Does 18F-FDG PET/CT improve the detection of posttreatment recurrence of head and neck squamous cell carcinoma in patients negative for disease on clinical follow-up?

UNLABELLED: Posttreatment surveillance for the recurrence of head and neck squamous cell carcinoma (HNSCC) is a diagnostic challenge. Tissue distortion from radiation and surgery can obscure early detection of recurrence by conventional follow-up approaches such as physical examination, CT, and MRI. Several studies have shown that 18F-FDG PET may be an effective technique for the detection of persistent, recurrent, and distant metastatic HNSCC after treatment. The aim of this prospective study was to determine the benefits of hybrid 18F-FDG PET/CT in detecting a subclinical locoregional recurrence of HNSCC and distant metastases. The study patients were considered cured of HNSCC on the basis of 12 mo of negative findings on conventional follow-up. We also assessed the diagnostic accuracy of 18F-FDG PET/CT in these patients. METHODS: Ninety-one patients cured of HNSCC without any clinical evidence of recurrence were included. Whole-body 18F-FDG PET/CT examination was performed 11.6+/-4.4 mo after the end of the treatment. The gold standard was histopathology or 6 mo of imaging follow-up. RESULTS: The whole-body 18F-FDG PET/CT examinations had negative results in 52 patients and positive results in 39. Nine of these patients who exhibited abnormal 18F-FDG uptake in the head and neck area did not have recurrent HNSCC (false-positive). Thirty had proven recurrence. The sensitivity and specificity of 18F-FDG PET/CT in this study for the diagnosis of HNSCC recurrence were 100% (30/30) and 85% (52/61), respectively. The positive predictive value was 77% (30/39). The negative predictive value was 100% (52/52). The overall accuracy was 90% (82/91). CONCLUSION: The results of our study confirm the high effectiveness of 18F-FDG PET/CT in the assessment of HNSCC recurrence and suggest that 18F-FDG PET/CT is more accurate than conventional follow-up physical examination alone in the assessment of recurrence after previous curative treatment for HNSCC and could be proposed systematically at 12 mo of the usual follow-up.

Management of suspected pulmonary embolism patients with low clinical and low V/Q probability.

OBJECTIVE: To assess whether guidelines for the management of suspected PE, recommending that ventilation/perfusion (V/Q) scintigraphy should be followed by other imaging in case of non-diagnostic result, and interpreted along with the clinical probability, are applied in daily practice. DESIGN: Two-year audit study. SETTING: Tertiary hospital in France. PARTICIPANTS: All patients referred to the nuclear medicine department for a suspected pulmonary embolism (PE), with a low clinical probability, a positive D-Dimer test, and a low V/Q scintigraphy. INTERVENTION: We reviewed medical records to collect data on further diagnostic strategy and therapeutic management. MAIN OUTCOME MEASURE: Thromboembolic risk during a three-month follow up in patients who did not undergo anticoagulation therapy on the basis of a negative diagnostic work up. RESULTS: Of the 456 selected patients, PE was excluded on the basis of a low pretest probability and a low V/Q scintigraphy probability without further testing in 184 (group 1). In the other 272 patients (group 2), 4 venous thromboembolism (VTE) events were diagnosed by leg vein ultrasonography and/or computed tomography pulmonary angiography. In patients who did not receive anticoagulant treatment during follow up, one patient from group 1 (0.6%, 95% confidence interval 0.1 to 3.3) and two patients from group 2 (0.9%, 95% CI 0.2 to 3.2) had an acute venous thromboembolic event. CONCLUSION: Different attitudes are adopted by physicians in patients with a low clinical probability and a low V/Q scintigraphy probability, without impact on safety, as assessed by a non-significant difference in the three-month thromboembolic risks between these two groups.

Does 18fluoro-fluorodeoxyglucose positron emission tomography improve recurrence detection in patients treated for head and neck squamous cell carcinoma with negative clinical follow-up?

