microscopic findings.

RESULTS

Presurgical MRI demonstrated heterogeneous signal characteristics of moderately hyperintense FNH on T2-weighted images and, after i.v. administration of superparamagnetic iron oxide particles, HCC in FNH was barely delineable. Both patients underwent successful right hemihepatectomy to remove the suspicious FNH with diameters of 12 and 14 cm; intralesional HCC diameters were 3 and 5 cm, respectively. Patients could be rapidly dismissed. However, one patient died after recurrence of HCC 1.5 years after surgery, whereas the other patient continues tumor-free 4 years after surgery. Alpha-feto-protein was normal in both patients.

CONCLUSION

In FNH with rapid growth tendency and heterogenic MR appearance, surgical removal should be considered to overcome the risk of inadequate therapy in the very rare group of patients with HCC in association with FNH.

Relevance of Image Fusion With MRI for the Interpretation of I-123 Iodo-Methyl-Tyrosine Scans in Patients With Suspected Recurrent or Residual Brain Tumor

PURPOSE

The aim of the study was to investigate the impact of MR/SPECT image fusion on the interpretation of I-123 iodo-methyl-tyrosine (IMT) SPECT examinations in patients with pretreated brain tumors.

MATERIAL AND METHODS

In this retrospective study, 45 consecutive patients with suspected recurrent/residual gliomas (n = 41) or cerebral metastases (n = 4) were included. SPECT studies were performed using a triple-head gamma-camera system 10 minutes after injection of 300 to 370 MBq (8.1-10 mCi) I-123 IMT. Concerning MR, T1-, T2-, and FLAIR-weighted sequences as well as contrast-enhanced T1-weighted sequences were acquired by 1.5-T or 3.0-T scanners. For image fusion, the MPI-tool software package was used. SPECT and MR/SPECT fusion images were anonymized and then independently evaluated by 3 observers aware of the clinical data. Tumor localization and extent were evaluated and correlated with histopathology or clinical follow up, including MR imaging.

RESULTS

In 10 of 45 (22%) patients, image fusion had a significant impact on the interpretation of scans: 5 suspected SPECT findings were correctly classified as physiological or therapy-related; in another 5 patients, image fusion added relevant clinical information on tumor extent (infiltration of the contralateral hemisphere n = 3, infiltration of the brain stem n = 2).

CONCLUSIONS

According to our data, image fusion is crucial for the interpretation of positive I-123 IMT SPECT findings.

Diagnostic value of 123I-IMT SPECT in the follow-up of head and neck cancer

BACKGROUND

Nuclear medicine imaging is increasingly used in the evaluation of tumors of the head and neck. In the current study, we assess the value of single-photon emission tomography (SPECT) using the amino acid tracer L-3-[123I]iodine-alpha-methyl-tyrosine (IMT) for the detection of recurrent head and neck cancer.

PATIENTS AND METHODS

45 consecutive patients with suspected recurrence of previously treated head and neck cancer were examined by IMT-SPECT using a dual head system with integrated low-dose computed tomography (CT). The accuracy of the IMT-SPECT was evaluated by correlating the findings with results of histology or clinical and CT/MRI (magnetic resonance imaging) follow-up examinations.

RESULTS

The sensitivity, specificity and accuracy of IMT-SPECT in the detection of recurrent/persistent tumors were 83, 89 and 84.5%, respectively. The positive and negative predictive value amounted to 96.5 and 60%, respectively.

CONCLUSION

IMT-SPECT using integrated low-dose CT appears to be a helpful complementary imaging tool for the detection of local recurrences and lymph node metastases of head and neck cancer and their differentiation from treatment-induced changes. The advantage of the method is the high positive predictive value in the diagnosis of relapsed tumors. However, a negative IMT-SPECT result does not exclude a recurrence.

FDG-PET in 10 children with non-Hodgkin's lymphoma: initial experience in staging and follow-up

BACKGROUND

The use of FDG-PET was evaluated for initial staging and therapy efficacy in paediatric patients with non-Hodgkin's lymphoma (NHL) and compared to the established conventional imaging modalities (CIM). The results of this retrospective analysis are presented in conjunction with a critical review of the current literature.

