Safety and efficacy of Holmium-166 selective internal radiotherapy of primary and secondary liver cancer confirmed by real-world data.

Purpose: Holmium-166 has emerged as a promising option for selective internal radiotherapy (SIRT) for hepatic malignancies, but data on routine clinical use are lacking. The purpose of this study was to describe the safety and effectiveness of Holmium-166 SIRT in real-world practice through retrospective analysis of a multicenter registry. Methods: Retrospective analysis was conducted on Holmium-166 SIRT procedures performed between July 15, 2019, and July 15, 2021, across seven European centers. Treatment planning, treatment realization and post-treatment follow-up were conducted according to routine local practice. Safety and effectiveness data were extracted from the patients' health records. Primary endpoint analysis was assessed for the entire study population with separate analysis for subgroups with hepatocellular carcinoma, metastatic colorectal cancer and intrahepatic cholangiocarcinoma. Results: A total of 167 SIRT procedures in 146 patients (mean age 66 ± 11 years, 68% male) were retrospectively evaluated. Most common tumor entities were hepatocellular carcinoma (n=55), metastatic colorectal cancer (n=35), intrahepatic cholangiocarcinoma (n=19) and metastatic neuroendocrine tumors (n=10). Nine adverse events grade ≥ 3 according to Common Terminology Criteria for Adverse Events were recorded, including one fatal case of radioembolization-induced liver disease. Response rates and median overall survival for the above mentioned subgroups were comparable to results from previous Holmium-166 trials as well as to results from Yttrium-90 registries. Conclusion: This study confirms that the safety and effectiveness of Holmium-166 SIRT derived from prospective trials also applies in routine clinical practice, reinforcing its potential as a viable treatment option for primary and secondary liver cancer.

Dependence of Renal Uptake on Kidney Function in [68Ga]Ga-PSMA-11 PET/CT Imaging.

(1) Background: PSMA ligand PET/CT is increasingly important for diagnostics of prostate cancer and other tumor diseases. In particular, the radiopharmaceutical [68Ga]Ga-PSMA-11 is widely used. Besides its tumor-specific binding, the uptake within the kidneys is dominant and seems to visualize the renal cortex specifically. Kidney diseases may alter the uptake of radiopharmaceuticals. Therefore, the correlation between renal uptake in PET/CT imaging and renal function should be investigated. (2) Methods: A group of 103 male patients were retrospectively evaluated for eGFR according to the CKD-EPI equation, tracer uptake intensity (SUVmax, SUVpeak, SUVmean), the molecular volume of the renal cortex, morphological kidney size, and total renal uptake. Manual and three different computer-assisted contouring methods (thresholds at 50% of SUVmax, 30% of SUVmax, and absolute SUV of 20) were used for measurements. Correlations between parameters were calculated using linear regression models. (3) Results: Renal SUVmax, SUVpeak, and SUVmean do not correlate with eGFR for manual or computer-assisted measurements. In contrast, molecular cortex volume shows a moderate correlation with eGFR (R2 = 0.231, p < 0.001), superior to morphological kidney size. A contouring threshold of 30% of SUVmax outperformed the other settings for renal cortex volume and total renal uptake. (4) Conclusions: Renal uptake of [68Ga]Ga-PSMA-11 cannot predict eGFR, but the functional renal cortex can be quantified by PET/CT imaging.

Transarterial Radioembolization (TARE) in Patients with Hepatocellular Carcinoma: A Comparison of Palliative with Bridging-to-Transplant Concepts.

We investigated transarterial radioembolization (TARE) as a palliative measure and bridging-to-transplant therapy in hepatocellular carcinoma (HCC) patients. A total of 167 patients (50 bridging, 117 palliative) with 245 TARE procedures were assessed. Fourteen patients underwent subsequent liver transplantation (LT). Patients undergoing LT exhibited significantly prolonged progression-free survival (PFS) compared to those with bridging-without-transplant (p = 0.033). No significant differences were observed between patients with bridging-without-transplant and palliative cases (p = 0.116). Median overall survival (OS) post-TARE was 16.6 months, with estimated OS rates at 6/12 months of 82.0%/60.5%, respectively. Patients who underwent LT demonstrated statistically significantly longer OS compared to those with bridging-without-transplant (p = 0.001). No marked outcome distinctions were found between bridging-without-transplant and palliative groups. The findings underscored the superiority of LT over alternative treatments. TARE served as an important component in non-LT scenarios, allowing for subsequent therapeutic options. The study reflected the highly variable and complex situations of patients with HCC, emphasizing the need for further investigations to define an optimal multimodal approach.