BACKGROUND: The aim of this study was to determine the benefits of 18fluoro-fluorodeoxyglucose positron emission tomography (18F-FDG PET) in the detection of head and neck squamous cell carcinoma (HNSCC) recurrence in patients with negative clinical follow-up. METHODS: Whole-body 18FDG-PET was performed in 30 patients treated for HNSCC without any clinical element for recurrence. RESULTS: Twenty-one negative PET and 9 positive results were seen. One patient with abnormal 18F-FDG uptake in the laryngeal area did not have recurrent HNSCC (false positive). Eight had proven recurrence. The sensitivity and specificity of 18F-FDG PET for the diagnosis of HNSCC recurrence were 100% (8/8) and 95% (21/22), respectively. The positive predictive value was 89% (8/9). The negative predictive value was 100% (21/21). The overall accuracy was 97% (29/30). CONCLUSION: The results of our study confirm the high effectiveness of 18F-FDG PET in assessment of HNSCC recurrence and suggest that it is more accurate than conventional physical examination follow-up alone.

Delayed gastric emptying scintigraphy in cystic fibrosis patients before and after lung transplantation.

BACKGROUND: The purpose of this study was to assess the rate of gastric emptying (GE) in cystic fibrosis patients scheduled for lung transplantation. METHODS: Thirty patients (20 males, 10 females, 22.6 +/- 6.4 years) were evaluated by GE scintigraphy before (1.58 +/- 1.11 years) and early after (5.8 +/- 2.6 weeks) heart-lung transplantation (n = 13) or lung transplantation (n = 17). Solid retention rates at 2 hours (RR2) and 3 hours (RR3) and half-emptying times (T50) of solids and liquids obtained before transplantation were compared with those after transplantation. Data were also compared with those obtained from a control group of 53 healthy volunteers. RESULTS: Before surgery, 20 patients (67%) showed a delayed GE (T50 of solids: patients 160.86 +/- 59.21 minutes vs controls 75.43 +/- 15.13 minutes, p < 0.0001), and 4 of them also had a delayed T50 of liquids. After surgery, the T50 of solids was considered unreliable (too much stasis) in 24 patients. Thus, analyses were done on the basis of solid retention rates. Twenty-nine patients (97%) showed very delayed GE compared with controls (p < 0.0001), 20 of whom also had a delayed T50 of liquids. RR2 and RR3 were significantly higher after surgery than before (RR2 = 86 +/- 17% and RR3 = 77 +/- 22% vs 50 +/- 24% and 27 +/- 24% after and before surgery, respectively, p < 0.0001). However, there was no correlation between pre- and post-transplantation scintigraphy results. CONCLUSIONS: Delayed GE of solids was a frequent abnormality in patients with end-stage cystic fibrosis, with a dramatic delay after surgery in almost all patients. These results emphasize the need for early management of such patients by dietary manipulation or prokinetic medications.

Optimized radioiodine therapy for Graves' disease: two MIRD-based models for the computation of patient-specific therapeutic 131I activity.

AIM: (131)I therapy is increasingly used for Graves' hyperthyroidism. Debate remains about the best method for calculating the activity to administer, as well as about the potential benefit of such computed activity. Several arguments plead, nevertheless, in favour of a personalized computation, such as inter-individual variations of thyroid volume and biokinetics. METHODS: A MIRD-based dosimetric approach, with an additional extension that takes into account the variation of thyroid mass during the treatment, has been developed. This approach includes the benefits of a personalized determination of biokinetics. Results were compared with those of six methods widely used in routine practice. Forty-one patients were enrolled (34 women, seven men; mean age +/-SD: 48.11 +/- 6.4 years). (131)I uptakes were measured at 4, 24 and 96 h (36.2 +/- 14.6%, 42.8 +/- 9.7% and 27.6 +/- 6.8%, respectively), following administration of the tracer. The kinetics of iodine in the thyroid were evaluated using a two-compartment model (effective half-life of 5.1 +/- 1.6 days). Computations of activities to deliver the doses prescribed by the physician were done with the eight formalisms. RESULTS: There was no statistical difference between results of the two MIRD-based formalisms (227 +/- 148 MBq and 213 +/- 124 MBq), which were also not significantly different from those obtained with the majority of the other methods (from 128 +/- 95 MBq to 275 +/- 223 MBq). However, a large intra-individual difference up to a factor of 2 between two given methods was found. CONCLUSION: The formalism developed appears to be a good compromise between all the common formalisms already used in many institutions. Furthermore, it allows the exposures of target volumes and non-target volumes to be planned individually and practical individual radiation protection recommendations to be implemented.

