Dentate Nucleus Signal Intensity Increases Following Repeated Gadobenate Dimeglumine Administrations: A Retrospective Analysis.

Background Increased cerebral signal intensity (SI) has been reported in patients undergoing MRI with gadolinium-based contrast agents (GBCAs). Published data on gadobenate dimeglumine have been somewhat contradictory. Purpose To evaluate the relationship between dosage of gadobenate dimeglumine and SI change at MRI following multiple gadobenate dimeglumine administrations. Materials and Methods In this retrospective study, patients referred for clinically indicated brain MRI from January 2006 through May 2016 were evaluated for inclusion. Eligible patients were between 18 and 90 years old at their baseline brain MRI and had never received a GBCA, had undergone three or more MRI examinations with gadobenate dimeglumine, and had the baseline scan and another brain MRI scan available for comparison. The primary group consisted of patients with four or fewer supratentorial lesions smaller than 3 cm who underwent axial T1-weighted MRI at 1.5 T. One patient had also undergone prior radiation therapy. The secondary group consisted of patients with a history of brain radiation therapy or craniotomy who underwent 1.5-T and 3-T same-plane T1-weighted MRI (in any order). The SI for up to eight brain MRI examinations per patient was measured, and relative SI changes from baseline to interval scans were calculated. A subgroup analysis was performed to assess the gadobenate dimeglumine washout since the last gadolinium exposure. All patients had normal renal and liver functions. Linear mixed regression analyses were performed for variables with P < .05. Results In 43 patients (14 men, 29 women; median age, 49 years; age range, 25-73 years), the dentate nucleus (DN)-to-middle cerebral peduncle (MCP) SI ratio showed a mean increase of 6.7% ± 3.9 in the primary group and 4.0% ± 2.7 in the secondary group (both P < .001) following the administration of 134 mL ± 141 gadobenate dimeglumine over 55 months ± 35.2. The DN/MCP SI ratio increased linearly with the amount of gadobenate dimeglumine, with a mean increase of 0.015% ± 0.004 per 1 mL of gadobenate dimeglumine (R2 = 0.3, P < .001). Conclusion In patients receiving multiple doses of gadobenate dimeglumine, a linear relationship existed between gadobenate dimeglumine administrations and an increase in the dentate nucleus-to-middle cerebral peduncle signal intensity ratio at MRI. © RSNA, 2020 See also the editorial by McDonald and Kallmes in this issue.

Comparison of hybrid FDG PET/MRI compared with PET/CT in colorectal cancer staging and restaging: a pilot study.

PURPOSE: We report our initial clinical experience from a pilot study to compare the diagnostic accuracy of hybrid PET/MRI with PET/CT in colorectal cancer and discuss potential PET/MRI workflow solutions for colorectal cancer. METHODS: Patients underwent both FDG PET/CT and PET/MRI (Ingenuity TF PET/MRI, Philips Healthcare) for rectal cancer staging or colorectal cancer restaging. The PET acquisition of PET/MRI was similar to that of PET/CT whereas the MRI protocol was selected individually based on the patient's medical history. One nuclear medicine physician reviewed the PET/CT studies and one radiologist reviewed the PET/MRI studies independently. The diagnostic accuracy of each modality was determined in consensus, using available medical records as a reference. RESULTS: Of the 12 patients enrolled, two were for initial staging and ten for restaging. The median scan delay between the two modalities was 60 min. The initial imaging was PET/CT in nine patients and PET/MRI in three patients. When PET/CT was performed first, the SUV values of the 16 FDG avid lesions were greater at PET/MRI than at PET/CT. In contrast, when PET/MRI was performed first, the SUV values of the seven FDG avid lesions were greater at PET/CT than at PET/MRI. PET/MRI provided more detailed T staging than PET/CT. On a per-patient basis, with both patient groups combined for the evaluation of N and M staging/restaging, the true positive rate was 5/7 (71%) for PET/CT and 6/7 (86%) for PET/MRI, and true negative rate was 5/5 (100%) for both modalities. On a per-lesion basis, PET/CT identified 26 of 29 (90%) tumor lesions that were correctly detected by PET/MRI. Our proposed workflow allows for comprehensive cancer staging including integrated local and whole-body assessment. CONCLUSIONS: Our initial experience shows a high diagnostic accuracy of PET/MRI in T staging of rectal cancer compared with PET/CT. In addition, PET/MRI shows at least comparable accuracy in N and M staging as well as restaging to PET/CT. However, the small sample size limits the generalizability of the results. It is expected that PET/MRI would yield higher diagnostic accuracy than PET/CT considering the high soft tissue contrast provided by MRI compared with CT, but larger studies are necessary to fully assess the benefit of PET/MRI in colorectal cancer.