[Normal values for adult thyroid volume on ultrasound - where do they come from and how should they be evaluated?] / Sonographische Normwerte für das Schilddrüsenvolumen Erwachsener ­ woher kommen sie und wie sind sie zu bewerten?

The upper limit for the thyroid volume is 18 ml for women and 25 ml for men. These reference values are used and taught in many clinics and practices across several disciplines. The thyroid volume is a relevant factor for the treatment course. But where do the standard values for thyroid volumes come from, what kind of studies have been carried out to establish them? Should these upper limits be used as an universal standard in clinical routine, and which factors can influence the physiological organ size? The following article is dedicated to a critical review of the commonly used reference values for the thyroid volume of adults.

Noninvasive Verification of a Very Small Intraocular Prostate Carcinoma Metastasis by 68Ga-PSMA-11 PET/CT.

ABSTRACT: A male patient underwent 68Ga-PSMA-11 PET/CT for the evaluation of a suspected intraocular metastasis in the right eye. Although the choroidal thickening was very small (4 × 2 mm), and ophthalmoscopy as well as MRI were inconclusive, PET/CT imaging showed distinct PSMA expression in the suspected lesion, confirming prostate cancer metastasis. The ability of dedicated PSMA ligand PET/CT imaging to detect small metastases, even with 68Ga-labeled ligands, has been demonstrated. Therefore, the use of further invasive diagnostic procedures could be avoided. Thus, the possibility of detecting intraocular metastases of prostate cancer should be considered in routine PET/CT imaging.

The effect of butylscopolamine on [18F]FDG uptake in the gastrointestinal tract is negligible and regionally variable.

BACKGROUND: Butylscopolamine (or hyoscine butylbromide, trade name Buscopan®) is occasionally administered as a premedication to reduce non-specific FDG uptake in the gastrointestinal tract based on its antiperistaltic effect. To date, there are no consistent recommendations for its use. The aim of this study was to quantify the reduction in intestinal and non-intestinal uptake by butylscopolamine administration and to derive relevance for clinical evaluation. RESULTS: 458 patients (PET/CT for lung cancer) were retrospectively reviewed. 218 patients with butylscopolamine and 240 patients without butylscopolamine had comparable characteristics. While the SUVmean in the gullet/stomach and small intestine was significantly reduced with butylscopolamine, the colon and rectum/anus showed no difference. The liver and salivary glands showed a reduced SUVmean, while skeletal muscle and blood pool were unaffected. An effect of butylscopolamine was particularly evident in men and patients under 65 years of age. There was no difference in the perceived confidence in the assessment of intestinal findings in the subjective evaluation, although in the butylscopolamine group further diagnostics appeared advisable more frequently. CONCLUSIONS: Butylscopolamine reduces gastrointestinal FDG accumulation only in selected segments and, despite a significant effect, only to a small extent. A general recommendation for the use of butylscopolamine cannot be derived from these results, its use for specific issues could be considered individually.

Medical Students' and Radiology Technician Trainees' eHealth Literacy and Hygiene Awareness-Asynchronous and Synchronous Digital Hand Hygiene Training in a Single-Center Trial.

Next to the known nosocomial infections, the COVID-19 pandemic was an example for the need for the immediate implementation of functioning hygiene concepts and knowledge transfer. The aim of this study was to evaluate the self-assessment of ehealth literacy in terms of finding, using and critically evaluating health information and theoretical and practical hygiene awareness on a voluntary participation basis at the Jena University Hospital in 2022. The well-established and validated eHEALS and WHO questionnaire on hand hygiene (HH) knowledge for healthcare workers was completely filled by 204 participants (191 medical students; 13 healthcare trainees). In a second step, after the questionnaire, 77 participants completed additional asynchronous, digitally guided self-training using DesiCoach 2Go. In the end, a synchronous hand disinfection was carried out in the hospital using Visirub, by separating it into a group without (n = 191; with and without HH questionnaire) and a group with (n = 31; with HH questionnaire) previously completed self-training. For the eHL, the respondents tended to have a positive self-assessment of finding, using and critically evaluating health information. The voluntary participants of the practical hand disinfection who had received self-training were able to achieve significantly better results (p = 0.0047), resulting in fewer wetting gaps in a subsequent performance with Visirub than those who had not received digital self-training. The survey showed that healthcare-related participants belonging to the "digital native" generation have above-average knowledge on HH and profit by digitally guided self-training.