PATIENTS AND METHODS

Ten paediatric patients with NHL were examined using whole-body FDG-PET initially (n = 6), during therapy (n = 5) and after completion of therapy (n = 5), respectively. FDG-PET findings were compared to CIM performed according to the protocol of the German NHL-BFM 95 study. The results were evaluated for their impact on disease classification and therapy decision (St. Jude, REAL) in correspondence to a clinical follow-up of at least 24 months.

RESULTS

Concerning initial staging, all lymphoma manifestations detected by conventional imaging were also detected by FDG-PET (15 nodal, 2 extranodal). Furthermore, an additional nodal lesion was detected by FDG-PET in three patients. This resulted in an upstaging followed by an intensified poly-chemotherapy in one patient. In five patients showing unclear residual masses on conventional imaging during therapy, FDG-PET indicated viable residual tumours in one case. This patient showed a relapse during follow-up while the four FDG-PET negative patients did not. After completion of initial therapy, FDG-PET revealed in one out of five patients persistent tumour metabolism in the primary lesions and also detected new manifestations. The patient died shortly after restaging due to disease progression.

CONCLUSIONS

These first results on the use of FDG-PET in paediatric non-Hodgkin lymphoma indicate a high potential to improve the therapeutic management.

Minimum intensity projections of the biliary system using 16-channel multidetector computed tomography in patients with biliary obstruction: comparison with MRCP

The objective was the evaluation of minimum intensity projections (MinIP) of 16-channel multidetector computed tomography (MDCT) data for the visualization of biliary ducts with magnetic resonance cholangiopancreatography (MRCP) as reference method. Twenty-five patients with biliary obstruction who received MDCT of the abdomen and MRCP without subsequent interventions were analysed. Coronal and axial MinIP were reconstructed from the MDCT-data. The evaluation of image quality and the quantitative comparison to MRCP was performed by two observers in consensus. The additional diagnostic value of MinIP compared with conventionally visualised MDCT was assessed by three independent observers. With MRCP as the reference method, MinIP was superior to conventional MDCT concerning the visualization of the extent of bile duct dilatation (r, 1.000 vs 0.699) and the correlation of diameter measurement (r, 0.979 vs 0.942). Subsidiary to conventional MDCT, MinIP revealed an improvement of visualization of the biliary system in 73% of cases. Concerning the additional diagnostic value, MinIP allowed for a better definition of the obstruction site in 13% of patients, and in one patient a change of diagnosis was observed. Thus, MinIP can improve the diagnostic assessment of biliary obstructions in MDCT imaging.

Magnetic resonance imaging in the assessment of cystic pancreatic lesions: differentiation of benign and malignant lesion status

PURPOSE

To characterize cystic pancreatic lesions and tumors with magnetic resonance imaging (MRI), and to assess the value of morphological criteria in differentiating pseudocysts versus cystic tumors and benign versus malignant cystic tumors.

MATERIAL AND METHODS

Twenty-three patients with cystic pancreatic tumors or lesions underwent plain and contrast-material-enhanced MRI, including magnetic resonance cholangiopancreatography (MRCP). The MR findings were characterized and analyzed by two readers, and the role of various imaging criteria and combinations thereof for final lesion assignment were assessed. Final diagnoses were obtained from the results of open surgery (n = 19) and/or biopsy (n = 4).

RESULTS

Final diagnoses included cystic tumors (n = 11) and pseudocysts (n = 12). The lesions were located in the head (56%) and body or tail (44%). Lesion diameters ranged from 7 to 50 mm. Various lesion contrast enhancement patterns were observed for both benign and malignant lesions. Serous cystadenomas were located in the head, they were lobulated, and had wall diameters < or = 2 mm; with the combination of these characteristics all patients with serous cystadenoma could be identified, whereas in no other patient was this constellation observed.

CONCLUSION

MRI facilitated the diagnosis of serous cystadenomas, although no definite morphologic criterion for the differentiation between pseudocysts and mucinous cystadenomas was identified. In consideration of the substantial therapeutic consequences, either diagnostics in unclear cystic pancreatic lesions should comprise cyst fluid analysis if necessary, or eligible patients should be referred for surgical resection.