Incidental Finding of Spindle Cell Sarcoma on 68 Ga-PSMA-11 PET/CT.

ABSTRACT: A 78-year-old man underwent 68 Ga-prostate-specific membrane antigen-11 (PSMA-11) PET/CT for biochemical recurrence of prostate adenocarcinoma following a simple prostatectomy. The scan showed PSMA-avid local recurrence within the prostatectomy bed and a suspicious right internal iliac nodal metastasis. In addition, there was a mildly avid subcutaneous lesion in the right flank, which revealed high-grade spindle cell sarcoma at histopathology. This case represents a potential pitfall for PSMA-11 PET imaging. The presentation of mildly avid, atypical soft tissue lesions should warrant a biopsy to allow for proper diagnosis and treatment management.

Prostatic Utricle Cysts as a Potential Pitfall in PSMA PET/CT Interpretation.

ABSTRACT: A 60-year-old man with T2aN0M0 prostate cancer underwent intensity-modulated radiotherapy targeting the prostate and seminal vesicles. Experiencing biochemical recurrence after 6 years, 68Ga-PSMA-11 PET/CT revealed focal radioactivity in the posterior midline of the prostate, identified as a prostatic utricle cyst on subsequent MRI. Similar findings appeared in a previous 18F-piflufolastat PET/CT, with negative biopsy results. The patient then received intensity-modulated radiotherapy directed to 2 PSMA-avid pelvic nodes and leuprolide acetate, achieving an undetectable PSA in 4 months. This case highlights a potential pitfall in PSMA PET interpretation associated with prostatic utricle cysts.

Radioactive Iodine Therapy in Differentiated Thyroid Cancer: An Update on Dose Recommendations and Risk of Secondary Primary Malignancies.

Radioactive iodine (RAI) therapy with iodine-131 is performed in select cases of differentiated thyroid cancer (DTC), typically for remnant ablation, adjuvant therapy, or treatment of known persistent disease. Herein, we review updated RAI dose recommendations and associated risks of secondary primary malignancy (SPM). RAI dose is usually chosen empirically based on the risk assessment of tumor recurrence and other factors. Dose recommendations differ slightly among relevant medical societies. As of April 2024, most medical societies, including the American Thyroid Association (ATA), European Thyroid Association (ETA), Society of Nuclear Medicine and Molecular Imaging/European Association of Nuclear Medicine (SNMMI/ EANM), and National Comprehensive Cancer Network (NCCN), recommend a dose of 1.11 GBq (30 mCi) I-131 for remnant ablation. For adjuvant therapy, the recommended RAI dose ranges from 1.11 to 3.7 GBq (30-100) mCi I-131, although doses up to 5.6 GBq (150 mCi) may also be considered. In patients with known or suspected metastatic disease, at least 3.7 GBq (100 mCi) I-131 should be administered, and RAI doses as high as 7.4 GBq (200 mCi) may be justified depending on the suspected tumor burden and extent. Dosimetry has the advantage of tailoring the RAI dose to each patient's pharmacokinetics, resulting in ≥ 7.4 GBq (200 mCi) of I-131 in most cases. There is an ongoing debate about the risk of developing SPM due to RAI therapy, with several multicenter studies and meta-analyses concerning SPM being published in the last 2 years. The incidence of RAI-associated SPM varies according to the study design and detection method. Several studies showed no increased incidence, and there was no specific secondary cancer or cancer group linked to RAI exposures. Some reports indicated that cumulative RAI doses exceeding 5.6-7.4 GBq (150-200 mCi) were found to represent an increased risk for developing SPM. However, a clearly defined dose threshold cannot be provided based on the current literature. Nonetheless, caution should be exercised when considering repeated RAI therapies for persistent metastatic PTC, with a cumulative dose exceeding 37.0 GBq (1,000 mCi), due to the potential risk of developing SPM and other long-term toxicity. Further research is warranted to understand better the relationship between RAI dose and the risk of SPM.

Sincalide-Stimulated Cholescintigraphy: A Retrospective Study and Proposal of a Modified Workflow.