Optimization of Thyroid Volume Determination by Stitched 3D-Ultrasound Data Sets in Patients with Structural Thyroid Disease.

Ultrasound (US) is the most important imaging method for the assessment of structural disorders of the thyroid. A precise volume determination is relevant for therapy planning and outcome monitoring. However, the accuracy of 2D-US is limited, especially in cases of organ enlargements and deformations. Software-based "stitching" of separately acquired 3D-US data revealed precise volume determination in thyroid phantoms. The purpose of this study is to investigate the feasibility and accuracy of 3D-US stitching in patients with structural thyroid disease. A total of 31 patients from the clinical routine were involved, receiving conventional 2D-US (conUS), sensor-navigated 3D-US (3DsnUS), mechanically-swept 3D-US (3DmsUS), and I-124-PET/CT as reference standard. Regarding 3DsnUS and 3DmsUS, separately acquired 3D-US images (per thyroid lobe) were merged to one comprehensive data set. Subsequently, anatomical correctness of the stitching process was analysed via secondary image fusion with the I-124-PET images. Volumetric determinations were conducted by the ellipsoid model (EM) on conUS and CT, and manually drawn segmental contouring (MC) on 3DsnUS, 3DmsUS, CT, and I-124-PET/CT. Mean volume of the thyroid glands was 44.1 ± 25.8 mL (I-124-PET-MC = reference). Highly significant correlations (all p < 0.0001) were observed for conUS-EM (r = 0.892), 3DsnUS-MC (r = 0.988), 3DmsUS-MC (r = 0.978), CT-EM (0.956), and CT-MC (0.986), respectively. The mean volume differences (standard deviations, limits of agreement) in comparison with the reference were -10.50 mL (±11.56 mL, -33.62 to 12.24), -3.74 mL (±3.74 mL, -11.39 to 3.78), and 0.62 mL (±4.79 mL, -8.78 to 10.01) for conUS-EM, 3DsnUS-MC, and 3DmsUS-MC, respectively. Stitched 3D-US data sets of the thyroid enable accurate volumetric determination even in enlarged and deformed organs. The main limitation of high time expenditure may be overcome by artificial intelligence approaches.

PET/CT of the Spleen with Gallium-Oxine-Labeled, Heat-Damaged Red Blood Cells: Clinical Experience and Technical Aspects.

Several scintigraphic techniques have been supplemented or replaced by PET/CT methods because of their superior sensitivity, high resolution, and absolute activity quantification capability. The purpose of this project was the development of a PET tracer for splenic imaging, its radiopharmaceutical validation, and its application in selected patients in whom unclear constellations of findings could not be resolved with established imaging methods. Heat-damaged red blood cells (RBCs) were labeled with [68Ga]gallium-oxine, which was produced from [68Ga]gallium and 8-Hydroxyquinoline (oxine) on an automated synthesizer. Ten patients underwent [68Ga]gallium-oxine-RBC-PET/CT for the classification of eleven unclear lesions (3 intra-, 8 extrapancreatic). [68Ga]gallium-oxine and [68Ga]gallium-oxine-labeled RBCs could be synthesized reproducibly and reliably. The products met GMP quality standards. The tracer showed high accumulation in splenic tissue. Of the 11 lesions evaluated by PET/CT, 3 were correctly classified as non-splenic, 6 as splenic, 1 as equivocal, and 1 lesion as a splenic hypoplasia. All lesions classified as non-splenic were malignant, and all lesions classified as splenic did not show malignant features during follow-up. PET/CT imaging of the spleen with [68Ga]gallium-oxine-labeled, heat-damaged RBCs is feasible and allowed differentiation of splenic from non-splenic tissues, and the diagnosis of splenic anomalies.

Excellent Response to Multimodal Therapy Approach in Hyperfunctioning Metastatic Follicular Thyroid Carcinoma Diagnosed on 123 I-SPECT/Ultrasound Fusion Imaging.