Comparison of gastric emptying scintigraphy based on the geometric mean of the gastric proportion of the abdominal radioactivity or on the geometric mean of the intragastric radioactivity.

PURPOSE: Using gastric emptying scintigraphy the gastric retention rate is commonly calculated within a gastric region of interest (intragastric method). This technique may have significant limitations when left oblique anterior views are acquired, due in part to attenuation resulting from intragastric redistribution. To minimize these drawbacks, it was proposed to express the intragastric content as a percentage of the abdominal radioactivity (abdominal method). Our goal was to compare these two methods when anterior-posterior scanning is used. METHODS: Antero-posterior scintigraphic data of 272 consecutive patients were analysed by both methods. Retention rates were obtained by both observation and calculation by power exponential fit. Gastric emptying parameters (half-emptying time of solids (T(50,S)) and liquids (T(50,L)), lag phase (T(lag)) time and real emptying time (T(RE))), and quality of fit were also computed and compared. RESULTS: For solids, the intragastric method resulted in weakly higher experimental retention rates, whereas retention rates were quite similar for liquids. Differences between experimental and calculated retention rates were smaller for abdominal method, for both liquids and solids. As a result, values for the quality of fit were higher for the abdominal method. Significant differences were observed only for calculated T(50,S) (122+/-46 min vs. 124+/-48 min, mean difference 2+/-2 min, P<0.00001) and T(RE) (163+/-64 min vs. 168+/-68 min, mean difference 4.5+/-3.8 min, P<0.05), respectively, for the abdominal and the intragastric methods. However, the Bland-Altman statistical method revealed good agreements (<5% outliers). CONCLUSION: Intragastric and abdominal methods can be used indifferently to treat antero-posterior data of gastric scintigraphy.

99mTc ovalbumin labelled eggs for gastric emptying scintigraphy: in-vitro comparison of solid food markers.

BACKGROUND: The reliability of solid phase gastric emptying measurements by scintigraphy requires a marker that remains within the solid component of the test meal, and which is not degraded by the gastric juice throughout the scintigraphic procedure. In Europe, foods are most often labelled with 99mTc rhenium sulfide macrocolloid (RSMC) but this solid phase marker was withdrawn from the market in January 2004. OBJECTIVE: To test other potential solid phase markers and to compare them to the reference marker RSMC. These markers were rhenium sulfide nanocolloid (RSNC), tin fluoride colloid (TFC), phytates and two albumins (Alb and AlbC). All were radiolabelled with 99mTc. METHODS: After quality control, each 99mTc marker was incorporated into the albumin of one egg. Then, egg white and yolk were mixed together, and a well-cooked omelette was prepared. Aliquots of the omelette were incubated with an acidic solution of pepsin at 37 degrees C which mimicked gastric juice. Unbound radioactivity in the supernatant fraction was measured at various times up to 3 h. RESULTS: The radiochemical purity was > 95% for all radiopharmaceuticals. During the in-vitro incubation, the percentage of 99mTc labelled colloids released from the omelette increased continuously: after 3 h, 5% for TFC and RSMC, 8% for phytates, and > 9% for the two albumins and RSNC. CONCLUSION: Considering quality controls and release of 99mTc during in-vitro incubation of the omelette, TFC showed the same behaviour as the reference marker RSMC. Thus, TFC seems to be the best candidate to replace RSMC for the radiolabelling of the solid phase of the gastric emptying test meal.