PURPOSE: Current guidelines for sincalide-stimulated cholescintigraphy (SSC) call for a 60-minute sincalide infusion, and a gallbladder ejection fraction (GBEF) ≥38% is considered normal. In this retrospective study, we hypothesize that most patients reach a normal GBEF by 30 minutes. METHODS: Eligible patients had undergone a 60-minute SSC from January to December 2019. The clinical SSC data were previously processed on a Xeleris workstation (GE Healthcare). In subjects with GBEF ≥38% based on standard SSC, the GBEF at 20 minutes and 30 minutes were retrospectively calculated using manual pixel height measurements. Receiving operating characteristic was analyzed to determine the best GBEF cutoff at 30 minutes. RESULTS: Of 302 subjects, mean age of 46 ± 17 years, 33 (10.9%) showed an abnormal GBEF <38% suggestive of functional gallbladder disorder. In the remaining 269 patients (89.1%) with a normal GBEF, 60.6% and 86.6% reached a normal GBEF at 20 minutes and 30 minutes, respectively. Moreover, a GBEF threshold >29.1% at 30 minutes was associated with a negative predictive value of 99.6%, indicating that a 60-minute SSC was not necessary. The GBEF values were not associated with sex, age, patient symptoms, or type of referral. Manually calculated GBEFs on the time-activity curve showed excellent correlation with the primary values. We propose a modified workflow that splits the 60-minute SSC into two 30-minute image sets to allow for a screening GBEF at 30 minutes. If GBEF is >29.1% at 30 minutes, the second image set may be stopped, and the examination is complete. CONCLUSIONS: The majority of patients (77.2%) undergoing the standard 60-minute SSC reach a normal GBEF already by 30 minutes. The proposed workflow shortens the SCC procedure by 30 minutes, while maintaining high diagnostic accuracy and contributing to improved procedure efficiency and reduced patient discomfort as well as symptoms.

Potential Pitfall of Fluciclovine PET/CT in Castrate-Resistant Prostate Cancer With Adrenal Metastasis.

ABSTRACT: An 83-year-old man with castrate-resistant prostate cancer underwent an 18 F-fluciclovine PET/CT scan, which was negative for local disease recurrence or locoregional lymphadenopathy, but there were multiple fluciclovine-avid bone metastases. In addition, mildly avid bilateral adrenal nodules were thought to be benign. However, on follow-up PET/CT 10 months later, while on additional therapy with enzalutamide, the bilateral nodules became mass lesions with interval decreased fluciclovine avidity. Adrenal metastases were suspected given their rapid growth, with subsequent CT-guided biopsy revealing metastatic prostate cancer without tumor necrosis. This false-negative case highlights the diagnostic challenge of fluciclovine PET in characterizing adrenal lesions.

Is there a common SUV threshold in oncological FDG PET/CT, at least for some common indications? A retrospective study.

PURPOSE: We retrospectively compared the maximum standard uptake value (SUVmax) of FDG PET in four different sites to evaluate whether a common diagnostic SUVmax threshold may exist in these tumor locations. We further postulate that the SUVmax thresholds are higher in thoracic lesions than in extrathoracic lesions. MATERIAL AND METHODS: N = 143 patients in four subgroups underwent a FDG PET/CT: a) 42 patients for solitary pulmonary nodules (SPNs) characterization with b) respective mediastinal lymph nodes (LNs), c) 65 patients for LN staging of head and neck cancer, and d) 36 cancer patients diagnosed with adrenal lesions. Receiver operating characteristics of SUVmax values were evaluated. RESULTS: The SUVmax were statistically significantly greater in malignant than in benign lesions. For SPNs and mediastinal LNs, a SUVmax > 3.6 each resulted in a sensitivity of 81% and 87%, and a specificity of 94% and 89%. For cervical LNs and adrenal glands, a SUVmax > 2.2 each showed a sensitivity of 98% and 100%, and a specificity of 83% and 93%. CONCLUSION: A common SUVmax threshold did not exist in the four studied subgroups. The variable FDG uptake in SPNs and mediastinal LNs are associated with the high prevalence of inflammation/infection within the chest. Similar SUVmax thresholds however may exist for extrathoracic regions where the prevalence of inflammation/infection is low.

PET/CT Limitations and Pitfalls in Urogenital Cancers.