ABSTRACT: An 83-year-old woman presented with new-onset hyperthyroidism and suspicious thyroid nodules on ultrasound (US). Conventional 99m TcO 4 thyroid scintigraphy showed hyperfunctioning areas that could not be clearly assigned to the US findings. With the aid of 123 I-SPECT/US fusion imaging, suspicious nodules were unambiguously identified as autonomously hyperfunctioning lesions. Additional 123 I whole-body scan revealed iodine-avid lymphonodular and pulmonal metastases. Clinical diagnosis of hormone-active thyroid carcinoma was made and histologically confirmed. Because of significant hyperthyroidism as well as multiple partially iodine-negative metastases, a multimodal treatment regime consisting of 131 I radioiodine therapy, surgery, and radiation therapy was conducted, leading to almost complete remission.

Distribution patterns of arterial affection and the influence of glucocorticoids on 18F-fluorodeoxyglucose positron emission tomography/CT in patients with giant cell arteritis.

BACKGROUND: Giant cell arteritis (GCA) with the involvement of extracranial vessels is increasingly coming into focus. Isolated aortic involvement in the acute phase of GCA is probably more frequent than estimated because only a minority of patients show typical symptoms. 18F-fluorodeoxyglucose positron emission tomography/CT (PET/CT) is a reliable imaging tool to diagnose patients with extracranial GCA. The aim of this retrospective study was to quantify arterial involvement at the onset of a newly diagnosed GCA by PET/CT and to evaluate the influence of glucocorticoid (GC) treatment on the diagnostic performance of this imaging technique. METHODS: The study included 60 patients with GCA at the onset of a GCA. All patients had undergone a PET/CT scan. 44 patients were GC naïve and 16 patients received GC. RESULTS: The most affected arteries were the ascending aorta (72%), followed by the brachiocephalic trunk (62%), aortic arch (60%) and descending aorta (60%). The aorta and its branches showed an inflammatory involvement in 83.3% of patients. A singular affection of the aorta and the brachiocephalic trunk was revealed in 20% of cases. GC-naïve patients (95.5%) had more frequently affected arteries compared with GC-treated patients (50%). CONCLUSION: Our study showed the frequent involvement of the thoracic aorta and brachiocephalic trunk in patients with GCA using PET/CT. Since these vascular compartments cannot be visualised by ultrasound, we advocate screening imaging of the aorta with PET/CT when GCA is suspected. Because the use of GC is associated with a marked decrease in the inflamed vascular segment in GCA, PET/CT should be performed as soon as possible.

Differentiation of Reversible Hemichorea Due to Vitamin B12 Deficiency From Huntington Disease Via FDG PET.

ABSTRACT: Vitamin B12 deficiency may present with diverse symptoms, complicating the differential diagnosis. Extrapyramidal movement disorders, for instance, are a rare manifestation of vitamin B12 deficiency. MRI of the brain frequently remains without conclusive findings. However, 18 F-FDG PET/CT may reveal characteristic changes in the metabolism of the basal ganglia and thus contribute to an accurate diagnosis. We demonstrate the case of a woman with left-sided hemichoreatic movements due to vitamin B12 deficiency showing a contralateral putaminal hypermetabolism, which normalized after vitamin B12 supplementation, ruling out other deviating causes, particularly Huntington disease.

Multimodal Characterization of a PSMA-Positive Thyroid Nodule Using 68Ga-PSMA and 124Iodine PET/US Fusion Imaging.

A 54-year-old male diagnosed with prostate cancer was referred for 68Gallium-PSMA-11 PET/CT. The scan revealed a solitary PSMA-positive thyroid lesion. On PET/ultrasound fusion imaging, a nodule with moderate risk of malignancy (TIRADS 4B) could be unambiguously correlated. Additional 124Iodine PET/ultrasound fusion imaging revealed normal iodine uptake within the PSMA-positive thyroid nodule. Fine-needle aspiration cytology was performed using an ultrasound needle-guidance system. The cytopathological investigation confirmed a benign thyroid nodule and excluded a thyroid carcinoma as well as a prostate cancer metastasis. Immunohistochemistry was positive for thyroglobulin staining.

Hepatobiliary Excretion PET/CT With 68Ga-TAoS-DAZA to Evaluate Bile Duct Patency.