Gastric scintigraphy with a liquid-solid radiolabelled meal: performances of solid and liquid parameters.

AIM: To assess the clinical performance of parameters of liquid-solid gastric emptying (GE) scintigraphy. METHODS: Fifty-three controls and 476 patients underwent GE scintigraphy using a liquid-solid test meal (non-ulcer dyspepsia, n=180; gastro-oesophageal reflux disease, n=123; dyspepsia after anti-reflux surgery, n=29; diabetes mellitus, n=96; cystic fibrosis prior to heart-lung transplantation, n=48). Time-activity curves were fitted by a power exponential function and half-emptying times (T1/2) were computed. The lag phase (Tlag) and constant emptying (TRE) times of solid emptying were also calculated using a mathematical method (maximum slope tangent method). RESULTS: TRE and T1/2 of solids were higher in each subgroup of patients vs. controls (P=0.0001) and in cystic fibrosis patients vs. gastro-oesophageal reflux patients (P=0.0001). Tlag was significantly higher only in non-ulcer dyspepsia patients vs. controls (P=0.001). There was no significant difference for liquid parameters. Using the mean+/-1.96 SD of the solid and liquid T1/2 values obtained in controls, GE was normal (n=251; 53%), delayed (n=183; 38%), accelerated (n=33; 7%) or mixed (n=9; 2%). Delayed solid T1/2 was the most prominent alteration (n=189), and alterations of liquid GE alone were present in only 24 (5%) patients. A good correlation was found between solid T1/2 and TRE (r=0.88), but no correlation between Tlag and TRE, suggesting that these estimates represent independent phases of GE. In 26 patients, all GE parameters of solids and liquids were normal except Tlag (n=8) or TRE (n=18). The lack of significant differences between the different patient subgroups did not allow emptying profiles to be drawn according to patient pathology. CONCLUSION: Liquid GE scintigraphy provided poor and unreliable information in terms of patient discrimination and the drawing of pathophysiological profiles of abnormal GE. Tlag and TRE may confirm GE alteration, especially when solid T1/2 values are at the superior limit of normality, and may improve the performance of GE scintigraphy, rather than using liquid parameters.

Octreotide imaging plus bone scintigrams to optimally localize gastroenteropancreatic neuroendocrine tumors.

PURPOSE: In-111 pentetreotide (Octreotide) is highly sensitive for detecting gastroenteropancreatic neuroendocrine tumors and their metastases. However, a lack of landmarks makes it difficult to localize them anatomically. To overcome this difficulty, the authors simultaneously obtained Octreotide and bone tomoscintigrams, in addition to standard planar images. They used a bicolor scale to display pairs of scintigrams to easily identify the distribution of both tracers. METHODS: Twenty-one hours after Octreotide injection, Tc-99m MDP was also administered to the patients. Three hours later, dual-energy planar and tomographic data were acquired simultaneously. The latter were reconstructed using a filtered back-projection algorithm using a Metz filter. Both sets of data were displayed simultaneously using a bicolor scale, such that Octreotide data appear in green and bone data in red. RESULTS: Planar, tomographic, and three-dimensional data were obtained. With this approach, foci of abnormal uptake are localized more precisely. Hard data can be transmitted easily to referring physicians, who appreciate this compact and efficient means to locate foci of abnormal uptake, especially during surgery planning. However, this method is not well suited to the visualization of small lesions with low Octreotide uptake because the intensity range is drastically reduced. Such lesions are better seen on Octreotide planar images and standard tomoscintigrams. CONCLUSIONS: This approach, which involves only standard image processing, provides landmarks to easily localize significant Octreotide uptake. It can be implemented readily in most nuclear medicine workstations. It complements but does not replace the usual method to display Octreotide data.