This Study is from AO Schäfer and M Lurz from Klinikum St. Georg Leipzig, Germany.  The study was approved by our institutional review board. Written informed consent was obtained from each patient for contrast-enhanced MRI and data analysis. Part of our performed study was to evaluate the performance of our novel found MRI-image sign called “Avocado-Sign” as potential MRI Image sign and potential MRI imaging biomarker for lymph node metastases in patients with rectal cancer on preoperative MRI scans. Histological examination of the surgical specimen where lymph node involvement can be confirmed served as reference. Avocado sign is a hypointense core in the center of lymph nodes on contrast enhanced T1 Dixon VIBE MRI Sequence, which may indicate the tumor cells infiltrating the lymph node. Size of the lymph nodes doesn’t matter; it is just the centric hypointense part. The avocado sign also differs from other signs of lymph node metastasis, such as irregular shape, spiculated margin, heterogeneous enhancement, or extra nodal extension.
Normal lymph nodes have usually no or a wall adjacent hypointense core, which is usually the fatty hilus. Histopathological examinations revealed that cancer infiltrates lymph nodes typically beginning in the center. That may be the correlate for the image sign. Inclusion criteria for this study were a histologically confirmed diagnosis of rectal cancer and a minimum age of 18 years. Patients with unresectable tumors and general contraindications to MRI were excluded.
106 Patients (80 male, 26 females, mean age 65 with a standard deviation of 8,4 years) with histological confirmed rectal cancer received baseline staging MRI with our special MRI sequence protocol for rectal cancer. 77 received a second MRI after neoadjuvant rct. All MRI examinations were performed using a 3.0 T system (MAGNETOM Prisma Fit; Siemens Healthineers, Erlangen, Germany) with a combination of body and spinal phased array coils. The specific imaging protocol for rectal cancer includes T2-weighted turbo spin echo (TSE) sequences acquired in three planes along the main tumor-axis, diffusion-weighted (DWI) sequence in the axial plane, and an axial high-resolution T1-weighted volumetric interpolated gradient echo sequence with Dixon fat-saturation technique (VIBE DIXON) after intravenous administration of a macrocyclic gadolinium chelate contrast agent (Prohance; Bracco, Milan, Italy). The amount of contrast was determined based on the individual patient's body weight, with a prescribed dose of 0.2 mL per kg body weight. A spasmolytic agent (Buscopan) was injected in two fractions at the beginning and the middle of the scan.

Sequence	sagittal T2-TSE	axial T2-TSE	coronal T2-TSE	Diffusion (b100/500/1000)	DIXON-VIBE (contrast enhanced)
TR (ms)	4170	4400	4400	3700	5,8
TE (ms)	72	71	71	59	2,5/3,7
FOV (mm)	220	220	220	220	270
Slice (mm)	3	2	2	2	1,5
Matrix	394/448	380/432	380/432	140/140	326/384
Acquisition time (min)
22:24	4:37	4:50	4:50	3:57	4:10

Lymph nodes were graded on a dichotomous scale as malignant if the Avocado sign was present (AS+) and as non-malignant (AS-) if proper imaging features were absent. The number and additional standard criteria of malignant lymph nodes were not taken into account. In case of disagreement between the raters, a third radiologist with 17 years of experience in abdominal imaging was consulted to make the final decision. The findings were compared with the histopathologic results of the resected specimen, where lymph node involvement was graded analogously as N+ if one or more lymph node metastases were confirmed and N- without confirmed lymph node metastases. Histopathologic examination was performed according to standardized criteria.
 We furthermore performed subgroup analysis and divided overall patient collective in those who received direct surgery (n=29) and those who received neoadjuvant therapy (n=77) before surgery. All statistics were performed with SPSS Statistics 26 (IMB; Armonk, USA).  Values are presented as mean ± standard deviation (SD) for normally distributed variables or median and range for non-normally distributed variables. The prevalence of the avocado sign and the presence of lymph node metastasis for the overall patient population and subgroups were analyzed using descriptive statistics, including frequency data and percentages. Test values such as sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were determined using 2x2 contingency table calculations. Interrater agreement was assessed using Cohen's kappa coefficient. A value of 0.81 to 1.00 was considered almost perfect agreement, 0.61 to 0.80 as substantial, 0.41 to 0.60 as moderate, 0.21 to 0.40 as fair, and less than 0.20 as poor agreement.

This were our rating results as well as histopathologic results. If you can’t calculate some of the test-values just set the value as 1 or leave them out. In a written draft give tables and figures with reference to them in the main text for all groups and results and compare them, instead of giving all the numbers in the main text. Describe only the most important values in the main text, Calculate Sensitivity, specificity, PPV, NPV and Accuracy for overall and subgroups:

Overall patient collective: 
Avocado-Sign detected in preoperative MRI (shortened in follow as Av+): 64 
No Avocado-Sign detected in preoperative MRI (shortened in follow as Av-): 42 
At least one histologically confirmed Lymph node metastasis in surgical specimen (shortened in follow as N+): 50
No Lymph node metastasis in surgical specimen (shortened in follow as N-): 56 
Av+N+: 46 
Av+N-: 18 
Av-N+: 4 
Av-N-: 38 

Directly operated patients:
Av+: 19 
Av-: 10 
N+: 16 
N-: 13 
Av+N+: 16 
Av+N-: 3 
Av-N+: 0 
Av-N-: 10 

Neoadjuvant treated patients:
Av+: 45 
Av-: 32 
N+: 34 
N-: 43 
Av+N+: 30 
Av+N-: 15 
Av-N+: 4 
Av-N-: 28 

Group	Sensitivity (%)	Specificity (%)	Accuracy (%)	PPV (%)	NPV (%)
Overall	92	68	78	72	90
Directly operated	100	77	87	84	100
Neoadjuvant treated	88	65	74	67	88

Please Draft a potential article for publishing in NEJM. Use structure and language as it is common in Publications of NEJM. Structure your text in Introduction, where you can refer to frequent recurrences in rectal cancer, partly due to incorrect decisions in the therapy regime or insufficient extent of surgical therapy, which may also be decided upon inadequacies in the initial staging. Often, remaining lymph node metastases, which are located e.g., on the pelvic wall or were misjudged in case of small size, are the origin of the recurrence. Continue with Material and Methods with subpoints patients and subgroups, MRI examination and histopathological examination and statistical analysis. Next big point is results where you first present the found results of the overall patient group, after that you go on with the performed subgroup analysis and after that you present the statistics. Calculate the test values from the given data of overall and subgroups and present them as table with reference to it in the main text. Only mention the most important values extra in the main text. Next big point is Discussion; Interpret our results here and extrapolate their implications for future decision making in therapy management of rectal cancer. Try to find explanations for our results, such as tissue changes in lymph node metastases due to neoadjuvant therapy, or other explanations that you can deduce by looking at current clinical studies of your training material and making logical connections. Also correlate our work with recently published scientific articles (cite sources in parentheses) and emphasize why we were able to show that, contrary to popular opinion, contrast agent administration is essential for the detection of lymph node metastases. Write it so that it sounds interesting and appealing for potential reviewers. Use precise academic, scientific, medical, and radiological high-level English language and terminology. Do not use phrases an AI would use. Take already published radiological articles of NEJM as template for language and structure of the text. Make the structure of the section how it is common in NEJM. Insert tables with references to them in the main text to make it easier for the reader to follow.

Draft should be 6000 Words with focus on Introduction and Discussion. 
Do not invent sources but research them in your training data or the Internet.

After finishing the draft give a table with potential critics from reviewers, examples from the text and solutions how to solve them.

Answer in Markdown.