ABSTRACT: Tri-alkoxysalicyl-1,4-diazepan-6-amine (TAoS-DAZA) ligands, radiolabelled with 68Ga, have been proposed as PET/CT agents for depiction and quantification of hepatobiliary function and evaluation of bile excretion. In the presented case, a patient with hepatocellulary carcinoma underwent PET/CT with the TAoS-derivate 68Ga-tri-methoxysalicyl-(TMoS)-DAZA to determine the patency of intrahepatic and extrahepatic bile ducts, in particular of a stent in the common bile duct. The PET/CT was performed without complications. Evaluation of bile excretion over time was possible. 68Ga-TAoS-DAZA PET/CT may be an option for dynamic imaging of the excretory hepatic function to visualize the biliary tree and to rule out cholestasis.

De Quervain Subacute Thyroiditis With Moderate PSMA Uptake Mimicking Thyroid Metastasis of Renal Cell Carcinoma.

ABSTRACT: PSMA-targeted PET/CT can be used for diagnosis and staging of clear cell renal cell carcinoma. A 68-year-old woman with suspected hepatic metastases from clear cell renal cell carcinoma underwent PET/CT with 68Ga-PSMA, which showed a focus of moderately increased tracer uptake in the right thyroid lobe. Sonography displayed a correlating hypoechogenic, ill-defined node (TIRADS 5). Right hemithyroidectomy was performed in the assumption of a solitary metastasis of renal cell carcinoma. Histologic examination revealed subacute granulomatous thyroiditis (De Quervain thyroiditis) without evidence of malignancy.

Transarterial Radioembolization Planning and Treatment with Microspheres Containing Holmium-166: Determination of Renal and Intestinal Radionuclide Elimination, Effective Half-Life, and Regulatory Aspects.

After transarterial radioembolization (TARE) with microspheres loaded with holmium-166, radioactivity is excreted from the body. The aim of this study was to evaluate radioactive renal and intestinal excretions after TARE planning and treatment procedures with holmium-166-loaded microspheres and to correlate the findings with the intratherapeutic effective half-life. Urinary and intestinal excretions of patients who underwent TARE procedures were collected during postinterventional intervals of 24 h (TARE planning) and 48 h (TARE treatment). Whole-body effective half-life measurements were performed. Calibrations of the 166Ho measuring system showed evidence of long-living nuclides. For excretion determination, 22 TARE planning procedures and 29 TARE treatment procedures were evaluated. Mean/maximum total excretion proportions of the injected 166Ho were 0.0038%/0.0096% for TARE planning procedures and 0.0061%/0.0184% for TARE treatment procedures. The mean renal fractions of all measured excretions were 97.1% and 98.1%, respectively. Weak correlations were apparent between the injected and excreted activities (R2 planning/treatment: 0.11/0.32). Mean effective 166Ho half-lives of 24.03 h (planning) and 25.62 h (treatment) confirmed low excretions. Radioactive waste disposal regulations of selected jurisdictions can be met but must be reviewed before implementing this method into clinical practice. Inherent long-living nuclide impurities should be considered.

The Dependence of Renal 68Ga[Ga]-DOTATOC Uptake on Kidney Function and Its Relevance for Peptide Receptor Radionuclide Therapy with 177Lu[Lu]-DOTATOC.

BACKGROUND: In addition to its SSTR-specific binding in tumors and healthy tissues, DOTATOC analogues accumulate in kidney parenchyma. Renal tracer uptake might be a surrogate of kidney function or dysfunction. This study aimed to evaluate if kidney function can be estimated from 68Ga[Ga]-DOTATOC uptake in PET/CT and its impact on the nephrotoxicity of 177Lu[Lu]-DOTATOC PRRT. METHODS: Two cohorts of patients (A: 128 diagnostic patients; B: 32 PRRT patients) were evaluated retrospectively. SUV values of the kidneys, physiologically SSTR-expressing organs and in background compartments were assessed. Kidney function was calculated as eGFR by CKD-EPI creatinine equation. Pearson's correlation coefficients and treatment-induced changes of uptake and kidney function were assessed and compared. RESULTS: Kidney function and renal DOTATOC uptake showed a significant inverse correlation (R2 = 0.037; p = 0.029). Evaluated models of PET/CT measurements were not able to predict kidney function sufficiently. The uptake of other organs did not depend on eGFR. While the renal uptake increased after PRRT (p < 0.001), the kidney function did not change significantly (p = 0.382). Neither low pre-therapeutic eGFR nor high pre-therapeutic kidney uptake were risk factors of PRRT-induced deterioration in kidney function. CONCLUSION: The relevance of kidney function for renal 68Ga[Ga]-DOTATOC uptake is limited. The nephrotoxicity of 177Lu[Lu]-DOTATOC PRRT might be low and cannot be reliably predicted by pre-therapeutic measurements.