Hybrid FDG PET/CT plays a vital role in oncologic imaging and has been widely adopted for the staging and restaging of a variety of malignancies. Its diagnostic value in urogenital malignancies is less well-known, not at least because of the variable FDG avidity of these tumor entities, the sites of these tumors, and technical challenges associated with sequential imaging of CT and PET. PET/CT interpretation thus can be especially challenging and is associated with many pitfalls, which can lead to both false-positive and false-negative diagnoses as well as incorrect assessment of metabolic change following therapy. Currently, FDG PET/CT is not the standard of care for the initial diagnosis or staging of early-stage or low-risk urogenital cancers; however, it can help evaluate distant metastatic disease, response to therapy, and disease recurrence in high-risk patients. Knowledge of imaging features of tumor metabolic avidity and pitfalls is essential for accurate interpretation.

18F-FDG PET/CT of patients with cancer: comparison of whole-body and limited whole-body technique.

OBJECTIVE: Use of the routine field of view for whole-body (18)F-FDG PET/CT can lead to underestimation of the true extent of the disease because metastasis outside the typical base of skull to upper thigh field of view can be missed. The purpose of this study was to evaluate the incremental added value of true whole-body as opposed to this limited whole-body PET/CT of cancer patients. MATERIALS AND METHODS: True whole-body FDG PET/CT, from the top of the skull to the bottom of the feet, was performed on 500 consecutively registered patients. A log was kept of cases of suspected malignancy outside the typical limited whole-body field of view. Suspected lesions in the brain, skull, and extremities were verified by correlation with surgical pathologic or clinical follow-up findings. RESULTS: Fifty-nine of 500 patients had PET/CT findings suggestive of malignancy outside the limited whole-body field of view. Thirty-one of those patients had known or suspected malignancy outside the limited whole-body field of view at the time of the true whole-body study. Among the other 28 patients, follow-up data were not available for two, six had false-positive findings, and new cancerous involvement was confirmed in 20. Detection of malignancy outside the limited whole-body field of view resulted in a change in management in 65% and in staging in 55% of the 20 cases. CONCLUSION: Our study showed that 20 of 500 (4.0%) of patients had previously unsuspected malignancy outside the typical limited whole-body field of view. Detection of such malignancy resulted in a change in management in 13 of 500 cases (2.6%). We propose that adopting a true whole-body field of view in the imaging of cancer patients may lead to more accurate staging and restaging than achieved with the routinely used limited whole-body field of view.

18F-Fluciclovine PET/MRI in a Patient With Squamous Cell Carcinoma of the Uterine Cervix Correlated With 18F-FDG PET/CT.

A 32-year-old woman with a FIGO (International Federation of Gynecology and Obstetrics) stage IIA invasive squamous cell carcinoma of the uterine cervix underwent a clinical FDG PET/CT scan, which revealed intense uptake in the primary. On research F-fluciclovine PET/MRI, the primary showed elevated fluciclovine uptake at 5 and 40 minutes after radiotracer injection, with no evidence of regional or distant metastasis. Fluciclovine PET may have diagnostic value for cervical cancer imaging with a potential advantage over FDG of minimal urinary activity from renal excretion; however, in this patient, the metabolic activity was inferior to that of FDG PET.

Differential 18F-FDG and 18F-Fluciclovine Uptake Pattern in a Patient With Poorly Differentiated Adenocarcinoma of the Lung and Prostate Cancer Biochemical Recurrence.

A 72-year-old man with a history of T1cN0M0 prostate adenocarcinoma and rising prostate-specific antigen underwent a fluciclovine PET/CT scan that showed high uptake in several para-aortic nodes, suspicious for prostate cancer. A right upper lobe single pulmonary nodule (SPN), demonstrated only mild uptake, which raised the suspicion for a lung primary. Subsequent FDG PET/CT showed high uptake in the SPN, revealing poorly differentiated adenocarcinoma at biopsy, but with no abnormal uptake in the para-aortic nodes. This case highlights the complementary potential of fluciclovine and FDG PET in patients with a history of prostate cancer biochemical recurrence and SPN.

68Ga-DOTATATE PET/MRI for Neuroendocrine Tumors: A Pictorial Review.

Neuroendocrine tumors (NETs) constitute a variety of neoplastic entities and exhibit variable degrees of neuroendocrine differentiation and phenotypes, as well as genetic profiles. Ga-DOTATATE PET is a novel imaging technique for NET. Although PET/CT is commonly utilized for oncologic imaging, PET/MRI is particularly suited for NETs, as MRI provides greater soft tissue contrast than CT, allowing for improved detection and characterization of NETs, particularly when liver metastasis is suspected or needs to be ruled out. The current pictorial review aims to illustrate the complementary advantages, as well as pitfalls of Ga-DOTATATE PET/MRI in the evaluation of NETs.

18F-FDG PET/MRI Primary Staging of Cervical Cancer: A Pilot Study with PET/CT Comparison.

We report our PET/MRI experience from a pilot study that compared the diagnostic performance of 18F-FDG PET/MRI versus PET/CT in staging of cervical cancer. Methods: Six adults with newly diagnosed cervical cancer underwent a single 18F-FDG injection with a dual-imaging protocol: standard-of-care PET/CT followed by research PET/MRI. The diagnostic interpretation and SUVmax for the 2 modalities were compared. Results: Both modalities detected all primary tumors (median size, 3.9 cm) and all 4 metastases present in 2 of the 6 patients (median size, 0.9 cm). PET/MRI provided greater diagnostic confidence than PET/CT and upstaged the disease in 4 patients. On the basis of the imaging findings alone, the additional information from PET/MRI would have led to a change in clinical management in 3 of 6 patients. The primary lesion showed a median SUV of 12.8 on PET/CT and 18.2 on PET/MRI (P = 0.03). SUVs, however, correlated strongly between the 2 modalities (ρ = 0.96, P < 0.001). Conclusion: Our pilot study supports the notion that PET/MRI has the potential to impact clinical decisions and treatment strategies in women with cervical cancer. Further studies are, however, warranted to define the value that PET/MRI adds to PET/CT.

Tumor volume delineation: A pilot study comparing a digital positron-emission tomography prototype with an analog positron-emission tomography system.

We evaluated the potential differences of a digital positron-emission tomography (PET) prototype equipped with photon-counting detectors (D-PET, Philips Healthcare, Cleveland, Ohio, USA) in tumor volume delineation compared with the analog Gemini TF PET system (A-PET, Philips). Eleven oncologic patients first underwent clinical fluorodeoxyglucose (FDG) PET/computed tomography (CT) on A-PET. The D-PET ring was then inserted between the PET and CT scanner of A-PET and the patient was scanned for the second time. Two interpreters reviewed the two sets of PET/CT images for image quality and diagnostic confidence. FDG avid lesions were evaluated for volume measured at 35% and 50% of maximum standard uptake value (SUV) thresholds (35% SUV, 50% SUV), and for SUV gradient as a measure of lesion sharpness. Bland-Altman plots were used to assess the agreement between the two PET scans. Qualitative lesion conspicuity, sharpness, and diagnostic confidence were greater at D-PET than that of A-PET with favorable inter-rater agreements. Median lesion size of the 24 measured lesions was 1.6 cm. The lesion volume at D-PET was smaller at both 35% SUV and 50% SUV thresholds compared with that of A-PET, with a mean difference of - 3680.0 mm3 at 35% SUV and - 835.3 mm3 at 50% SUV. SUV gradient was greater at D-PET than at A-PET by 49.2% (95% confidence interval: 34.1%-60.8%). Given the smaller volume definition, coupled with improved conspicuity and sharpness, digital PET may be more robust and accurate in tumor rendering compared with analog PET not only for radiotherapy planning but also in prognostication and systemic treatment monitoring.

Increased 18F-FDG uptake in the posterior ocular bulb is associated with brain metastasis: a retrospective study.

OBJECTIVE: An observation of increased (18)F-FDG uptake in the posterior ocular bulb led us to the hypothesis that increased posterior ocular bulb uptake is likely abnormal and may indicate intracranial lesions. MATERIALS AND METHODS: Fifteen healthy volunteers and 35 patients with lung carcinoma-14 without brain metastasis and 21 with brain metastases-were retrospectively studied. The individuals underwent whole-body PET/CT including the brain with low-dose and unenhanced CT. Two nuclear medicine physicians visually analyzed the posterior ocular bulb uptake of both eyes. Standardized uptake values (SUVs) in the posterior ocular bulb were compared among the study groups. A radiologist reviewed brain MRI scans for abnormalities in the ocular bulbs and orbits. RESULTS: Visual interpretation showed normal FDG uptake at the posterior ocular bulb in 14 of the 15 healthy volunteers and 12 of the 14 (86%) patients without brain metastasis. Seventeen of the 21 (81%) patients with brain metastases showed increased uptake in the posterior ocular bulb. Visual interpretation showed no statistically significant difference between the healthy volunteers and patients without brain metastasis (p = 0.671). However, there was a significant difference between the patients with brain metastases and healthy volunteers as well as patients without brain metastasis (both, p < 0.001). High interrater agreement (kappa = 0.83) was noted. Brain MRI showed no abnormalities at the posterior ocular bulb in all study subjects. SUV results were inaccurate because of the intense tracer activity in the posterior orbit nearby. A good correlation between visually increased posterior ocular bulb uptake and the presence of brain metastasis was present (Cramer's V = 0.61). CONCLUSION: Visually increased FDG uptake along the posterior ocular bulb is an abnormal finding and may indicate intracranial structural abnormalities such as brain metastases.