PSMA-PET/CT in Patients with Recurrent Clear Cell Renal Cell Carcinoma: Histopathological Correlations of Imaging Findings.

PET/CT with prostate-specific membrane antigen (PSMA)-targeted tracers has been used in the diagnosis and staging of patients with clear cell renal cell carcinoma (ccRCC). For ccRCC primary tumors, PET parameters were shown to predict histologic grade and features. The aim of this study was to correlate PSMA PET/CT with histopathological findings in patients with metastatic recurrence of ccRCC. Patients with ccRCC who underwent PSMA-targeted PET/CT and subsequent histopathological evaluation of suspicious lesions were included. Specimens underwent immunohistochemical marking. Lesion diameter, volume and tracer uptake were correlated with the extent and intensity of molecular PSMA expression and with clinical findings. Twelve PET-positive lesions of nine patients were evaluated. Eleven ccRCC metastases and one prostate carcinoma were detected histopathologically. Molecular PSMA expression was detected in all lesions, which intensity and distribution did not correlate with PET parameters. PSMA-targeted PET/CT is a feasible tool for the evaluation of patients with ccRCC but cannot reliably predict histologic features of metastases. PSMA may also be expressed in malignant lesions other than ccRCC, leading to incidental detection of these tumors.

Dynamic PET/CT with the Hepatobiliary Tracer [68Ga]Ga-Tmos-DAZA for Characterization of a Hepatic Tumor.

Established imaging modalities for the characterization of liver tumors are computed tomography (CT), magnetical resonance (MR) imaging, sonography, and hepatobiliary scintigraphy. In some cases, their results may be inconclusive or certain examinations not possible due to contraindications. Positron emission tomography (PET)/CT has the capability of dynamic imaging with high temporal resolution. With radiolabeled tri-alkoxysalicyl-1,4-diazepan-6-amine (TAoS-DAZA) tracers, imaging of liver perfusion and hepatobiliary function is possible in a single examination. In the presented case, the PET/CT was performed in a patient with suspected hepatocellular carcinoma and atypical CT findings. PET imaging characteristics were consistent with a hepatocellular carcinoma (HCC). PET with DAZA ligands may be a supplemental method for liver tumor characterization in difficult cases.

Radioembolization With Holmium-166 Polylactic Acid Microspheres: Distribution of Residual Activity in the Delivery Set and Outflow Dynamics During Planning and Treatment Procedures.

PURPOSE: To evaluate the microsphere outflow dynamics and residual Ho-166 activity during and after transarterial radioembolization planning and treatment procedures, and to assess the distribution and predilection sites of residual activity in the proprietary delivery set and the microcatheter. MATERIALS AND METHODS: Fifteen planning and 12 therapeutic radioembolization procedures were performed with poly-l-lactic acid microspheres loaded with Ho-166. The amount and distribution of residual activity was assessed by dose calibrator measurements and SPECT imaging. The activity flow profile from the microcatheter was assessed dynamically. For planning procedures, different injection methods were evaluated in order to attempt to decrease the residual activity. RESULTS: The median residual activities for planning and treatment procedures using standard injection methods were 31.2% (range 17.3%-44.1%) and 4.3% (range 3.5%-6.9%), respectively. Planning residual activities could be decreased significantly with 2 injection methods similar to treatment procedures, to 17.5% and 10.9%, respectively (P = 0.002). Main predilection sites of residual microspheres were the 3-way stopcock and the outflow needle connector. During treatment procedures, more than 80% of the injected activity is transferred during the first 3 injection cycles. CONCLUSION: After treatment procedures with holmium-loaded microspheres, mean residual activity in the delivery set is reproducibly low and between reported values for glass and resin microspheres. The majority of microspheres is transferred to the patient during the second and third injection cycle. An estimated residual waste of 3% to 4% may be included in the treatment activity calculation. For planning procedures, a modified injection technique should be used to avoid high residual activities.