Extrapulmonary small cell carcinoma: involvement of the brain without evidence of extracranial malignancy by serial PET/CT scans.

BACKGROUND: Extrapulmonary small cell carcinoma (EPSCC) involving the brain is a rare manifestation of an uncommon tumor type. CASE PRESENTATION: We report a 59 year-old Caucasian female diagnosed with an EPSCC involving the left parietal lobe without detectable extracranial primary tumor followed by serial positron emission tomography/computed tomography (PET/CT) imaging. Histopathological examination at both initial presentation and recurrence revealed small cell carcinoma. Serial PET/CT scans of the entire body failed to reveal any extracranial [18F]2-fluoro-2-deoxy-D-glucose (FDG) avid lesions at either diagnosis or follow-up. CONCLUSION: Chemotherapy may show a transient response in the treatment of EPSCC. Further studies are needed to help identify optimal treatment strategies. Combination PET/CT technology may be a useful tool to monitor EPSCC and assess for an occult primary malignancy.

Spinal cord metastases from lung cancer: detection with F-18 FDG PET/CT.

Preoperative F-18 FDG PET/CT study in this 57-year-old woman showed an FDG avid lesion in the left upper lung without evidence of lymphadenopathy or distant metastasis. She underwent a left upper lobectomy in June 2005 revealing moderately poorly differentiated adenocarcinoma (pT3N0M0) and subsequent chemotherapy completed December 2005. Nine months later, a left parietal lobe metastatic lesion was surgically resected. A true whole body FDG PET/CT study in November 2006 for restaging demonstrated new FDG avid spinal cord foci, which were highly suspicious for spinal cord metastases; these lesions were confirmed by MRI. Clinically, the patient recently developed back pain without evidence of neurologic deficits.

Multipurpose computed tomography window for fusion display with functional imaging.

Current positron emission tomography/computed tomography (PET/CT) and single photon emission CT (SPECT)/CT displays have major drawbacks, in that the CT only shows one tissue type at a time, which leads to a suboptimal fusion display. We developed a multipurpose CT level/window aiming at enhancing fusion display. A total of thirty CT examinations as part of fluorodeoxyglucose PET/CT examinations (15 were open source from the OsiriX website and 15 from our PET facility) and the open-source software MIPAV were used. During the development phase, a nuclear medicine physician manually modified the lookup table in a way that preserved the soft tissue contrast as well as enhanced the lung and bone tissue as much as possible. The developed multipurpose CT window was used in the subsequent validation phase and scored by two nuclear medicine physicians, who scored the image quality based on a 3-point score. Descriptive statistics was used to summarize the visual scores. The multipurpose CT window is a composite of several segments of linear CT levels/windows and contains an inverted linear level/window in the low range of Hounsfield unit designed to enhance lung/soft tissue contrast. In doing so, the multipurpose CT window preserves the high soft tissue contrast; the visualization of the lung parenchyma is satisfactory; the contrast for the bone tissue is improved but remains suboptimal when compared with conventional bone window. The multipurpose CT window was found to be "very useful" (median score 3; 95% confidence interval [CI] 2.0-3.0) for the purpose of fusion with functional imaging, with a prevalence asymmetry index 0.97 (95% CI 0.83-1.0). The multipurpose CT window was developed for image fusion and is not intended for diagnostic purposes. It shows favorable similarities to conventional CT windows with only minor artifacts and allows for enhanced visualization of fused PET/CT and SPECT/CT images. The multipurpose CT window is particularly valuable for case review/demonstrations on standard personal computers and handheld devices (smartphones, tablets).